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Biomedical subjects

M Karplus

Publications and source records attributed to M Karplus.

At least 271 records · Page 15Linked to original sources
PubMed1981

Cesarean section--a review of two annual periods separated by a ten-year interval.

In the Soroka Medical Center in Beer-Sheba during the two annual periods 1969 and 1979, 693 cesarean sections were performed, of which 633 are presented. The main reasons for the rise in cesarean section rate from 2.6% in 1969 to 8.0% in 1979 were evaluated. Cesarean sections were performed more often for fetal indications during 1979 than in 1969, reflecting the change in our approach to the management of the fetus at risk. The increase in the cesarean section rate was concomitant with a drop in the perinatal mortality from 23/1000 in 1969 to 13.1/1000 in 1979.

Breech Presentation↗
PubMed1980

Internal mobility of ferrocytochrome c.

In the refinement of the X-ray diffraction structures of molecules, it is conventional to introduce atomic 'temperature factors' of the Debye-Waller form to characterize the widths of the electron density peaks corresponding to the atoms. Although these factors are known to include a variety of contributions other than thermal fluctuations of the atomic positions, recent progress in the refinement of protein structures has led to inferences concerning atomic mobilities from the temperature factor data for several proteins. Atomic position fluctuations can be calculated independently by the molecular dynamics method, in which the classical equations of motion for the atoms of an equilibrated protein are solved on a computer. We now show that the X-ray diffraction and dynamical simulation methods yield similar pictures of the atomic mobility in tuna ferrocytochrome c.

Animals↗
PubMed1980

A conformational isomer of bovine pancreatic trypsin inhibitor protein produced by refolding.

Refolding of the bovine pancreatic trypsin inhibitor protein (BPTI) after reduction of its three cysteine disulphide linkages can occur when the reduced protein is placed in a suitable oxidizing medium (ref. 1 and refs therein). The refolding process has been studied by trapping chemically intermediates which contain only one or two disulphide bonds (ref. 1 and refs therein). We report here that during structural studies of these intermediates by NMR, we have found that complete re-oxidation of the protein results in substantial quantities of a metastable folded species which is identical to native BPTI in its covalent bonding (including the disulphide bonds) but possesses a somewhat different conformation. The existence of such a species is supported by circular dichroism measurements on refolded BPTI. This novel form of BPTI is of considerable interest because it can be used to provide information about the folding mechanism and conformational stability of the protein.

Animals↗
PubMed1980

Malformation syndrome associated with small extra chromosome.

We report an infant with a previously apparently unreported lethal malformation syndrome concentrated primarily on the left half of the body, but including midline defects such as meningomyelocele, cleft lip and cleft palate, and imperforate anus. The infant also had a small extra metacentric chromosome in 60% of lymphocytes. It is postulated that the small extra chromosome (whose origin remains unknown) caused the infant's condition, and that its asymmetry is compatible with an uneven distribution of the normal and aneuploid cell lines in the two halves of the body during critical phases of prenatal development.

Abnormalities, Multiple↗
PubMed1980

Internal dynamics of proteins. Short time and long time motions of aromatic sidechains in PTI.

Theoretical approaches to the internal dynamics of proteins are outlined and illustrated by application to the aromatic sidechain motions of tyrosines in the bovine pancreatic trypsin inhibitor. High frequency torsional oscillations are obtained from a molecular dynamics simulation, while the longer time ring rotations are analyzed by use of adiabatic energy minimization and special transition-state trajectory techniques.

Animals↗
PubMed1979

Side-chain torsional potentials: effect of dipeptide, protein, and solvent environment.

Side-chain torsional potentials in the bovine pancreatic trypsin inhibitor are calculated from empirical energy functions by use of the known X-ray structure of the protein and the rigid-geometry mapping technique. The potentials are analyzed to determine the roles and relative importance of contributions from the dipeptide backbone, the protein, and the crystalline environment of solvent and other protein molecules. The structural characteristics of the side chains determine two major patterns of energy surfaces, E(X1,X2): a gamma-branched pattern and a pattern for longer, straight side chains (Arg, Lys, Glu, and Met). Most of the dipeptide potential curves and surfaces have a local minimum corresponding to the side-chain torsional angles in the X-ray structure. Addition of the protein forces sharpens and/or selects from these minima, providing very good agreement with the experimental conformation for most side chains at the surface or in the core of the protein. Inclusion of the crystalline environment produces still better results, especially for the side chains extending away from the protein. The results are discussed in terms of the details of the interactions due to the surrounding, calculated solvent-accessibility figures and the temperature factors derived from the crystallographic refinement of the pancreatic trypsin inhibitor.

Animals↗