Hydrophobic interaction methyl esters

In dicyanocobalt(III) a,b,c,d,e,g-hexamethyl-f-stearylamide cobyrinate (derivative 3) the six peripheral amide groups of vitamin B12 have been replaced with methyl ester groups, and the proximal base of the vitamin at the f-position with a stearylamide group (11). Electrodes prepared with this ionophore and DOS as the plasticizer were also selective for thiocyanate and nitrite over the rest of the anions tested. The main anionic interferent was salicylate. In all cases, the response of the electrodes to the preferred anions was sub-Nemstian. Overall, the selectivity pattern obtained with ionophore 3 is similar to that of 2 and to that of the hydrophobic cobyrinate-based electrodes reported previously (5, 12, 13). This observation suggests that in all cobyrinate ionophores the anions interact with the cobalt(III) center, and that the side chains of the corrin ring have a small effect on the selectivity of this interaction. 

Wennemers and Still have recently reported that common, commercially available dyes (such as rhodamine methyl ester, crystal violet, Safranine O, phenol red, xylenol orange, etc.) bind certain acylated tripeptides attached to hydrophilic poly(ethylene glycol)-polystyrene beads with high selectivity in water [76], They suggested that hydrophobic interactions and electrostatic interactions are the driving forces for the binding. 

Hydrophobic interactions may also serve to purify products of combinatorial syntheses. As an example, penta-O-lauroyl-l-thio-p-galactose was subjected to a Michael addition to a,p-unsaturated ketones or to alkylation by a-chloro ketones followed by reduction of the keto groups or by reductive alkylation with amino acid esters. The reaction mixtures were passed through Cl8 silica gel, whereby the desired products were adsorbed while unwanted products were washed away. Desorption was carried out with pentane, and the hydrophobic labels were removed with methanolic sodium methoxide.The methyl laurates were finally separated from the desired products by chromatography on silica... 

Following the classical syntheses of aromatic a-sialosides by phase transfer catalysis starting with the per-O-acetylated sialosyl chloride methyl ester, further aromatic a-sialosides could be prepared with sesamol (4), 2-chloro -nitrophenol (5), and 4-chloro-5-methyl-4-nitrophenol (6) [36]. In TcTS-sialylations none of these modified donor substrates showed any sialylation of methyl p-lactoside (7) to give the methyl sialyllactoside (8). It may be assumed that both steric and electronic factors affect interactions with aromatic and/or hydrophobic amino acid residues in the enzyme (Scheme 1). 

Entrapment within polyacrylamide beads Reaction with cyanogen bromide-treated copolymers of acrylamide and 2-hydroxyethyl methacrylate Reaction with glutaraldehyde-treated polyacrylamide and with copolymers of acrylamide and methyl methacrylate Reaction with glutaraldehyde-treated polyacrylamide beads Coating on a platinum electrode and enclosure within nylon netting Hydrophobic interaction with cellulose esters and with phenoxyacetylated-dextran and other derivatives of glass... 

The catalytic effects of poly(3-methyl-l-vinylimidazolium iodide) poly(3-n-hexadecyl-l-vinylimidazolium iodide), and their monomeric analogs on the alkaline hydrolysis of a series of neutral and anionic nitro-phenyl esters were studied in order to elucidate the contribution of hydrophobic and electrostatic interactions to their esterolytic efficiency. 

B/C, whereby the molecule assumes a sigmoidal conformation that allows both head groups to interact in identical mode with the SI pockets (Fig. 2.13). The (4-amino-methyl)benzyl group inserts into the SI pockets to a 2.6 A distance from the Asp 189 carboxylate, and additional hydrogen bonds with residues of the protease surface are coordinating the carboxamide and ester groups, while the hydrophobic spacer acts as an optimal tether (Figs. 2.13 and 2.14). 

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