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Biomedical subjects

J M Sanderson

Publications and source records attributed to J M Sanderson.

At least 19 recordsLinked to original sources
PubMed2001

A supramolecular system for quantifying aromatic stacking interactions.

A supramolecular complex for investigating the thermodynamic properties of intermolecular aromatic stacking interactions has been developed. The conformation of the complex is locked in a single well-defined conformation by an array of H-bonding interactions that force two aromatic rings on one end of the complex into a stacked geometry. Chemical double-mutant cycles have been used to measure an anthracene-aniline interaction (+0.6 +/- 0.8 kJ mol(-1)) and a pentafluorophenyl-aniline interaction (-0.4 +/- 0.9 kJ mol(-1)) in this system. Although the interactions are very weak, the pentafluorophenyl interaction is attractive, whereas the anthracene interaction is repulsive: this is consistent with the dominance of pi-electron electrostatic interactions. The nitropyrrole subunits used to control the conformation of these complexes lead to problems of aggregation and multiple conformational equilibria. The implications for the thermodynamic analysis are examined in detail, and the double-mutant-cycle approach is found to be remarkably robust with respect to such effects, since systematic errors in individual experiments are removed in a pair-wise fashion when the cycle is constructed.

Journal Article↗
PubMed2001

Quantitative determination of intermolecular interactions with fluorinated aromatic rings.

The chemical double mutant cycle approach has been used to investigate substituent effects on intermolecular interactions between aromatic rings and pentafluorophenyl pi-systems. The complexes have been characterised using 1H and 19F NMR titrations, X-ray crystal structures of model compounds and molecular mechanics calculations. In the molecular zipper system used for these experiments, H-bonds and the geometries of the interacting surfaces favour the approach of the edge of the aromatic ring with the face of the pentafluorophenyl pi-system. The interactions are generally repulsive and this repulsion increases with more electron-withdrawing substituents up to a limit of +2.2 kJ mol(-1), when the complex distorts to minimise the unfavourable interaction. Strongly electron-donating groups cause a change in the geometry of the aromatic interaction and attractive stacking interactions are found (-1.6 kJ mol(-1) for NMe2). These results are generally consistent with an electrostatic model: the polarisation of the pentafluorophenyl ring leads to a partial positive charge located at the centre and this leads to repulsive interactions with the positive charges on the protons on the edge of the aromatic ring; when the aromatic ring has a high pi-electron density there is a large electrostatic driving force in favour of the stacked geometry which places this pi-electron density over the centre of the positive charge on the pentafluorophenyl group.

Crystallography, X-Ray↗
PubMed1979

Cellular aggregation and trauma in cardiotomy suction systems.

Experiments in dogs showed that the high levels of cellular aggregation and trauma caused by cariodtomy suction can be considerably reduced by the avoidance of air aspiration. A hypothesis is proposed to explain this on the basis of shear stresses in the inlet cannula. Roller pump suction was also found to be slightly more traumatic than vaccum suction, but contact of the blood with the pericardium had no effect so long as the pericardium and epicardium had been previously washed with saline.

Air↗
PubMed1977

Right-sided endocarditis involving both tricuspid and pulmonary valves in a patient with ventricular septal defect.

A patient with alpha-haemolytic streptococcus endocarditis on a ventricular septal defect is described. The disease spread to involve both tricuspid and pulmonary valves which were largely destroyed. The patient developed severe right heart failure with pronounced rise in right atrial pressure. This led to right-to-left shunting through the foramen ovale with systemic embolization. She was successfully treated by operative closure of the defects and double right-sided valve replacement.

Adult↗
PubMed1976

Cellular aggregation and destruction during blood circulation and oxygenation.

Platelet and leucocyte aggregation and severe haemolysis may occur in blood during the preparation of an extracorporeal circuit for open-heart surgery. Experiments with dog blood showed that both processes result from bubble oxygenation but not from circulation of diluted blood and that they appear to be inhibited by the presence of acid citrate dextrose and heparin, or citrate phosphate dextrose and heparin, but not by heparin alone.

Animals↗
PubMed1975

Low-dose heparin prophylaxis against fatal pulmonary embolism.

A prospective randomised controlled trial in 500 patients over the age of 50 who were undergoing major surgery showed that low-dose subcutaneous heparin was an effective prophylactic measure against fatal pulmonary embolism. None of the 252 patients who received perioperative heparin cover died of fatal pulmonary embolism while eight of the 236 who did not receive heparin prophylaxis died of fatal pulmonary embolism. These results were statiscally significant (P less than 0.01).

Aged↗
PubMed1975

Complete interruption of aortic arch, without persistent ductus arteriosus, in an adult.

A case of complete interruption of the aortic arch in an adult is presented and the previous 8 reported cases are reviewed. Obliteration of the ductus is a feature of these cases, in contrast to the more common variety found in early childhood. Comments are made on the clinical distinction between the adult type of complete interruption of the aortic arch and coarctation of the aorta.

Adolescent↗