Glycolipid Compounds

The synthesis of the tumor-associated glycolipid antigen sialyl Le dimer 32 has been reported, and glycolipid compound 33 has also been prepared. ... 

The precise chemical nature of some of the ligands involved in selectin-ligand interactions has been determined. All three selectins bind sialylated and fucosy-lated oligosaccharides, and in particular all three bind sialyl-Lewis (Figure 47-12), a structure present on both glycoproteins and glycolipids. Whether this compound is the actual ligand involved in vivo is not estab-... 

Some alcohols, arylamines, and phenols are sulfated. The sulfate donor in these and other biologic sulfation reactions (eg, sulfation of steroids, glycosaminoglycans, glycolipids, and glycoproteins) is adenosine 3 -phos-phate-S -phosphosulfate (PAPS) (Chapter 24) this compound is called active sulfate. ... 

The cardanyl glycolipids behave as amphiphilic compounds and are able to self-assemble in water to form twisted fibers, helical coils, and high axial ratio nanotubes... 

Compound lipids (phospholipids, sphingolipids, glycolipids, and cholesterol and its esters) that make part of the biomembrane are subject to a less active renew-al as compared with triacylglycerides. Their renewal is associated either with the restoration of an impaired portion of the membrane, or with the replacement of a defective molecule by a new one. 

Mucolipids (See Section VI).—Compounds which have a fatty residue bound to a carbohydrate residue are known as mucolipids. These substances are sometimes termed lipocarbohydrates, glycolipids, etc., and some may contain amino acid units and phosphorus. 

In about 1936, sialic acid was discovered by Blix, who found it to be a component of submaxillary-gland proteins, and who described many of its properties. However, little notice was taken of this work at the time it was published. In 1941, Klenk, who was working on glycolipids of the brain, described a compound, later shown to be a methyl glycoside of sialic acid, that had been obtained by treatment of a lipid fraction with 5% methanolic hydrogen chloride at 105°. In 1954, Klenk and Faillard reported the first isolation of pure N-acetyl-neuraminic acid from animal sources. 

Resorcinol A. 20 g 1 1 resorcinol in water B. Concentrated HC1 C. 0.1 mol 1 1 copper sulphate D. Water Mix A,B,C,D( 10 80 0.5 10) Gangliosides Compounds containing sialic acid residues react to give blue-violet spots. Other glycolipids give yellow spots... 

PAS staining (periodic acid - Schiff s reagent) colors compounds with vicinal hydroxyl groups, i.e., mainly oligosaccharide side chains in glycoproteins, glycolipids, and nucleic acids. The sensitivity and stability is much lower than the silver staining Protocol 2.4.2.S but more specific. 

The name glycolipid usually refers to the natural compounds, whereas more generally, the terms amphiphilic carbohydrate , neoglycolipid or hydropho-bized carbohydrate (H-carbohydrate) are used for synthetic unnatural structu-... 

The mesogenic structures of glycolipids are due to the occurrence, on the same molecule, of a hydrophilic and a hydrophobic moiety often referred to as head and tail respectively. As a result, glycolipids are able to self-organize into a large variety of mesophases also called liquid crystals (Fig. 2) [ 10]. Supramolecular assemblies of mesogenic compounds can be caused by a rise in temperature (thermotropic liquid crystals) or by the addition of water (lyotropic liquid crystals) they result from different responses of the carbohydrate and the alkyl chain to temperature or solvent (water), respectively. 

The structure and function of cell membranes have long been associated with lyotropic liquid crystalline phases. Since most of the glycolipids are amphitropic (both thermotropic and lyotropic) their was an increase of interest in the comparison of the structures of both types of mesophases formed by the same compound. 

The key-step of the synthesis of glycolipids, and more generally of amphiphilic carbohydrates, is the covalent coupling of a hydrophilic carbohydrate with a lipophilic compound. A hydrophilic or hydrophobic spacer may be inserted between them in order to control the hydrophilic-lipophilic balance (HLB). This modulation allows to obtain variously organized systems with the same polar head and apolar tail. 

Since drugs interact with optically active, asymmetric biological macromolecules such as proteins, polynucleotides, or glycolipids acting as receptors, many of them exhibit stereochemical specificity. This means that there is a difference in action between stereoisomers of the same compound, with one isomer showing pharmacological activity while the other is more or less inactive. In 1860, Louis Pasteur was the first to demonstrate that molds and yeasts can differentiate between (+)- and (-)-tartarates, utilizing only one of the two isomers. 

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