Dextran sources

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. 

Glucose A 6-carbon sugar molecule, which is the building block of natural substances like cellulose, starch, dextrans, xanthan, and some other biopolymers and used as a basic energy source by the cells of most organisms. 

Aqueous standard solutions are a source of certain difficulties In electrothermal atomic absorption spectrometry of trace metals In biological fluids The viscosities and surface tensions of aqueous standard solutions are substantially less than the viscosities and surface tensions of serum, blood and other proteln-contalnlng fluids These factors Introduce volumetric disparities In pipetting of standard solutions and body fluids, and also cause differences In penetration of these liquids Into porous graphite tubes or rods Preliminary treatment of porous graphite with xylene may help to minimize the differences of liquid penetration (53,67) A more satisfactory solution of this problem Is preparation of standards In aqueous solutions of metal-free dextran (50-60 g/llter), as first proposed by Pekarek et al ( ) for the standardization of serum chromium analyses This practice has been used successfully by the present author for standardization of analyses of serum nickel The standard solutions which are prepared In aqueous dextran resemble serum In regard to viscosity and surface tension Introduction of dextran-contalnlng standard solutions Is an Important contribution to electrothermal atomic absorption analysis of trace metals In body fluids. 

The naturally-occurring 1,6-linked glucose polymers furnish other sources of 2,3,4-trimethyl-D-glucose, which has been isolated from the hydrolysis products of the methyl ethers of gentiobiose,112 118 melibiose,114 raffmose106 116 and dextran.78 74,116... 

Hydrolysis by endo-( 1 -> 3)-a-D-glucanase has demonstrated the presence of consecutive a-(l - 3) linkages in a number of streptococcal a-D-glucans (mutans). Insoluble a-D-glucans produced by S. mutans OMZ 176 and OMZ65 were hydrolyzed by endo-(l- 3)-a-D-glucanase, whereas the soluble polysaccharides from the same sources, and dextran T-2000, were... 

The richest dietary sources of total iron are organ meats (liver and kidney), egg yolk, dried legumes, com, molasses and parsley. Liver is particularly valuable because of the high absorbability of its iron. However, only about 10% of dietary iron is absorbed. Iron deficiency anemia can be treated with soluble iron(II) compounds providing 200 mg in three or four daily divided doses. Oral iron(II) sulfate is the least expensive and is in wide use. Ascorbic acid increases the absorption efficiency of iron(II) sulfate. Parenteral administration of iron is used when oral iron is ineffective. Iron-dextran, a colloid formed from iron(III) chloride and an alkali-modified dextran, is one of several preparations available which has found extensive clinical use. It contains up to 28% Fe by weight and has a structural similarity to ferritin. Transfusion therapy may also be used in severe chronic anemia or acute hemorrhage. 

The phosphatidyl cholines PCs used in this study were obtained from the Sigma Chemical Co. The DPPC used here showed swelling behavior in CaCl2 solutions similar to that of DPPC previously obtained from other sources (I). All lipids showed less than 1% impurity by thin-layer chromatography (TLC). Water was doubly distilled and salts were of reagent grade. Dextran was obtained from Pharmacia Chemicals and mixed in known proportions with salt solutions prior to contact with lipid. 

Dextran is a unique polysaccharide because of its structure (only glucose units), purity, defined branching pattern depending on the microbial sources and defined molecular weight. Today, it is produced on a commercial scale resulting from optimised biotechnological processes for the biosynthesis of dextran using preferably Leuconostoc mesenteroides. 

The final chapter by Thomas Heinze, Tim Liebert, Brigitte Heublein, and Stephanie Hornung represents the important interaction of cellulose research and development with other related polysaccharides. The authors describe the sources, structure, properties, and applications of dextran and functionalized dextranes including their use as bioactive materials. 

Dextran is a glucose polymer where the glucose residues are mainly linked by al-6 bonds. However, a few branches also occur. These are typically formed by a 1-2, al-3 or al-4 bonds depending on the bacterial or yeast species that is the source of the dextran. 

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