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Minor Deviations (minor + deviation)
Kinds of Minor Deviations Selected AbstractsStructural analysis of an "open" form of PBP1B from Streptococcus pneumoniaePROTEIN SCIENCE, Issue 7 2006Andrew L. Lovering Abstract The class A PBP1b from Streptococcus pneumoniae is responsible for glycosyltransferase and transpeptidase (TP) reactions, forming the peptidoglycan of the bacterial cell wall. The enzyme has been produced in a stable, soluble form and undergoes time-dependent proteolysis to leave an intact TP domain. Crystals of this TP domain were obtained, diffracting to 2.2 Ĺ resolution, and the structure was solved by using molecular replacement. Analysis of the structure revealed an "open" active site, with important conformational differences to the previously determined "closed" apoenzyme. The active-site nucleophile, Ser460, is in an orientation that allows for acylation by ,-lactams. Consistent with the productive conformation of the conserved active-site catalytic residues, adjacent loops show only minor deviation from those of known acyl-enzyme structures. These findings are discussed in the context of enzyme functionality and the possible conformational sampling of PBP1b between active and inactive states. [source] Development of the pelvis and posterior part of the vertebral column in the AnuraJOURNAL OF ANATOMY, Issue 1 2005Hana Ro, ková Abstract The anuran pelvic girdle is unique among all amphibians in that its acetabular portion is located far posterior to the sacrum, lateral to the postsacral (= caudal) vertebral column, which is reduced to a single rod-like element called the urostyle. This situation in the adult is strikingly different not only from that in ancestral temnospondyls but also in other modern amphibians. Because there is no fossil that would document this evolutionary anatomical modification except for Triadobatrachus, the only data may be inferred from development in modern anurans. We chose seven anuran species (belonging to the genera Discoglossus, Bombina, Pelobates, Bufo, Rana and Xenopus), representing the principal locomotory types (saltation, swimming, crawling and burrowing). Development of the pelvic girdle was studied on cleared and stained whole mounts and partly on serial histological sections. The basic developmental pattern was similar in all species: the pelvis on both sides develops from two centres (puboischiadic and iliac, respectively). The ilium then extends vertically towards the sacral vertebra and later rotates posteriorly so that ultimately the acetabulum is lateral to the tail (= urostyle). Only minor deviations from this pattern were found, mainly associated with differences in water and terrestrial dwelling. [source] Comparative analysis of the within-population genetic structure in wild cherry (Prunus avium L.) at the self-incompatibility locus and nuclear microsatellitesMOLECULAR ECOLOGY, Issue 11 2006SILVIO SCHUELER Abstract Gametophytic self-incompatibility (SI) systems in plants exhibit high polymorphism at the SI controlling S -locus because individuals with rare alleles have a higher probability to successfully pollinate other plants than individuals with more frequent alleles. This process, referred to as frequency-dependent selection, is expected to shape number, frequency distribution, and spatial distribution of self-incompatibility alleles in natural populations. We investigated the genetic diversity and the spatial genetic structure within a Prunus avium population at two contrasting gene loci: nuclear microsatellites and the S -locus. The S -locus revealed a higher diversity (15 alleles) than the eight microsatellites (4,12 alleles). Although the frequency distribution of S -alleles differed significantly from the expected equal distribution, the S -locus showed a higher evenness than the microsatellites (Shannon's evenness index for the S -locus: E = 0.91; for the microsatellites: E = 0.48,0.83). Also, highly significant deviations from neutrality were found for the S -locus whereas only minor deviations were found for two of eight microsatellites. A comparison of the frequency distribution of S -alleles in three age-cohorts revealed no significant differences, suggesting that different levels of selection acting on the S -locus or on S- linked sites might also affect the distribution and dynamics of S -alleles. Autocorrelation analysis revealed a weak but significant spatial genetic structure for the multilocus average of the microsatellites and for the S -locus, but could not ascertain differences in the extent of spatial genetic structure between these locus types. An indirect estimate of gene dispersal, which was obtained to explain this spatial genetic pattern, indicated high levels of gene dispersal within our population (,g = 106 m). This high gene dispersal, which may be partly due to the self-incompatibility system itself, aids the effective gene flow of the microsatellites, thereby decreasing the contrast between the neutral microsatellites and the S -locus. [source] Hiding cusps in cores: kinematics of disc galaxies in triaxial dark matter haloesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, Issue 3 2006Eric Hayashi ABSTRACT We study the kinematics of gaseous discs in triaxial dark matter haloes using the closed-loop orbit solutions in non-axisymmetric potentials. The orbits are in general non-circular and, for a given triaxiality, their ellipticity depends on the ratio of escape to circular velocities, V2esc/V2c. This ratio increases steeply towards the centre for cold dark matter (CDM) halo density profiles, implying that even minor deviations from spherical symmetry may induce large deviations from circular orbits in the velocity field of a gaseous disc, especially near the centre. This result suggests that caution should be exercised when interpreting constraints on the presence of density cusps in the dark halo derived from the innermost velocity profile. Simulated long-slit rotation curves vary greatly in shape, depending primarily on the viewing angle of the disc and on its orientation relative to the principal axes of the potential. ,Solid-body' rotation curves , typically interpreted as a signature of a constant density core in the dark matter distribution , are often obtained when the slit samples velocities near the major axis of the closed-loop orbits. Triaxial potentials imprint specific symmetries in 2D velocity fields, generally inducing ,twists' in the isovelocity contours and antisymmetric patterns in opposite quadrants. We suggest that triaxial haloes may be responsible for the variety of shapes of long-slit rotation curves of low surface brightness (LSB) galaxies, as well as for the complex central kinematics of LSBs, which are sometimes ascribed to the presence of ,radial motions' in the gas. We argue that LSB rotation curves might be reconciled with the structure of CDM haloes once the effects of halo triaxiality on the dynamics of gaseous discs are properly taken into account. [source] Constraints on jet X-ray emission in low/hard-state X-ray binariesMONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY: LETTERS (ELECTRONIC), Issue 1 2005Thomas J. Maccarone ABSTRACT We show that the similarities between the X-ray properties of low-luminosity accreting black holes and accreting neutron stars, combined with the differences in their radio properties, argue that the X-rays from these systems are unlikely to be formed in the relativistic jets. Specifically, the spectra of extreme island-state neutron stars and low/hard-state black holes are known to be quite similar, while the power spectra from these systems are known to show only minor differences beyond what would be expected from scaling the characteristic variability frequencies by the mass of the compact object. The spectral and temporal similarities thus imply a common emission mechanism that has only minor deviations from having all key parameters scaling linearly with the mass of the compact object, while we show that this is inconsistent with the observations that the radio powers of neutron stars are typically about 30 times lower than those of black holes at the same X-ray luminosity. We also show that an abrupt luminosity change would be expected when a system makes a spectral state transition from a radiatively inefficient jet-dominated accretion flow to a thin disc-dominated flow, but that such a change is not seen. [source] Validation of 15 microsatellites for parentage testing in North American bison, Bison bison and domestic cattleANIMAL GENETICS, Issue 6 2000R D Schnabel Fifteen bovine microsatellites were evaluated for use in parentage testing in 725 bison from 14 public populations, 178 bison from two private ranches and 107 domestic cattle from five different breeds. The number of alleles per locus ranged from five to 16 in bison and from five to 13 in cattle. On average, expected heterozygosity, polymorphism information content (PIC) and probability of exclusion values were slightly lower in bison than in cattle. A core set of 12 loci was further refined to produce a set of multiplexed markers suitable for routine parentage testing. Assuming one known parent, the core set of markers provides exclusion probabilities in bison of 0·9955 and in cattle of 0·9995 averaged across all populations or breeds tested. Tests of Hardy-Weinberg and linkage equilibrium showed only minor deviations. This core set of 12 loci represent a powerful and efficient method for determining parentage in North American bison and domestic cattle. [source] | |||||||||||||