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Biomedical subjects

M N Jones

Publications and source records attributed to M N Jones.

103 records · Page 6Linked to original sources
PubMed1975

D-glucose permeability of black lipid membranes modified by human erythrocyte membrane fractions.

The D-glucose permeabilities of bimolecular lipid membranes formed from egg lecithin, cholesterol and human erythrocyte membrane fractions obtained using several fractionation procedures have been measured in order to assess their monosaccharide transport activity. The electrical properties of the bilayers containing the membrane fractions have also been measured and the bilayer thicknesses calculated. The observed D-glucose permeability coefficients are several orders of magnitude lower than that of the human erythrocyte membrane, indicating that none of the membrane fractions possessed significant glucose carrier activity. It is concluded that more refined techniques for incorporating membrane fractions into BLMs will be necessary before the monosaccharide transport system can be simulated in vitro.

Animals↗
PubMed1975

The interaction between bovine serum albumin and surfactants.

1. Potassium n-decyl phosphate binds exothermically to bovine serum albumin at pH 7.0 to form a specific complex containing approx. 60 phosphate anions. 2. The formation of the complex is accompanied by changes in the u.v. difference spectrum of the protein. 3. At higher phosphate concentrations (above 0.4mM) surfactant molecules continue to be bound, and the protein undergoes a gross change in conformation. 4. n-Dodecyltri-methylammonium bromide binds endothermically to bovine serum albumin at pH7.0 but the extent of binding for a given free surfactant concentration is less than for the phosphate surfactant. 5. Binding is accompanied by a small change in the specific viscosity and by changes in the u.v. difference spectrum of the protein. 6. It is suggested that over the surfactant concentration ranges studied n-decyl phosphate ions first bind to the C-terminal part of the protein and then to the more compact N-terminal part whereas n-dodecyltrimethylammonium ions bind only to the C-terminal part of bovine serum albumin.

Dialysis↗
PubMed1975

A theoretical approach to the binding of amphipathic molecules to globular proteins.

1. A theory based on a multiple equilibrium model with stoicheiometric binding constants has been formulated. It is applicable to the interaction of amphipathic molecules with charged macromolecules. 2. The theory has been applied to the binding of sodium n-dodecyl sulphate to ribonuclease A, beta-lactoglobulin and bovine serum albumin. 3. Over the ranges of surfactant concentration where binding is non-co-operative and co-operative, the experimental data can be satisfactorily fitted with energy and co-operatively parameters which are of comparable magnitude for the three globular proteins. 4. The results imply that the energy of interaction of sodium n-dodecyl sulphate with the proteins is equivalent to the formation of approximately four CH2 hydrophobic bonds.

Lactoglobulins↗
PubMed1973

The interaction between ribonuclease A and surfactants.

1. U.v. difference spectra show that the anionic surfactant sodium n-dodecyl sulphate unfolds ribonuclease A at pH7.3 and 10.3, but that the cationic surfactant n-dodecyltrimethylammonium bromide does not affect the conformation of the enzyme. 2. Equilibrium-dialysis experiments show that sodium n-dodecyl sulphate binds to ribonuclease A, but no binding of n-dodecyltrimethylammonium bromide could be detected at pH7.3. 3. The enzymic activity of ribonuclease A is unaffected by n-dodecyltrimethylammonium bromide up to a concentration of 0.03m at 25 degrees C. 4. Ultracentrifuge studies support the conclusion that n-dodecyltrimethylammonium bromide does not interact significantly with ribonuclease A. 5. The enthalpy change as measured by microcalorimetry on binding of sodium n-dodecyl sulphate to ribonuclease A is consistent with an exothermic enthalpy of binding occurring simultaneously with an endothermic enthalpy of chain unfolding.

Calorimetry↗
PubMed1973

The effect of surfactant structure on ribonuclease A-surfactant interactions.

The enzymic activity of ribonuclease A was measured in the presence of several surfactants at pH7.2. Cationic surfactants with trimethylammonium and pyridinium head groups do not deactivate or denature the enzyme, whereas n-dodecylamine hydrochloride, like the anionic surfactant sodium n-dodecyl sulphate, deactivates and denatures ribonuclease A.

Cytidine↗
PubMedDate not supplied

Delayed haemolytic transfusion reactions due to anti-C.

In 5 patients of phenotype ccDEe or ccDEE, the transfusion of 2--14 U of C-positive blood was folloued 5--9 days later by haemoglobinuria lasting 2--4 days. Anti-C was the only antibody present in all 5 cases but was always of low titre; with CC cells the maximum titre recorded with the indirect antiglobulin test was 8 and with the agglutination of enzyme-treated cells, 128. The discordance between the weakness of the antibody in vivo and the amount of haemoglobin released intravascularly is surprising but may be related to the type of IgG molecule of which anti-C is composed.

Female↗