Correlative light-electron microscopy (CLEM) is the combination of an
optical microscope
The optical microscope, also referred to as a light microscope, is a type of microscope that commonly uses visible light and a system of lenses to generate magnified images of small objects. Optical microscopes are the oldest design of micro ...
- usually a
fluorescence microscope
A fluorescence microscope is an optical microscope that uses fluorescence instead of, or in addition to, scattering, reflection, and attenuation or absorption, to study the properties of organic or inorganic substances. "Fluorescence microsco ...
- with an
electron microscope
An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...
. In an integrated CLEM system, the sample is imaged using an electron beam and an optical light path simultaneously. Traditionally, samples would be imaged using two separate microscopy modalities, potentially at different facilities and using different sample preparation methods. Integrated CLEM is thus considered to be beneficial because the methodology is quicker and easier, and it reduces the chance of changes in the sample during the process of data collection. Overlay of the two images is thus performed automatically as a result of the integration of two microscopes.
This technique is used in order to obtain information at different length scales: the electron microscope provides high-resolution information down to the nano-scale, while the fluorescence microscope highlights the regions of interest. CLEM is used for various disciplines in the
life sciences
This list of life sciences comprises the branches of science that involve the scientific study of life – such as microorganisms, plants, and animals including human beings. This science is one of the two major branches of natural science, th ...
, including
neuroscience
Neuroscience is the science, scientific study of the nervous system (the brain, spinal cord, and peripheral nervous system), its functions and disorders. It is a Multidisciplinary approach, multidisciplinary science that combines physiology, an ...
,
tissue research, and
protein
Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, res ...
research.
Fluorescence microscope
In preparation for imaging with a fluorescence microscope, different methods can be used, such as
fluorophore
A fluorophore (or fluorochrome, similarly to a chromophore) is a fluorescent chemical compound that can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with se ...
s or dyes,
immunolabeling, and genetically encoded fluorescent proteins. Different fluorescent labels can be used in order to highlight multiple regions of interest in the sample. Recently Kumar et al
combined FRET based molecular tension measurements with cryo-electron microscopy to study how force on talin (a focal adhesion protein which directly links integrins to actin) is related to actin organization. Regions of high talin tension have highly aligned and linear filamentous actin while regions of low tension have less well-aligned actin structure.
Electron microscope
The electron microscope is used to obtain structural information at the nano-scale. Unlike an optical microscope, an electron microscope is able to surpass the
diffraction limit
The resolution of an optical imaging system a microscope, telescope, or camera can be limited by factors such as imperfections in the lenses or misalignment. However, there is a principal limit to the resolution of any optical system, due to t ...
of light. This is because the wavelength of accelerated electrons is much shorter than the wavelength of visible light.
References
Further reading
*
*
{{refend
Electron microscopy