Reactivity of iso-diiodomethane and iso-iodoform, isomers of CH2I2 and CHI3, toward the double bond of a variety of cycloalkenes.

The metastable CH2I-I and CHI2-I isomers formed by UV photolysis of CH2I2 and CHI3 transfer methylene and iodomethylene groups, respectively, to a variety of cycloalkenes, leading to their cyclopropanation. More than a 100-fold increase of the reaction rate with increasing solvent polarity suggests a dipolar transition state. The fastest second-order rates observed were in CH3CN.

The different conformations of the glycerol region of crystalline acylglycerols.

From nearly 40 crystal structures of glycerolipids, accumulated during three decades, preferred structural features are now emerging regarding favored conformations of lipid molecules and the molecular arrangement at the surface of lipid assemblages. Comparisons with conformations of glycerolipid molecules in lipid-protein complexes and in dynamic systems, studied by spectroscopic methods and molecular modeling, show the general validity of these preferred solid-state conformations.

Orientation of the saccharide chains of glycolipids at the membrane surface: conformational analysis of the glucose-ceramide and the glucose-glyceride linkages using molecular mechanics (MM3).

Preferred conformations of the saccharide-ceramide linkage of glucosylceramides with different ceramide structures (normal and hydroxy fatty acids) were investigated by molecular mechanics (MM3) calculations and compared with conformational features obtained for glucosylglycerolipids (diacyl and dialkyl analogues). Relaxed energy map calculations with MM3 were performed for the three bonds (C1'-O1-C1-C2, torsion angles phi, psi, and theta 1) of the glucose-ceramide/diglyceride linkage at different values of the dielectric constant. For the phi torsion of the glycosidic C1'-O1 bond the calculations show a strict preference for the +sc range whereas the psi/theta 1 energy surface is dependent on the structure of the lipid moiety as well as on the dielectric constant (epsilon).

Steric presentation and recognition of the saccharide chains of glycolipids at the cell surface: favoured conformations of the saccharide-lipid linkage calculated using molecular mechanics (MM3).

The orientation of the saccharide moiety of glycolipids at the membrane surface is determined by an interplay of different steric factors, e.g. the conformation of the saccharide chain, the conformation of the saccharide-lipid linkage and restrictions due to the membrane surface.

Characterisation of the anti-A antibody response following an ABO incompatible (A2 to O) kidney transplantation.

Anti-A,B antibodies produced in a blood group OLe(a-b-) recipient receiving a kidney graft from a blood group A2Le(a-b+) donor have been analysed for their ability to bind to different glycosphingolipid antigens. Solid-phase RIA using pure glycosphingolipid antigens and a chromatogram binding assay using total nonacid glycosphingolipid fractions from erythrocytes of different human blood group phenotypes together with pure glycolipid antigens were used as assay systems. Serum antibodies were shown to bind equally well to A (types 1, 2, 3 and 4) and B (types 1 and 2) antigenic structures but no binding to H antigens (types 1, 2 and 4) was detected.

Saccharide orientation at the cell surface affects glycolipid receptor function.

Three allelic variants of P-pilus-associated G-adhesins (lectins) with different cell-binding properties were recently described. Here we have analyzed Escherichia coli HB101 strains expressing the recombinant G-adhesin variants for their ability to agglutinate erythrocytes from various species as this relates to the glycosphingolipid (GSL) composition in the erythrocyte membranes. All three variants exhibit similar specificities for the globo-series GSLs affixed to artificial surfaces.

The effect of hydrogen bonds on the conformation of glycosphingolipids. Methylated and unmethylated cerebroside studied by X-ray single crystal analysis and model calculations.

The conformation and molecular packing of permethylated beta-D-galactosyl-N-octadecanoyl-D-spingosine (cerebroside) was determined by X-ray single crystal analysis at 185 K (R = 0.16). The lipid crystallizes in the orthorhombic space group P2(1)2(1)2(1) with the unit cell dimensions a = 8.

Conformational analysis of blood group A-active glycosphingolipids using HSEA-calculations. The possible significance of the core oligosaccharide chain for the presentation and recognition of the A-determinant.

Conformational analysis of four different A-active glycosphingolipids, A types 1-4, was carried out using HSEA-calculations with the GESA-program. In their minimum energy conformations the oligosaccharide chains are more or less curved; in particular the type 3 and 4 have a strongly bent shape. When the carbohydrate structures are linked to ceramide, using the conformational features predominantly observed in crystal structures of membrane lipids, rather drastic differences in the orientation of the oligosaccharide chains are obtained.

Preferred conformation and dynamics of the glycerol backbone in phospholipids. An NMR and X-ray single-crystal analysis.

The conformation of the glycerol group of a number of diacyl and monoacyl (lyso) phospholipids differing in the chemical nature of the head group was studied by 1H high-resolution NMR and X-ray crystallography. The NMR measurements were carried out with solutions or micellar dispersions of the lipids in deuteriated organic solvents or 2H2O. Both solutions, in which the lipid is present as monomers, and lipid micelles give rise to good high-resolution NMR spectra exhibiting spin coupling hyperfine interactions.

On the dissection of binding epitopes on carbohydrate receptors for microbes using molecular modelling.

The most common receptors for microbes on animal cells seem to be carbohydrates. One characteristic property of microbial protein-carbohydrate interaction is the recognition of sequences placed within an oligosaccharide chain. This leads to a series of isoreceptors defined as saccharides carrying the particular receptor sequence with different neighbouring groups.

Identification of a blood group A active hexaglycosylceramide with a type 1 carbohydrate chain in plasma of an A1 Le(a-b-) secretor.

A blood group A active hexaglycosylceramide with a type 1 carbohydrate chain was identified in the plasma of an A1 Le(a-b-) secretor. The analysis was done on the total non-acid glycosphingolipid fraction using mass spectrometry, NMR spectroscopy, and anti-A antibody immunostaining on thin-layer chromatograms.

Conformation and packing properties of membrane lipids: the crystal structure of sodium dimyristoylphosphatidylglycerol.

The conformation and molecular packing of sodium 1,2-dimyristoyl-sn-glycero-phospho-rac-glycerol (DMPG) have been determined by single crystal analysis (R = 0.098). The lipid crystallizes in the monoclinic spacegroup P2(1) with the unit cell dimensions a = 10.

Interactions and space requirements of the phosphate head group in membrane lipids. The crystal structure of disodium lysophosphatidate dihydrate.

The packing arrangement and molecular conformation of lysophosphatidate (disodium 3-lauroyl-DL-glycero-1-phosphate dihydrate (LPA] was determined by single crystal analysis. The lipid crystallizes in the triclinic space group P1 with unit cell dimensions of a = 7.74, b = 5.

New gangliosides from human erythrocytes.

We have identified a number of gangliosides from human erythrocytes that have not previously been detected in these cells, including two new compounds. The gangliosides were separated into monosialo- and disialoganglioside fractions by DEAE-column chromatography. Two monosialogangliosides that have not been previously detected in these cells are GM2 and GM1.

Further characterization of the structure of GM1b ganglioside from rat ascites hepatoma.

A ganglioside named GM1b (Hirabayashi, Y., Taki, T., and Matsumoto, M.

Chemical structures of three fucogangliosides isolated from nervous tissue of mini-pig.

In the nervous tissue of miniature pig, type Göttingen, three fucosyl-containing gangliosides are major gangliosides. All three were found in dorsal-root ganglia and spinal cord, but only two of them in the forebrain. The concentrations of these gangliosides were increased in chloroquine intoxication.