Carbohydrate composition, determination

Carbohydrate composition, determined by HPLC, are expressed as % by weight. All values are averages of two separate determinations. 

Table II. Carbohydrate compositions (weight percentage) of individual oligomer peaks purified (QAE-Sephadex or HPLC ion-exchange separation, respectively) from mixtures of citrus pectin oligomers or B fruit extracts Compositions shown are for peaks whose biological activity is described in Figure 4. Uronic acid values are based on colorimetric assay. Proportions of neutral sugars were determined by GC and adjusted so that totals equal 100%. In fact, some oligomers (G7 peaks 8, 9 and 10. B extract peak 10) produced small (less than 1 % of the total integrated area), unknown peaks in the GC chromatograms.

Honey has been produced in Lithuania since the ancient times. Baltrusaityte et ah (2007a,b) recently reported antimicrobial and antioxidant properties of Lithuanian honeys. Kaskoniene et ah (2010) characterized the carbohydrate composition of Lithuanian honeys obtained from various sources and determined if there was any relationship between pollen content and the content of the carbohydrate in the honey. 

Numerous furan and pyran derivatives, many of which originate from heat treatment of carbohydrates, largely determine the odor of processed foods. Of this group, 2,5-dimethyl-4-hydroxy-277-furan-3-one and maltols are used in fairly large quantities in flavors. The following compounds are used in relatively small amounts in flavor compositions ... 

Finally, this section would remain incomplete without a few comments on the applications of HPLC to a particular group of carbohydrates—polysaccharides—whose determination, both qualitatively and quantitatively, has received much less attention than the rest (56). This may be surprising when the importance of these compounds, in terms of both functional properties and nutrition, is considered, but it is not so surprising when the difficulty of the analyses required is studied. High-performance LC can be used in this field, either to characterize the polysaccharides per se or to study their carbohydrate composition and the nature of bonding after acid or enzymic hydrolysis. 

The problem of determining the structure of a polysaccharide is similar to that of determining the amino acid sequence of a protein, but it is complicated by the additional structural features unique to carbohydrates branching and linkage isomerism. The elements of carbohydrate chemistry discussed in following paragraphs are those relevant to the problems of determination of carbohydrate composition and the structure of polysaccharides. 

The partial specific volume, v, (for mudns, normally in the range of 0.60 to 0.65 mL/g) has to be determined separately v is usu y obtained from a plot of solution density versus concentration. The accuracy with which this value can be obtained (compare Section IV,3,a for refractive increment measurements) will largely be affected by errors in concentration measurement, although the final value can be checked by calculation by using the Traube rule (see, for example. Ref. 71), if the amino add and carbohydrate composition of the mucin are known. 

The preferred methods to determine the carbohydrate composition of glycolipids are based on gas chromatographic analysis of the individual sugar components such as methylglycosides or alditol acetate derivatives (15,16). 

The other analytical methods involving biomass composition that are currently in development (FT-IR, NIR, and pyMBMS) are able to resolve and quantify individual sugar composition. This is not possible with HR-TGA however, in conjunction with H nuclear magnetic resonance (NMR), sugar residues can be identified, and their abundance can be determined. Carbohydrate compositional profiles of lignocellulosic biomass can be accurately quantified based on the 600 MHz H-NMR spectram of unpurified acid hydrolyzates wherein the hemicellulose and cellulose ftactions of biomass have been reduced to a mixmre of sugars in acidic solution [23]. 

The carbohydrate composition and lignin were determined using the NREL laboratory analytical procedures (http //wwwl.energy.gov/biomass/analytical procedures.html). The moisture content of the bagasse samples was determined using a moisture analyzer (Computrac MAX 1000, Arizona Instrument Corporation, Tempe, AZ, USA). 

The unique carbohydrate composition of the glycoproteins that constitute the antigenic determinants on red blood cells in part contributes to the relative immuno-genicity of the A, B, and Rh (D) red blood cell groups in human blood. 

Freeman and Daniel 226) one of 124,000 both being based on sedimentation-equilibrium studies, and in addition, the amino acid and carbohydrate composition suggest a molecular weight near 130,000 119). These studies appear to establish the molecular weight of ceruloplasmin to be near 124,000—134,000. Morell et al. 134) have carefully determined the Cu content and dry weight of the protein finding a value of 0.275 0.009%, w/w Cu which for a molecular weight of... 

Elwood, P., et al. (1988). Determination of the Carbohydrate Composition of Mammalian Glycoproteins by Capillary Gas Chromatography/Mass Spectrometry, Anal. Biochem. 175 202-221. 

The carbohydrate composition of human placental 3-D-2-acetamido-2-deoxy-hexosidases A, B, and heat-converted B was determined by g.l.c. Similar quantities of D-mannose, 2-acetamido-2-deoxy-D-glucose, and D-galactose are present in the A and B isoenzymes, whereas 7V-acetylneuraminic acid is found in s nificant amount in only the A isoenzyme.The heat-converted -D-acetamido-2-deoxy-hexosidase B also contains only trace amounts of A-acetylneuraminic acid, but is about 1.5-fold richer in D-mannose and 2-acetamido-2-deoxy-D-glucose, and nearly two-fold richer in D-galactose than native 3-D-2-acetamido-2-deoxy-hexosidase B. Since native and converted B are thought to be composed of four identical protein chains, these results suggest that there may be variable glycosylation of these chains. 

The carbohydrate composition (neutral carbohydrates only) was monitored during the isolation process with a High Performance Liquid Chromatography (HPLC) method . The lignin content was determined gravimetrically and spectrometrically in the usual manner . ... 

The carbohydrate composition (neutral carbohydrates and uronic acid residues) of the isolated xylan was determined by enzymatic hydrolysis and subsequent capillary zone electrophoresis analysis (ENZ/CZE) according to a method described elsewhere... 

ID and 2D NMR spectroscopy has been applied to determine the carbohydrate composition of honeys, as well as to detect honey adulteration by sugar syrups. Artifidal adulteration of honey, although it is an illegal practice, has become more and more attractive to producers due to limited production level in recent years. 

Pepsins and Pepsinogens.—The carbohydrate compositions and some sequences of amino-acids have been determined for glycopeptides derived from pepsinogens isolated from Japanese monkeys. Glycopeptides released by successive treatments of pepsinogen I with thermolysin and aminopeptidase contained 2-amino-... 

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