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At least 55 records · Page 3Linked to original sources
PubMed1989

[The effect of water content on wear of Bis.GMA-Tri.EDMA based composite resins].

The wear properties of Bis.GMA-Tri.EDMA based composite resins to an Ag-Pd-Cu-Au alloy examined, using a trial sliding frictional wear testing machine, and the effects of water in a specimen on wearing characteristics were discussed. The water absorbed into the specimens softened the surface of the material and decreased the wear-resistant properties of them. On the other hand, the increase of Bis.GMA content improved slightly the wear characteristics. In the range of 60-76 wt% filler content, the wear of experimental composite resin decreased according to increase of filler content. In the case of 50 wt% filler content resins, however, the wear of experimental composite resins was significantly less than in the other cases. There was high negative correlation between wear rate and Vicker's hardness of experimental composite resins (r = -0.84). In addition, there was high correlation between wear rate and amount of absorbed water in the specimens of 76 wt% filler (r = 0.92).

Bisphenol A-Glycidyl Methacrylate↗
PubMed1979

DNA base compositions and photoreactivation capabilities of six Hansenula species.

The DNA base compositions and photoreactivable sectors of six species of Hansenula were determined. The G+C ratios revealed two groups; the first had values of 38 to 44% and the second had lower values of 32-36%. Hansenula muscicola could not repair the UV-induced damage; whereas, H. dryadoides, H. lynferdii, H. ofunaensis, H. philodendra, and H. syndowiorum could do so.

Ascomycota↗
PubMed1973

Minor base composition of "70S-associated" 4S RNA from avian myeloblastosis virus.

Using a chemical isotope derivative method, we have determined the minor base composition of the "70S-associated" 4S RNA isolated from avian myeloblastosis virus. The minor base composition of this "70S-associated" 4S RNA is strikingly similar to that of the corresponding "free" 4S RNA of the virion. This minor base content, plus the capacity to esterify amino acids, establishes that both of these virion 4S RNA fractions contain transfer RNA. The percentage of minor bases in virion "70S-associated" 4S RNA is, however, much lower than in "free" 4S virion RNA and in myeloblast 4S RNA. The implication is that the "70S-associated" 4S RNA fraction as isolated herein also contains RNA that is not transfer RNA. This latter RNA may represent either degradation products of high molecular weight RNA or indigenous 4S RNA of undetermined function.

Animals↗
PubMed1990

Chloroplast genes transferred to the nuclear plant genome have adjusted to nuclear base composition and codon usage.

During plant evolution, some plastid genes have been moved to the nuclear genome. These transferred genes are now correctly expressed in the nucleus, their products being transported into the chloroplast. We compared the base compositions, the distributions of some dinucleotides and codon usages of transferred, nuclear and chloroplast genes in two dicots and two monocots plant species. Our results indicate that transferred genes have adjusted to nuclear base composition and codon usage, being now more similar to the nuclear genes than to the chloroplast ones in every species analyzed.

Base Composition↗
PubMed1966

Deoxyribonucleic acid base composition of some members of the Micrococcaceae.

Auletta, Angela E. (Catholic University, Washington, D.C.), and E. R. Kennedy. Deoxyribonucleic acid base composition of some members of the Micrococcaceae. J. Bacteriol. 92:28-34. 1966.-Thirty-seven strains from the genera Micrococcus, Staphylococcus, Gaffkya, and Sarcina were examined for deoxyribonucleic acid base composition and biochemical activity. Organisms were tested for production of catalase, coagulase, deoxyribonuclease, oxidase, phosphatase, hydrogen sulfide, indole, and acetoin; nitrate reduction; gelatin, starch, and urea hydrolysis; citrate and ammonium phosphate utilization; NaCl tolerance; growth at 10 and 45 C, and growth in litmus milk. They were tested for production of acid from dextrose and mannitol under anaerobic conditions, and for aerobic production of acid from dextrose, mannitol, lactose, sucrose, raffinose, maltose, xylose, and glycerol. Organisms could be divided into two groups on the basis of guanine-cytosine (GC) content. Group I had an average GC content of 32%, and included all organisms which produced acid from dextrose. Group II had an average GC content of 62%, and included those organisms incapable of producing acid from dextrose under anaerobic conditions. Sarcina ureae had a GC content of 43%.

Carbohydrate Metabolism↗
PubMed1988

Effect of base composition at the center of inverted repeated DNA sequences on cruciform transitions in DNA.

We have analyzed the effect of base composition at the center of symmetry of inverted repeated DNA sequences on cruciform transitions in supercoiled DNA. For this we have constructed two series of palindromic DNA sequences: one set with differing center and one set with differing center and arm sequences. The F series consists of two 96-base pair perfect inverted repeats which are identical except for the central 10 base pairs which consist of pure AT or GC base pairs. The S series was constructed such that the overall base composition of the inverted repeats was identical but in which the positioning of blocks of AT- and GC-rich sequences varied. The rate of cruciform formation for the inverted repeats in plasmid pUC8 was dramatically influenced by the 8-10 base pairs at the center of the inverted repeat. Inverted repeats with 8-10 AT base pairs in the center were kinetically much more active in cruciform formation than inverted repeats with 8-10 GC base pairs in the center. These experiments show a dominant influence of the center sequences of inverted repeats on the rate of cruciform formation.

Base Sequence↗
PubMed1977

Base composition of DNA from some reptiles.

The DNA base composition was studied in 9 reptilian species (4 chelonians, 3 saurians, and 2 ophidians) by the thermal denaturation method. This preliminary investigation has brought to light differences in GC percentages and in the shape of melting curves between chelonian DNA and that from saurians and ophidians.

Animals↗
PubMed1968

Deoxyribonucleic acid base composition of the genus Lactobacillus.

Deoxyribonucleic acids of 45 strains of Lactobacillus and 5 strains of Bifidobacterium which had been analyzed for base composition by chromatographic means were examined at equilibrium in a CsCl density gradient. Regression analysis showed that there have been systematic errors involved in the estimation of guanine plus cytosine (GC) content by the chemical method, and that the relation between buoyant density and base composition is indeed linear and best fitted by the equation GC = 10.309 (rho-1.662), which compares well in slope with the equation of Schildkraut, Marmur, and Doty. With the improved data obtained in this study, the specific groupings of the species of both genera were reevaluated.

Centrifugation, Density Gradient↗
PubMed1990

Dependence of the torsional rigidity of DNA on base composition.

The Escherichia coli phage 434 repressor binds as a dimer to the operator of the DNA helix. Although the centre of the operator is not in contact with protein, the repressor binding affinity can be reduced at least 50-fold by changing the sequence there: operators with A.T base pairs near their centre bind the repressor more strongly than do operators with G.C base pairs at the same positions. To explain these observations, it has been proposed that the base composition at the centre of the operator affects the affinity of the operator for repressor by altering the ease with which operator DNA can undergo the torsional deformation necessary for complex formation. In this model, the variation in binding affinity would require the torsion constant to have specific values and to change in a sequence-dependent manner. We have now measured torsion constants for DNAs with widely different base compositions. Our results indicate that the torsion constants depend only slightly on the overall composition, and firmly delimit the range of values for each. Even the upper-limit values are much too small to account for the observed changes in affinity of the 434 repressor. These results rule out simple models that rely on substantial generic differences in torsion constant between A.T-rich sequences and G.C-rich sequences, although they do not rule out the possibility of particular sequences having abnormal torsion constants.

Base Composition↗
PubMed1975

Studies on the species, amount and base composition of nucleic acids in psoriatic scales and normal horny layer.

The amount of RNA as well as DNA is considerably increased in psoriatic scales as compared with normal horny layer; RNA was characterized as a low-molecular tRNA; as concerns the base composition of DNA, no particularities in comparison with other DNA species were found, and the base composition of tRNA revealed that cytosine and guanosine are in excess; pseudouridine could not be detected in psoriatic tRNA.

Adolescent↗
PubMed1987

Repair of a mismatch is influenced by the base composition of the surrounding nucleotide sequence.

Heteroduplexes with single base pair mismatches of known sequence were prepared by annealing separated strands of bacteriophage lambda DNA and used to transfect Escherichia coli. A series of transition (G:T and A:C) and transversion (G:A and C:T) mismatches located throughout most of the bacteriophage lambda cI gene has been examined. The results suggest that the transition mismatches are generally better repaired than the transversion mismatches and that, at least for the transversion mismatches studied, repair efficiency increases with increasing G:C content in the neighboring nucleotide sequence. This specificity of the E. coli mismatch repair system can account, in part, for the similar frequencies of base substitution mutations throughout the E. coli genome.

Bacteriophage lambda↗
PubMed1971

Quantitative aspects of deoxyribonucleic acid renaturation: base composition, state of chromosome replication, and polynucleotide homologies.

The base composition of a deoxyribonucleic acid (DNA) sample affects its intrinsic rate of renaturation. In agreement with the information of Wetmur and Davidson, it was established that high guanosine plus cytosine (GC) DNA renatures faster than expected from analytical measurement of its molecular weight. A calculated correction factor of 1.8% of the observed C(0)t(.5) is required for every mole per cent GC difference from 51% GC. The correction factor is now established in the range of 32 to 65% GC. Renaturation of DNA mixtures prepared from pairs of organisms has been studied. When no similarity existed between the two organisms, the observed C(0)t(.5) of the mixture was the sum of the independently determined C(0)t(.5) values. Lack of additivity was correlated with similarities in polynucleotide sequence of the reassociating DNA molecules. A quantitative relationship was formulated to relate C(0)t(.5) values of renatured DNA mixtures to per cent binding ("homology"). Finally, it was demonstrated that DNA prepared from log-phase cells renatures faster than stationary-phase DNA and also departs from theoretical second-order kinetics.

Autoradiography↗
PubMed1991

Numerical analysis and DNA base compositions of some thermophilic Bacillus species.

Morphological, physiological, and biochemical characteristics and the DNA base compositions of 133 thermophilic Bacillus strains were determined. A total of 54 of these strains were received as identified species (mainly Bacillus stearothermophilus, Bacillus coagulans, Bacillus brevis, and Bacillus licheniformis) from international culture collections, and 79 newly isolated strains, which were isolated mainly from sugar diffusion juices of Italian plants, were also examined. Numerical taxonomy techniques (simple matching coefficient and unweight pair grouping using the mathematical average) and DNA G + C values showed that the strains aggregated into nine clusters. Both B. licheniformis and B. brevis were well separated from the other organisms. B. stearothermophilus and B. coagulans were confirmed as separate clusters and exhibited greater heterogeneity than previously shown. The B. stearothermophilus strains clustered into four groups, three of which have been recognized previously by other authors; the members of the fourth group had distinctive characteristics, including considerable biochemical inertness, an inability to grow at temperatures greater than 60 degrees C, and a high G + C content. Within the B. coagulans cluster the strains with characteristics very similar to those of the new species Bacillus smithii clustered together. However, the remaining strains were still clearly separated into two groups; one of these groups was considered B. coagulans sensu stricto, and the other was distinguished by morphological and biochemical criteria, such as spores which do not swell the sporangia, utilization of citrate, a higher proteolytic activity, and acidification of some carbohydrates. Our results were confirmed by comparing them with distinctive characteristics of recently described thermophilic Bacillus species.

Aerobiosis↗
PubMed1974

Characterization of ribonucleic acids from the venom glands of Crotalus durissus terrifucus (Ophidia, Reptilia) after manual extraction of the venom. Studies on template activity and base composition.

RNA synthesis in the venom glands of Crotalus durissus terrificus was stimulated by the manual extraction of the venom (milking). RNA was extracted from venom glands activated by milking and fractionated by centrifugation through sucrose density gradients. Template activity for protein synthesis and base composition of the RNA fractions were studied. RNA fractions that sediment between 18S and 4S had the highest template activity. The base composition analysis indicated that the 28S and 18S rRNA have a C+G content of 65.4 and 58% respectively. The ;melting' temperature (T(m)) of DNA in 0.15m-NaCl-0.015m-trisodium citrate, pH7.0, was 85 degrees C, corresponding to a C+G content of 38%. The base ratio of the RNA fractions that showed a high template activity was intermediate between that of rRNA and homologous DNA. The possible role of these fractions in the synthesis of the two main toxins (crotoxin and crotamine) of the South American rattlesnake's venom is discussed.

Animals↗
PubMed1976

Cardiac and skeletal muscle acid-base composition during metabolic acidosis in dogs.

Nephrectomized, open chested dogs were infused with 25-30 ml.kg(-1) body weight of 0.15 M NaCl (group I), 0.15 MHCl (Group II) or 0.3 M lactic acid (Group) III). Pulmonary ventilation was maintained constant in the three groups. Intracellular pH was calculated with the CO2 method. No significant intracellular or extracellular acid-base changes were produced in Group I. A similar degree of extracellular acidosis was achieved in Groups II and III. In spite of constant arterial PCO2, the PCO2 of mixed, coronary sinus and femoral vanous blood increased moderately after the infusion in Groups II and III. It was calculated that less than half of the HCl acid infused remained in the extracellular space. However, no significant changes were observed in the acid-base composition of skeletal muscle in either Group II or III. Comparison of the cardiac muscle cell acid-base composition of Group I with that of Groups II and III whows that metabolic acidosis of the degree and duration produced in these experiments does not produce appreciable myocardial acidosis.

Acid-Base Equilibrium↗