Aspartic Acid-Aspartate and Glutamic Acid-Glutamate Hydrogen Bonds Having Great Proton Polarizability — IR Investigations

α-Amino and α-carboxylate group protected aspartate (Z-asp-OMe) and glutamate (Z-glu-OBZl) solutions in CH2Cl2 are studied as function of the addition of the respective salts by IR spectroscopy. The antisymmetrical stretching vibration of the -CO2 c- groups shifts to the position where v C = O of the acid groups is observed, indicating that both anions in the acid-anion complexes are strongly influenced by the proton. With the formation of these complexes a continuum arises preferentially in the region 1600-900 cm-1 demonstrating that the OH · · · O- ⇌ -O · · · HO bonds formed show great proton polarizability. These hydrogen bonds are short and the proton potential is probably a broad flat well. The degree of the formation of these hydrogen bonds is determined. Finally, it is discussed that positive charge can easily be translocated via such hydrogen bonds in protein molecules.