Induced Circular Dichroism in Side-Chain Chromophores

4 Induced Circular Dichroism in Side-Chain Chromophores 

In the preceding Section (5.3) the CD bands in the near ultraviolet region are assigned to those of tyrosyl and phenylalanyl residues, whose thermal motions are restricted sterically keeping their geometry constant around the main chain in the proteins. The CD spectrum of aromatic moieties provides a good measure for the analysis of motional freedom around a given amino acid residue. Better examples have been reported on several kinds of amino acids and their polymers. 

On the other hand, the dilute solution of poly(p-benzyl-L-aspartate) in chloroform or dichloromethane gives a weak but existant CD band centered at 252 nm. A large positive CD band at 222 nm means that poly(p-benzyl-L-aspartate) (PBLA) exists in the left-handed a-helical form. Poly(y-p-nitrobenzyl-L-glutamate) also shows a definite negative CD band around 275 nm, even if the concentration of the polymer 

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