Biomaterial Database

Crystal and molecular structures of the isomeric dipeptides alpha-L-aspartyl-L-alanine and beta-L-aspartyl-L-alanine. 1987

C H Görbitz

Department of Chemistry, University of Oslo, Norway.

The crystal and molecular structures of the alpha- and beta-L-Asp isomers of L-aspartyl-L-alanine have been determined at 120 K using 1226 and 1609 reflections (I greater than 2.5 sigma I), respectively. The space group for the alpha-isomer is P2(1), with cell parameters a = 4.788(1), b = 16.943(4), c = 5.807(1) A and beta = 107.55(2) degrees; final R factor 0.042. The space group for the beta-isomer is P2(1)2(1)2(1) with a = 4.845(1), b = 9.409(2) and c = 19.170(3) A; final R-factor 0.047. The two peptides crystallize as zwitterions with the side-chain acidic groups ionized. Each molecule adopts a trans configuration at the peptide bond with both carboxyl groups situated on the same side of the peptide plane. The geometries of the aspartyl moieties do, however, differ in the two structures. The peptide bond is significantly longer in the beta-isomer than in the alpha-isomer, with C-N 1.344(3) and 1.328(4) A, respectively. A very short intermolecular carboxyl...carboxyl hydrogen bond (O...O = 2.502(4) A) is observed in the crystals of the alpha-isomer.

UI	MeSH Term	Description	Entries
D008968	Molecular Conformation	The characteristic three-dimensional shape of a molecule.	Molecular Configuration,3D Molecular Structure,Configuration, Molecular,Molecular Structure, Three Dimensional,Three Dimensional Molecular Structure,3D Molecular Structures,Configurations, Molecular,Conformation, Molecular,Conformations, Molecular,Molecular Configurations,Molecular Conformations,Molecular Structure, 3D,Molecular Structures, 3D,Structure, 3D Molecular,Structures, 3D Molecular
D003460	Crystallization	The formation of crystalline substances from solutions or melts. (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)	Crystalline Polymorphs,Polymorphism, Crystallization,Crystal Growth,Polymorphic Crystals,Crystal, Polymorphic,Crystalline Polymorph,Crystallization Polymorphism,Crystallization Polymorphisms,Crystals, Polymorphic,Growth, Crystal,Polymorph, Crystalline,Polymorphic Crystal,Polymorphisms, Crystallization,Polymorphs, Crystalline
D004151	Dipeptides	Peptides composed of two amino acid units.	Dipeptide
D013237	Stereoisomerism	The phenomenon whereby compounds whose molecules have the same number and kind of atoms and the same atomic arrangement, but differ in their spatial relationships. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 5th ed)	Molecular Stereochemistry,Stereoisomers,Stereochemistry, Molecular,Stereoisomer