Saccharide molecule

The reaction mixture is often complicated by condensation of mono-saccharidic molecules yielding unwanted homodisaccharides. This problem is also reduced by the minimum water approach (water activity of ca. 0.7-0.8). The organic solvent at low concentration probably deactivates the enzyme due to structural changes whereas high solvent concentrations with the necessary minimum water cause fixation of the enzyme structure in its active conformation. Unfortunately, glycosidases are rather instable in low-water media. This is a big drawback compared to highly solvent-resistant lipases.94... 

Transglycosidation with retention of configuration (Chipman and Sharon, 1969) would be more difficult to explain if an open-chain carbonium ion were formed in lysozyme reactions, necessitating an equilibrium reaction with free aldehyde. It seems unlikely, however, that a cyclic carbonium ion intermediate could have a sufficiently long lifetime to react with a saccharide molecule that can bind to the enzyme only after displacement of the leaving group in a fairly aqueous environment (above discussion). Therefore, the concept of a cyclic carbonium ion also presents difficulties for interpretation and should not be accepted uncritically. 

Saccharide molecules can be interlinked while producing a water molecule. In this way polysaccharides are formed. Well-known examples are cellulose and starch. In Fig. 3.21 you can see a small piece of a polysaccharide chain. 

Fig. 3.20 Ring closing reaction in a saccharide molecule and an example of a...

C-NMR relaxation parameters may also be employed to access the rates of overall and internal motions for saccharide molecules.230 Longitudinal and transversal heteronuclear relaxation times as well as hetero-nuclear NOEs depend on the molecular motion of the molecule, including overall and internal motions. Thus, careful analysis of these parameters can be employed to demonstrate the presence of conformational heter-eogeneity and/or dynamics, as well as the restriction to motion and the timescale of the existing fluctuations. Different examples of application of this methodology to trisaccharides,231 232 tetrasaccharides,233 pentasaccharides,234 and polysaccharides235,236 have been described. 

C NMR was a reliable source of detection and identification of carbon nuclei in the saccharide molecule. However, greater quantities were requiredfor ID experiments as compared with H NMR spectroscopy and often extended periods for acquisition (sometimes 3 days) were required. The H- C heteronuclear multiple quantum correlation (HMQC) was one experiment that allowed the assigiunent of carbon resonances, by correlation with their proton nuclei, and where smaller quantities were used. A conscious ID P NMR investigation quickly revealed the presence of phosphate or a 2-aminoethyl phosphate unit in the core OS. 2D H-3 P HMBC NMR spectroscopy was a reliable method for efficient detection and sometimes placement of the phosphate substituents. 

The hydrazine derivatives of saccharide are here discussed in sections on saccharide azines, which are formed when one hydrazine molecule reacts with two saccharide molecules saccharide hydrazones and glycosylhy-drazines, which are the tautomeric acyclic and cyclic products formed when one hydrazine molecule reacts with one sugar residue saccharide osazones and poly(hydrazones), which are formed when two or more hydrazine molecules are linked to a saccharide residue and, finaly, hydrazones of carba-sugars and related compounds. 

After oxidation of the saccharide molecules of polysaccharide [110], glycophase-CPG... 

Receptors containing diboronic acids can precisely recognize saccharide molecules. 

Covalent cross-linking by way of non-saccharide molecules, other than phosphate and sulphate, probably does occur and there are two classes of residue that might well be involved, which are borate and silicate. Borate is the less likely of the two, since its esters with sugars and other polyols are stable only at fairly high pH and it tends to form internal esters with sugars rather than cross-linking them. However, in special environments it might cross-link symmetrically. 

Water-soluble biocompatible rhamnose-coated Fc304 4.0nm nanoparticles of (299) have been obtained by the organic phase covalent anchorage of acetate-protected rhamnose on the nanoparticles surface via the - P(0)(0SiMc3)2 moiety linker. In comparison to the previously published nanoparticles coated with other saccharide molecules, the present nanoparticles were mono-dispersed, their size could be controlled and they presented a good stability due to the covalent anchorage of rhamnose to the surface of the nanoparticles. 

Not only Oj " and HO, but also alkyl or alkoxyl radicals (R ) were formed when saccharides such as glucose, fructose and sucrose were added into the xanthine oxidase/hypoxanthine system containing iron (Luo et al. 2001). The generated amount of R depended on the kind and concentration of saccharides added into this system. In the absence of saccharides no R were detected, indication that there is an interaction between the saccharide molecules and the free radicals generated from the iron containing hypoxanthine/xanthine oxidase system. 

The loss of carbon atoms, which is correlated with the removal of acetyl groups, explains the film thickness of 17 A, as determined with XPS after deprotection of the molecules at the surface. The higher value found for the film that was deprotected prior to adsorption can be understood in terms of a higher density of saccharide molecules on the surface after adsorption from solution. Steric reasons are probably responsible for the higher space requirement per molecide in its protected form (AHS) compared to a deacetylated molecule (DHS) due to the bulky protective acetoxy groups. 

A trisaccharide is a carbohydrate that is composed of three sugar ("saccharide") molecules. Consider a trisaccharide composed of three different sugars and represented by A-B-C. In acidic solution, the carbohydrate will hydrolyze in two possible ways ... 

Polyoses are also polysaccharides, but with lateral chains and ramifications. Between 50 and 200 saccharide molecules are polymerized. Galactoglucomannan or 4-0-methylglucuronoxylan is the main constituent. The polyoses connect the polysaccharides with the lignin in the cell wall. They determine the swelling and shrinkage of wood. 

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