Carbohydrates branched

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 antigenic determinants of the ABO and Lewis blood group substances are sugars at the ends of these carbohydrate branches. 

Credi, Raymo and coworkers reported in 2002, the preparation of a new type of carbohydrate-coated, dendronized ferrocenes [46], The structures of these den-drimers are illustrated by compounds 14 and 15. Binding interactions with p-CD were investigated by liquid secondary ion mass spectrometry, 11 NMR spectroscopy, voltammetry and circular dichroism. Upon addition of P-CD, cyclic voltammetric experiments showed data similar to those obtained with our dendronized ferrocenes, that is, a CD-induced current level decrease and anodic half-wave potential shift. At 22°C, these authors obtained K values of 2,000 200 and 1,300 200 M-1 for the complexation of 14 and 15, respectively, by p-CD in 0.1MNaClO4. Similar dendrimers in which carbohydrate branches are covalently attached to both cyclopentadienyl rings of the ferrocene residue were not bound at all by P-CD, reflecting the shielding of the core ferrocene center in these more symmetric compounds. 

Morimoto M, Saimoto H, Shigemasa Y. Biological activities of carbohydrate branched chitosan derivatives. Trends Glycosci Glycotechnol 2002 14 205. 

Carbohydrates that have a carbon substituent attached to the mam chain are said to have a branched chain d Apiose and l vancosamme are representative branched chain carbohydrates... 

The Fischer projection of the branched chain carbohydrate D apiose has been presented in Section 25 12... 

Branched chain carbohydrate (Section 25 12) Carbohydrate in which the main carbon chain bears a carbon substituent in place of a hydrogen or hydroxyl group Bromohydrin (Section 6 17) A halohydnn in which the halo gen IS bromine (see halohydnn)... 

Although carbohydrates/polysaccharides exist in such huge amounts, their industrial processing is expensive due to enormous quality fluctuations of succeeding raw material batches. The reason for these fluctuations is a high variability on the molecular level, particularly in the degree of polymerization distribution, in branching characteristics, and in complex interactive properties. 

FIGURE 16.1 Preparative SEC of short-chain (scb) branched glucans of small" (<3S /u.m) starch granules of potato species Ostara separated on Sephacryl S-1000 (88 X 2.6 cm) eluent 0.005 M NaOH the normalized chromatogram (area = 1.0) was constructed from an off-line determined carbohydrate content of succeeding 5-ml fractions flow rate 0.67 ml/mln V d = 185 ml, V, = 460 ml fraction I high dp fraction fraction 2 low dp fraction. 

FIGURE 16.16 Nonbranched/long chain branched glucans of potato starch dissolved in hot water-steam and 0.1 M NaOH 1.2 ml of the 18-mg/ml solution was separated on Sepharose CL 2B (88 X 1.6 cm) 3-ml fractions were collected for further analysis normalized (area = 1.0) eluogram profiles (ev) constructed from an off-line determined mass of carbohydrates of each of the fractions flow rate 0.15 ml/min V. , = 70 ml, = 180 ml eluent 0.01 tA NaOH. 

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