Hydrogen bonds, infrared spectral properties

Hanlon and Klotz (1968) have discussed the use of near-infrared spectroscopy for studying structural problems of biochemistry. In particular, they have considered the equilibrium state of the peptide unit in a number of synthetic polyamino acids (poly-L-alanine, poly-L-leucine, poly-L-methionine, and poly-y-benzyl-L-glutamate) as a function of solvent composition under conditions where the transitions in other physical properties of these polymers have been interpreted as simple peptide, hydrogen-bonded, helix-to-coil transitions. Their spectral data demonstrate that these conversions involve protonated peptide species and are far more complicated than investigators of these processes had assumed. 

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