阅读说明：本技术 分析用试样的制备方法、分析方法和分析用试样的制备用试剂盒 (Method for preparing sample for analysis, method for analysis, and kit for preparing sample for analysis ) 是由 西风隆司 于 2019-08-23 设计创作，主要内容包括：提供分析用试样的制备方法、分析方法和分析用试样的制备用试剂盒。本发明的课题在于将分析对象的含内酯结构的唾液酸与其他唾液酸相区别并进行分析。一种分析用试样的制备方法,其用于进行试样中含有的含内酯结构的糖链的分析,该制备方法具备：进行第1酰胺化反应的步骤,在试样中加入含有与含内酯结构的唾液酸反应的氨、胺或它们的盐作为第1亲核试剂的第1酰胺化反应溶液,对含内酯结构的唾液酸进行酰胺化；以及,进行第2反应的步骤,用除完全甲基化以外的方法对第1酰胺化反应中未被酰胺化的唾液酸的至少一部分进行修饰。(Provided are a method for preparing an analysis sample, an analysis method, and a kit for preparing an analysis sample. The present invention addresses the problem of analyzing lactone structure-containing sialic acid to be analyzed while distinguishing it from other sialic acids. A method for preparing a sample for analysis for analyzing a sugar chain containing a lactone structure contained in the sample, the method comprising: a step of performing an amidation reaction of 1 st, in which a1 st amidation reaction solution containing, as a1 st nucleophile, ammonia, amine or a salt thereof which reacts with the lactone structure-containing sialic acid is added to a sample to amidate the lactone structure-containing sialic acid; and a step of carrying out a2 nd reaction in which at least a part of sialic acid which is not amidated in the 1 st amidation reaction is modified by a method other than complete methylation.)

1. A method for preparing a sample for analysis,

which is used for analyzing sugar chains containing a lactone structure contained in a sample,

the preparation method comprises the following steps:

a step of performing an amidation reaction of 1 st, in which an amidation reaction solution of 1 st containing, as a nucleophilic reagent of 1 st, ammonia, amine or a salt thereof that reacts with the lactone-structure-containing sialic acid is added to the sample to amidate the lactone-structure-containing sialic acid; and the number of the first and second groups,

a step of carrying out a2 nd reaction in which at least a part of sialic acid not amidated in the 1 st amidation reaction is modified by a method other than complete methylation.

2. The method for preparing a sample for analysis according to claim 1, wherein,

the time for contacting the sample with the 1 st amidation reaction solution in order to perform the 1 st amidation reaction is shorter than 30 minutes.

3. The method for preparing a sample for analysis according to claim 1, wherein,

the 1 st amidation reaction solution does not contain a dehydration condensation agent that reacts with sialic acid.

4. The method for preparing a sample for analysis according to claim 1, wherein,

the amine is a primary amine.

5. The method for preparing a sample for analysis according to claim 1, wherein,

the amine contains an alkyl group.

6. The method for preparing a sample for analysis according to claim 5, wherein,

the alkyl group has no branch.

7. The method for preparing an analysis sample according to any one of claims 1 to 6, wherein,

the pH of the 1 st amidation reaction solution is 8.0 or more.

8. The method for preparing an analysis sample according to any one of claims 1 to 6, wherein,

the 1 st amidation reaction solution contains an amine or a salt thereof,

the concentration of the amine or salt thereof is 0.5M or more.

9. The method for preparing an analysis sample according to any one of claims 1 to 6, wherein,

the 2 nd reaction is carried out in a state where the sample is bound or adsorbed to a solid carrier.

10. The method for preparing an analysis sample according to any one of claims 1 to 6, wherein,

in the 2 nd reaction, the sample after the 1 st amidation reaction is brought into contact with a2 nd reaction solution,

the 2 nd reaction solution further contains ammonia, amine, alcohol or their salts as the 2 nd nucleophile which react with the sialic acid which is not amidated in the 1 st amidation reaction,

amidating or esterifying at least a part of sialic acid not having the lactone structure contained in the sample before the 1 st amidation reaction by the 2 nd reaction,

the 1 st nucleophile is different from the 2 nd nucleophile.

11. The method for preparing a sample for analysis according to claim 10, wherein,

the 2 nd reaction solution contains a dehydration condensation agent.

12. The method for preparing an analysis sample according to any one of claims 1 to 6, wherein,

in the 2 nd reaction, the sample after the 1 st amidation reaction is brought into contact with a2 nd reaction solution,

the reaction solution 2 contains an alkylating agent for ester synthesis.

13. The method for preparing an analysis sample according to any one of claims 1 to 6, wherein,

in the 2 nd reaction, at least a portion of the sialic acid is modified based on the manner in which the sialic acid is attached.

14. The method for preparing a sample for analysis according to claim 13, wherein,

the 2 nd reaction modifies α 2, 3-sialic acid, at least one of α 2, 8-sialic acid and α 2, 9-sialic acid, and α 2, 6-sialic acid with different modifications.

15. An analysis method comprising:

a step of preparing a sample for analysis by the method for preparing a sample for analysis according to any one of claims 1 to 14; and the number of the first and second groups,

and a step of analyzing the prepared sample for analysis.

16. The assay of claim 15, wherein,

the prepared sample for analysis is analyzed by at least one of mass spectrometry and chromatography.

17. A kit for preparing a sample for analysis,

which contains at least one of ammonia, amines and salts thereof,

the method for preparing an analysis sample according to any one of claims 1 to 14.

Technical Field

The present invention relates to a method for preparing an analysis sample, an analysis method, and a kit for preparing an analysis sample.

Background

Sialic acid is a sugar that is present in a large amount in a living body, is contained in a sugar chain that binds to a protein in a living body, and is present at a non-reducing end of the sugar chain in many cases, and therefore, sialic acid is disposed on the outer side of the molecule in such a glycoprotein molecule and can be directly recognized by other molecules, and thus, has an important role.

Heretofore, it has been known that a lactone structure exists in gangliosides and lactooligosaccharide chains of glycolipids (see non-patent document 1). the polysialic acid structure frequently expressed in the brain contains α 2,8-, α 2, 9-linked sialic acids, but these are also considered to be likely to form a lactone structure.A lactone structure is contained in sugar chains of biopharmaceuticals, particularly antibody drugs.A non-patent document 2 describes that certain biostimulants contain a lactone structure.

No method has been established for distinguishing and quantitatively detecting sialic acid containing a lactone structure from sialic acid containing no lactone structure. The sialic acid containing a lactone structure is one water molecule (H) smaller than the sialic acid containing no lactone structure₂O) and therefore can be distinguished using mass spectrometry. However, the lactone structure is extremely unstable and is easily hydrolyzed even in water, and is more rapidly hydrolyzed under acidic or basic conditions. Therefore, in particular, when the sugar chain is cleaved by an enzymatic method or a chemical method and analyzed as a free sugar chain, or when the sugar chain is digested by a protease and analyzed as a glycopeptide, the successful incorporation of the sugar chain cannot be confirmed due to the decompositionThe ester structure was quantitatively analyzed.

In mass spectrometry and the like, modification of sialic acid is performed as a pretreatment for sialic acid-containing sugar chains. The defects such as ionization inhibition and sialic acid detachment are overcome by neutralizing the carboxyl group of sialic acid having a negative charge by esterification, amidation, or the like. Further, a method of specifically quantifying sialic acid by a ligation method has been proposed (see patent document 1 and non-patent document 3). However, this method cannot distinguish between sialic acid originally present in the lactone structure and normal sialic acid that is not.

Non-patent document 4 detects the lactone of gangliosides by performing mass spectrometry after aminolysis and complete methylation. However, complete methylation has a limitation that the hydroxyl groups of the sugar chain are completely methylated.

Disclosure of Invention

Problems to be solved by the invention

A method for discriminating sialic acid containing a lactone structure originally contained in a sample from sialic acid containing no lactone structure and quantifying the same with high accuracy is required.

Means for solving the problems

A method for preparing an analysis sample according to a preferred embodiment of the present invention is a method for analyzing a lactone structure-containing sugar chain contained in a sample, the method including: a step of performing 1 st amidation reaction in which a1 st amidation reaction solution containing, as a1 st nucleophile, ammonia, amine or a salt thereof that reacts with the lactone structure-containing sialic acid is added to the sample to amidate the lactone structure-containing sialic acid; and a step of carrying out a2 nd reaction in which at least a part of sialic acid not amidated in the 1 st amidation reaction is modified by a method other than complete methylation.

In a more preferred embodiment, the time for contacting the sample with the 1 st amidation reaction solution for performing the 1 st amidation reaction is shorter than 30 minutes.

In a more preferred embodiment, the 1 st amidation reaction solution does not contain a dehydration condensation agent that reacts with sialic acid.

In a further preferred embodiment, the amine is a primary amine.

In a further preferred embodiment, the amine contains an alkyl group.

In a further preferred embodiment, the alkyl group has no branch.

In a more preferred embodiment, the pH of the 1 st amidation reaction solution is 8.0 or more.

In a more preferred embodiment, the 1 st amidation reaction solution contains an amine or a salt thereof, and the concentration of the amine or the salt thereof is 0.5M or more.

In a more preferred embodiment, the 2 nd reaction is carried out in a state where the sample is bound to or adsorbed on a solid phase carrier.

In a more preferred embodiment, the sample subjected to the 1 st amidation reaction is brought into contact with a2 nd reaction solution in the 2 nd reaction, the 2 nd reaction solution further contains ammonia, amine, alcohol or a salt thereof as a2 nd nucleophile, which reacts with the sialic acid that is not amidated in the 1 st amidation reaction, and at least a part of the sialic acid that does not have the lactone structure contained in the sample before the 1 st amidation reaction is amidated or esterified by the 2 nd reaction, and the 1 st nucleophile is different from the 2 nd nucleophile.

In a more preferred embodiment, the reaction solution 2 contains a dehydration condensation agent.

In a more preferred embodiment, the sample subjected to the 1 st amidation reaction in the 2 nd reaction is brought into contact with a2 nd reaction solution, and the 2 nd reaction solution contains an alkylating agent for ester synthesis.

In a more preferred embodiment, at least a part of the sialic acid is modified according to the mode of linkage of sialic acid in the reaction 2.

In a further preferred embodiment, the reaction 2 is modified with different modifications to α 2, 3-sialic acid, α 2, 8-sialic acid and/or α 2, 9-sialic acid and α 2, 6-sialic acid.

An analysis method according to a preferred embodiment of the present invention includes: a step of preparing an analysis sample by the method for preparing an analysis sample; and analyzing the prepared sample for analysis.

In a further preferred embodiment, the prepared sample for analysis is analyzed by at least one of mass spectrometry and chromatography.

The reagent kit for preparing an analysis sample according to a preferred embodiment of the present invention contains at least one of ammonia, an amine, and a salt thereof, and is used in the method for preparing an analysis sample.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, sialic acid containing a lactone structure originally contained in a sample can be discriminated from sialic acid containing no lactone structure and quantified with high accuracy.

Drawings

FIG. 1 is a flow chart illustrating the flow of an analysis method of one embodiment.

FIG. 2 is a flow diagram illustrating the flow of an analysis method of one embodiment.

Fig. 3 (a), 3 (B) and 3 (C) are schematic diagrams showing the structure of sugar chains contained in the samples used in the examples.

FIG. 4 shows a mass spectrum obtained by mass spectrometry in a negative ion mode of a reaction product after specific modification of the linkage form of sialic acid to sugar chains contained in a sample.

FIG. 5 is a mass spectrum obtained by subjecting a sugar chain contained in a sample to specific modification such as amidation of a lactone and linkage of sialic acid, and then subjecting the reaction product to mass spectrometry in a negative ion mode.

FIG. 6 is a mass spectrum obtained by subjecting a sugar chain contained in a sample to specific modification such as amidation of a lactone, binding to a hydrazide bead, and linkage of sialic acid, and then subjecting the reaction product to mass spectrometry in a negative ion mode.

FIG. 7 shows a mass spectrum obtained by mass spectrometry in a negative ion mode of a reaction product after nonspecific modification of the sugar chain contained in a sample with a sialic acid linkage system.

FIG. 8 is a mass spectrum obtained by subjecting a sugar chain contained in a sample to lactone amidation and sialic acid linkage non-specific modification, and then subjecting the reaction product to mass spectrometry in a negative ion mode.

FIG. 9 is a mass spectrum obtained by mass spectrometry in a negative ion mode of a reaction product after subjecting a sugar chain contained in a sample to amidation of a lactone, binding to a hydrazide bead, and nonspecific modification of the linkage mode of sialic acid.

Fig. 10 is a mass spectrum obtained by subjecting a sugar chain released from α 2, 3-sialoglycopeptide to lactonization and aminolysis, and then subjecting the reaction product to mass spectrometry in a negative ion mode, wherein (a) of fig. 10 is a mass spectrum in which the concentration of methylamine at the time of aminolysis is 1%, and (b) of fig. 10 is a mass spectrum in which the concentration of methylamine at the time of aminolysis is 10%.

Fig. 11 is a graph showing the relationship between the concentration of the aqueous methylamine solution at the time of aminolysis and the efficiency of carrying out amidation.

Fig. 12 is a graph showing the kind of amine and the formation ratio of each reaction product at the time of aminolysis.

Fig. 13 is a graph showing the kind of amine and the formation ratio of the solvent to each reaction product at the time of aminolysis.

Fig. 14 is a graph showing the pH at the time of aminolysis and the production ratio of each reaction product.

FIG. 15 is a mass spectrum obtained by subjecting a sugar chain free from fetuin glycoprotein to lactonization and aminolysis, and then subjecting the reaction product to mass spectrometry.

FIG. 16 is a graph showing the formation ratio of each reaction product when a sugar chain released from α 2, 3-sialoglycopeptide is subjected to lactonization, then bound to a HILIC carrier, and subjected to aminolysis before and after elution.

Detailed Description

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. The following embodiment shows a method for preparing an analysis sample for analyzing lactones in sugar chains originally contained in a sample. The inventors have found that a reaction solution containing ammonia, amine or a salt thereof which reacts with a lactone structure-containing sialic acid is added to a sample to amidate the lactone structure-containing sialic acid contained in the sample and quantify the amidation.

Embodiment 1

Fig. 1 is a flowchart showing a flow of an analysis method in the method for preparing an analysis sample according to the present embodiment. This analysis method is used for analyzing lactones in sugar chains originally contained in a sample. In step S1001, a sample containing a sugar chain is prepared.

The method for preparing an analysis sample according to the present embodiment is used to modify a lactone-structure-containing sialic acid contained in a sugar chain, and is preferably used to analyze the linkage form of sialic acid, and therefore the sugar chain in the sample preferably contains a sugar chain that may have sialic acid at the terminal, such as an N-linked sugar chain, an O-linked sugar chain, or a glycolipid-type sugar chain.

After step S1001 ends, the process proceeds to step S1003.

(1 st amidation reaction)

In step S1003, the 1 st amidation reaction is performed, specifically, the sample is brought into contact with a reaction solution for amidating lactone structure-containing sialic acid (hereinafter referred to as the 1 st amidation reaction solution), and the lactone structure-containing sialic acid originally contained in the sample is amidated. The present inventors have found that a lactone can be directly amidated in a rapid manner, completely different from the conventional knowledge that a lactone is ring-opened by hydrolysis and then a carboxyl group is amidated. This reaction is a reaction other than hydrolysis since it can be suitably carried out under anhydrous conditions, and is considered to be aminolysis based on the interaction between an amino group and a lactone. The ring opening and amidation of a lactone with ammonia, an amine, or a salt thereof, which can be performed under anhydrous conditions, is hereinafter referred to as aminolysis. The lactone or lactone structure originally contained in the sample is appropriately referred to as a lactone or lactone structure to be analyzed. Since this aminolysis reaction does not substantially require a dehydration condensation agent, only lactonized sialic acid can be selectively amidated without affecting normal sialic acid which is not a lactone structure.

The lactone structure in sialic acid can be analyzed, for example, as a lactone structure formed between sialic acid and a monosaccharide adjacent to the sialic acid, or as a lactone structure formed inside sialic acid.

An operation for removing the 1 st amidation reaction solution from the sample after the 1 st amidation reaction is performed. The operations for removing the 1 st amidation reaction solution were: the 1 st amidation reaction solution is separated from the sugar chains bound to the solid phase carrier by centrifugation or the like, and washed with a washing solution, or the sample is dried and solidified by concentration by centrifugation under reduced pressure, and the concentration of the reagent necessary for the 1 st amidation reaction is not particularly limited as long as it is sufficiently low.

The 1 st amidation reaction solution contains ammonia, amine or a salt thereof. In order to avoid accidental lactonization of sialic acid in the sample, which is not lactonized originally, the 1 st amidation reaction solution preferably contains no or substantially no dehydration condensation agent. Alternatively, the 1 st amidation reaction solution preferably contains only a dehydration condensation agent at a sufficiently low concentration that such undesirable lactonization does not occur. Preferably, the 1 st amidation reaction is performed only by contacting the sample with the 1 st amidation reaction solution, and the lactone to be analyzed is stabilized by a simple operation.

(amine in amidation reaction 1.)

In the case where an amine is used in the 1 st amidation reaction, the amine contained in the 1 st amidation reaction solution is preferably a primary amine, more preferably a primary amine having a linear hydrocarbon group, and still more preferably a primary amine having a linear alkyl group. The amine contained in the 1 st amidation reaction solution is preferably a primary amine having a linear alkyl group, and is preferably a primary amine having 10 or less carbon atoms, more preferably a primary amine having 7 or less carbon atoms, still more preferably methylamine, ethylamine, propylamine, butylamine, pentylamine, and most preferably methylamine. The amine contained in the 1 st amidation reaction solution is preferably one having a linear structure without a branch (hereinafter, the "branch" indicates a branch of a hydrocarbon chain) or having a small number of carbon atoms because the lactone to be analyzed can be amidated more efficiently.

When the amine contained in the 1 st amidation reaction solution is a primary amine having an unsaturated chain hydrocarbon group, the unsaturated chain hydrocarbon group preferably has a double bond, more preferably the unsaturated chain hydrocarbon group has an Allyl group (Allyl), and most preferably the amine is an Allyl amine (Allylamine). The amine contained in the 1 st amidation reaction solution may be a primary amine containing a hydroxyl group, and in this case, ethanolamine is preferable. The amine contained in the 1 st amidation reaction solution may contain various functional groups other than alkyl groups. As a result of the 1 st amidation reaction, the sugar chain is modified in such a manner as to contain such a functional group, thereby making it easier to separate the sugar chain subjected to the modification not only by mass spectrometry but also by chromatography or the like.

The 1 st amidation reaction solution may contain a salt of the above-mentioned amine.

(concentration of amidation reaction solution 1.)

The concentration of ammonia, amine or salt thereof in the 1 st amidation reaction solution is preferably 0.1M or more (M is mol/l), more preferably 0.3M or more, still more preferably 0.5M or more, still more preferably 1.0M or more, and most preferably 3.0M or more. As a preferable example, the 1 st amidation reaction solution contains ammonia or a primary amine, particularly methylamine, and the concentration of the primary amine such as ammonia or methylamine is preferably 0.1M or more, more preferably 0.3M or more, further preferably 0.5M or more, further preferably 1.0M or more, and most preferably 3.0M or more. The higher the concentration of the amine or the like in the 1 st amidation reaction solution is, the more reliably the amidation of the lactone to be analyzed can be performed.

(solvent for amidation reaction solution 1.)

The solvent of the 1 st amidation reaction solution may be an aqueous solvent or an organic solvent. The solvent may be a dehydrated solvent or an anhydrous solvent in which a dehydration operation is performed to suppress the water content, and the water content may be appropriately adjusted from the viewpoint of preventing hydrolysis of the lactone to be analyzed and reliably initiating rapid amidation. The solvent of the 1 st amidation reaction solution preferably contains at least one of methanol and Acetonitrile (ACN).

It should be noted that the 1 st amidation reaction solution may contain a considerable amount of water (H)₂O), the solvent of the 1 st amidation reaction solution may be water.

(pH of amidation reaction solution 1)

The pH of the 1 st amidation reaction solution is preferably 7.7 or more, more preferably 8.0 or more, further preferably 8.8 or more, and most preferably 10.3 or more. If the pH of the 1 st amidation reaction solution is increased, the lactone to be analyzed can be amidated more reliably, and therefore, it is preferable.

(time for initiating the 1 st amidation reaction)

The 1 st amidation reaction is completed within several seconds to several minutes. Therefore, in order to amidate a lactone by the 1 st amidation reaction, the time for contacting the sample with the 1 st amidation reaction solution (hereinafter referred to as reaction time) is preferably less than 1 hour, more preferably less than 30 minutes, further preferably less than 15 minutes, further preferably less than 5 minutes, and most preferably less than 1 minute. Preferably, the sample may be washed with the 1 st amidation reaction solution, or the sample held on a carrier or the like may be subjected to liquid circulation only for a short time. Further, the sample may be mixed with the 1 st amidation reaction solution and dried without setting the reaction time. Thus, the 1 st amidation reaction is completed in a short time, and thus, the unstable lactone can be prevented from being decomposed to impair quantitativity of analysis of the sugar chain. Further, by setting the reaction time of the 1 st amidation reaction to be short, the analysis of the sample can be performed more efficiently.

(phase for carrying out amidation reaction No. 1)

The state of the sample at the time of initiating the 1 st amidation reaction is not particularly limited as long as the sample can be brought into contact with the 1 st amidation reaction solution, and when the reaction is carried out in a solid phase, the accuracy of quantifying the lactone to be analyzed is lowered due to lactonization of sialic acid at the time of the solid phase reaction, and therefore, the 1 st amidation reaction is preferably carried out in a liquid phase.

When the sample contains a glycoprotein, a glycopeptide, or a glycolipid, the sugar chain may be released from the glycoprotein, the glycopeptide, or the glycolipid after the 1 st amidation reaction, and as a method for releasing the sugar chain, there may be employed a method of using an enzyme treatment such as N-glycosidase, O-glycosidase, glycosphingolipid endoglycosidase (Endoglycoceramidase), hydrazine decomposition, β dissociation by an alkali treatment, or the like.

When the sample contains a glycopeptide or glycoprotein, after the 1 st amidation reaction, as described in the section "inhibition of side reaction of glycopeptide and glycoprotein" described later, treatment for inhibiting side reaction of peptide portion can be appropriately performed. Further, a glycopeptide or a glycoprotein having a large number of amino acid residues in a peptide chain is preferably used by cleaving the peptide chain by an enzyme or the like. For example, in the case of preparing a sample for mass spectrometry, the number of amino acid residues in the peptide chain is preferably 30 or less, more preferably 20 or less, and still more preferably 15 or less. On the other hand, in the case where it is required to clarify the origin of the peptide to which the sugar chain is bonded, the number of amino acid residues in the peptide chain is preferably 2 or more, more preferably 3 or more.

As the digestive enzyme for cleaving a peptide chain of a glycopeptide or glycoprotein, trypsin, Lys-C, arginine endopeptidase, chymotrypsin, pepsin, thermolysin, proteinase K, pronase E, and the like can be used. More than 2 of these digestive enzymes may be used in combination. The conditions for cleaving the peptide chain are not particularly limited, and an appropriate protocol depending on the digestive enzyme to be used can be employed. Before the cleavage, a modification treatment or an alkylation treatment of the protein or peptide in the sample may be performed. The conditions of the modification treatment and the alkylation treatment are not particularly limited. Further, the peptide chain may be cleaved not by enzymatic cleavage but by chemical cleavage or the like. If the lactone to be analyzed can be quantified with a desired accuracy, the treatment for liberating the sugar chain, suppressing the side reaction, or cleaving the peptide may be performed before the 1 st amidation reaction.

After step S1003 is completed, the process proceeds to step S1005.

In step S1003, the lactone to be analyzed is amidated and stabilized. The method for preparing an analysis sample and the analysis method of the present embodiment specifically modify sialic acid that is not amidated in step S1003 in a linking manner, and analyze the sialic acid in a manner different from sialic acid containing a lactone to be analyzed.

(lactonization reaction)

In step S1005, a lactonization reaction (hereinafter, referred to as lactonization reaction, unless otherwise mentioned, referred to as lactonization reaction in step S1005) is performed in which a sample is brought into contact with a reaction solution for lactonization (hereinafter, referred to as lactonization reaction) to lactonize at least a part of sialic acid contained in a sugar chain, the lactonization reaction modifies a part of sialic acid that is not lactonized, and the lactonization reaction lactonizes α 2, 3-sialic acid, α 2, 8-sialic acid, and α 2, 9-sialic acid as appropriate.

The lactonization reaction solution contains a dehydration condensation agent and a nucleophile containing an alcohol, an amine, or a salt thereof. The species and concentration of the dehydration condensation agent and the nucleophile are adjusted so as to selectively initiate dehydration or nucleophilic reaction depending on the mode of sialic acid attachment.

The lactone resulting from intramolecular dehydration of the carboxyl group of α 2, 3-sialic acid is a six-membered ring, and it is possible that the lactone resulting from intramolecular dehydration of the carboxyl group of α 2, 6-sialic acid is a seven-membered ring, therefore α 2, 3-sialic acid, which produces a six-membered ring more stable than a seven-membered ring, is more easily lactonized than α 2, 6-sialic acid, and furthermore, the carboxyl group of α 2, 3-sialic acid is located at a more sterically hindered position than the carboxyl group of α 2, 6-sialic acid, so that a larger molecule is less likely to react with α 2, 3-sialic acid than α 2, 6-sialic acid.

The nucleophile contained in the lactonization reaction solution (hereinafter, referred to as the 2 nd nucleophile) is different from the nucleophile contained in the 1 st amidation reaction solution (hereinafter, referred to as the 1 st nucleophile). When analyzing the analysis sample obtained by the method for preparing an analysis sample according to the present embodiment by mass spectrometry, the 1 st nucleophile and the 2 nd nucleophile are selected so as to have different masses. When the analysis sample obtained by the method for producing an analysis sample according to the present embodiment is analyzed by chromatography, the 1 st nucleophile and the 2 nd nucleophile have different substituents, which are preferable because they are easily separated from each other in chromatography.

(dehydration condensation agent in lactonization reaction)

The dehydration condensation agent preferably contains carbodiimide. This is because if carbodiimide is used, the carboxyl group existing at a site having a large steric hindrance is less likely to be amidated than when a phosphonium dehydration condensation agent (so-called BOP reagent) or a uronium dehydration condensation agent is used as the dehydration condensation agent. Examples of carbodiimides include: n, N '-Dicyclohexylcarbodiimide (DCC), N- (3-dimethylaminopropyl) -N' -Ethylcarbodiimide (EDC), N '-Diisopropylcarbodiimide (DIC), 1-tert-butyl-3-ethylcarbodiimide (BEC), N' -di-tert-butylcarbodiimide, 1, 3-di-p-toluoyl-carbodiimide, bis (2, 6-diisopropylphenyl) carbodiimide, bis (trimethylsilyl) carbodiimide, 1, 3-bis (2, 2-dimethyl-1, 3-dioxolan-4-ylmethyl) carbodiimide (BDDC), salts thereof.

(additive in lactonization)

In order to promote the dehydration condensation by the dehydration condensation agent and suppress the side reaction, it is preferable to use an additive having high nucleophilicity in addition to the carbodiimide. As the additive having high nucleophilicity, 1-hydroxybenzotriazole (HOBt), 1-hydroxy-7-aza-benzotriazole (HOAt), 4- (dimethylamino) pyridine (DMAP), ethyl 2-cyano-2- (hydroxyimino) acetate (Oxyma), N-hydroxy-succinimide (HOSu), 6-chloro-1-hydroxy-benzotriazole (Cl-HOBt), N-hydroxy-3, 4-dihydro-4-oxo-1, 2, 3-benzotriazine (HOOBt), and the like are preferably used.

(nucleophile (2 nd nucleophile) in lactonization)

The amine used as the 2 nd nucleophile preferably contains a primary or secondary alkylamine having 2 or more carbon atoms, the primary alkylamine is preferably ethylamine, propylamine, isopropylamine, butylamine, sec-butylamine, tert-butylamine, and the like, the secondary alkylamine is preferably dimethylamine, ethylmethylamine, diethylamine, propylmethylamine, isopropylmethylamine, and the like, and an amine having a branched alkyl group such as isopropylamine is preferably used from the viewpoint of preventing the amidation of a carboxyl group present at a site having a large steric hindrance, such as a carboxyl group of α 2, 3-sialic acid, and in the case of using an amine as the nucleophile in the lactonization reaction solution, a part of the carboxyl group of sialic acid such as α 2, 6-sialic acid is amidated depending on the linking mode of the sialic acid.

The alcohol used as the 2 nd nucleophile is not particularly limited, and for example, methanol, ethanol and the like can be used, and when the alcohol is used as the nucleophile in the lactonization reaction solution, some of the carboxyl groups of sialic acid such as α 2, 6-sialic acid are esterified depending on the mode of linkage of sialic acid.

The 2 nd nucleophile may contain a salt of the above nucleophile.

(regarding the concentrations of dehydration condensing agent and amine)

The concentration of the dehydration condensation agent in the lactonization reaction solution is, for example, preferably 1 mM-5M, more preferably 10 mM-3M. When carbodiimide is used in combination with a highly nucleophilic additive such as HOAt or HOBt, the concentration of each is preferably within the above range. The concentration of the amine in the lactonization reaction solution is preferably 0.01 to 20M, and more preferably 0.1 to 10M. The reaction temperature in the lactonization reaction is preferably about-20 ℃ to 100 ℃, and more preferably about-10 ℃ to 50 ℃.

(phase for carrying out lactonization reaction)

The lactonization reaction can be carried out in the liquid or solid phase. The state of the sample at the time of initiating the lactonization reaction is not particularly limited as long as the sample can be brought into contact with the lactonization reaction solution, but it is preferable to bring the sugar chains contained in the sample after the 1 st amidation reaction into contact with the lactonization reaction solution in a state of being bound to or adsorbed to a solid support.

When the reaction is carried out in a solid phase, the solid phase carrier is not particularly limited as long as it can immobilize a sugar chain, a glycopeptide, a glycoprotein, or the like. For example, a solid support having an epoxy group, a tosyl group, a carboxyl group, an amino group, or the like as a ligand can be used for immobilizing glycopeptides or glycoproteins. In addition, for immobilizing sugar chains, a solid phase carrier having a hydrazide group, an aminoxy group, or the like as a ligand can be used. Further, it is also preferable that the sugar chain is adsorbed to a stationary phase which is a carrier for hydrophilic interaction chromatography (hereinafter referred to as HILIC), and it is further preferable that the carrier for HILIC contains an amide group.

By carrying out the reaction in a state where the sample is immobilized on the solid carrier, the removal of the reaction solution and the desalting and purification are facilitated, and the preparation of the sample can be simplified. In the case of using a solid carrier, when a sample is immobilized in the state of glycoprotein or glycopeptide and cleaved with glycosidase such as PNGase F after the lactonization reaction, the sample after the lactonization reaction may be collected as free sugar chains.

The sample after the lactonization reaction may be subjected to purification, desalting, solubilization, concentration, drying, and other treatments by known methods, if necessary. The same applies to the before and after the 2 nd amidation reaction described later.

For the release of the sample from the solid phase carrier, the conditions described for the 2 nd amidation reaction described later can be employed. By carrying out the reaction in a state where the sample is immobilized on the solid phase carrier, removal of a lactonization reaction solution after the lactonization reaction and the like are facilitated, and sialic acid can be efficiently modified.

After step S1005 ends, the process proceeds to step S1007.

(2 nd amidation reaction)

In step S1007, a2 nd amidation reaction is performed in which the sample is brought into contact with a reaction solution (hereinafter referred to as a2 nd amidation reaction solution) to amidate the lactonized sialic acid in step S1005, thereby obtaining an analysis sample.

The composition, pH and reaction time of the 2 nd amidation reaction solution are selected from the same conditions as those of the 1 st amidation reaction.

The dehydration condensation agent is not required for the 2 nd amidation reaction, but the dehydration condensation agent may be contained in the 2 nd amidation reaction solution. The 2 nd amidation reaction solution may be prepared, for example, by adding ammonia, amine or a salt thereof without removing the lactonization reaction solution added to the sample at step S1005. Thus, the 2 nd amidation reaction can stabilize the lactone formed by a simple operation.

The nucleophile (referred to as the 3 rd nucleophile) contained in the 2 nd amidation reaction solution is different from both the 1 st nucleophile and the 2 nd nucleophile described above. When analyzing the analysis sample obtained by the method for producing an analysis sample according to the present embodiment by mass spectrometry, the 1 st nucleophile, the 2 nd nucleophile, and the 3 rd nucleophile are selected so that all of them have different masses. The 1 st, 2 nd and 3 rd nucleophiles are selected according to the mass resolution of mass spectrometry to mass separate the resulting modified body with high accuracy. The 1 st nucleophile, the 2 nd nucleophile and the 3 rd nucleophile may be different substances or may be the same substance having different masses by using a stable isotope. Alternatively, an isobaric (isobaric) tag such as iTRAQ may be used. In this case, since the tag is designed so that m/z of the product ion obtained by fragmentation between the 1 st and 2 nd mass spectrometry is different, the sialic acid linkage system and the lactone body can be identified by tandem mass spectrometry (MS/MS). In this way, when performing mass spectrometry of 2 or more stages on modified bodies modified with the 1 st nucleophile, the 2 nd nucleophile and the 3 rd nucleophile, respectively, it is sufficient to separate these modified bodies at any one stage by different m/z. When the analysis sample obtained by the method for producing an analysis sample according to the present embodiment is analyzed by chromatography, it is preferable that the 1 st nucleophile, the 2 nd nucleophile and the 3 rd nucleophile have different substituents in order to facilitate the separation from each other by chromatography.

(phase for carrying out amidation reaction No. 2)

The 2 nd amidation reaction may be carried out in a liquid phase or a solid phase. In the case where the 2 nd amidation reaction is performed in a state where the sample is immobilized on a solid phase, the 2 nd amidation reaction may be performed while the sample subjected to the lactonization reaction is maintained in a state where the sample is immobilized on a solid phase. Alternatively, the sample may be subjected to lactonization and then immobilized on a solid phase to perform the 2 nd amidation reaction.

When the 2 nd amidation reaction is carried out in a solid phase, the same carrier as that used for the lactonization reaction can be used as the solid phase carrier. For the immobilization of the sample on the solid support, the conditions described for the lactonization reaction can be used. In the case of performing the 2 nd amidation reaction in a solid phase, the sample immobilized on the solid phase carrier may be amidated by allowing the 2 nd amidation reaction solution to act on the sample, and then the sample may be separated from the carrier by a chemical method, an enzymatic reaction, or the like and collected. For example, glycoproteins or glycopeptides immobilized on a carrier can be enzymatically cleaved and recovered by glycosidase such as PNGase F or digestive enzyme such as trypsin, or sugar chains bound to a solid carrier having a hydrazide group can be released and recovered by a weakly acidic solution. HILIC can be prepared by subjecting a2 nd amidation reaction solution containing acetonitrile or the like as a solvent to a2 nd amidation reaction, and eluting a sample with an aqueous solution such as water.

By the above-mentioned preparation method, sialic acid having a lactone structure originally contained in a sample is modified with a1 st nucleophile in a1 st amidation reaction, sialic acid of a linkage type which is not easily lactonized, such as α 2, 6-sialic acid, is modified with a2 nd nucleophile in an lactonization reaction, and sialic acid which has a linkage type which is easily lactonized and does not originally have a lactone structure in a sample, such as α 2,3-, α 2, 8-and α 2, 9-sialic acid, is lactonized in an lactonization reaction, and is modified with a 3 rd nucleophile in a2 nd amidation reaction.

After step S1007 ends, the process proceeds to step S1009.

In step S1009, the sample is analyzed by at least one of mass spectrometry and chromatography. The mass of each sugar chain subjected to modification other than lactonization in each reaction is different among the 1 st amidation reaction, lactonization reaction, and 2 nd amidation reaction. Therefore, these sugar chains can be separated by mass spectrometry according to the presence or absence of the lactone structure to be analyzed and the linkage mode of sialic acid.

The ionization method in mass spectrometry is not particularly limited, and a matrix-assisted laser desorption ionization (MALDI) method, an Electrospray (ESI) method, a nano-electrospray ionization (nano-LSI) method, or the like can be used. The ionization method is particularly preferably MALDI method. Ionization in mass spectrometry may use any of a positive ion mode and a negative ion mode. The mass spectrometry can be performed in multiple stages, and thus the structure of the sugar chain and the structure of the peptide chain can be appropriately analyzed, except for the sialic acid linkage system.

In the case of analysis by chromatography, liquid chromatography is preferred. The column used for liquid chromatography is not particularly limited, and a hydrophobic reverse phase column such as C30, C18, C8, and C4, a carbon column, a normal phase column for HILIC, and the like can be suitably used. For precise analysis of components in a sample by multiple separations, it is preferable to perform measurement by mass spectrometry after performing liquid chromatography. In this case, it is more preferable to directly ionize the eluate from the liquid chromatograph by ESI or the like in the mass spectrometer with on-line control.

The intensity of the sugar chain having a lactone structure-containing sialic acid to be analyzed, the proportion of the sugar chain having a lactone structure-containing sialic acid to be analyzed in the sugar chain having sialic acid, or the proportion of the sugar chain having a lactone structure-containing α 2, 3-sialic acid to be analyzed in the sugar chain having α 2, 3-sialic acid can be calculated, and the like, and the same applies to α 2, 8-sialic acid, α 2, 9-sialic acid, and the method of analyzing the data obtained by mass spectrometry or chromatography is not particularly limited.

After step S1009 is finished, the process is finished.

(suppression of side reactions of glycopeptides and glycoproteins)

When a glycopeptide or glycoprotein is added with the 1 st amidation reaction solution, lactonization reaction solution, and 2 nd amidation reaction solution to modify sialic acid as described above, side reactions such as intramolecular dehydration condensation may occur between the modified sialic acid and an amino group or a carboxyl group located at a side chain of an amino acid contained in the glycopeptide or glycoprotein and a terminal of a main chain. In this case, there is a problem that peaks of a mass spectrum corresponding to a sugar chain to be analyzed are separated, and analysis becomes difficult.

The inventors have found that side reactions of the peptide moiety mainly originate from the presence of the amino group, and that side reactions of the peptide moiety can be suppressed when sialic acid is modified by blocking the amino group by chemical modification or the like before sialic acid is modified. See in particular the following documents: takashi Nishikaze, Sadanori Sekiya, Shinichi Iwamoto, Koichi tanaka, "A Universal Approach to linkage-Specific differentiation for colloidal Acids on Glycopeptides," Journal of The American Society for Mass Spectrometry, 6.2017, Volume 28, Issue 1Supplement, poster number MP 091. The modification by lactonization or the like in the present embodiment can be applied to glycopeptides and glycoproteins in the same manner as described above. For example, a glycopeptide or a glycoprotein is subjected to a reaction for blocking an amino group such as dimethylamidation or guanylation, and lactonization and 2 nd amidation reactions are performed. In this case, if a method of forming a lactone according to the linkage form of sialic acid is used, the linkage form of sialic acid can also be identified.

Some of the glycopeptides are less likely to cause side reactions in terms of the properties due to the amino acid sequence. For example, glycopeptides produced by digesting the Fc region of IgG with a digestive enzyme such as trypsin do not have lysine, and the N-terminal amino group is also rapidly cyclodehydrated in the presence of a dehydration condensation agent to be pyroglutamated (pyroglu). As a result, the amino group is no longer present, and therefore prior blocking of the amino group by dimethylamide, guanidation, or the like is not required. With respect to this glycopeptide, mass spectra satisfying analysis can be obtained by performing the 1 st amidation reaction, lactonization reaction, and 2 nd amidation reaction without blocking the amino group.

(reagent kit for preparation of sample for analysis)

Provided is a kit for preparing an analysis sample (hereinafter referred to as a preparation kit) which is suitable for use in the method for preparing an analysis sample according to the present embodiment. The preparation kit is not particularly limited as long as it contains the 1 st nucleophile-containing solution in the 1 st amidation reaction, and may contain reagents and any consumables used for mass spectrometry other than the reagents. By preparing the sample for analysis using the preparation kit, the sample for analysis can be prepared more efficiently.

Embodiment 2

The method for preparing an analysis sample according to embodiment 2 is performed in the same flow as the method for preparing an analysis sample according to embodiment 1, but differs from embodiment 1 in that: the sample subjected to the 1 st amidation reaction is subjected to a reaction for modifying sialic acid (hereinafter referred to as a non-specific modification reaction) without distinguishing the mode of linkage of sialic acid, in other words, without non-specifically modifying the mode of linkage of sialic acid.

Fig. 2 is a flowchart showing a flow of an analysis method in the method for preparing an analysis sample according to the present embodiment. Steps S2001 and S2003 are the same as steps S1001 and S1003 in the above embodiment, and therefore, the description thereof is omitted. After step S2003 ends, the process proceeds to step S2005.

In step S2005, a nonspecific modification reaction is performed, specifically, the sample subjected to the 1 st amidation reaction is brought into contact with a reaction solution for performing the nonspecific modification reaction (hereinafter referred to as a nonspecific modification reaction solution), and sialic acid having no lactone structure contained in the sample before the 1 st amidation reaction is modified. The nonspecific modification reaction modifies each sialic acid contained in the sample regardless of the mode of linkage of the sialic acid, and gives a sample for analysis.

The nonspecific modification reaction solution contains a dehydration condensation agent and a nucleophile containing an alcohol, ammonia, amine or a salt thereof.

The nucleophile contained in the non-specific modification reaction solution (hereinafter referred to as the 4 th nucleophile) is different from the 1 st nucleophile contained in the 1 st amidation reaction solution. When analyzing the analysis sample obtained by the method for preparing an analysis sample according to the present embodiment by mass spectrometry, the 1 st nucleophile and the 4 th nucleophile are selected so as to have different masses. The 1 st and 4 th nucleophiles are selected according to the mass resolution of mass spectrometry to mass separate the resulting modified body with high accuracy. As described above, the 1 st nucleophile and the 4 th nucleophile may be different substances, or may be the same substance whose mass is different by using a stable isotope, an isobaric label, or the like. When the analysis sample obtained by the method for producing an analysis sample according to the present embodiment is analyzed by chromatography, it is preferable that the 1 st nucleophile and the 4 th nucleophile have different substituents because they can be easily separated from each other by chromatography.

(dehydration condensation agent in nonspecific modification reaction)

The dehydration condensation agent is preferably a substance that exhibits high reaction efficiency even with respect to a carboxyl group present in a site having a large steric hindrance, and is preferably a phosphonium dehydration condensation agent or a uronium dehydration condensation agent.

Examples of the phosphonium based dehydration condensation agent include (benzotriazole-1-yloxy) tris- (dimethylamino) phosphonium (BOP), benzotriazole-1-yloxytris (pyrrolidinyl) phosphonium hexafluorophosphate (PyBOP), tris (dimethylamino) phosphonium bromohexafluorophosphate (BroP), tris (pyrrolidinyl) phosphonium hexafluorophosphate (PyBroP), (7-azabenzotriazole-1-yloxy) tris (pyrrolidinyl) phosphonium hexafluorophosphate (PyAOP), and chloro-tris-pyrrolidinylphosphonium hexafluorophosphate (PyCloP). these are collectively referred to as "BOP reagent" and exhibit high reaction efficiency even for a carboxyl group present in a site having a large steric hindrance, and therefore, amidation can be performed with high reaction efficiency for a site having a large steric hindrance such as a carboxyl group of α 2, 3-sialic acid.

Examples of the uronium dehydration condensation agent include: (1-cyano-2-ethoxy-2-oxoethylideneaminoxy) dimethylamino-morpholinyl-carbenium hexafluorophosphate (COMU), 2- (1H-benzotriazol-1-yl) -1,1,3,3 Hexafluorophosphate (HBTU), 2- (7-azabenzotriazol-1-yl) -1,1,3,3 Hexafluorophosphate (HATU), 2- (1H-benzotriazol-1-yl) -1,1,3, 3-tetramethyluronium tetrafluoroborate (TBTU), 2- (5-norbornene-2, 3-dicarboxyimide) -1,1,3, 3-tetramethyluronium tetrafluoroborate (TNTU), O- (N-succinimidyl) -1,1,3, 3-tetramethyluronium tetrafluoroborate (TSTU), and the like. Among these uronium salts, COMU is particularly preferred.

Among the above, a phosphonium dehydration condensation agent is preferably used from the viewpoint of improving the amidation efficiency of lactone. In order to accelerate the reaction, it is preferable to add a base such as N-methylmorpholine at a concentration of about 0.01 to 80 wt% based on the whole reaction system. By adding the alkali in the above concentration range to the reaction system, the reaction efficiency is improved, and side reactions, precipitation of other reagents, and the like can be suppressed. When N-methylmorpholine is contained as a base in the reaction system, the concentration is preferably 1 to 50% by weight. The conditions for amidation (reaction temperature, reaction time, etc.) are not particularly limited, and known conditions for amidation of sialic acid and the like can be directly applied.

(nucleophile (4 th nucleophile) in lactonization)

α 2 the carboxyl group of 3-sialic acid is present at a site having a large steric hindrance, and therefore, in order to improve the efficiency of nucleophilic reaction, it is preferable to use an amine having a small molecular volume as the amine used as the nucleophilic reagent, and examples of preferable amines to be used in the nonspecific modification reaction include primary alkylamines such as methylamine, ethylamine, propylamine, isopropylamine, butylamine, sec-butylamine, and tert-butylamine, and secondary alkylamines such as dimethylamine, ethylmethylamine, diethylamine, propylmethylamine, and isopropylmethylamine, and the number of carbons of the alkylamines is preferably 5 or less, more preferably 3 or less, among the above amines, primary alkylamines are preferable, primary linear alkylamines are more preferable, and methylamine and ethylamine are particularly preferable.

The nucleophilic reagent used for the nonspecific modification reaction is particularly preferably methylamine hydrochloride or ethylamine hydrochloride because of its high reactivity and few side reactions. Of these, methylamine hydrochloride or ethylamine hydrochloride is further preferably used together with PyAOP and N-methylmorpholine.

When an alcohol is used as the nucleophile, the nucleophilic reagent is not particularly limited, and for example, methanol, ethanol, or the like can be used. In the case where an alcohol is used as the nucleophile for non-specific modification of the reaction solution, the carboxyl group of sialic acid is esterified.

The 4 th nucleophile may contain a salt of the above nucleophile. Further, the nonspecific modification reaction can be carried out without using a dehydration condensation agent. For example, the carboxyl group of sialic acid can be methyl-esterified by reacting methyl iodide as an alkylating agent for ester synthesis in a solution containing DMSO as a solvent. Reference may be made in particular to the paper by Powell et al (Powell, A.K.; Harvey, D.J. RapidCommun. Mass. spectra. 1996,10(9), 1027-. As another example, methyl esterification using MTT reagent as an alkylating agent for ester synthesis can be used. Reference may be made in particular to the document of Miura et al (Miura, Y.; Shinohara, Y.; Furukawa, J.; Nagahori, N.; Nishimura, S. -I.Chem.Eur.J.2007,13 (17); 4797) 4804). The nonspecific modification reaction using these alkylating agents for ester synthesis can be carried out in either solid phase or liquid phase.

(regarding the concentrations of dehydration condensing agent and amine)

The concentration of the dehydration condensation agent in the nonspecific modification reaction solution is, for example, preferably 1 mM-5M, more preferably 10 mM-3M. The concentration of the amine in the non-specific modification reaction solution is preferably 0.01 to 20M, and more preferably 0.1 to 10M.

(phase for non-specific modification reaction)

The nonspecific modification reaction can be carried out in a liquid phase or a solid phase, as in the lactonization reaction described above.

When the non-specific modification reaction is carried out in a solid phase, the same substances as those described for the lactonization reaction can be used as the solid phase carrier. For the immobilization of the sample on the solid support, the conditions described for the lactonization reaction can be used. For the liberation of the sample from the solid phase carrier, the conditions described for the 2 nd amidation reaction can be employed. By carrying out the reaction in a state where the sample is immobilized on the solid carrier, removal of a nonspecific modification reaction solution after the nonspecific modification reaction, desalting and purification, and the like are facilitated, and sialic acid can be modified efficiently.

By the above-mentioned preparation method, sialic acid having a lactone structure originally contained in a sample is modified by the 1 st nucleophile in the 1 st amidation reaction. Sialic acid originally contained in the sample and having no lactone structure is modified by the 4 th nucleophile in the nonspecific modification reaction.

After step S2005 is completed, the process proceeds to step S2007. Step S2007 is the same as step S1007 in the above embodiment, and therefore, description thereof is omitted.

The above-mentioned embodiments 1 and 2 are not particularly limited as long as sialic acid is modified by a method other than complete methylation after sialic acid containing a lactone structure originally contained in a sample is amidated, and then other sialic acid is modified by amidation or esterification. While complete methylation allows methylation of all the hydroxyl groups of the sugar chain, the present invention is not limited to this, and modification suitable for the analysis to be carried out can be suitably carried out.

The present invention is not limited to the contents of the above embodiments. Other ways that can be conceived within the scope of the technical idea of the invention also fall within the scope of the invention.