Glycosylation increase

Previous work had shown that with three differently glycosylated forms of glucose oxidase, as the degree of glycosylation increased the enthalpy of activation for fecat increased and indications of tunneling disappeared. For example, with the least glycosylated variant (136 kDa) was 1.47, well above the semiclassical... 

Post-translational Modifications, Exemplified by Glycosylation, Increase Protein Diversity... 

Evolution has provided the cell with a repertoire of 20 amino acids to build proteins. The diversity of amino acid side chain properties is enormous, yet many additional functional groups have been selectively chosen to be covalently attached to side chains and this further increases the unique properties of proteins. Diese additional groups play a regulatory role allowing the cell to respond to changing cellular conditions and events. Known covalent modifications of proteins now include phosphorylation, methylation, acetylation, ubi-quitylation, hydroxylation, uridylylation and glycosyl-ation, among many others. Intense study in this field has shown the addition of a phosphate moiety to a protein... 

From a mass spectrometry perspective, these modifications, such as phosphorylation or glycosylation, manifest themselves as an increase in the molecular weight of both the parent protein and also of the polypeptides (produced by enzymatic digestion) containing the modification. 

The effects of pH under model conditions (0.6 to 5.5 for 24 hr) were covered by Nielsen et al. for four anthocyanins (3-O-glucoside, glycosylated cyanidin, rutinoside, and delphinidin rutinoside). After 24 hr, over 90% of the anthocyanins were intact up to pH 3.3, while instabihty greatly increased at pH greater than 4.5. 

Supercritical fluid extraction (SEE) is another modern separation technology usually employed to extract lipophilic compounds such as cranberry seed oil, lycopene, coumarins, and other seed oils. Anthocyanins generally and glycosylated anthocyanins in particular were considered unsuitable for SEE due to their hydrophilic properties, since SEE is applicable for non-polar analytes. However, a small amount of methanol was applied as co-solvent to increase CO2 polarity in anthocyanin extraction from grape pomace. New applications of SEE for anthocyanin purification have been reported for cosmetic applications from red fruits. ... 

Amadori-type early glycosylation products (Brownlee et /., 1988). Protein that has been glycated in vitro is con-formationally altered. For example, the amount of early glycosylation products in vivo in diabetics, whether on haemoglobin (Hb) or basement membrane, increases when blood glucose levels are normalized by treatment. 

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