Does anyone happen to know what temperature disulpide bonds would need to be at to break in a lving organism? I am aware these are relatively strong bonds and that the reducing environement inside a cell would reduce this stablilty but I can seem to find a rough estimate of the temperature.

Strictly speaking this is a chemistry rather than a biology question. Googling this I am unable to find an answer, though I am sure it would be very much higher than any living organism could withstand.

I would agree with David re temperature. My recollections of chemistry from the distant past is that intense heat - in the absence of a reducing environment - is required to break covalent bonding like disulphide bonds, unlike other types of molecular interactions like hydrogen bonding. Maybe you can get an idea of bond strength by searching bond energy (the energy required to break a mole of molecules into individual atoms) - I think that may tell you that in general S-S bonds are weaker than C-C or C-H bonds? In the presence of water I think the temperature to break a S-S bond may be around 150-250 degrees Celcius (the basis for some hair-curling irons?) - I guess it would be a lot higher without water…but it’s only a guess and I may be completely wrong!

Last edited by Steve Lolait (28th Nov 2010 16:16:01)

I can't throw any numbers in here, but I suspect that the answer would be entirely contextual. Disulfide bonds are very plastic and in proteins can vary in length and angle a great deal. Any deviation away from the theoretical ideals would lower the cleavage energy.

As the previous answers have alluded to, we can safey consider disulfide links to be as stable as any of the other covalent links within a protein, at least when working in a biologically-relevent temperature range (less then 100 degrees C) and in an oxidising environment. When we run protein gels, we heat samples to 96 degrees C to denature the proteins, but also have to add a reductant to break any disulfides.

In short, I don't believe that s-s bonds are heat labile at any temperature you are going to find within a living system!

With regards to the hair-straiteners, I suspect that what you are doing is denaturing then re-naturing the proteins (or at least the protein complexes) in each strand with heat, not breaking many (if any) covalent bonds. Chemical straighteners do alter s-s bonds, but that is with reduction-oxidation, not direct application of heat.

Last edited by John Steemson (29th Nov 2010 00:35:39)