MICROSCOPY Flashcards
(112 cards)
Basic microscopy:
- Bright field illumination
- Does not revel differences in brightness between structural details (no contrast)
Basic microscopy:
* Phase-Contrast Microscopy:
Enhances contrast in transparent samples (e.g., live cells, unstained biological specimens).
Basic microscopy:
* Differential Interference Contrast (DIC) Microscopy:
Produces high-contrast, pseudo-3D images without staining.
- Fluorescence microscopy identify cells and sub-microscopic cellular components with a high degree of specificity
DIC contrast
Produces high-contrast, pseudo-3D images without staining.
- Transparent objectives can be seen using the difference in light’s refraction when transmitted through the varying thickness of the specimen
Phase contrast
Enhances contrast in transparent samples (e.g., live cells, unstained biological specimens).
Phase contrast
changes in refractive index?
- Changes in refractive index of a sample cause light rays to be shifts in phase comparted to one another
Phase contrast
minute variations
- Phase contrast translates minute variations in phase into corresponding changes in brightness in the image
Phase contrast
seeing…
morphology
Contrast by staining
- Cells/tissues can also be identifiable by specific histochemical staining and visualized by normal transmitted light
Fluorescence microscopy:
- Live-Cell Fluorescence Microscopy
(with genetically encoded fluorescent proteins): Requires no chemical fixation, allowing imaging of living cells.
- The light energy emitted is always of a longer wavelength than the light energy absorbed, due to energy lost during the transient excited lifetime
- Absorption, excitation, different state of energy, emits
* (needs to get rid of energy it just absorbed in order to return to stable)
Fluorescence microscopy:
the light spectrum
- Within the electromagnetic spectrum the “optical” spectrum regime covers the range of wavelengths from 10^-3m (infrared) to 10^-8m (UV)
- Application of this concept
- Need to know the specific wave length
- Can use multiple wavelengths at the same time
Fluorescence microscopy:
Excitation and emission
- Fluorescence is the emission of light from a compound following absorption of light of a shorter wave wavelength
- The goal is illuminating the specimen with an excitation wavelength to capture emitted light and block the reflected light
- Genetically encoded fluorescent proteins (e.g. GFP, Cherry) can be used to “tag” specific proteins in cells or fluorescent gyes can be attached to probes (antibodies or peptides) to visualize cellular structures
Fluorescent microscopy in life sciences:
- Fluorophores used in fluorescent microcopy can be divided into three classes
1) Organic dyes
2) Fluorescent protein
3) Quantum dots or nanoparticles (more niche, mostly used in drug delivery)
Fluorescent microscopy: how do you choose the right microscope technique?
wide-field - illumination
Uses broad (non-focused) light, typically from a mercury, halogen, or LED source.
Fluorescent microscopy: how do you choose the right microscope technique?
wide-field - depth of field
Captures light from all focal planes, leading to out-of-focus blur in thick samples.
Fluorescent microscopy: how do you choose the right microscope technique?
wide-field - resolution
: Limited due to light scattering from out-of-focus planes.
Fluorescent microscopy: how do you choose the right microscope technique?
wide-field - speed
Faster imaging, suitable for live-cell imaging.
Fluorescent microscopy: how do you choose the right microscope technique?
wide-field - best for
Thin samples, whole-tissue sections, and fast imaging.
Fluorescent microscopy: how do you choose the right microscope technique?
laser scanning confocal microscopy - illumination
Uses a focused laser beam that scans point by point.
* Every image is clear and in focus
* Take several images and reconstruct 3 dimensional view
* No background or foreground image
Fluorescent microscopy: how do you choose the right microscope technique?
laser scanning confocal microscopy - depth of field
A pinhole removes out-of-focus light, improving optical sectioning.
Fluorescent microscopy: how do you choose the right microscope technique?
laser scanning confocal microscopy - resolution
Higher than wide-field due to controlled depth and reduced background noise.
Fluorescent microscopy: how do you choose the right microscope technique?
laser scanning confocal microscopy - speed
Slower because it scans sequentially, but provides 3D reconstruction capabilities.
Fluorescent microscopy: how do you choose the right microscope technique?
laser scanning confocal microscopy - best for
Thick samples, high-resolution imaging, and 3D reconstruction.
Fluorescent microscopy: how do you choose the right microscope technique?
laser scanning confocal microscopy - used for
- Used for: localization/co-localization of proteins, imaging multiple fluorescent stains, 3D visualisation of stainings quantification of protein expression
- Used for: visualtion of structures between 200nm and 1cm in size which can be fluorescently labelled, cell biology, tissue biology, neurobiology