Polypeptide glutamic acid, influence

Aspartic and glutamic acids are themselves negatively charged under physiological conditions. This allows them to chelate certain metal ions, and also to markedly influence the conformation adopted by polypeptide chains in which they are found. 

Figure 4. Influence of urea and pH on the solubilities of synthetic polypeptide copolymers of glutamine and glutamic acid (17)...

For natural polyelectrolytes and polypeptides, the term transition means the passage from an ordered state (e.g. helix for poly-L-glutamic acid) to a disordered one under the influence of different factors i.e. chemical agents, temperature, ionization. 

L-aspartate (7), y-[2-(9-carbazoIyl)ethyl]-L-glutamate(8), N -[(9-carbazolyl)-carbonyl]-L-lysine (9), and 2-[(9-carbazolyI)ethyl]-L-cysteine (10). No detailed information on the optical rotatory properties of the indicated polymers has been reported, whereas a great deal of attention has been focused on the dichroic absorption properties especially for different samples of poly(8). While the first three polymers are characterized by an a-helix structure in both solution and solid state, poly(lO) may assume antiparallel pleated-sheet and normal antiparallel P-forms. Apparently, the presence of the bulky side group does not substantially affect the conformational structure imposed by the polypeptide backbone. Additionally in concentrated solutions, the cholesterogenic propensity of polypeptides such as those based on L-glutamic acid, L-aspartic acid, and L-lysine is not appreciably influenced by the steric and electronic characteristics of the carbazole moiety anchored via different spacers to the peptide units. 

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