β -sheets can be either intra- or intermolecular, but α -helices are always intramolecular. Briefly explain why this is the case.

Answer 1

Hi Lilly B.,

A correction: the sheets themselves aren't intra- or inter-molecular! The bonding between the residues for an a-coil woiuld be said to be intramolecular -- it holds together nicely on its own. Whereas, a b-sheet is stabilized not only internally, but it MAY be part of an assemblage of such sheets which MIGHT self-assemble into a block of stacked sheets. The stabilization as a block there would be intermolecular.

Note that these structures are solvent dependent! Put the protein into a denaturing medium, and it soups out to a random coil. Getting proteins into their proper tertiary structure is the job of chaperonins, if I recall. Without that, you would be disorganized at a molecular level, and die.

--Cheers, --Mr. d.