Experimental methods in polymer degradation

Rabek, Jan F.

doi:10.1007/978-94-011-1274-1_10

Cited by 100 publications

(174 citation statements)

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“…The loss of the peak areas and downfield displacement of the carbon atom signals in the backbone can be explained in terms of restricted mobility, intermolecular interaction and ordered-disordered conformation. 21 These results suggest that the immobilization of the main chain by binding with intra-and inter-molecular hydrogen bonds re- z in the aqueous solution agree basically with the theoretical curves for triple helix 13 calculated from Yamakawa-Yoshizaki theory for a wormlike cylinder 22 for q = 100 nm and from the Benoit-Doty expression for KP wormlike chain 23 for q = 120 (nm), respectively. It was confirmed that the L-FV-IA as triple-stranded helix in the 0.2 M NaCl aqueous solution and as single-stranded flexible chains in DMSO.…”

Section: Resultssupporting

confidence: 77%

Transition from Triple Helix to Coil of Lentinan in Solution Measured by SEC, Viscometry, and 13C NMR

Zhang

Zhou

et al. 2002

Polym J

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ABSTRACT:Lentinan, β-(1 → 3)-D-glucan with (1 → 6) branching, was isolated from Lentinus edodes. Weightaverage molecular weight M w , radius of gyration < s 2 > 1/2 z and intrinsic viscosity [η] of Lentinan in 0.2 M NaCl aqueous solution, dimethylsulfoxide (DMSO) and water/DMSO mixtures were measured by light scattering (LS), size exclusion chromatography (SEC) combined with LS, and viscometry. The results indicated that the glucan exists mainly as triple-helical chains in 0.2 M NaCl aqueous solution and water/DMSO mixtures with over 20 wt% water content, and as single-flexible chain in DMSO. The data from SEC-LS, viscosity and 13 C NMR measurements proved strongly that the helix-coil conformation transition occurred in a narrow range from 80 to 85 wt% DMSO aqueous solution, accompanying with obvious changes of M w , < s Chihara et al. have reported that the β-(1 → 3)-Dglucan, Lentinan, obtained from Lentinus edodes has a strong antitumour activity against sarcoma 180 implanted subcutaneous in mice. 1 Thereby, the importance of the polysaccharides has provided a major impetus for increasing attention. Particularly mushroom polysaccharides have been used as functional food, and are developed in the field of new drugs. 2 The structural analysis may offer the most fundamental knowledge to understand the functions of polysaccharide, but the diversity and irregularity of polysaccharide chain make the structural analysis a formidable task. 3 Although a monosaccharide unit is common to many polysaccharides, its linkage mode varies and characteristic functions properties will appear accordingly. It is worth noting that polysaccharides in aqueous solution exhibit different chain conformation such as single helix, 4 triple helix, 5 random coil, 6 and aggregate, 7 even if their backbone all are β-(1 → 3)-D-glucan. However, conformation and its transition from an ordered state to a disordered for β-(1 → 3)-D-glucan in solution have not been fully investigated.Helix conformations of β-(1 → 3)-D-glucan with two (1 → 6)-glucosyl side groups for every five residues isolated from Lentinus edodes have been reported, based on analysis from the results of X-Ray diffraction 8 and 13 C NMR. 9-12 However, it has long been suspected to be a triple helix of the β-D-glucan in aqueous solution without strong evidence. In our recent work, 13 experimental results from light scattering have indicated that the predominant species of the β-D-glucan in 0.5 M NaCl aqueous solution exist as triple-helical chains with high rigidity, and in dimethylsulfoxide (DMSO) as single-flexible chains. The single or multiple helices of biopolymers in aqueous solution aggregate easily to form gel. The gelation and the helical state may be induced by lowering the temperature, by changing the solvent, or by adding salt. 14 The gel-forming ability of polysaccharide is of considerable importance in view of their biological functions. 15 Moreover, helixcoil transitions are important in biology, as they appear in proteins and DNA. 16 In this work, the conformation ...

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Section: Resultssupporting

confidence: 77%

Transition from Triple Helix to Coil of Lentinan in Solution Measured by SEC, Viscometry, and 13C NMR

Zhang

Zhou

et al. 2002

Polym J

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“…11 Information on the unperturbed dimensions, starting from the viscosity results, was obtained from the Kurata-StockmayerFixman (KSF) equation 12,13 :…”

Section: Resultsmentioning

confidence: 99%

Unperturbed dimensions and the theta temperature of dextran in aqueous solutions

Güner

1999

J. Appl. Polym. Sci.

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Intrinsic viscosity measurements were carried out on dextran samples (of different molecular weights) in aqueous solutions at 25, 28, 31, 34, 37, 40, and 43°C. The extrapolation methods were used for the data; they gave unperturbed dimensions, K 0 , of the chain. The unperturbed root-mean-square end-to-end distance ͗r 2 ͘ 0 1/ 2 calculated for the polymer samples in water indicate that the polymer coils are slightly contracted in this solvent as the temperature is increased. The long-range interaction parameter, B, was also determined. In aqueous dextran solutions, this showed a significant decrease in the long-range interactions between 25 and 43°C. The values of ⌰ ϭ 317.82 and 316.57 K were obtained from the temperature dependence of the interaction parameter B in the Kurata-Stockmayer-Fixman and Berry equations. Calculated values were interpreted mainly on the basis of hydrogen-bond formation between polymer segments and dextran-water molecules in solution.

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“…The PeakFit software, version 4.12 (SeaSolve Inc, Framingham, MA) was used for the calculation of the areas. The degree of crystallinity was found from the equation [15]:…”

Section: Powder X-rays (P-xrd) Characterizationmentioning

confidence: 99%

Effect of Polymorphism on the Particle and Compaction Properties of Microcrystalline Cellulose

Rojas¹

2013

Cellulose - Medical, Pharmaceutical and Electronic Applications

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Experimental methods in polymer degradation

Cited by 100 publications

References 0 publications

Transition from Triple Helix to Coil of Lentinan in Solution Measured by SEC, Viscometry, and 13C NMR

Transition from Triple Helix to Coil of Lentinan in Solution Measured by SEC, Viscometry, and 13C NMR

Unperturbed dimensions and the theta temperature of dextran in aqueous solutions

Effect of Polymorphism on the Particle and Compaction Properties of Microcrystalline Cellulose

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