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Biomedical subjects

M Karplus

Publications and source records attributed to M Karplus.

At least 307 records · Page 17Linked to original sources
PubMed1972

Nuclear magnetic resonance determination of the angle psi in peptides.

A simple theoretical model is used to suggest that the NCCH coupling constant, Jnh, has a dihedral angle dependence that can serve for estimating the angle Psi in peptides. Some experimental comparisons are made to test the model; they include a new measurement of Jnh in N-acetylglycine.

Magnetic Resonance Spectroscopy↗
PubMed1971

Ring orientation in -ionone and retinals.

The ring orientation in beta-ionone, all-trans retinal, and 11-cis retinal, relative to that of the polyene chain, has been determined by means of semi-empirical calculations and magnetic resonance measurements of the nuclear Overhauser effect and long-range coupling constants. The experimental results yield a distorted s-cis conformation about the C(6)-C(7) "single bond", with the torsional angle in the range 30 degrees to 70 degrees . This agrees well with the semi-empirical potential function, which has a broad, rather flat minimum for angles from 40 degrees to 120 degrees . The temperature dependence of the NMR results provide confirmation for the form of the torsional potential.

Butanones↗
PubMedDate not supplied

Quantitative structure-activity relationship studies of progesterone receptor binding steroids.

The selection of appropriate descriptors is an important step in the successful formulation of quantitative structure-activity relationships (QSARs). This paper compares a number of feature selection routines and mapping methods that are in current use. They include forward stepping regression (FSR), genetic function approximation (GFA), generalized simulated annealing (GSA), and genetic neural network (GNN). On the basis of a data set of steroids of known in vitro binding affinity to the progsterone receptor, a number of QSAR models are constructed. A comparison of the predictive qualities for both training and test compounds demonstrates that the GNN protocol achieves the best results among the 2D QSAR that are considered. Analysis of the choice of descriptors by the GNN method shows that the results are consistent with established SARs on this series of compounds.

Neural Networks, Computer↗
PubMedDate not supplied

Effect of position changing on bilirubin levels during phototherapy.

OBJECTIVE: Turning of infants during phototherapy for hyperbilirubinemia is practiced in many nurseries. However, there is little research evidence in support of this practice. This study examined the effect of turning on serum total bilirubin concentration and on the duration of phototherapy. STUDY DESIGN: We first conducted a pilot study in term infants requiring phototherapy using transcutaneous bilirubinometry in order to determine the time required to clear the skin of bilirubin. This "blanching time" was found to be approximately 150 minutes. We then conducted a randomized study comparing turning the baby during phototherapy with care in the supine position only. RESULTS: Thirty term infants were enrolled in the study (turned - 14; supine - 16). No differences were found between the groups in baseline data, such as birth weight, gestational age, age at start of phototherapy, or type of feeds. Infants in the supine group showed a significantly larger drop in serum total bilirubin concentration and required a shorter duration of phototherapy. CONCLUSION: We conclude that infants should be nursed supine during phototherapy. Based on these results, we propose a modification to the traditional model of bilirubin kinetics during phototherapy.

Bilirubin↗
PubMedDate not supplied

Hemolytic disease of the newborn due to anti-PP1 P k (anti-Tj a).

A newborn infant of genotype P2p suffering from ABO-like hemolytic disease was born to a mother of the very rare genotype pp. The disease was severe enough to require exchange transfusions with pp blood. The mother and other members of the family with the same rare pp blood provided compatible donor blood for transfusions of the mother herself and for replacement transfusion of her affected infant. The mothers serum contained IgM molecules and also IgG molecules capable of crossing the placenta to induce a hemolytic process on the infant's red blood cells. The genotype of the P1 negative father was very likely P2P2 so that the genotype of the affected infant had to be P2p. A search of the literature revealed an earlier report from Japan in which the genotype of the P1 positive father was P1P2. As was to be expected the genotype of this affected infant was P2p.

Abortion, Spontaneous↗
PubMedDate not supplied

Solution conformations of human growth hormone releasing factor: comparison of the restrained molecular dynamics and distance geometry methods for a system without long-range distance data.

A series of three-dimensional structures of the 1-29 fragment of human growth hormone releasing factor in trifluoroethanol have been determined by molecular dynamics and distance geometry methods. The resulting structures satisfy information from nuclear Overhauser effect (NOE) distance data and an empirical potential energy function. Although the polypeptide was found to have an ordered structure in all simulations, the NOE data were not sufficient for global convergence to a unique three-dimensional geometry. Several satisfactory structures have been determined, all of which are extended conformations consisting of a short beta-strand and two alpha-helices (residues 6-13 and residues 16-29) connected by short segments of less well defined secondary structure. Because of the lack of NOE data connecting the helix segments, their relative orientation is not uniquely determined.

Growth Hormone-Releasing Hormone↗