Neuraminic acid effects

Even less is known about the effects of ozone on carbohydrates. Buell et al. observed a decrease in the depolymerization of hyaluronic acid after treatment of the lungs of ozone-exposed rabbits (1 ppm for 1 h) with hyaluronidase. B. Goldstein et al. reported a loss in membrane neuraminic acid of red cells exposed in vitro to high concentrations of ozone. It would be important to study the effects of ozone on respiratory tract mucus, which is rich in carbohydrates, including neuraminic acid. This could indude determination of foe extent to which ozone is able to penetrate mucus that is unaltered, whether foe reaction of ozone with mucus results in the formation of cytotoxic intermediates, and evaluation of the interaction in mucus of ozone with other air pollutants, particularly sulfur dioxide. Of possible pertinence is a study by Falk et who observed that ozone produced a loss in foe viral hemagglutinating ability of snail mucus. 

Pichierri, F, Matsuo, Y, Effect of protonation of the A-acetyl neuraminic acid residue of sialyl Lewis a molecular orbital study with insights into its binding properties toward the carbohydrate recognition domain of E-selectin, Bioorg. Med. Chem. Lett., 10, 2751-2757, 2002. 

Sialylation Glycosylation Stereoselectivity Glycosyl donor Glycosyl acceptor Sialic acid Neuraminic acid Solvent effect Auxiliary... 

V-acetyl neuraminic acid (sialic acid) nuclear magnetic resonance nuclear Overhauser effect phenyl... 

In ketopyranoses, the reluctance of carbon substituents to become axial acts in the same direction as the anomeric effect, so that the OH-axial pyranose anomer is overwhelmingly predominant, as in fructopyranose and A -acetyl-neuraminic acid (Figure 2.19). 

Eliminations. Exposure of o -phenylsulfanyl and a-phenyl-selenyl derivatives of neuraminic acid to DMTST and DBU effected an elimination reaction to give unsaturated compounds (eq 12). Interestingly, no reaction occurred with methylsulfanyl derivatives under the same conditions. 

The effect of cortisone and. thyroxine on j8-D-glucuronidase levels in rat forebrain and cerebellum have been examined during early postnatal development. To investigate the chemical relationships between rat liver lysosomal and microsomal j3-D-glucuronidase, which are essentially identical catalytically and in reactivity with antibody and are similar in molecular weight, the two enzymes were isolated by procedures in which modifications of the proteins were avoided. The enzymes were found to differ in both carbohydrate and amino-acid compositions. The microsomal enzyme contained much more D-mannose and, in contrast to the lysosomal enzyme, contained neuraminic acid but no D-glucose. 

The use of other compounds or modified sugars is permitted by the sialic acid biosynthetic pathway due to its promiscuous nature. Modified N-acyl-maimosamine derivatives have been shown to be effectively metabolized into corresponding N-acyl-modified neuraminic acid and incorporated into sialylglycoconjugates [52-54]. As possible as this may seem, it should be noted that these are actually "unnatural" and may be associated with as-yet-unknown consequences. 

In di-O-acetylated neuraminic acids the effects of 0-acetylation on the chemical shifts of skeleton protons are composed of the individual contributions of each O-acetyl group. Apparently, the induced shifts are additive. This is a general phenomenon, which can be illustrated for the peracetylated neuraminic acid. The IH-NMR spectrum of this compound is shown in Fig. 4.The resonance positions of H5, H6, H7, H8, H9, and H9 can be estimated on the basis of the presumed a-and -effects of 0-acetylation at position C4, Cl, C8, and C9. 

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