Geoff Brownsey - Academia.edu (original) (raw)

Papers by Geoff Brownsey

The Plant Journal, 2007

In addition to the role of the cell wall as a physical barrier against pathogens, some of its con... more In addition to the role of the cell wall as a physical barrier against pathogens, some of its constituents, such as pectin-derived oligogalacturonides (OGA), are essential components for elicitation of defence responses. To investigate how modifications of pectin alter defence responses, we expressed the fruit-specific Fragaria • ananassa pectin methyl esterase FaPE1 in the wild strawberry Fragaria vesca. Pectin from transgenic ripe fruits differed from the wild-type with regard to the degree and pattern of methyl esterification, as well as the average size of pectin polymers. Purified oligogalacturonides from the transgenic fruits showed a reduced degree of esterification compared to oligogalacturonides from wild-type fruits. This reduced esterification is necessary to elicit defence responses in strawberry. The transgenic F. vesca lines had constitutively activated pathogen defence responses, resulting in higher resistance to the necrotropic fungus Botrytis cinerea. Further studies in F. vesca and Nicotiana benthamiana leaves showed that the elicitation capacity of the oligogalacturonides is more specific than previously envisaged.

Amorphous Food and Pharmaceutical Systems, 2007

Abstract Influence of Physical Ageing on Physical Properties of Starchy Materials Denis Lourdiqa ... more Abstract Influence of Physical Ageing on Physical Properties of Starchy Materials Denis Lourdiqa Paul Colonna, a Geoff Brownsey, b and Steve Ringb" INSTITUT NATIONAL DE LA RECHERCHE AGRONOMIQUE, BP 71627, 44316 NANTES CEDEX, FRANCE ...

Electro-Optics and Dielectrics of Macromolecules and Colloids, 1979

A combination of laser line broadening and electro-optic techniques has been used to investigate ... more A combination of laser line broadening and electro-optic techniques has been used to investigate the stability of suspensions of the rigid needle-shaped clay sepiolite. In distilled water, sepiolite is negatively charged. Addition of the surfactant CTAB was used to take the clay through its iso-electric point. The minimum stability of the suspension occur-red at the surfactant concentration at which (a) the anisotropy (△α) of the electrical polarisability (α), obtained from electric birefringence data, showed a minimum value, and (b) the electrophoretic mobility, obtained from laser line broadening in electric fields, was zero. The minimum in △α was attributed to the isolation of the bulk polarisation contribution from the otherwise predominant interfacial polarisation contribution.

Journal of the Chemical Society, Faraday Transactions 2, 1979

... Report no. RC3924,1972. lo J. C. Brown and PN Pusey, J. Phys. D, 1974,7, L31. l1 T. A. King a... more ... Report no. RC3924,1972. lo J. C. Brown and PN Pusey, J. Phys. D, 1974,7, L31. l1 T. A. King and MF Treadaway, JCS Furaday II, 1977, 73, 1616. l2 KA Stacey, Light Scattering in PhysicaE Chemistry (Butterworth, London, 1956). l3 B. H. Zimm, J. Chem. Phys., 1948, 16, 1099. ...

Macromolecules, 1996

have been extended in order to image networks and gels formed by the bacterial polysaccharide gel... more have been extended in order to image networks and gels formed by the bacterial polysaccharide gellan gum. Networks were formed by air-drying solutions of K + gellan onto freshly cleaved mica. AFM images were obtained in the direct current contact mode at constant force under butanol. Network formation can be inhibited by diluting the stock gellan solution or by converting K + gellan into the tetramethylammonium salt form. Inhibition of network formation led to AFM images of heterogeneous populations of gellan aggregates (gel precursors). Attempts have been made to image the surface of bulk aqueous gellan gels under butanol. The quality of the images obtained improved with increasing gel modulus. For rigid acid-set gellan gels, molecular resolution was achieved, revealing a bifurcated branched fibrous network.

Journal of Colloid and Interface Science, 1978

International Journal of Biological Macromolecules, 1997

The effects of selective removal of acetyl or succinyl substituents on the functionality of succi... more The effects of selective removal of acetyl or succinyl substituents on the functionality of succinoglycan polysaccharide have been studied by comparing the behaviour of the polysaccharides isolated from native Rhizobium meliloti strain Rml021, and genetically modified R. meliloti species. Removal of the succinyl groups was found to dramatically improve pseudoplasticity of the aqueous succinoglycan samples and also increase the cooperativity of the order-disorder transition exhibited by the polysaccharide. Removal of the acetyl substituent led to a decrease in the order-disorder transition temperature, whereas the removal of the succinyl groups led to an increase.

Carbohydrate Polymers, 1990

... Carbohydrate Polymers 13 (1990) 387-397 Gelation of Sugarbeet and Citrus Pectins using Enzyme... more ... Carbohydrate Polymers 13 (1990) 387-397 Gelation of Sugarbeet and Citrus Pectins using Enzymes Extracted from Orange Peel Gary Williamson, Craig B. Faulds, Jennifer A. Matthew, David B. Archer, Victor J ... Michel, F., Thibault, J.-E, Mercier, C., Heitz, E &amp;amp; Pouillade, E (1985). ...

Carbohydrate Polymers, 1998

Chemical mutagenesis or exposure to antibiotic stress of Sphingomonas paucimobilis ATCC 31461 and... more Chemical mutagenesis or exposure to antibiotic stress of Sphingomonas paucimobilis ATCC 31461 and R40 have been used to isolate mutants producing modified gellan gum polysaccharides. N.m.r. and conventional carbohydrate analysis methods have been used to characterise these polysaccharides. The 1H and 13C n.m.r. spectra of gellan gum have been fully assigned and the anomeric regions have been shown to be

Biophysical Journal, 2005

Concentrated solutions of bovine b-lactoglobulin were studied using osmotic stress and rheologica... more Concentrated solutions of bovine b-lactoglobulin were studied using osmotic stress and rheological techniques. At pH 6.0 and 8.0, the osmotic pressure was largely independent of NaCl concentration and could be described by a hard sphere equation of state. At pH 5.1, close to the isoelectric point, the osmotic pressure was lower at the lower NaCl concentrations (0 mM, 100 mM) and was fitted by an adhesive hard sphere model. Liquid-liquid phase separation was observed at pH 5.1 at ionic strengths of 13 mM and below. Comparison of the liquid-liquid and literature solid-liquid coexistence curves showed these solutions to be supersaturated and the phase separation to be nonequilibrium in nature. In steady shear, the zero shear viscosity of concentrated solutions at pH 5.1 was observed at shear rates above 50 s ÿ1. With increasing concentration, the solution viscosity showed a progressive increase, a behavior interpreted as the approach to a colloidlike glass transition at ;60% w/w. In oscillatory shear experiments, the storage modulus crossed the loss modulus at concentrations of 54% w/w, an indication of the approaching glass transition. Comparison of the viscous behavior with predictions from the Krieger-Dougherty equation indicates the hydrodynamic size of the protein decreases with increasing concentration, resulting in a slower approach to the glass transition than a hard sphere system.

Biophysical Journal, 2003

The glass-like transition behavior of concentrated aqueous solutions of bovine serum albumin was ... more The glass-like transition behavior of concentrated aqueous solutions of bovine serum albumin was examined using rheological techniques. At mass fractions [0.4, there was a marked concentration dependence of viscosity with a glasslike kinetic arrest observed at mass fractions in the region of 0.55. At mass fractions [0.6 the material behaved as a solid with a Young's modulus rising from ;20 MPa at a mass fraction of 0.62-1.1 GPa at 0.86. The solid was viscoelastic and exhibited stress relaxation with relaxation times increasing from 33 to 610 s over the same concentration range. The concentration dependence of the osmotic pressure was measured, at intermediate concentrations, using an osmotic stress technique and could be described using a hard sphere model, indicating that the intermolecular interactions were predominantly repulsive. In summary, a major structural relaxation results from the collective motion of the globules at the supra-globule length scale and, at 208C, this is arrested at water contents of 40% w/w. This appears to be analogous to the glass transition in colloidal hard spheres.

Biomacromolecules, 2005

Fourier transform infrared (FT-IR) spectroscopy was used to monitor changes in the secondary stru... more Fourier transform infrared (FT-IR) spectroscopy was used to monitor changes in the secondary structure of wheat prolamins, the main components of gluten, during mechanical deformation in a series of cycles of extension and relaxation. A sample derived from protein bodies isolated from developing grain showed a buildup of persistent-sheet structure. In gluten, the ratio of-sheet to random and-turn structures changed on extension. After the applied force was released, the sample recovered some of its original shape and structure, but the material became stiffer in consecutive extension cycles. The relationship between gluten structure and mechanical properties is discussed in terms of a model in which conversion of-turn to-sheet structure is a response to extension and a means by which elastic energy is stored in the system.