Biomedical subjects

BS Murray

Publications and source records attributed to BS Murray.

3 recordsLinked to original sources

PubMed2000

Surface Activity and Critical Aggregation Concentration of Pure Sugar Esters with Different Sugar Headgroups.

We have studied the surface properties of a series of enzymatically synthesized sugar monoesters of xylose, galactose, sucrose, and lactose with different hydrophobic chain lengths (C12-C16) and purified, chemically synthesized sucrose esters that, unlike the enzymatically synthesized samples, contain a mixture of isomers. Data obtained have been compared with those for dodecanoic glucoside and maltoside acetals, and also a commercial sucrose myristate. Nearly all of the sugar esters studied brought about a significant reduction of the surface tension of water (to 31.0-43.0 mN m(-1)). A reduction in the critical aggregation concentration (CAC) of the surfactants with increasing carbon chain length was observed. Surfactants with more hydrophilic headgroups exhibited higher CAC, though this trend was moderated by the alkyl chain length. Comparing the chemically synthesized sucrose esters with their enzymatically synthesized equivalents revealed only minor differences in the CAC and the surfactant efficiency, indicating that the exact point of esterification might not be critical for the surfactant's properties. The presence of 0.1 M NaCl, KCl, or CaCl(2) did not significantly alter the surface behavior of the chemically synthesized esters, indicating the absence of surface-active species with charged headgroups. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Monitoring Protein Fouling of Metal Surfaces via a Quartz Crystal Microbalance.

A quartz crystal microbalance (QCM) has been used to study the fouling of chromium and hydrophobically modified gold surfaces when heated with milk proteins. Solutions of pure beta-lactoglobulin and a commercial skimmed milk powder were studied at 3 wt%, neutral pH, and before and after heating the solutions to 80 degrees C. The ease of removal of the adsorbed protein by rinsing with buffer and 1 wt% Tween 20 was also studied. The beta-lactoglobulin behaved rather similarly on the hydrophobic gold and chromium surfaces: Tween 20 was not particularly effective in removing this protein after heating. On the other hand, Tween 20 seemed more efficient at removing the heated skimmed milk protein from the hydrophobic gold surface, but less efficient at removing the skimmed milk from the chromium surface (which also exhibited the highest adsorbed amounts of either protein). On chromium, trypsin followed by buffer removed almost all the beta-lactoglobulin but had little effect on the adsorbed layers from skimmed milk. These changes are interpreted in terms of the hydrodynamic thickness of the adsorbed films and lead to the conclusion that the QCM is a highly sensitive way of monitoring adsorbed film properties during heating, cooling, and detergent action. Copyright 2000 Academic Press.

Journal Article↗

PubMed2000

Determination of Interparticle Forces by Colloidal Particle Scattering: A Simulation Study.

Colloidal particle scattering is a recently developed method for the determination of forces between micron-sized particles, which has given promising results. Inversion of the experimental scattering results to retrieve the interaction force requires the development of reliable computer code to match theory and experiment. We review the method used, discuss some operational details, and present some validating results for shear and sedimentation fields that compare favorably with the literature. We have used the simulation to compare particle scattering in a simple shear field for a range of exponential surface forces and discuss the sensitivity of these results to changes in potential parameters. We also discuss the sensitivity in relation to sources of error and their magnitude. In particular, we have incorporated a Brownian dynamics algorithm and compared the level of thermal noise with a simple theoretical formula. We introduce a straightforward means of representing the data and find that order of magnitude changes in the parameters evoke changes in the scattering pattern roughly equivalent to the Brownian noise level for a typical experiment with Pe=120. The results demonstrate the ability of the method, in principle, to distinguish between interaction potentials of different ranges and energy parameters. Copyright 2000 Academic Press.

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