ABSTRACT
6-O-alpha-D-Galactopyranosyl-D-glucopyranose (melibiose) derivatives with alkyl groups at the terminal 1-O and 6'-O positions have been synthesized. They show thermotropic and lyotropic liquid-crystal properties. The d-spacings of the strong inner X-ray diffraction rings correspond to approximately 0.9 times the extended length of the molecule. The molecules are therefore either extended in monomolecular layers or U-shaped in bimolecular layers.
Subject(s)
Melibiose/analogs & derivatives , Melibiose/chemistry , Alkylation , Calorimetry , Carbohydrate Sequence , Crystallography, X-Ray , Disaccharides/chemistry , Magnetic Resonance Spectroscopy , Microscopy , Molecular Sequence DataABSTRACT
Transferred nuclear Overhauser effect (TRNOE) experiments have revealed a change in the torsion angles about the alpha-1-6 glycosidic bond of methyl beta-melibioside upon binding of the melibioside to the ricin B-chain (Rb). A full relaxation rate matrix simulation of experimental buildup curves aided in quantitative interpretation of 1D selective inversion recovery TRNOE experiments. The data are consistent with a model in which both major (omega approximately 170 degrees) and minor (omega approximately -60 degrees) conformers for methyl beta-melibioside are significantly populated in solution while the Rb/methyl beta-melibioside complex has little of the minor conformer populated. The results indicate that the ricin B-chain excludes binding of certain ligand conformations on the basis of unfavorable interactions between the protein surface and remote portions of the disaccharide system.
Subject(s)
Melibiose/analogs & derivatives , Ricin/chemistry , Ligands , Magnetic Resonance Spectroscopy , Melibiose/chemistry , Models, Molecular , Molecular Conformation , Plant Lectins , Plants, Toxic , Ricinus/chemistryABSTRACT
Maclurin, the potent non-specific blood-group hemagglutinin present in extracts of Maclura pomifera, has been purified by a new biospecific affinity-chromatographic procedure. Additional studies have indicated that this hemagglutinin occurs as five closely related tetrameric protein isoforms derived from two non-covalently-linked polypeptide chains, mol. wts. ca. 10,000 and 13,000 respectively. Buffer electrofocusing fractionated the lectin into 12 components; the major isolectin exhibited an isoelectric point at pH 4.8.
