Deuterium NMR study of the structure and dynamics of the side chains of several solid polyglutamates

Journal Article · Thu Aug 27 04:00:00 EDT 1987 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100302a038· OSTI ID:6087101

Meirovitch, E; Samulski, E T; Leed, A; Scheraga, H A; Rananavare, S; Nemethy, G; Freed, J H

A /sup 2/H NMR study of polycrystalline powders and oriented films of several selectively deuterium-labeled poly(..gamma..-benzyl L-glutamate) (PBLG) and poly(..gamma..-ethyl L-glutamate) (PELG) homopolymers is reported. The deuterium labels on the ester side chain of PBLG indicate the presence of two polymer species below 330 K. A phase transition is detected at 330 K. The phase transition observed at 330 K, associated with the side-chain melting phenomenon, is likely to be accompanied by rotational or translational diffusion of the helices while they maintain their axial orientation. Furthermore, a comparison with the authors conformational analysis suggests a high degree of cooperativity between the adjacent helices. With powders and films of PELG, the dominant motion at low temperatures (besides rapid methyl rotation) can be interpreted either as a discrete jump rotation with 3-fold symmetry but about a diffusion axis that does not coincide with the O/sup eta/-C/sup zeta/ bond, or in terms of a three-site jump motion about this bond among unevenly populated sites. Motional averaging becomes very effective and isotropic in nature at about room temperature. This abrupt change from anisotropic to isotropic motion is indicative of a phase transition. Results obtained with oriented films indicate that the PBLG benzene rings orient preferentially parallel to the axes of the polymer helices, consistent with theoretical predictions, whereas the PELG ethyl groups are distributed randomly in space.

• Research Organization: Weizmann Institute of Science, Rehovot, Israel
• OSTI ID: 6087101
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 91:18; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
400202 -- Isotope Effects
Isotope Exchange
& Isotope Separation
AMINO ACIDS
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CONFIGURATION INTERACTION
DATA
DEUTERIUM
DEUTERIUM COMPOUNDS
EXPERIMENTAL DATA
GLUTAMIC ACID
HYDROGEN COMPOUNDS
HYDROGEN ISOTOPES
INFORMATION
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
POLYMERS
RESONANCE
SPECTRA
STABLE ISOTOPES
STRUCTURAL CHEMICAL ANALYSIS