CONFORMATIONS OF POLY-L-VALINE IN SOLUTION

In order to test theoretical predictions that poly‐L‐valine can exist in an α‐helical conformation, water‐soluble block copolymers of L‐valine and D, L‐lysine were prepared. By carrying out the synthesis on a resin support (with the use of N‐carboxyanhydrides) contamination of the individual blocks by any unreacted monomer from the previous block was avoided. A single glycine residue was incorporated at the C‐terminus of the chain for use in amino acid analyses. Using optical rotatory dispersion and circular dichroism criteria, about 50% of the short valine block of (D, L‐lysine HCl)18‐(L‐valine)15‐(D, L‐lysine‐HCl)16‐glycine was found to be in the right‐handed α‐helical conformation in 98% aqueous methanol, in water, the polymer appears to be a dimer, with the valine block being involved in the formation of an intermolecular β‐structure. Copyright © 1968 John Wiley & Sons, Inc.