Science Buddies: "Ask an Expert"

At what temperature range are proteins stable?

Hi,

Different proteins are stable at different temperatures, ranging from heat-shock proteins (high temperature stability), to those present in extremeophiles (both high and low temperature stability). Do you try to find some background information using a web search? I found a paper that you may be interested in: http://www.science.siu.edu/zoology/sear ... 995ARP.pdf

What determines if a protein is stable or not stable? Would it just be the deterioration of the peptide bonds or the moment when it can no longer be in the same structure?

Hi,

I found this site this morning, but you hadn't asked this question yet! I think this is going to help you:

http://www.cryst.bbk.ac.uk/PPS2/project ... index.html

Please let me know if that isn't quite what you are looking for. Basically, lots of things affect protein stability. Protein modifications (like glycosylation, etc), temperature, pH, time, their location in the cell, interaction with other proteins and concentration can all affect protein stability. I am sure there are more I did not list!

Typically a protein is considered "stable" if it is able to perform it's intended purpose. This can mean a lot of things that sunmoonstars has mentioned, a conformational(overall shape) change can influence it's function and it's function depends on what kind of protein it is. Such as your lab partner asked about GFP, green fluorescent protein is a protein the emits green light, it would be considered to be unstable if it was unable to emit those photons(light).

Hi Han Phan,

You have already gotten some great advice from sunmoonstars and tyber. Tyber is correct in explaining that a protein is considered "stable" if it is able to maintain its function.

Just to clarify, GFP performs fluorescence, which means that it absorbs light from one wavelength and emits light at a different wavelength. GFP absorbs ultraviolet light and emits green light in response. GFP would no longer be functioning if it did not emit green light when you shine UV light on it. (It does not emit green light all by itself!)