Vibrational Dynamics of Poly(L-glutamic acid) (β2 Form)

Abstract

ABSTRACT:The dispersion curves for /J2 sheet form of poly(L-glutamic acid) (PLG) are reported alongwith full normal coordinate analysis. Several earlier assignments have been revised. Characteristic features of the dispersion curves, such as repulsion, exchange of character etc., are discussed. Separate contributions to the heat capacity due to purely skeletal, pure side chain, and mix-modes have also been calculated via density-of-states. It is found that the maximum contribution comes from the mixed modes and minimum from the pure backbone modes.

Conformational symmetry and vibrational dynamics of polymers

“…This provides a good handle for conformation classification on the basis of the dispersion profile [4]. The results are presented for α-helical [poly(L-valine) (PLV), poly(L-leucine) (PLL), poly(L-glutamic acid) (PLG), poly(β-benzyl-L-aspartate) (PBLA)], β-sheet [poly(L-serine) (PLS), PLV], ω-helical [PBLA, poly-N ε (p-bromobenzoyl-L-ornithine) (PBRBO)], and 3-fold [polyglycine II (PG II), poly-(L-hydroxyproline) (PLHP), poly-L-proline II (PLP II)] polypeptides [5][6][7][8][9][10][11][12][13][14][15][16].…”

“…1 (a) Low-frequency dispersion curves of α-helical polypeptides. PLL: poly(L-leucine) [5]; PLG: poly(L-glutamic acid) [6]; PLV: poly(L-valine) [7]; PBLA: poly(β-benzyl-L aspartate) [8]. (b) α-helix.…”

“…In the present communication, we have tried to show how the dispersion profile of low-frequency modes reflects the symmetry of the polymer chain. This has been done in a variety of symmetry groups [4][5][6][7][8][9][10][11][12][13][14][15][16]. Strong supporting evidence of the spectral parameters (constants of IR and Raman) is obtained from quantum chemical [Hartree-Fock (HF), post-HF, and density functional theory (DFT)] [17][18][19][20] and molecular dynamical (MD) approaches.…”