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)1 6 ‐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.