Monday, 26 November 2012

Seeing Cells


Science images are becoming commonplace on social networks. But how are these beautiful, artistic images made and what use are they in research?

Human cells stained and probed for DNA, actin and protein.
I (Heather Doran) took this image -  please don't reuse it. 

I've taken quite a few images throughout my PhD. So many my university computer struggles under the weight of them. I've been taking microscopic images of cells to understand how the cell cytoskeleton allows them to move. And it has been one of the most interesting and favourite parts of my PhD project.

There are a number of ways of creating these images. The images all represent one or two components of the cell. Cells need to be fixed (in a fixative, like methanol or paraformaldehyde, to preserve them and the proteins and structures inside the cell). Different fixatives can be used depending on what it is you are looking for and how you are looking for it. Fixatives stop all movement, any reactions happening in the cell(s) and preserve and protect from degradation.

Once fixed, you can 'probe' the cells for what you want to look at..

I stain the DNA with various stains (below is a DAPI) stain. DAPI binds to A-T rich areas of DNA and becomes fluorescent. This is useful as all the cells I look at contain a nucleus containing DNA, the DAPI staining is strong and allows me to find, and focus on the cells under the microscope.




I also stain the cells for actin (actin is a vital part of the cell cytoskeleton - what helps the cell keep its shape) with something called phalloidin, which is actually a toxin that binds to the actin. If you attach a fluorescent tag to the phalloidin molecule, you can see the actin in the cell. 



Look for particular proteins using a primary antibody directed against particular proteins of interest. Antibodies detect a specific epitope on the antigen (which in this case would be the protein of interest). Then you can use a secondary antibody, that detects the primary antibody, but the secondary antibody has a fluorescent tag attached... and you can see if the protein is there, and where it is in the cell.




There are other ways of looking at proteins, the primary antibody can have a fluorescent tag itself, or you can genetically modify the cell so it expresses a protein that has a fluorescent tag attached. 

For the physics of fluorescent microscopy and confocal microscopy (which allows you to take a slice of a cell) see this fabulous explanation here.

All the images featured were taken by me. Please don't reuse them without permission. Thanks! 

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