Dextran from, structure

Her early endeavors to characterize the branch points in starch, and pursuit of the then-elusive a-(l — 6) linkage in starch, drew Dr. Jeanes to dextrans, since these polysaccharides contain a-(l — 6) linkages as their main structural feature. Dextrans are a family of D-glucans produced micro-bially from sucrose they contain from 50 to 100% a-(l — 6) linkages, depending on the microbial strain used. Dr. Jeanes became an authority on dextran sources, structures, and industrial applications. She published comprehensive bibliographies on dextran, the first in 1950 and another in 1978. These were a labor of love, produced with much effort before the days of automated data retrieval. 

Both and H n.m.r. measurements on a bacterial dextran and its acetylated derivative and on a synthetic tri-O-benzyldextran have revealed the main features of their linear a-(l - 6)-linked structures. Bacterial dextrans from Streptococcus viridans B-1351, Streptobacterium dextranicum B-1254, and four strains of Leuconostoc mesenteroides have been subjected to methylation analysis.They differed with respect to the ease of methylation and subsequent hydrolysis of the methylated polysaccharides, owing to significant differences in the frequency and type of chain-branching. An enzymic approach has been used to obtain information on the frequency and distribution of chain-branching in dextrans. Thus, B-512 native dextran was treated with an endo-dextranase (from Pseudomonas UQM 733) and the products were examined by quantitative t.l.c. The relative amount of each oligosaccharide (i.e. linear isomalto-oligosaccharides of DP 2-5... 

Our results confirm those of Lindberg and Svensson who analyzed the structure of a dextran from the same origin via permethylation and hydrolysis. From G.C.-M.S. analysis of the hydrolysis products they concluded the irregularities in the main chain to be 3) linkages. 

A reducing disaccharide, consisting of D-glucose and D-fructose, named levjcrose 214) is formed in the reaction mixture to the extent of about 3 % during the synthesis of dextran from sucrose by an enzyme isolated from the microorganism Leuconostoc mesenteroides. Its specific rotation is [a]o —6.8° (in water) m.p. 161-162°C. Methylation studies show that its structure is 5-0-a-D-glucopyranosyl-D-fructopyranose. 

This class of polysaccharide was well known in sugar refineries as the causative agent of ropiness it was formed from cane or beet sugar by bacteria of the Leuconostoc genus. Over many years, numerous papers were published, mainly with E. J. Bourne [Adv. Carbohydr. Chem. Biochem., 34 (1977) 1-22] and S. A. Barker as co-authors, describing the isolation, purification, properties, and structural features of dextrans. 

Structure of the Dextran Synthesised from Sucrose by a New Strain of Betacoccus arabinosa-ceous" M. Stacey and G. Swift, J. Chem. Soc., (1948) 1555-1559. 

Dextran is produced from sucrose by a number of bacteria the major ones being the nonpathogenic bacteria Leuconostoc mesenterodes and Leuconostoc dextranicum. As expected, the structure (and consequently the properties) of the dextran is determined by the particular strain that produces it. 

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