Dextran studies

These three independent structural methods give data for all dextrans which are in accord with each other. The 27 dextrans studied represent 25 structues which differ in type or degree of branching. Such extensive cross-referencing of data give us increased confidence with regard to spectra-to-structure relationships. 

The individual abilities of 14 dextrans to precipitate (l->6)-specific antibodies from four difFerent sera were found to be dependent upon the proportion of (l->6)-linked n-glucopyranosyl residues in each dextran. On a molar basis, the most effective inhibitors of these precipitin reactions are isomaltotetraose (structure 46, n = 2) and isomaltopentaose (structure 46, n = 3), from which it was concluded that all of the dextrans studied possessed numerous terminal, nonreducing sequences... 

Biopolymer Extraction. Research interests involving new techniques for separation of biochemicals from fermentation broth and cell culture media have increased as biotechnology has grown. Most separation methods are limited to small-scale appHcations but recendy solvent extraction has been studied as a potential technique for continuous and large-scale production and the use of two-phase aqueous systems has received increasing attention (259). A range of enzymes have favorable partition properties in a system based on a PGE—dextran—salt solution (97) ... 

L. mesenteroides strain NRRL B-512F produces a water-soluble dextran with 95% a(l 6) main-chain linkages and 5% a(l 3) branch linkages (78). This strain was subcultured from NRRL strain B-512, isolated in 1943. Strain NRRL B-512F is the strain used for commercial dextran production in the United States and most other countries. Nearly all of the studies done on the industrial production and utilisation of dextran have used this strain. 

A1 tern an and low molecular weight alteman fractions from F mesenteroides B-1355 are being studied as hulking agents for reduced calorie foods (124), and dextran oligomers containing a(l — 2)-linkages have been proposed for similar appHcations (211). 

Acrylamide graft copolymers such as those with starch (qv)(131), dextran (132), and lignin (qv) (133), have been studied to try to reduce copolymer costs. A general disadvantage of acrylamide copolymers is greater cost compared to partially hydroly2ed polyacrylamides. 

Stacey, Maurice, 1-19 amino sugar work, 15 analytical chemistry, 18 authoring papers, 4 awards, 6, 19 childhood, 1-2 community roles, 3-4 desosamine work, 14-15 dextran work, 8-9 DNA studies, 11-12... 

Most frequently, SEC with dextran-, pullulan-, or polystyrene calibration standards has been used to characterize the molecular properties of xylans. However, as for viscometric studies [108], a sufficient solvent ionic strength is a prerequisite for useful SEC measurements of charged polysaccharides, including glucuronoxylans [111-113]. An advantage of the SEC technique is that the presence of protein and phenolic components or oxidative changes can be detected by simultaneous ultraviolet (UV) detection. 

A prehminary study of the use of larch AGs in aqueous two-phase systems [394] revealed that this polysaccharide provides a low-cost alternative to fractionated dextrans for use in aqueous two-phase, two-polymer systems with polyethylene glycol (PEG). The narrow molecular-weight distribution (Mw/Mn of 1-2) and low viscosity at high concentration of AG can be exploited for reproducible separations of proteins under a variety of conditions. The AG/PEG systems were used with success for batch extractive bioconversions of cornstarch to cyclodextrin and glucose. 

Works where study the hydrodynamic properties of a biopolymers in aqueous solution at different temperatures are made by Guner (1999), and Guner Kibarer (2001) for dextran Ghen Tsaih (1998) and Kasaii (2008) for chitosan, Bohidar for gelatin (1998), and Monkos for serum proteins (1996,1997,1999, 2000, 2004 and 2005). 

Amylose and dextran have been studied in aqueous solution as the xanthate derivatives. Dextran xanthate has no observable c.d., but amylose xanthate in aqueous solution has a complex c.d. that indicates an organized structure. 

A carboxymethyl derivative of dextran has been prepared in order to study the effect of charge density, concentration, degree of neutralization. 

Laurent, T. C., The interaction between polysaccharides and other macromolecules. VI. Further studies on the solubility of proteins in dextran solutions, Acta Chem. Scand., 17, 2664, 1963. 

Dextran was chosen to study for the following reasons. First, it is water soluble allowing three dimensional modification employing aqueous solution and classical interfacial condensation routes. Second, it is readily available in industrial quantities. Third, it is available in a range of molecular weight allowing product modification to be studied as a function of dextran chain size. Fourth, it is generally considered to be an under-utilized natural feedstock. 

An underlying assumption is that dextran is a representative polysaccharide and that results derived from its study can be applied to other polysaccharides. Effected modifications are intended to occur throughout the dextran material rather than only at the surface. This is achieved by employing solutions containing dissolved dextran. 

The investigation of the chemical modification of dextran to determine the importance of various reaction parameters that may eventually allow the controlled synthesis of dextran-modified materials has began. The initial parameter chosen was reactant molar ratio, since this reaction variable has previously been found to greatly influence other interfacial condensations. Phase transfer catalysts, PTC s, have been successfully employed in the synthesis of various metal-containing polyethers and polyamines (for instance 26). Thus, the effect of various PTC s was also studied as a function of reactant molar ratio. 

Tables I-IV contain results as a function of initial base, presence or absence of an added PTC, organometallin reactant and molar ratio of reactants. On a strictly molar ratio of reactant sites basis, the balancing of net quantity of reactants should occur at an organcmetallic/dextran molar ratio of 3 2. The present studies are consistent with earlier studies that showed the maximums occurring away frem this 3 2 ratio. The values cited in Table V for reactant muximums should be considered only as general. Results contained in Table I will be utilized to illustrate how the parameters of percentage yield and position of the maximum of precentage yield as reactant molar ratio is varied might be employed to indicate if the added PTC...

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