Here are the answers given in the back of Stryer for those of you who do not own one:

p. 22, #1 The first mutation destroys activity because valine occupies more space than alanine, and so the protein must take a different shape. The second mutation restores activity because of a compensatory reduction of volume; glycine is smaller than isoleucine.

p. 22, #2 Glutamate, aspartate, and the terminal carboxylate can form salt bridges with the quanidinium group of arginine. In addition, this group can be a hydrogen bond donor to the side chains of glutamine, asparagine, serine, threonine, aspartate, and glutamate, and the main chain carbonyl.

p. 28, #1 Disulfide bonds in hair are broken by adding a thiol and applying gentle heat. The hair is curled, and an oxidizing agent is added to re-form disulfide bonds to stabilize the desired shape.

p. 28, #2 The native conformation of insulin is not the thermodynamically most stable form. Indeed, insulin is formed from proinsulin, a single-chain precursor containing 33 additional residues. In proinsulin, residue 30 of the future B chain of insulin is linked to residue 1 of the future A chain.

-- Irina Sigal (sigalir@umdnj.edu), August 29, 1999