Exposed hydroxyl groups

When starch is heated in excess water, the crystalline structure is disrupted (due to breakage of hydrogen bonds) and water molecules become linked by hydrogen bonding to the exposed hydroxyl groups of amylose and amylopectin. This causes an increase in granule swelling... 

Treatment of this last intermediate with lithium in liquid ammonia and ert-butanol reduces the aromatic A ring to the 1,4-dihydrobenzene stage the benzyl ether at position 17 is cleaved reductively at the same time. The newly exposed hydroxyl group is... 

The results were negative, to the disappointment of the researchers. It is pretty generally accepted that 6-HO-DMT is inactive. I am not too surprised. There are so few things with open and exposed hydroxyl groups that succeed in making it through the lipid barriers to the brain. 

Plasma-desorption mass spectrometry is another technique that has been applied successfully to the detection of readily removable fatty acyl substituents in intact glycolipids and their acylated derivatives. The specific location of the fatty acyl substituents in the ring of the glycosyl residues, as in LOS antigens, is determined by methylation under nonbasic conditions (see Section II.lb), followed successively by O-deacylation, ethylation of the exposed hydroxyl groups, and GC-MS analysis of partially alkylated alditol acetates21 ethyl groups denote the sites of previous O-acylation. 

Starch is the most common polymer found in plants. Large amounts of starch can be obtained from tubers such as potatoes, from cereals such as rice, and from seeds such as corn. The starch molecule is heavily hydrated as it contains many exposed hydroxyl groups, which form hydrogen bonds on coming into contact with water. Starch is constituted of linear polymers (amylose) and of branched polymers... 

The most important storage polysaccharides are starch in plant cells and glycogen in animal cells. Both polysaccharides occur intracellularly as large clusters or granules (Fig. 7-14). Starch and glycogen molecules are heavily hydrated, because they have many exposed hydroxyl groups available to hydrogen-bond with water. Most plant cells have the ability to form starch, but it is... 

These drugs are metabolized by cytochrome P450. Those drugs with exposed hydroxyl groups on the ring structure (e.g., morphine) are glucuronidated. while those with ester groups (e.g., heroin) are hydrolyzed. One or more active metabolites may be produced. 

Due to the chemical composition of the pentose residues of the bases, DNA strands have directionality. One end of a DNA polymer contains an exposed hydroxyl group on the deoxyribose this is known as the 3 end of the molecule. The other end contains an exposed phosphate group this is the 5 end. The directionality of DNA is vitally important to many cellular processes, since double helices are necessarily directional (a strand running 5 -3 pairs with a complementary strand running 3 -5 ) and processes such as DNA replication occur in only one direction. All nucleic acid synthesis in a cell occurs in the 5 -3 direction, because new monomers are added via a dehydration reaction that uses the exposed 3 hydroxyl as a nucleophile. 

Many inorganic and polymeric sorbents were tested for SPE pre-concentration of phenol and its derivatives before hypercrosslinked sorbents became commercially available. Early experiments revealed that both the end-capped silica-based C-8 and C-18 reversed phases and the phases with exposed hydroxyl groups retain polar phenoHc compounds rather weakly [219—221 ]. On the one hand, dispersion interactions between aromatic rings and aliphatic chains of the above packings are rather weak, whilst, on the other hand, dipole—dipole interactions of the polar solutes with water molecules or formation of hydrogen bonds between them hold phenolic compounds predominandy in water. 

Glycerol has three exposed hydroxyl groups, resulting in a compound completely miscibile in water at all concentrations. Fatty acids... 

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