Conformational studies of poly(l-tyrosine) in solvent mixtures of dimethylsulphoxide with water and trimethylphosphate

The conformational behaviour of poly( l -tyrosine) has been studied in dimethylsulphoxide/water and dimethylsulphoxide/trimethylphosphate solvent systems. The evidence provided by nuclear magnetic resonance and infrared spectroscopy shows that the conformation of the polymer in dimethylsulphoxide is most probably the random coil. Addition of 20% D 2 O or 50% trimethylphosphate to the dimethylsulphoxide/poly( l -tyrosine) solution results in a conformational transition of the polymer which can be followed by both infra-red and nuclear magnetic resonance spectroscopy and changes in optical rotation. The evidence supports the conclusion that this transition is to a largely, though not fully, right-handed α-helical conformation.