Purification of carbohydrates

If the sample has been obtained from a natural source, such as a cell or tissue extract, protein and/or nucleic acid might be present. The presence of protein and nucleic acid can be determined by measuring the absorbance at 280 nm and 254 nm, respectively. The nature of the carbohydrate is also important, that is, is it a 

Essentials of Carbohydrate Chemistry Springer-Verlag New York Inc. 1998 

If the polysaccharide is composed of uronic acid residues, it can be specifically precipitated by lowering the pH. Different pH values between 5 and 1 can be used to precipitate polysaccharides with different amounts and kinds of uronic acids [6]. Likewise, mixtures of neutral polysaccharides can. sometimes be precipitated by differential alcohol precipitation in which the polysaccharides have different water solubilities due to differences in their degrees of branching [7]. Saccharides with certain specific structures can be selectively separated by using lectins (see section 12.10). 

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Several methoxy-substituted benzyl etbers have been prepared and used as protective groups. Tbeir utility lies in tbe fact that they are more readily cleaved oxidatively than tbe unsubstituted benzyl etbers. These etbers are not stable to metbyl(trifluorom ethyl)dioxirane, which oxidizes the aromatic ring. The relatedp-(dodecyloxy)benzyl ether has been prepared to facilitate chromatographic purification of carbohydrates on Ci8 silica gel. The table below gives the relative rates of cleavage with dichloro-dicyanoquinone (DDQ). ... 

Linhardt RJ and Bazin HG (2001) Separation and purification of carbohydrates. Glycoscience 1 63-74. 

Purification of carbohydrate-binding proteins from Dictyostelium discoideum by afiinity chromatography 224... 

In addition to the various fluorousprotecting groups designed to ease the purification of carbohydrate intermediates, a range of fluorous groups have been reported with the potential for applications in the construction of... 

When ionic liquids are used as replacements for organic solvents in processes with nonvolatile products, downstream processing may become complicated. This may apply to many biotransformations in which the better selectivity of the biocatalyst is used to transform more complex molecules. In such cases, product isolation can be achieved by, for example, extraction with supercritical CO2 [50]. Recently, membrane processes such as pervaporation and nanofiltration have been used. The use of pervaporation for less volatile compounds such as phenylethanol has been reported by Crespo and co-workers [51]. We have developed a separation process based on nanofiltration [52, 53] which is especially well suited for isolation of nonvolatile compounds such as carbohydrates or charged compounds. It may also be used for easy recovery and/or purification of ionic liquids. 

Mond process The purification of nickel by the formation and decomposition of nickel carbonyl, monomer A small molecule from which a polymer is formed. Examples CH2=CH2 for polyethylene NH2(CH2)6NH2 for nylon, monoprotic acid A Bronsted acid with one acidic hydrogen atom. Example CH COOI I. monosaccharide An individual unit from which carbohydrates are considered to be composed. Example C6H(206, glucose, multiple bond A double or triple bond between two atoms. 

Purification of the conjugates may be done by reverse phase HPLC separation. Dry the reaction solution under a nitrogen stream and reconstitute in a minimum volume of acetonitrile/water (1 1, v/v). Apply the sample to a 5 pm Cig-silica HPLC column (250 X 4.6 mm, Nucleosil). Elute with a gradient of water to acetonitrile at a flow rate of 1 ml/minute over a time course of 30 minutes. Free BNAH and BNAH-glycan derivatives can be monitored by absorbance at 275 nm. The conjugate peak also will be positive for carbohydrate by reaction with orcinol, which can be detected by spray after spotting a small eluted sample on a TLC plate. 

First, the above-mentioned sensors have major drawbacks, as the detection and recognition event is a function of the nature and characteristics of the side chains, and the side chain functionalization of the CP requires advanced synthesis and extensive purification of numerous monomeric and polymeric derivatives. Second, this generation of sensors primarily employed optical absorption as the source for detection, resulting in lower sensitivity when compared with other sensing systems for biological processes. However, the use of fluorescence detection within these sensing systems could justify continued development. More recent examples include a fluorescent polythiophene derivative with carbohydrate functionalized side chains for the detection of different bacteria [15] and novel synthesis schemes for ligand-functionalization of polythiophenes [16]. 

Most eukaryotic mRNA molecules have up to 250 adenine bases at their 3 end. These poly (A) tails can be used in the affinity chromatographic purification of mRNA from a total cellular RNA extract. Under high salt conditions, poly (A) will hybridize to oligo-dT-cellulose or poly(U)-sepharose. These materials are polymers of 10 to 20 deoxythymidine or uridine nucleotides covalently bound to a carbohydrate support. They bind mRNA containing poly (A) tails as short as 20 residues. rRNA and tRNA do not possess poly (A) sequences and will not bind. After washing the mRNA can be eluted with a low salt buffer. 

Figure 2. Representative fractionations employed in the purification of Populus deltoides LCCs. a, initial fractionation of high ("A") and low ("B") molecular weight components through Bio-Gel P-6 b, re-fractionation of "B" through Bio-Gel P-6 c, penultimate fractionation of ARBI on Sephadex G-50 d, penultimate fractionation of Cl components on Sephadex G-50. A280, (O—O) carbohydrate, ( — ).

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