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Biomedical subjects

B Cornell

Publications and source records attributed to B Cornell.

7 recordsLinked to original sources
PubMed2000

Orientation dependence of NMR relaxation time, T(1rho), in lipid bilayers.

The orientation dependence of the low frequency NMR relaxation time, T(1rho), of protons in aligned phospholipid bilayers was measured using 13C cross polarisation and direct proton experiments. The contribution of intra- and inter-molecular interactions to proton T(1rho) was determined by using dimyristoyl phosphatidylcholine (DMPC) with one hydrocarbon chain deuterated and dispersed in perdeuterated DMPC. The results indicated that intramolecular motions on the kHz timescale were the major cause of T(1rho) relaxation in phospholipid bilayers.

Carbon Isotopes↗
PubMed1999

Erratum

The paper 'Interference of rheumatoid factor activity by aspartame, a dipeptide methyl ester' by Paul A. Ramsland, Bahereh F. Movafagh, Morris Reichlin and Allen B. Edmundson, J. Mol. Recognit. 1999; 12: 249--257, was published without the required colour plates. The publisher would like to apologise for this omission. The article is reprinted here in full. Please replace the previously published pages with those following. The electronic version of the article, including the colour plates, can be downloaded from the Wiley Interscience website at http://www.interscience.wiley.com. The plates have been included in the original paper, which appeared in Issue 4 of the journal.

Journal Article↗
PubMed1996

The phosphorus-31 spectra of dielectrophoretically reoriented tubules in the HII phase of DOPE.

31P electric field nuclear magnetic resonance measurements are described which assess the effect of electric field on the orientation of tubules comprising the HII phase of dioeleoylphosphatidylethanolamine. A model, based on dielectrophoretic effects, was used to predict that a field of 4 MV/m would change the orientation of the lipid tubules in a HII phase. The excitation pulse was biphasic to help discriminate electric field interactions with free ions or permanent dipoles from interactions with induced dipoles, as well as to control the problems of ohmic heating, electrolysis and polarisation associated with dc or unbalanced ac excitation voltages. Spectra consistent with irreversible electrorotation and with reversible and transient electrorotation were observed. No response to the electric field was seen in certain cases. The conditions for irreversible and reversible electrorotation and failure to rotate have been tabulated and are discussed. Finally, some simple models are considered, in order to calculate the energies involved, if the observed NMR spectra are interpreted as arising from lipid HII phase reorientations.

Electric Impedance↗
PubMed1994

The effect of pulsed electric fields on the phosphorus-31 spectra of lipid bilayers.

A technique is described for measuring the effect of electric fields on the conformation of lipid bilayer membranes by solid state nuclear magnetic resonance. An apparatus was devised to obtain spectra from samples of aligned phospholipid dispersions at varying electric field strengths up to 100 MV/m. Measurements were carried out on membranes made from dioleoylphosphatidylethanolamine and dioleoylphosphatidylcholine, which resulted in electric field induced phase changes. Calibration experiments were performed using bilayers formed from dimyristoylphosphatidylcholine with glycerol and with a nematic liquid crystal. An electric field induced change, from L alpha to HII, was also seen in a dimyristoylphosphatidylcholine/alamethicin bilayer.

Electricity↗
PubMed1987

Gramicidin A--phospholipid model systems.

Gramicidin A forms ion-conducting channels which can traverse the hydrocarbon core of lipid bilayer membranes. The structures formed by gramicidin A are among the best characterized of all membrane-bound polypeptides or proteins. In this review a brief summary is given of the occurrence, conformation, and synthesis of gramicidin A, and of its use as a model for ion transport and the interaction of proteins and lipids in biological membranes.

Gramicidin↗
PubMedDate not supplied

The ion channel switch biosensor.

A biosensor technology is described which provides a direct measurement for functional molecular interactions, at the surface of a tethered bilayer membrane, through the electrical transduction of chemically modified ion-channels. High sensitivity of analyte detection is achieved due to the large flux of ions transmitted through the ion channel. The biomimetic sensor surface allows the molecular recognition to be measured in complex biological matrices (such as blood and sera) without compromising sensitivity. We have used the sensor for activity and concentration measurements for a range of analytes, which include bacteria, DNA, proteins and drugs. We have a quantitative model for the biosensor performance which is described by three-dimensional molecular interactions with the membrane surface and two-dimensional molecular interactions within the tethered bilayer.

Biosensing Techniques↗