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Öğe A novel global hydrodynamic analysis of the molecular flexibility of the dietary fibre polysaccharide konjac glucomannan(2009) Kök, Mehmet Şamil; Abdelhameed A.S.; Ang, Shirley; Morris, Gordon A.; Harding, Stephen E.Konjac glucomannans have been widely considered in health food products although their hydrodynamic properties have been poorly understood. The weight-average molecular weight (Mw); sedimentation coefficient (s020,w) and intrinsic viscosities ([?]) have been estimated for five different preparations. The decrease in both intrinsic viscosity and sedimentation coefficient with molecular weight enables the estimation of molecular flexibility in terms of persistence length (Lp) using the traditional Bohdanecky-Bushin and Yamakawa-Fujii analyses for intrinsic viscosity and sedimentation data respectively. However, this requires an assumption of the mass per unit length ML. Advantage can now be taken of a recent development in data interpretation which allows the estimation of Lp from combined intrinsic viscosity and sedimentation coefficient data and also an estimate for ML. Using this "global" procedure an estimate of (13 ± 1) nm is found for Lp and a value of (330 ± 10) g mol-1 nm-1 for ML.. The value for Lp suggests a molecule of considerable flexibility, comparable to galactomannans (Lp ? 8-10 nm) but not as flexible as pullulan (Lp ? 1-2 nm). © 2009 Elsevier Ltd. All rights reserved.Öğe Polysaccharide drug delivery systems based on pectin and chitosan(Nottingham Univ Press, 2010) Morris, Gordon A.; Kök, Mehmet Şamil; Harding, Stephen E.; Adams, Gary G.Chitosans and pectins are natural polysaccharides which show great potential in drug delivery systems. Chitosans are a family of strongly polycationic derivatives of poly-N-acetyl-Dglucosamine. This positive charge is very important in chitosan drug delivery systems as it plays a very important role in mucoadhesion (adhesion to the mucosal surface). Other chitosan based drug delivery systems involve complexation with ligands to form chitosan nanoparticles with can be used to encapsulate active compounds. Pectins are made of several structural elements the most important of which are the homogalacturonan (HG) and type I rhamnogalacturonan (RG-I) regions often described in simplified terms as the "smooth" and "hairy" regions respectively. Pectin HG regions consist of poly-glacturonic acid residues which can be partially methyl esterified. Pectins with a degree of methyl esterification (DM) > 50% are known as high methoxyl (HM) pectins and consequently low methoxyl (LM) pectins have a DM < 50%. Low methoxyl pectins are of particular interest in drug delivery as they can form gels with calcium ion (Ca2+) which has potential applications especially in nasal formulations. In this chapter we will discuss the physicochemical properties of both chitosans and pectins and how these translate to current and potential drug delivery systems.Öğe Structure and heterogeneity of gliadin: a hydrodynamic evaluation(Springer, 2010) Ang, Shirley; Kogulanathan, Jana; Morris, Gordon A.; Kök, Mehmet Şamil; Shewry, Peter R.A study of the heterogeneity and conformation in solution [in 70% (v/v) aq. ethanol] of gliadin proteins from wheat was undertaken based upon sedimentation velocity in the analytical ultracentrifuge, analysis of the distribution coefficients and ellipsoidal axial ratios assuming quasi-rigid particles, allowing for a range of plausible time-averaged hydration values. All classical fractions (alpha, gamma, omega(slow), omega(fast)) show three clearly resolved components. Based on the weight-average sedimentation coefficient for each fraction and a weight-average molecular weight from sedimentation equilibrium and/or cDNA sequence analysis, all the proteins are extended molecules with axial ratios ranging from similar to 10 to 30 with alpha appearing the most extended and gamma the least.
