Light pad microscope for spatially resolved fluorescence correlation spectroscopy
阅读说明:本技术 用于空间解析荧光相关光谱学的光垫显微镜 (Light pad microscope for spatially resolved fluorescence correlation spectroscopy ) 是由 麦克尔·克诺普 马尔特·瓦克斯穆特 热雷米·卡普拉德 于 2012-02-14 设计创作,主要内容包括:本公开内容教导了显微镜(1),其具有用于照明样品或物体(18)的照明光路(20)和用于观察所述样品的观察光路(40,50),所述显微镜包括在照明光路中的照明光路聚焦装置,所述照明光路聚焦装置限定沿着所述照明光路的照明方向和其垂直方向延伸的基本上二维的样品或物体照明区域(22)。所述显微镜进一步包括在照明光路中的用于有选择地照明所述基本上二维的物体照明区域的部分(10)的照明区域界定装置(27),其中所述基本上二维的物体照明区域的该部分在所述照明方向和其垂直方向中的至少一个方向上被界定。(The present disclosure teaches a microscope (1) having an illumination light path (20) for illuminating a sample or object (18) and an observation light path (40,50) for observing the sample, the microscope comprising an illumination light path focusing means in the illumination light path defining a substantially two-dimensional sample or object illumination area (22) extending along an illumination direction of the illumination light path and a direction perpendicular thereto. The microscope further comprises an illumination area defining means (27) in the illumination light path for selectively illuminating a portion (10) of the substantially two-dimensional object illumination area, wherein the portion of the substantially two-dimensional object illumination area is defined in at least one of the illumination direction and a direction perpendicular thereto.)
1. A microscope having an illumination light path (20) for illuminating a sample (8) and at least one observation light path (40,50) for observing the sample (8), the microscope comprising an illumination light path focusing device (23) in the illumination light path (20), the illumination light path focusing device (23) defining a substantially two-dimensional object illumination region (22), the object illumination region (22) extending along an illumination direction of the illumination light path (20) and a direction perpendicular thereto, and
illumination area defining means (27,29) in said illumination light path (20), said illumination area defining means (27,29) for selectively illuminating a portion (10) of said substantially two-dimensional object illumination area (22), wherein said portion (10) of said substantially two-dimensional object illumination area is defined in at least one of said illumination direction and said perpendicular direction.
2. The microscope as claimed in claim 1, wherein the illumination path focusing means (23) comprises at least one of a cylindrical lens (23), a distortion shaping lens, a one-dimensional array of spherical lenses or a one-dimensional array of aspherical lenses.
3. The microscope of claim 1 or 2, wherein the illumination path focusing means (23) comprises at least one distortion shaping mirror.
4. Microscope according to any one of the preceding claims, wherein the illumination area defining means (25) comprise at least a first aperture (29), the first aperture (29) being adapted to define the portion of the substantially two-dimensional object illumination area (22) in the illumination direction.
5. The microscope of any one of the preceding claims, wherein the illumination area defining means comprises at least a second aperture (27), the second aperture (27) being adapted to define the portion of the substantially two-dimensional object illumination area in a direction perpendicular to the illumination direction.
6. The microscope of any preceding claim, wherein the illumination region defining means (23,27) comprises a beam shaper.
7. The microscope of any one of the preceding claims, wherein the viewing direction of the at least one viewing optical path (40,50) is substantially perpendicular to the illumination direction and the substantially two-dimensional object illumination area (22).
8. The microscope of any preceding claim, further comprising an adjustable detection aperture (573) in the detection light path (50), the adjustable detection aperture (573) being capable of reducing the effective viewing area in one or two dimensions.
9. The microscope of claim 8, wherein the portion (10) of the substantially two-dimensional object illumination area (22) and the effective observation/observation area are congruent and/or coincide.
10. The microscope of claim 9, wherein the portion (10) of the substantially two-dimensional object illumination area (22) and the effective observation/observation area are movable through the sample (8) in unison and/or coincidentally.
11. The microscope of any one of the preceding claims, further comprising an additional objective (61) for illuminating and observing a sample (8) arranged in the sample illumination area.
12. The microscope as claimed in claim 11, wherein the additional objective (61) is a component of a fluorescence microscope (6).
13. The microscope of claim 11 or 12, wherein the additional objective (61) is part of an inverted microscope (6).
14. A method of detecting a sample, the method comprising:
illuminating a two-dimensional portion of the sample by focusing an illumination beam (20) onto a substantially two-dimensional object illumination area (22), the substantially two-dimensional object illumination area (22) extending in an illumination direction of the illumination beam (20) and a direction perpendicular thereto;
wherein illuminating the two-dimensional portion further comprises delimiting the substantially two-dimensional object illumination area (22) to selectively illuminate a portion (10) of the substantially two-dimensional object illumination area (22), wherein the portion of the substantially two-dimensional object illumination area is delimited at least in the illumination direction.
15. The method of claim 14, further comprising viewing the substantially two-dimensional object illumination area in a viewing direction, the viewing direction being substantially perpendicular to the illumination direction.
16. The method of claim 14 or 15, further comprising moving at least one of the substantially two-dimensional object illumination area (22) or the portion (10) of the substantially two-dimensional object illumination area across the sample (8).
17. The method of any one of claims 14-16, further comprising determining signal fluctuations in said portion (10) of said substantially two-dimensional object illumination area.
18. The method of any one of claims 14-17, further comprising determining a fluorescence intensity contrast for calibration.
Technical Field
The present invention relates to optical microscopes, in particular to optical microscopes with a defined focal volume (focal volume) and methods suitable for the determination of fluctuations in the concentration of a sample.
Background
Diffusion fundamentally contributes to the movement of soluble molecules, and thus to the spatiotemporal aspects of many biological processes, from regulation of cell division and signal transduction within cells, to hormonal regulation at tissue origin, and to morphogenic gradients during development. Quantifying the diffusive properties of biomolecules in complex cellular environments is very challenging. Devices and methods that enable direct analysis of diffusion processes are very rare and are all specifically tailored to individual problems.
The determination of the properties and behaviour of biomolecules, in particular proteins, and in particular in their natural environment, is a key step in elucidating and analyzing their function and the mechanisms behind cellular and developmental processes. Fluorescence Correlation Spectroscopy (FCS) [1,2] is a known method for analyzing the mobility of molecules, which provides information on the mobile and immobile parts of the labeled molecules, their diffusion properties and concentrations, and the co-diffusion of different labeled molecules interacting.
Confocal laser scanning microscopy (confocal microscope) is the instrument of choice for living cell imaging with high resolution [3] and for FCS, since confocal laser scanning microscopy in combination with hypersensitive photon counting using Avalanche Photodiodes (APDs) makes diffraction limited imaging possible. FCS measurements using confocal laser scanning microscopy have been applied to quantify the kinetics of protein complex formation involved in signalling (4 by EMBL and 5 by others) to study the maturation of mrnps with export-competence [6,7] or to characterize morphogenic gradients [8 ]. FCS measurements using confocal laser scanning microscopy are referred to as confocal FCS in this disclosure. However, confocal FCS experiments are still challenging due to the inherent limitations imposed by the serial practice of confocal FCS data acquisition from one point to another, along with the low overall fluorescence photon yield of photons input into the sample due to out-of-focus illumination [9 ]. In general, confocal laser scanning microscopes allow the determination of only one or a few points per cell at a specific selected position [4,10,11 ].
In other words, confocal FCS does not provide sufficient spatially resolved information to produce images of cells and other biological samples that would otherwise be able to visualize the dispersion process across the entire cell or organism and other protein parameters (e.g., protein interactions) from the FCS.
Another disadvantage of the known method and device is that diffuse spatially resolved imaging is limited or impossible.
Disclosure of Invention
The present disclosure teaches a microscope having an illumination light path for illuminating a sample or object and an observation light path for observing the sample. The microscope includes an illumination light path focusing arrangement in the illumination light path, the illumination light path focusing arrangement defining a substantially two-dimensional sample or object illumination region extending along an illumination direction of the illumination light path and a direction perpendicular thereto. The two-dimensional object or sample illumination area may be considered a light strip or light sheet (light-sheet). Since the illumination light is shaped into the two-dimensional sample illumination area, the illumination light path focusing means may be understood as a light path shaping means.
The microscope further comprises in the illumination beam path an illumination area defining means for selectively illuminating a part of the illumination area of the substantially two-dimensional object, wherein the part of the illumination area of the substantially two-dimensional object is defined at least in the illumination direction and/or in a direction perpendicular thereto. The light strip is thus delimited in at least one of the illumination direction and its perpendicular direction, substantially forming part of the substantially two-dimensional object illumination area, also referred to as "light pad". The thickness of the substantially two-dimensional object illumination area and the thickness of the light pad are much smaller than the illumination direction length and its perpendicular direction width. For example, the length in the illumination direction and the width in the perpendicular direction of the portion of the substantially two-dimensional object illumination area may be about 6 times or more than about 6 times the thickness of the portion of the substantially two-dimensional object illumination area.
The illumination path focusing (and shaping) device may include at least one of a cylindrical lens, an anamorphic shaping lens, a one-dimensional array of spherical or aspherical lenses. The illumination path focusing (and shaping) means may further comprise at least one distortion shaping mirror.
The illumination area defining means may comprise at least a first aperture for defining the portion of the substantially two-dimensional object illumination area in the illumination direction. The illumination area defining means may further comprise at least a second aperture for defining the portion of the substantially two-dimensional object illumination area in a direction perpendicular to the illumination direction. At least one of the first and second apertures may be adjustable and may be a circular aperture or a rectangular hole or slit.
The viewing direction of the viewing optical path may be substantially perpendicular to the illumination direction. The substantially two-dimensional object illumination area is then adjusted to lie within the focal plane of the detection objective. In this respect, the microscope may be based on a single plane illumination microscope having an illumination area which is defined at least in the illumination direction. Other viewing directions may also be used in conjunction with the present disclosure.
The detection or viewing optical path may include at least one spatial filter allowing to delimit the detection area to the portion of the substantially two-dimensional illumination area.
The observation and detection of the sample may be carried out using one or more arrays of detector pixels (such as at least one of a CCD camera or an EM-CCD camera) onto which the substantially two-dimensional object illumination and detection areas are projected/imaged using the observation optical path.
The present disclosure also teaches methods for viewing/detecting a sample. The method includes illuminating a two-dimensional portion of the sample by focusing an illumination beam onto a substantially two-dimensional object illumination area extending in an illumination direction of the illumination beam and a direction perpendicular thereto, wherein illuminating the two-dimensional portion further includes defining the substantially two-dimensional object illumination area to selectively illuminate a portion of the substantially two-dimensional object illumination area, wherein the portion of the substantially two-dimensional object illumination area is defined in at least one of the illumination direction and a direction perpendicular to the illumination direction. This portion of the substantially two-dimensional object illumination area may be referred to as a light pad.
The method may comprise moving at least one of the substantially two-dimensional object illumination area or the portion of the substantially two-dimensional object illumination area through the sample. This can be used to scan the entire sample. The movement of the illumination area of the substantially two-dimensional object and/or the part thereof in the sample may be performed in 3D by moving at least one illumination objective, by moving the illumination beam path focusing means or an element thereof, by scanning with a scanning unit, by moving the illumination area defining means and by changing the collimation of the illumination beam path, which may be done by manipulating the wavefront, for example with a Spatial Light Modulator (SLM) or with a mirror having a variable curvature.
In order to obtain an image of the distribution of e.g. fluorescent molecules over the illumination area and the detection area of the substantially two-dimensional object, the recordings of the light from the sample over each pixel of the detector pixel array over a certain time period may be combined.
Light from the sample may be recorded at each pixel of the detector pixel array at a series of short time intervals, and a spatio-temporal correlation analysis may be applied to the recordings to obtain FCS data for each pixel on the detector array.
The method may further comprise determining signal fluctuations in the portion of the substantially two-dimensional object illumination area. The temporal tracking of the fluorescence intensity over each pixel or over an area or portion of the substantially two-dimensional object illumination area may be analyzed for fluctuations. The fluctuation analysis may be at least one of a temporal autocorrelation analysis, a temporal cross-correlation analysis between signals from different pixels, a temporal cross-correlation analysis between signals from different spectral channels, a photon count histogram, a photon coincidence analysis between signals from different pixels, a photon coincidence analysis between signals from different spectral channels, and other methods known to those skilled in the art.
Drawings
Further aspects and details of the invention will become apparent upon reading the detailed description with reference to the drawings in which:
FIG. 1 shows FCS imaging based on light sheet with diffraction limited light pad;
FIG. 2 shows the microscope of FIG. 1a in more detail;
FIGS. 3a to 3c schematically illustrate an optical light pad;
FIG. 4 schematically illustrates the optical properties of a light pad microscope;
FIG. 5 shows the ID-FCS assay in solution;
FIG. 6 shows the effect of cell culture medium on a focused light sheet;
fig. 7 shows FCS imaging results of protein concentration and mobility in MDCK cells and in wing imago discs from drosophila larvae recorded with the light pad microscope;
FIG. 8 shows confocal FCS measurements in vivo for comparison;
FIG. 9 shows 1D-FCS assays for adult discs of wings and 3T3 cells from Drosophila larvae; and
fig. 10 shows a spatially resolved analysis of HP1 α mobility in 3T3 cells by FCS imaging.
Detailed Description
The invention will now be described with reference to the accompanying drawings. It should be understood that the examples, embodiments and aspects of the invention described herein are merely exemplary and do not limit the scope of the claims in any way. The invention is defined by the claims and their equivalents. It is to be understood that features of one embodiment or aspect of the invention may be combined with features of one or more other aspects and/or embodiments of the invention, and it is to be understood that not all of the example and embodiment features are necessary to practice the invention.
The present disclosure teaches a new microscope called light-
The
The
The
To shape the
A multi-slit arrangement in the
In order to collect the emitted fluorescence, a
The
For
The second
For the acquisition of one-dimensional (1D) -FCS data, the optical path 50 (fig. 1a and 2) to the
The fluorescent signal can be collected, for example, for 30-60s per assay. To assess the overall background of the assay, the laser may be turned off before and/or at the time of the assay (e.g., 5 s).
Two-dimensional (2D) -FCS measurements can be performed according to the same procedure as in 1D-FCS. The
Although the imaging
The laser power for imaging the FCS can be determined at the focal plane using an illumination lens, for example a Nova II power meter (Ophir Optronics, jershire, israel) equipped with a PD300 detector. In a typical example of an in vivo experiment in 1D-/2D-FCS, the
Furthermore, the axial scanning of the
Each pixel of the
The optical properties of the
The light-
The
Alternatively, standard confocal fluorescence images, image stacks and FCS data can be acquired on the
Fig. 4a shows an illuminated slide sheet imaged with an imaging camera (z-axis is the view direction) and visualized by illumination with Alexa488 dissolved in water. The dashed area highlights the
The total PSF was characterized by analyzing the image stack of individual fluorescent microspheres 20nm in diameter (see axis definition in fig. 4 e). Fitting of the image stack of microspheres according to a 3D Gaussian function (FIG. 2f), a lateral (x-y)1/e of 370 + -20 nm can be used2Radius and axial (z)1/e of 410 + -40 nm2Radius, which means that the PSF is almost isotropic, with a single observation volume of 0.31 fL. The transverse and axial intensity distributions extracted from the 3D stack were compared by yeast cells expressing the membrane protein Pma1 fused to GFP (fig. 4g-h), confirming the isotropic profile of the PSF.
Fig. 4i-l shows a direct comparison of the same microspheres characterized using a Leica SP5 confocal microscope equipped with a 1.2NA water immersion objective and used for confocal FCS. According to the same protocol, a transverse 1/e of 240. + -.10 nm is obtained2Radius and axial (z)1/e of 600 + -20 nm2The radius, i.e., the PSF, is significantly more anisotropic, having a volume of 0.19 fL. Overall, the PSF of the light pad microscope is isotropic and about 1.6 times greater than that of a standard confocal microscope, and thus small enough to enable FCS measurements. Furthermore, in contrast to conventional light sheet microscopes, the
FIG. 5 shows an example of in vitro 1D/2D-FCS recordings. In this application, the
To show the performance of the light pad microscope 1And to verify the specifications measured, FIG. 5c shows the 1D-FCS record for diffusion of Alexa488 solution in distilled water. The 60 individual ACFs are shown in fig. 5c, and the recordings from the pixel ranges marked in fig. 5d show only small variations in amplitude and time dependence. Fitting ACF with a one-component free diffusion model, previously determined axial focal radius of 410nm and independently determined 320 μm by cross-correlation analysis (see below and FIG. 5e)2s-1The effective transverse focal radius of 490. + -.30 nm can be achieved (retrieval) (FIG. 5 d). For comparison, we calculated the theoretical expected value: since we applied 3-pixel binning to the data (FIG. 5f), we applied a 3x190 nm long rectangular detection profile and 1/e with 370nm as determined above2The gaussian function of the radius is convolved to obtain an effective detection profile that fits well to a 1/e with 500nm2The radius of the Gaussian function is consistent with the experimental result. The effective focal volume including the combining (binning) was 0.57 fL. The number of molecules obtained from the fit can be converted into a concentration profile (fig. 5d), which is almost constant along the line, so that the fluorophore concentration used can be well obtained. Thus, 1D-FCS of Alexa488 adequately confirmed imaging-based PSF assays in an independent manner.
In addition to the calculated ACF, one can calculate the spatial cross-correlation as a function of the inter-pixel distance as shown in FIGS. 5e-f and by fitting equation (2) globally to the CCF for pixel distances of 0-4, we obtain 320 + -10 μm as independent fitting parameters2s-1The diffusion coefficient of (c).
Figure 6 shows the effect of the refractive index of the cell culture medium on the focusing of the
FIG. 6c shows
Data processing analysis
The following provides embodiments for data processing and data analysis that may be used with the present disclosure. It will be appreciated by those skilled in the art that other methods of data processing and data analysis may be used depending on the parameters to be studied. Known data processing and data analysis methods for the diffusion of fluorescent molecules (or fluorescent particles) can be used in the present disclosure.
For theFor each pixel measured 1D-FCS and 2D-FCS, the intensity time trace F from pixel x in line y can be extracted from the image file after subtracting the data obtained for the first 5s or another part of the total acquisition time as background signal and after converting the pixel grey values to photoelectron numbers as described previouslyx,y(t) of (d). From the obtained fluorescence intensity trace and confocal FCS measurement, an autocorrelation function (ACF) and a cross-correlation function (CCF) were calculated according to the following formulas.
The slow variations due to e.g. photo bleaching can be corrected by means of a moving average. The resulting ACF and CCF can be fitted by using, for example, Matlab software (The MathWorks corporation) using a non-linear least squares Levenberg-Marquardt algorithm with The following general model functions.
Where N is the number of (apparent) molecules whose lifetime in the non-fluorescent state is τblinkThe molecular fraction theta of (A) represents the molecular scintillation and takes into account the time of diffusion dependence taudiff,i=w0 2/(4Di) Abnormal diffusion of the two components f1,f2=1-f1Transverse and axial focal radius w0And z0Component i ═ 1,2 apparent diffusion coefficient DiAnd exception parameters αi. In the case of CCF, the pass includes the pixel size δ and the pixel index x1、y1、x2、y2The second index term of (2) takes into account the pixel shift, and for ACF, the term is 1. Curve fitting was performed without any scintillation contribution, Θ being 0, for the 1D-FCS and 2D-FCS data for fluorescent microspheres and Alexa 488. For green fluorescent proteinConfocal and 1D-FCS data of classes, the non-fluorescence lifetime can be set to 100. mu.s. For 2D-FCS data, a temporal resolution of 0.7ms can ignore the flicker contribution, i.e., Θ equals 0. For a one-component fit, set
In this way, fitting parameters, goodness of fit R, can be establishedadj 2And pixel intensity profiles (1D-FCS) and maps (2D-FCS). To exclude noisy data and/or unsatisfactory fit and to sort out those regions for which the resulting concentration, diffusion coefficient and component scores are plotted, the intensity and/or R may be determinedadj 2The atlas is thresholded to produce a binary mask.
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