Estimation of molecular environment for amino acids in proteins by monolayer behaviors of the amino acid derivative polymers on a water surface

The behaviors of polymer monolayers on a water surface were investigated by the measurement of surface pressure-area isotherms. A good correlation of the collapse pressure of the monolayer with the hydropathy scales of the na tural amino acid rather than the hydrophobicity scales was observed. It is concluded that the amino acid residue in the polymer monolayer on the water surface exists in a similar molecular environment to that of the polypepti des. The hydropathy scale for the amino acid residue can be obtained experi mentally from the collapse pressure of the corresponding monolayer, and tha t for unnatural amino acid residues also was examined. Moreover, the depend ence of the hydrophobic character of the amino acid on temperature is also investigated by the change in the collapse pressure of the amino acid deriv ative polymer monolayers.