Gel permeation chromatography and the Mark-Houwink relation for pectins with different degrees of esterification

Anger, H.; Berth, Gisela

doi:10.1016/0144-8617(86)90019-6

Cited by 98 publications

(41 citation statements)

References 12 publications

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“…In general, the viscosity of a polymer solution is proportional to the MW of a polymer with Mark-Houwink relationship (Anger et al, 1984). As expected, the MWs of all the resins used in this work were well in the agreement with the theoretical relationship with an increasing order of UF resin < two-step MUF resin < one-step MUF resin < MF resin.…”

Section: Resultssupporting

confidence: 76%

Measurement of Molecular Weights of Melamine-Urea-Formaldehyde Resins and Their Influences to Properties of Medium Density Fiberboards

Jeong¹,

Park²

2016

Journal of the Korean Wood Science and Technology

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This study attempted to measure molecular weight (MW) of melamine-urea-formaldehyde (MUF) resins prepared by two different synthesis methods: the one-step MUF resins were synthesized in one batch procedure, while the two-step MUF resins were prepared by a physical mixing of urea-formaldehyde (UF) resin with melamine-formaldehyde (MF) resin that had been synthesized in a separate procedure. The properties of medium density fiberboard (MDF) panels bonded with two types of MUF resins were also investigated. MWs of these MUF resins were measured using gel permeation chromatography (GPC). In addition, this study measured the MWs of one-step MUF resin during its synthesis procedure. The performance of two types of MUF resins was evaluated by determining properties of MDF panels prepared in laboratory. As the synthesis procedure progressed, both number average MW (M n ) and weight average MW (M w ) of one-step MUF resin gradually increased, while the polydispersity index (PDI) decreased. And low MW species of the resin predominantly decreased as the synthesis step progressed. The one-step MUF resin showed greater M n and M w than those of the two-step ones even though the PDI values of both resins were very similar each other. As expected, the one-step MUF resin resulted in better properties of MDF panels than those of two-step resins. In particular, the one-step MUF resin provided better internal bond (IB) strength and thickness swelling (TS) with MDF panels than those of two-step ones, indicating better water resistance of the one-step resin. These results suggest that the preparation method of MUF resins have a great impact on the MW and final panel properties.

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Section: Resultssupporting

confidence: 76%

Measurement of Molecular Weights of Melamine-Urea-Formaldehyde Resins and Their Influences to Properties of Medium Density Fiberboards

Jeong¹,

Park²

2016

Journal of the Korean Wood Science and Technology

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“…28 The chemical composition of alginate (corresponding to 39% guluronic (G) and 61% mannuronic (M) acids) and the degree of pectin esterification (13%), were determined by infrared and H-NMR spectroscopies, according to Filippov 29 and Gransdalen…”

Section: Methodsmentioning

confidence: 99%

Dynamic light scattering and viscosimetry of aqueous solutions of pectin, sodium alginate and their mixtures: effects of added salt, concentration, counterions, temperature and chelating agent

Lima¹,

Soldi²

2009

J. Braz. Chem. Soc.

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Efeitos de adição de sal, concentração, presença de contraíons, temperatura e agente quelante em soluções aquosas de pectina, alginato de sódio e misturas destes foram analisadas por viscosimetria e espalhamento de luz dinâmico (DLS). A viscosidade intrínseca dos sistemas binários diminuiu com a adição de sal e com o aumento da temperatura, porém, mostrou-se insensível à adição de NaEDTA. Como esperado, a viscosidade intrínseca do sistema ternário alginato/pectina/água foi igual a média da viscosidade intrínseca determinada para os sistemas binários. Estudos de DLS indicaram a ocorrência de uma distribuição bimodal (presença dos modos de relaxação rápido e lento) para ambos os sistemas binários e ternários a 25 °C, refletindo um processo de agregação. No caso do modo lento de relaxação, um aumento significativo do raio hidrodinâmico foi observado tanto para os sistemas binários como ternário, na presença de NaCl e KCl a 25 °C. No entanto, a 80 °C, o raio hidrodinâmico correspondente ao modo lento em soluções de KCl foi praticamente constante para todos os sistemas estudados e não foi observado para o sistema binário alginato/solução aquosa.The effects of added salt, concentration, counterions, temperature and chelating agent on aqueous solutions of pectin, sodium alginate and their mixtures were analyzed by viscosimetry and dynamic light scattering (DLS) techniques. The intrinsic viscosity of the binary systems decreased with the addition of salt and with temperature, while it was found to be insensitive to the addition of NaEDTA. As expected the intrinsic viscosity of the ternary alginate/pectin/water system was equal to the average of the intrinsic viscosity for the binary systems. The DLS studies indicated a bimodal distribution (fast and slow relaxation modes) for both binary and ternary systems at 25 °C, reflecting aggregation. A significant increase in the hydrodynamic radius, in the case of the slow mode, was observed for the binary and ternary systems in the presence of NaCl and KCl at 25 °C. However, at 80 °C the hydrodynamic radius for the slow mode in KCl solutions was practically constant for all the studied systems, except for the alginate binary solutions in which were not observed.

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“…Intrinsic viscosity was determined by using an Ubbelohde viscosimeter at 25.0°C and pH 6.0 in 0.155 M NaCl (high-methoxyl pectins) or in 0.05 M NaCl-0.005 M sodium oxalate (low-methoxyl pectins). The relationship between intrinsic viscosity and the average molecular weight of pectins is described by the Mark-Houwink equation (2).…”

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confidence: 99%

Degradation of Pectins with Different Degrees of Esterification by Bacteroides thetaiotaomicron Isolated from Human Gut Flora

Dongowski

Lorenz

Anger

2000

Appl Environ Microbiol

119

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A complete human fecal flora and cultures of defined species obtained from fecal flora were investigated in vitro to determine their ability to ferment the dietary fiber pectin. Bacteroides thetaiotaomicron was tested as a pectin-degrading microorganism alone and in coculture with Escherichia coli. Macromolecular pectins with different degrees of esterification were used as substrates in microbial degradation studies. The levels of oligogalacturonic acids formed in batch cultures were estimated during a 24-or 48-h incubation period by using highperformance thin-layer chromatography and high-performance anion-exchange chromatography. The spectrum and the amount of unsaturated oligogalacturonic acids formed as intermediate products of pectin fermentation changed permanently in the culture media during incubation with the complete fecal flora. After 24 h, no oligogalacturonic acids were detected. The pectin-degrading activities of pure cultures of B. thetaiotaomicron were lower than the pectin-degrading activity of a complete fecal flora. Cocultures of B. thetaiotaomicron and E. coli exhibited intermediate levels of degradation activity. In pure cultures of E. coli no pectin-degrading activity was found. Additionally, the rate of pectin degradation was affected by the degree of esterification of the substrate. Saturated oligogalacturonic acids were not found during pectin fermentation. The disappearance of oligogalacturonic acids in the later stages of fermentation with both the complete fecal flora and B. thetaiotaomicron was accompanied by increased formation of short-chain fatty acids.In human nutrition, pectin is one of the most important sources of dietary fiber. It is present in vegetables and fruits as a component of the plant cell wall. Pectin consists mainly of long linear chains of ␣-1,4-glycoside-linked D-galacturonic acid (homogalacturonan; "smooth" regions) which are partially esterified with methanol. In addition, branched and complex pectic substances are present in the cell wall (rhamnogalacturonans I and II; "hairy" regions) (45). Like other types of dietary fiber, pectin is not depolymerized by endogenous gastrointestinal enzymes during passage through the stomach and the small intestine. A number of physiological effects of pectin or pectin-containing diets have been described; these effects include decreasing serum cholesterol levels (17), increasing fecal excretion of steroids (24), interacting with metal ions (25), and interacting with bile acids in vitro (11). These effects depend on the macromolecular state of pectin.In the colon, pectin is fermented more or less completely by the microflora, as shown previously (8,9,18,28,48). However, there have been only a few studies in which the intermediate steps in pectin degradation by gastrointestinal microorganisms have been examined. On the other hand, the end products of bacterial fermentation of pectin are well known; a spectrum of short-chain fatty acids (SCFA) and different gases (CO 2 , H 2 , H 2 S, CH 4 ) are formed. In some studies it was s...

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Gel permeation chromatography and the Mark-Houwink relation for pectins with different degrees of esterification

Cited by 98 publications

References 12 publications

Measurement of Molecular Weights of Melamine-Urea-Formaldehyde Resins and Their Influences to Properties of Medium Density Fiberboards

Measurement of Molecular Weights of Melamine-Urea-Formaldehyde Resins and Their Influences to Properties of Medium Density Fiberboards

Dynamic light scattering and viscosimetry of aqueous solutions of pectin, sodium alginate and their mixtures: effects of added salt, concentration, counterions, temperature and chelating agent

Degradation of Pectins with Different Degrees of Esterification by Bacteroides thetaiotaomicron Isolated from Human Gut Flora

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