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Ab initio-based vibrational analysis of α-poly(L-alanine)

✍ Scribed by Sang-Ho Lee; Samuel Krimm

Publisher
Wiley (John Wiley & Sons)
Year
1998
Tongue
English
Weight
445 KB
Volume
46
Category
Article
ISSN
0006-3525

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✦ Synopsis

Polarized ir and Raman spectra have been obtained on oriented films of a-helical poly(L-alanine) (a-PLA) and its N-deuterated derivative. These improved spectra permit a more complete assignment of observed bands to A-, E 1 -, and E 2 -species modes. A new empirical force field has been refined, based on ab initio force fields of N-methylacetamide and L-alanyl- L-alanine, which reproduces observed frequencies above 200 cm 01 to less than 5 cm 01 . A new transition dipole coupling treatment avoids the weak coupling and perturbation approximations, and can now account for the newly observed and reassigned amide I (E 2 ) mode. As a result of this improved force field, several other observed bands have also been reassigned.

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