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J E Jentoft

Publications and source records attributed to J E Jentoft.

28 records · Page 2Linked to original sources
PubMed1985

MOLECULAR DESIGNER: an interactive program for the display of protein structure on the IBM-PC.

A BASIC interactive graphics program has been developed for the IBM-PC which utilizes the graphics capabilities of that computer to display and manipulate protein structure from coordinates. Structures may be generated from typed files, or from Brookhaven National Laboratories' Protein Data Bank data tapes. Once displayed, images may be rotated, translated and expanded to any desired size. Figures may be viewed as ball-and-stick or space-filling models. Calculated multiple-point perspective may also be added to the display. Docking manipulations are possible since more than a single figure may be displayed and manipulated simultaneously. Further, stereo images and red/blue three-dimensional images may be generated using the accompanying DESIPLOT program and an HP-7475A plotter. A version of the program is also currently available for the Apple Macintosh. Full implementation on the Macintosh requires 512 K and at least one disk drive. Otherwise this version is essentially identical to the IBM-PC version described herein.

Computer Graphics↗
PubMed1983

31P NMR studies of energy metabolism in perfused rat kidney.

Conventional biochemical analyses have demonstrated significant alterations in high-energy phosphate metabolism during shock, but the time course of these changes cannot be followed in individual animals because these analyses are invasive and destructive. This study sought to evaluate the utility of 31P NMR as a means of following phosphorus metabolites under various conditions, including those designed to model the shocked state. Twenty adult albino rats were subject to a modified Wiggers' model of hemorrhagic shock lasting from 5 to 140 min. ATP was determined on extracts of the kidneys of each animal both by a biochemical assay and by integration of 31P NMR resonance signals. The equation for renal ATP content plotted versus time for enzymatically determined ATP was 1.79 - 0.0097x (r = 0.83, P less than 0.01) as compared to 1.76 - 0.0093x (r = 0.69, P less than 0.01) for NMR-determined ATP. Isolated, normal rat kidneys perfused with oxygenated, modified Krebs' solution while in the NMR spectrometer maintained normal ATP levels for several hours. ATP/ADP ratios were greater than those observed by conventional enzymatic analysis. Temporary anoxia, induced by substituting 100% N2 for 95% O2:5% CO2, resulted in decreases in ATP content, which reverted to normal with reinstitution of oxygenation. Intracellular pH changed in accordance with perfusate pH during anoxia. It is concluded that 31P NMR studies of the perfused rat kidney have immediate application for the nondestructive study of energy metabolism in shock and ischemia.

Adenosine Diphosphate↗
PubMed1983

Crystallocryoglobulinemia resulting from human monoclonal antibodies to albumin.

Two patients had a previously unrecognized form of crystallocryoglobulinemia. Their clinical presentations were similar, consisting of necrotizing vasculitis and purpura involving the legs. Analysis of each cryoglobulin complex showed that two components, albumin and a monoclonal IgG-lambda, were present, and both components were needed in a fixed ratio for precipitation. In addition, cryoprecipitation occurred in serum, but not plasma, due to citrate inhibition of complex formation. Our findings suggest that the monoclonal IgGs have the properties of antibodies directed specifically against a calcium-dependent antigenic site on human albumin, and that the resultant IgG-lambda-albumin immune complexes crystallized in the cold.

Adult↗
PubMed1982

Intramolecular interactions of amino groups in 13C reductively methylated hen egg-white lysozyme.

Reductive methylation of hen egg-white (HEW) lysozyme with [13C]formaldehyde and NaCNBH3 and subsequent 13C NMR spectroscopy reveal resonances for each of the mono- and dimethyl derivatives of the six lysyl epsilon-amino groups and the NH2 terminus. Each resonance has a unique chemical shift, pKa, and chemical shift change upon deprotonation. The assignment of the resonances arising from the N alpha,N-dimethyl and N alpha-monomethyl NH2 terminus has been made as have resonance assignments for the two lysyl residues which crystallographic studies indicate are involved in ion pair interactions (Imoto, T., Johnson, L. N., North, A. C. T., Phillips, D. C., and Rupley, J. A. (1972) in The Enzymes (Boyer, P. D., ed) 3rd Ed, Vol. 7, pp. 665-868, Academic Press, New York). One resonance, tentatively assigned to the lysine 1 (epsilon NH3+) which forms an ion pair with glutamic acid 7 (gamma COO-), has a highly perturbed chemical shift which shows a biphasic titration curve (N epsilon, N-dimethyl pKa values 10.0 and 2.6). A similar titration curve is observed for a N epsilon-monomethyl lysyl residue. The resonance for lysine 13 (epsilon NH3+), which forms an ion pair with the carboxyl terminus, leucine 129 (alpha COO-), has been assigned by removal of leucine 129 with carboxypeptidase whereupon only one pair of mono- and dimethyl lysyl resonances is greatly perturbed. The pKa of N epsilon,N-dimethyl lysine 13 is 9.3 in des-Arg-Leu-lysozyme in contrast to 9.8 for the intact enzyme. Thus, it appears that both of the intramolecular ion pairs predicted by x-ray crystallography exist in the solution structure of HEW lysozyme.

Amino Acids↗
PubMed1982

Characterization of a human cryoglobulin complex: a crystalline adduct of a monoclonal immunoglobulin G and albumin.

An unusual human cryoglobulin complex was characterized as a two-component system containing monoclonal immunoglobulin G (IgG) and serum albumin in a 1:2 mole ratio. This complex appeared to be an antibody-antigen complex, since the mole ratio was appropriate and the isolated Fab of the IgG associated with the albumin. The cryoglobulin apparently arose as a result of specific association and/or aggregation of the IgG albumin adduct, since the cryoglobulin complex formed a crystalline precipitate. The IgG and albumin were separated and characterized with respect to immunological cross-reactivities, sedimentation velocities, isoelectric properties, and amino acid composition. The extent of precipitation of the cryoglobulin complex was maximal at pH 7.8, was decreased by added ions including citrate, ethylenediaminetetraacetic acid, NaCl, and CaCl2, and was decreased by increasing temperature. Both the nature of the cold-precipitable complex and the solubility properties differed from those described for other cryoglobulins.

Antibodies, Monoclonal↗
PubMed1981

[13C]Methylated ribonuclease A. 13C NMR studies of the interaction of lysine 41 with active site ligands.

A unique resonance in the 13C NMR spectrum of [13C]methylated ribonuclease A has been assigned to a N epsilon, N-dimethylated active site residue, lysine 41. The chemical shift of this resonance was studied over the pH range 3 to 11, and the titration curve showed two inflection points, at pH 5.7 and 9.0. The higher pKa, designated pKa1, was assigned to the ionization of the lysyl residue itself while the pKa of 5.7, designated pKa2, was assigned on the basis of its pKa to the ionization of a histidyl residue which is somehow coupled to lysine 41. Both pKa values are measurably perturbed by the binding of active site ligands including nucleotides, nucleosides, phosphate, and sulfate. In most cases, the alterations in pKa values induced by the ligands were larger for pKa2. The ligand-induced perturbations in pKa2 generally paralleled those reported for histidine 12, another active site residue (Griffin, J. H., Schechter, A. N., and Cohen, J. S. (1973) Ann. N. Y. Acad. Sci. 222, 693-708). The sensitivity of the N epsilon, N-dimethylated lysine 41 resonance to the histidyl ionization may result from a conformational change in the active site region of ribonuclease which is coupled to the histidyl ionization. This coupling between lysine 41 and another ribonuclease residue, which has not been documented previously, offers new insight into the interrelationship between residues in the active site of this well characterized enzyme.

Animals↗
PubMed1977

Relaxation spectra of yeast hexokinases. Isomerization of the enzyme.

Yeast hexokinase isozymes P1 and P11 exhibit a pH dependent, rapid relaxation process at 15 degrees C at enzyme concentrations of 100-474 muM and over a pH range of 6-8. The process was detected by equilibrium temperature jump spectroscopy using the indicator probe phenol red. The value of 1/tau varies from about 6 ms-1 at pH 8 for both isozymes to 50 ms-1 for P1 and 85 ms-1 for P11 at pH 6. The data are consistent with a mechanism involving an enzyme isomerization coupled to an ionization. The forward rate constant for the isomerization of the proposed mechanism varies between 3 and 7 ms-1; the ratio of the reverse rate constant to the ionization Ka is between 0.5 and 2 X 10(11) M-1 S-1; the estimated pKa varies between 5.5 and 6.1. The ranges of values in rate constants and pKa represent variations observed between preparations of the same isozyme and between isozymes. The isomerization rate is at least 50 times faster than catalysis under all conditions and the pKa is lower than that controlling activity. The rate of isomerization is unchanged by addition of sugar and nucleotide ligands, but the amplitude of the process is perturbed. These data imply that isomerizing and ionizing forms are sensitive to events at the active site. These equilibria between forms of hexokinase are fast enough, and have the right properties, to be important to the mechanism and regulation of the enzyme.

Adenosine Triphosphate↗