Carbohydrates, stabilization, borates

Other studies have supported the reports of considerable stabilisation of carbohydrates by borates the thermal stability of ribose increases under acidic conditions, while glucose is favoured under basic conditions. Thus, the pre-RNA world chemistry of furanosyl borate diesters of ribose could have taken place at high temperatures and low pH. A pre-metabolism world at high temperatures and in the basic pH range would have involved glucose borates and anion borates (Scorei and Cimpoia u, 2006). 

If it is true that the structural form of D-glucose which reacts with boric acid is the a-D-pyranose form, then that form probably exists in a boat or twist conformation in the complex. This implies that the study of the stability constants of sugar borate ester might give information about the ability of various carbohydrates to form such boat or twist conformations (10, 21). 

Prepare the protein or macromolecule to be thiolated in a non-amine-containing buffer at pH 8.0. For the modification of ribosomal proteins (often cited in the literature) use 50 mM triethanolamine hydrochloride, 1 mM MgCl2, 50 mM KC1, pH 8. The magnesium and potassium salts are for stabilization of some ribosomal proteins. If other proteins are to be thiolated, the same buffer may be used without added salts for stabilization. Alternatively, 50 mM sodium phosphate, 0.15 M NaCl, pH 8, or 0.1 M sodium borate, pH 8.0 may be used. For the modification of polysaccharides, use 20 mM sodium borax, pH 10, to produce reactivity toward carbohydrate hydroxyl residues. Dissolve the protein to be modified at a concentration of 10 mg/ml in the reaction buffer of choice. Lower concentrations also may be used with a proportional scaling back of added 2-iminothiolane. 

Using an approach based on the well-known formation of complexes between borate and diols, the carbohydrate heterogeneity of a mAb was demonstrated by CZE [153]. Three partially resolved peaks were observed after optimization of the conditions to 150 mM borate, pH 9.4, on a fused-silica capillary. The method was further used to monitor batch-to-batch consistency and for stability testing. 

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