The fact is that for any given chain of amino acids, a lot of three dimensional conformations are possible. which begs the question: why is a particular arrangement favored over others? Let's assume for now that the answer lies in energy and that the least energy conformation is the most stable and hence the most favorable. One way of studying protein folding (and hence stability) is to denature the protein, then remove the denaturing agent and monitoring its refolding in vitro. Those interested can look up Anfinsen's ground breaking study (click here) in this area for which he was awarded the Nobel prize in Chemistry in 1972.
However, if we are looking at protein folding in the context of energy then we can't disregard entropy because in the equilibrium between a large number of possible (and random) conformations and one particular conformation there is a strong thermodynamic push for the protein to stay in the former. How is it then that biological polymers can assume well defined and consistent structures? In actuality, flexible polymers with a large number of possible conformations do not spontaneously fold into a particular well defined structure.
And that's where the Ramachandran Plot comes in once again. A lot of arrangements are disallowed merely on the basis of stearic clashes or in the words of Stryer and co. (our Biochemistry text): 'The rigidity of the peptide unit and the restricted set of allowed psi and phi angles limits the number of structures accessible to the unfolded form sufficiently to allow protein folding to occur.'
So there you go folks: I don't know if you had the same 'Uh DUH' moment that I did upon finding this out but its zero-one so far in the organization vs. entropy death match with the REAL winner being Nature, Mother Earth, Gaia, the Big Poobah in the Sky or Captain Planet, whatever you want to call it. Does the answer seem too simple? That's because we haven't really explored the complexities of the question. Until next time...
And because that's enough science for now and we can't have a post without a picture, I present to you:
One Hrithik Roshan looking creepy and spider-like (possibly in a Pepsi ad). Because really what is a blog without an arachnid person on it? Or shameless peddling of products? Enjoy!