摘要:

AbstractThe general strategies and methods applied in the analysis of the primary structure of polysaccharides and derivatives are shortly lined out. Methods involving complete degradation of the polysaccharide are discussed in more detail. Advantages of the reductive‐cleavage method compared to classical methylation analysis are illustrated by giving some examples of applicatio

ISSN:1022-1360    

DOI:10.1002/masy.19950990103

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractSeveral new phenylcarbamate derivatives of cellulose and amylose having fluoro and methyl groups or 4‐trimethylsilyl substituent on the phenyl groups were prepared and their chiral recognition abilities as chiral stationary phases for HPLC were evaluated. These derivatives are soluble in chloroform and exhibit chiral discrimination in1H NMR spectroscopy. Based on the above results and molecular mechanics calculation of interaction energies between the derivatives and enantiomers, the mechanism of chiral discrimination is discusse

ISSN:1022-1360    

DOI:10.1002/masy.19950990104

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractTwo‐dimensional C‐H correlation NMR spectra are presented for the native cellulose types Iα and Iβ fromCladophorasp. A remarkable difference of correlation peaks between Iα and Iβ was observed, which indicates an essential structure difference between the two types of native ce

ISSN:1022-1360    

DOI:10.1002/masy.19950990105

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe molecular characteristics of sodium hyaluronate and amylose in various solvents are discussed by summarizing our recent studies. Data for the intrinsic viscosity and the radius of gyration are analyzed on the basis of the wormlike or helical wormlike chain, with excluded‐volume effects taken into account by the Yamakawa‐Stockmayer‐Shimada theory. The unperturbed hyaluronate molecule in 0.2 M or 0.5 M aqueous NaCl is shown to behave like a wormlike chain with Kuhn's segment length of about 8 nm. Amylose in the unperturbed state is more flexible, regardless of the kind of solvent, its stiffness parameter being about one half that for the hyaluronate chain, but it assumes an irregular helical conformation similar to what is predicted by conformation ana

ISSN:1022-1360    

DOI:10.1002/masy.19950990106

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

Abstract(1→4)‐α‐ and (1→4)‐β‐D‐linked glucosidic oligosaccharide chains were generated by the Monte Carlo method, and the scattering from the systems composed of simulated chains was calculated to compare with the results of small‐angle X‐ray scattering from the oligosaccharides in aqueous solution. By extending the simulation to a longer chain, a single chain conformation of (1→4)‐α‐ and (1→4)‐β‐D‐linked polysaccharides was evaluated. On the basis of the simulation, the suprastructure of (1→4)‐α‐ and (1→4)‐β‐D‐linked polysaccharides and their gel formation mechanism were discussed in some detail by analyzing the small‐angle X‐ray scattering from the aqueous sol

ISSN:1022-1360    

DOI:10.1002/masy.19950990107

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe equatorial configuration of the β(1,4)‐glycosidic bond predestines a stretched chain conformation. These topological characteristics form the basis for laterally aggregated supramolecular structures in the solid state as well as in the concentrated solution regime. Partially substituted derivatives develop water solubility, but the dissolution process stops at a certain colloidal level. The aggregates show structural properties which are best described by afringed micelle.These objects are built up of laterally aggregated chains forming astemand have a peripheral shell of dangling chain sections. The striking dynamic properties indicate no segment interpenetration, and the particles lose gradually their shell mobility as the overlap concentration is exceed

ISSN:1022-1360    

DOI:10.1002/masy.19950990108

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractSmall‐amplitude dynamic measurements of aqueous starch polysaccharide solutions are performed by a Bohlin controlled‐stress rheometer with air bearing. Three classes of starch polysaccharides–native starches, fractions of starches and hydrolysed starches–are compared in their molecular composition and rheological properties during and after the gelation process. Viscoelastic properties of solutions and gels are recorded in dependence on temperature and time, yielding storage and loss moduli during and after sol‐gel transition. Hot concentrated aqueous solutions are cooled down from 90 °C to 5 °C at a rate of 1 °C/min. Measurements are carried out at 0,1 Hz and 5% strain amplitude deformation. The typical course of the moduli of gelling starch polysaccharide solutions shows a liquid‐like behavior (G”>G') in the upper temperature level between 60 and 90 °C, a jumpwise increase with ensuing intersection of G' and G” below 60 °C and a solid‐like behavior (G'>G”) at lower temperatures with a slightly in time growing storage modulus. Storage and loss moduli depend on molecular composition and concentration of the substance. The process of starch polysaccharide aggregation is discussed with regard to theories of physical gelation b

ISSN:1022-1360    

DOI:10.1002/masy.19950990109

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractGel‐sol transition of sodium type gellan solutions with and without salts is studied by dynamic viscoelastic measurements and differential scanning calorimetry (DSC). Mechanical spectra show that gellan aqueous solutions behave as an entangled polymer solution in the concentration range around 2 wt.‐% at temperatures>15°C and as a weak gel below this temperature. Concentrated solutions (>3 wt.‐%) show a true gel behavior below 30°C. The two step transition is observed for 2∼3 wt.‐% gellan aqueous solutions in thermal scanning rheological (TSR) measurements; the transition at a higher temperature is attributed to a coil‐helix transition whilst the transition at a lower temperature is attributed to sol‐gel transition. The transition observed in dilute solutions of gellan is attributed to the coil‐helix transition whilst the sol‐gel transition occurs simultaneously with coil‐helix transition in more concentrated solutions (>3 wt.‐%). The sol‐gel transition temperature shifts to higher temperatures with increasing concentration of the added salts. Junction zones formed in the presence of divalent cations are far more heat resistant than those with monovalent cations judging from both DSC and TSR, however, the possibility of the formation of junction zones by covalent bonds or b

ISSN:1022-1360    

DOI:10.1002/masy.19950990110

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractInclusion complexes of slightly hydroxypropylated amylose with organic guest molecules have been investigated by means of c.d. spectroscopy and microcalorimetry in aqueous solution. From these results, the structure of the complexes and the mechanism of their fomation are deduced. It is concluded that amylose can adjust its helix conformation to the shape and structure of the guest molecule included. Investigations about intramolecular and intermolecular crosslinking of amylose indicate that the complexing behavior of amylose can be manipulated specifically.

ISSN:1022-1360    

DOI:10.1002/masy.19950990111

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractReadily processed clear fruit juices contain variable amounts of colloidally dissolved pectic substances. Separation of fruit juice polysaccharides by anion‐exchange‐chromatography yielded mainly arabinogalactans (type II) and rhamnogalacturonans. The addition of small amounts of the residual pectins to colloid free juices resulted in a up to 60 % reduction of the flux rates in micro‐ and ultrafiltration sy

ISSN:1022-1360    

DOI:10.1002/masy.19950990112

出版商:Hüthig&Wepf Verlag    

年代:1995

数据来源: WILEY