Biomedical subjects

Michael J Blandamer

Publications and source records attributed to Michael J Blandamer.

4 recordsLinked to original sources

PubMed2004

The nature of the micellar stern region as studied by reaction kinetics. 2.

The nature of rate-retarding effects of cationic micelles on the water-catalyzed hydrolyses of a series of para-substituted 1-benzoyl-1,2,4-triazoles (1a-f) and 1-benzoyl-3-phenyl-1,2,4-triazole (2) has been studied using kinetic methods. A comparison is drawn between medium effects in the micellar Stern region and in model solutions for the micellar Stern region. Simple model solutions involving concentrated aqueous solutions of a small ionic molecule resembling the surfactant headgroup, as reported before,(1) were improved. New model solutions for alkyltrimethylammonium bromide micelles contain both tetramethylammonium bromide (TMAB), mimicking micellar headgroups, and 1-propanol, mimicking hydrophobic tails. The rate-retarding effect of micelles on the hydrolysis of 1a-f and 2 is caused by the high concentration of headgroups as well as by hydrophobic tails in the Stern region where 1a-f and 2 bind to the micelle. Individual contributions of these interactions are quantified. Rate-retarding effects found for different probes, with different sensitivities for interactions as they occur when the probe binds to the micellar Stern region, as well as the micellar Stern region's micropolarity as reported by the E(T)(30) probe, are satisfactorily reproduced by new model solutions containing both TMAB and 1-propanol.

Journal Article↗

PubMed2003

Kinetics of hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solution as a function of temperature near the temperature of maximum density, and the isochoric controversy.

At temperatures above and below the temperature of maximum density, TMD, for water at ambient pressure, pairs of temperatures exist at which the molar volumes of water are equal. First-order rate constants for the pH-independent hydrolysis of 1-benzoyl-1,2,4-triazole in aqueous solution at pairs of such isochoric temperatures show no unique features. Taken together with previously published kinetic data for the hydrolysis of a range of simple organic solutes in both water and D2O near their respective TMDs, we conclude that special significance in the context of rates of chemical reactions in aqueous solutions should not be attached to the isochoric condition.

Journal Article↗

PubMed2003

Three important calorimetric applications of a classic thermodynamic equation.

The thermodynamic background to three calorimetric techniques is discussed; (i) titration microcalorimetry, (ii) adiabatic calorimetry, and (iii) heat conduction calorimetry. Relevant equations for each technique are derived from a common equation for the enthalpy H of a closed system. General patterns which emerge in the measured parameters are presented for adiabatic and heat conduction calorimeters linked to applications of these techniques.

Calorimetry↗

PubMed2002

Self-assembly does not account for the hydrophobic effect.

Marmur has claimed that large values of activity coefficients for nonelectrolytes, particularly in the context of hydrophobic interactions between solutes in aqueous solution at ambient temperature and pressure, cannot be accounted for by thermodynamics, and has suggested that association (self-assembly) of solute molecules in solution solves this dilemma. We show that the analysis of Marmur is incorrect, specifically because the equilibrium in solution between monomeric solute molecules and associated solute molecules is entirely ignored. We show further that activity coefficients such as that for nitromethane solute in hexane solvent, 39.7, and that for solute hexane in solvent water, 4.48 x 10(5), can be calculated as 31.9 and 4.71 x 10(5), respectively, by methods based on well-known molecule-molecule interactions. No assumption of self-assembly is required.

Journal Article↗