title: Poly(alpha-alkyl gamma-glutamate)s of microbial origin. 2. On the microstructure and crystal structure of poly(alpha-ethyl gamma-glutamate)s.
abstract: The stereochemical microstructure and crystalline structure of nearly racemic poly(alpha-ethyl gamma,DL-glutamate) obtained by esterification of biosynthetic poly(gamma-glutamic acid) were examined by NMR, DSC, and powder X-ray diffraction. The two enantiomerically pure poly(alpha-ethyl gamma-glutamate)s, as well as the racemic stereocopolymers with random and alternating microstructure, were prepared by chemical synthesis and studied in parallel to help in the interpretation of the data. The (13)C NMR analysis revealed that biosynthetic poly(alpha-ethyl gamma,DL-glutamate) consists of a block stereocopolymer accompanied by minor amounts of a mixture of the two optically pure homopolymers. The polymer is crystalline, with a degree of crystallinity and crystal structure essentially similar to those displayed by the optically pure polymers but clearly different from the alternating copolymer. Conversely, the racemic stereocopolymer with a random microstructure prepared by chemical synthesis is amorphous. The crystal structure of the racemic mixture of the D- and L-homopolymers seems to be very close to that of the biosynthetic stereocopolymer, although some indications suggesting the existence of a stereocomplex were found.
authors.affiliation: Departament d'Enginyería Química, Universitat Politécnica de Catalunya E.T.S. d'Enginyers Industrials de Barcelona, Diagonal 647, 08028 Barcelona, Spain.
authors.forename: Antxon
authors.initials: A
authors.lastname: Martínez de Ilarduya
authors.forename: Najim
authors.initials: N
authors.lastname: Ittobane
authors.forename: Marta
authors.initials: M
authors.lastname: Bermúdez
authors.forename: Abdelilah
authors.initials: A
authors.lastname: Alla
authors.forename: Mustafa
authors.initials: M
authors.lastname: El Idrissi
authors.forename: Sebastián
authors.initials: S
authors.lastname: Muñoz-Guerra
mesh_terms: D001419:Bacteria / Q000737:chemistry; D002152:Calorimetry, Differential Scanning; D003460:Crystallization; D004951:Esterification; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D011099:Polyglutamic Acid / Q000737:chemistry*; D013237:Stereoisomerism; D014961:X-Ray Diffraction
chemical_list: D011099:Polyglutamic Acid