Biomedical subjects

D E Palmer

Publications and source records attributed to D E Palmer.

2 recordsLinked to original sources

PubMed1989

Interactive NMR and computer simulation studies of lanthionine-ring structures.

We report progress in elucidating the structure of nisin, a naturally occurring peptide antibiotic. Nisin contains five rings constrained by lanthionine or methyllanthionine bridges, as well as alpha, beta-unsaturated amino acids. We have determined conformations for two model compounds of ring A and a derivative of ring B through interactive nmr and computer simulation studies. High-resolution nmr techniques provides structural information, which was further refined through molecular dynamics simulations. These methods are being applied to the remaining constrained fragments of the molecule. This conformational information will be employed in an aufbau approach to determining the structure of the entire molecule.

Alanine↗

PubMed1987

Diagnostic levels of ultrasound may disrupt myelination.

Neonatal rats 3 to 5 days of age were exposed to the ultrasound beam from a medical ultrasound imaging system. Dorsal nerve roots were examined by electron microscopy. Comparison between exposed and sham-exposed controls revealed disruption of the nodes of Ranvier attributable to ultrasound. Morphologic changes ranged from vacuole formation in the paranodal region to frank demyelination and were still evident after 24 h of recovery. Rats of this age are at a stage of myelination similar to that of a human fetus 4 to 5 months. The ultrasound intensities used in this study are consistent with those used for human imaging (SPTA 0.135 mW/cm2, SATA 0.045 mW/cm2, SPTP 8.7 W/cm2, SPPA 1.9 W/cm2), but the relevance of these findings to clinical ultrasound will require further study.

Animals↗