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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

The effect of synthetic homopolymer poly I:C on the synthesis of nucleic acids, protein and interferon in spleen cells normally and with radiation

A comparative study is reported of the effect of the synthetic homopolymer poly I:C and Newcastle Disease virus on the synthesis of RNA, DNA, total protein and interferon in the spleen of nonradiated and radiated mice. In radiated animals, poly I:C and NDV had no stimulating effect on the synthesis of RNA; administration of both inducers to radiated mice did not significantly affect the content of lymphoid cellular elements in the spleen. However, while reduction of RNA synthesis, caused by radiation, also increases slightly under the effect of poly I:C and the virus, the synthesis of interferon in spleen cells and in the entire body is activated.

Antropova, Y. N.↗
NASA NTRS1976

Electrophoretic separation of proteins in space

Commercially available and synthetic wide range and short range ampholytes used in the isoelectric focusing of proteins was analyzed by ion exchange chromatography. A pH gradient over the pH range 3.8 to 11.0 was used to elute the ampholytes from a column of a sulfonated polystyrene resin. The wide range ampholytes were resolved into some 60 to 70 ninhydrin positive components. The recovery obtained with the method was quantitative. Acid short range ampholytes have approximately 35 components which elute readily from the ion exchange resin. Basic short range ampholytes gave about 50 components, most of which eluted at alkaline pH.

Brown, R. K.↗
NASA NTRS1977

Determination of the D and L isomers of some protein amino acids present in soils

The D and L isomers of some protein amino acids present in soils were measured by using a gas chromatographic technique. The results of two processing procedures were compared to determine the better method. Results of the comparison indicated that the determination of D and L percentages requires amino acid purification if one is to obtain accurate data. It was found that very significant amounts of D-alanine, D-aspartic acid, and D-glutamic acid were present in the contemporary soils studied. Valine, isoleucine, leucine, proline, and phenylalanine generally contained only a trace to very small amounts of the D isomer. It is probable that the D-amino acids from the alanine, aspartic, and glutamic acids are contributed to the soil primarily via microorganisms. The finding of very significant quantities of some D-amino acids (about 5-16%) in present-day soils may alert some investigators of geological sediments to a possible problem in using amino acid racemization as an age-dating technique.

Pollock, G. E.↗
NASA NTRS1979

Effects of gravity on contractile proteins

A method was established for the isolation and purification of nuclei in high yield from the microplasmodia of Physarum flavicomum. Purified nuclei were resistant to breakage by methods commonly employed for isolated plant and animal nuclei. Several methods for the extraction of nuclear protein were compared. Incubation of nuclear lysates with either 2 M NaCl, with or without 5 M urea, or 1 M CaCl2 resulted in the extraction of nuclear action together with histones. The histones were chemically fractionated into the 5 basic groups common to other eucaryotic tissue. Amino acid analyses of the total histone were also performed. Nuclear actin was found to have a molecular weight of 41,000 ? 4,000 daltons as determined by SDS polyacrylamide gel electrophoresis. The amino acid composition of the nuclear action was established.

Henney, H. R., Jr.↗
NASA NTRS1978

Polyglutaraldehyde - A new reagent for coupling proteins to microspheres and for labeling cell-surface receptors

Glutaraldehyde polymerized in basic aqueous solutions was found to react with low molecular weight amines, immunoglobulins and hemoglobin. The polyglutaraldehyde was covalently bound to hydrophilic microspheres. The rate of addition of proteins to the polyglutaraldehyde-derivatized microspheres was investigated spectrophotometrically as a function of pH and temperature. The reaction of polyglutaraldehyde was found to be faster than that of the monomer. The findings led to successful labeling of human lymphocyte subpopulations.

Rembaum, A.↗
NASA NTRS1980

Effect of hyperbaric oxygenation on carbohydrate metabolism protein synthesis in the myocardium during sustained hypodynamia

Glycolysis and the intensity of protein synthesis were studied in 140 white male rats in subcellular fractions of the myocardium during 45 day hypodynamia and hyperbaric oxygenation. Hypodynamia increased: (1) the amount of lactic acids; (2) the amount of pyruvic acid; (3) the lactate/pyruvate coefficient; and (4) the activities of aldolase and lactate dehydrogenase. Hyperbaric oxygenation was found to have a favorable metabolic effect on the animals with hypodynamia.

Makarov, G. A.↗
NASA NTRS1980

Displacement of plasma protein and conduction velocity in rats under action of acceleration forces and hypokinesia

The permeability of capillary vessels was investigated in order to determine if acceleration alone or following prolonged hypokinesia would induce changes in the vascular wall leading to the penetration by l-albumins and/or proteins with larger molecules. In rats undergoing action of +5 Gz accelerations, no increase in vascular permeability, as tested with the use of (Cr-5k)-globulin, was demostrated. In rats immobilized for 4 weeks before centrifugation, rather weak migration of (Cr-51)-globulin from the vessels was observed. Immobilization resulted also in lowering of conduction velocity in the sciatic nerve.

Baranski, S.↗
NASA NTRS1980

Effect of restricted mobility on RNA content and nucleotide composition and on protein content in motoneurons of spinal cord anterior horns

An investigation into the effect of hypokinesia on the ribonucleic acid (RNA) content, the nucleotide composition, and dynamics of protein content in the motoneuron of the rat spinal cord anterior horns is described. Methodology and findings are presented. The study results showed that the nucleotide composition of the total cellular RNA at all the studied periods of hypokinesia remained unchanged and is characteristic for the cytoplasmic, high polymer ribosomal RNA. This means that with a change in the functional state of the neuron the newly formed RNA of the nerve cell has the same composition of bases as the original RNA that belongs to the ribosomal type.

Gorbunova, A. V.↗
NASA NTRS1980

Studies of the chemical basis of the origin of protein synthesis Initiation and direction of peptide growth

The data presented in this paper show that the ease of nonenzymatic activation of carboxylic acids by ATP at pH 5 varies directly with the pKa of the carboxyl group, and is consistent with the idea that it is the protonated form of the carboxyl group which participates in the activation reaction. Consequently, since most N-blocked amino acids have higher pKas than do their unblocked forms, they are activated more readily, and it has been demonstrated that this principle applies to peptides as well, which are activated more rapidly than single amino acids. It is proposed that this fact may be partly responsible for the origin of two important features still observed in contemporary protein synthesis: (1) initiation in prokaryotes is accomplished with an N-blocked amino acid, and (2) elongation in all living systems occurs at the carboxyl end of the growing peptide.

Mullins, D. W., Jr.↗
NASA NTRS1980

Modelling of DNA-protein recognition

Computer model-building procedures using stereochemical principles together with theoretical energy calculations appear to be, at this stage, the most promising route toward the elucidation of DNA-protein binding schemes and recognition principles. A review of models and bonding principles is conducted and approaches to modeling are considered, taking into account possible di-hydrogen-bonding schemes between a peptide and a base (or a base pair) of a double-stranded nucleic acid in the major groove, aspects of computer graphic modeling, and a search for isogeometric helices. The energetics of recognition complexes is discussed and several models for peptide DNA recognition are presented.

Rein, R.↗
NASA NTRS1981

The chemical basis for the origin of the genetic code and the process of protein synthesis

The principles upon which the process of protein synthesis and the genetic code were established are elucidated. Extensive work on nuclear magnetic resonance studies of both monomermonomer and monoamino acid polynucleotide interactions is included. A new method of general utility for studying any amino acid interacting with any polynucleotide was developed. This system involves the use of methyl esters of amino acids interacting with polynucleotides.

Source record↗
NASA NTRS1982

The chemical basis for the origin of the genetic code and the process of protein synthesis

The major thrust is to understand just how the process of protein synthesis, including that very important aspect, genetic coding, came to be. Two aspects of the problem: the chemistry of active aminoacyl species; and affinities between amino acids and nucleotides, and specifically, how these affinities might affect the chemistry between the two are stressed.

Source record↗
NASA NTRS1984

Computer simulation of protein systems

Ligand binding to dihydrofolate reductase (DHFR) is discussed. This is an extremely important enzyme, as it is the target of several drugs (inhibitors) which are used clinically as antibacterials, antiprotozoals and in cancer chemotherapy. DHFR catalyzes the NADPH (reduced nicotinamide adenine dinucleotide phosphate) dependent reduction of dihydrofolate to tetrahydrofolate, which is used in several pathways of purine and pyrimidine iosynthesis, including that of thymidylate. Since DNA synthesis is dependent on a continuing supply of thymidylate, a blockade of DHFR resulting in a depletion of thymidylate can lead to the cessation of growth of a rapidly proliferating cell line. DHFR exhibits a significant species to species variability in its sensitivity to various inhibitors. For example, trimethoprim, an inhibitor of DHFR, binds to bacterial DHFR's 5 orders of magnitude greater than to vertebrate DHFR's. The structural mechanics, dynamics and energetics of a family of dihydrofolate reductases are studied to rationalize the basis for the inhibitor of these enyzmes and to understand the molecular basis of the difference in the binding constants between the species. This involves investigating the conformational changes induced in the protein on binding the ligand, the internal strain imposed by the enzyme on the ligand, the restriction of fluctuations in atom positions due to binding and the consequent change in entropy.

Osguthorpe, D. J.↗
NASA NTRS1983

Evolutionary connections of biological kingdoms based on protein and nucleic acid sequence evidence

Prokaryotic and eukaryotic evolutionary trees are developed from protein and nucleic-acid sequences by the methods of numerical taxonomy. Trees are presented for bacterial ferredoxins, 5S ribosomal RNA, c-type cytochromes , cytochromes c2 and c', and 5.8S ribosomal RNA; the implications for early evolution are discussed; and a composite tree showing the branching of the anaerobes, aerobes, archaebacteria, and eukaryotes is shown. Single lines are found for all oxygen-evolving photosynthetic forms and for the salt-loving and high-temperature forms of archaebacteria. It is argued that the eukaryote mitochondria, chloroplasts, and cytoplasmic host material are descended from free-living prokaryotes that formed symbiotic associations, with more than one symbiotic event involved in the evolution of each organelle.

Dayhoff, M. O.↗
NASA NTRS1985

Isolation of Hybridomas for Golgi-associated Proteins and a Plant Calmodulin

The demonstration of a role for calcium in the mechanism of the gravitropic response indicates a role for calmodulin. Localization studies indicate that plant cell walls have a high content of calmodulin which suggests a regulatory role for CaM in both gravitropic curvature and auxin-induced growth. Auxin regulation of cell wall loosening and elongation is the basis for most models of this phenomenon. Auxin treatment of pea stem tissue rapidly increases the ctivity of Golgi-localized B-1,4-glucan synthase (GS), an enzyme involved in biosynthesis of wall xyloglucan which apparently constitutes the substrate for the wall loosening process. In order to determine whether auxin stimulates GS activity either by modulation of existing enzyme or induces de novo formation of Golgi glucan synthase, a study was undertaken to isolate and quantitate glucan synthase. This enzyme appears to be an integral protein of the Golgi membrane and has resisted isolation with retention of activity. The production of monoclonal antibody for glucan synthase was undertaken due to the inability to isolate GS by standard detergent/liposome techniques.

Kuzmanoff, K. M.↗
NASA NTRS1985

Protein crystal growth results from shuttle flight 51-F

The protein crystal growth (PCG) experiments run on 51-F were analyzed. It was found that: (1) sample stability is increased over that observed during the experiments on flight 51-D; (2) the dialysis experiments produced lysozyme crystals that were significantly larger than those obtained in our identical ground-based studies; (3) temperature fluctuations apparently caused problems during the crystallization experiments on 51-F; (4) it is indicated that teflon tape stabilizes droplets on the syringe tips; (5) samples survived during the reentry and landing in glass tips that were not stoppered with plungers; (6) from the ground-based studies, it was expected that equilibration should be complete within 2 to 4 days for all of these vapor-diffusion experiments, thus it appears that the vapor diffusion rates are somewhat slower under microgravity conditions; (7) drop tethering was highly successful, all four of the tethered drops were stable, even though they contained MPD solutions; (8) the PCG experiments on 51-F were done to assess the hardware and experimental procedures that are developed for future flights, when temperature control will be available. Lysozyme crystals obtained by microdialysis are considerably larger than those obtained on the ground, using the identical apparatus and procedures.

Bugg, C. E.↗