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Distinct Positions (distinct + position)

Distribution by Scientific Domains

Medical Sciences	40%

Selected Abstracts

Microtubule sliding movement in tilapia sperm flagella axoneme is regulated by Ca2+/calmodulin-dependent protein phosphorylation

CYTOSKELETON, Issue 8 2006
Masaya Morita
Abstract Demembranated euryhaline tilapia Oreochromis mossambicus sperm were reactivated in the presence of concentrations in excess of 10,6 M Ca2+. Motility features changed when Ca2+ concentrations were increased from 10,6 to 10,5 M. Although the beat frequency did not increase, the shear angle and wave amplitude of flagellar beating increased, suggesting that the sliding velocity of microtubules in the axoneme, which represents dynein activity, rises with an increase in Ca2+. Thus, it is possible that Ca2+ binds to flagellar proteins to activate flagellar motility as a result of the enhanced dynein activity. One Ca2+ -binding protein (18 kDa, pI 4.0), calmodulin (CaM), was detected by 45Ca overlay assay and immunologically. A CaM antagonist, W-7, suppressed the reactivation ratio and swimming speed, suggesting that the 18 kDa Ca2+ -binding protein is CaM and that CaM regulates flagellar motility. CaMKIV was detected immunologically as a single 48 kDa band in both the fraction of low ion extract of the axoneme and the remnant of the axoneme, suggesting that CaMKIV binds to distinct positions in the axoneme. It is possible that CaMKIV phosphorylates the axonemal proteins in a Ca2+/CaM-dependent manner for regulating the dynein activity. A 32P-uptake in the axoneme showed that 48, 75, 120, 200, 250, 380, and 400 kDa proteins were phosphorylated in a Ca2+/CaM kinase-dependent manner. Proteins (380 kDa) were phosphorylated in the presence of 10,5 M Ca2+. It is possible that an increase in Ca2+ induces Ca2+/CaM kinase-dependent regulation, including protein phosphorylation for activation/regulation of dynein activity in flagellar axoneme. Cell Motil. Cytoskeleton 2006. © 2006 Wiley-Liss, Inc. [source]

Helicobacter pylori mutagenesis by mariner in vitro transposition

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 2 2001
Betty P Guo
Abstract We have developed a method for generating transposon insertion mutants using mariner in vitro mutagenesis. The gene of interest was PCR-amplified and cloned. A kanamycin-marked mariner transposon was randomly inserted into the purified plasmid in an in vitro transposition reaction. After repair and propagation in Escherichia coli, purified mutagenized plasmid was introduced into Helicobacter pylori by natural transformation. Transformants were selected by plating on kanamycin. Mutants were predominantly the result of double homologous recombination, and multiple mutants (with insertions in distinct positions) were often obtained. The site of insertion was determined by PCR or sequencing. We have made mutations in known or potential virulence genes, including ureA, hopZ, and vacA, using kanamycin- and kanamycin/lacZ -marked transposons. Colonies carrying a kanamycin/lacZ transposon appeared blue on medium containing the chromogenic agent X-gal, allowing discrimination of mutant and wild-type H. pylori in mixed competition experiments. [source]

Bacterial community profiles of endodontic abscesses from Brazilian and USA subjects as compared by denaturing gradient gel electrophoresis analysis

MOLECULAR ORAL MICROBIOLOGY, Issue 1 2007
J. C. Machado de Oliveira
This study compared the bacterial community profiles of the microbiota associated with acute apical abscesses from Brazilian and USA patients using denaturing gradient gel electrophoresis (DGGE). DNA was extracted from purulent exudate aspirates and part of the 16S rRNA gene was amplified by polymerase chain reaction and separated by DGGE. The resulting banding patterns, which were representative of the bacterial community structures in samples from the two locations, were then compared. Distinct DGGE banding patterns were observed from different samples. Ninety-nine bands with distinct positions in the gels were detected, of which 27 were found only in the USA samples and 13 were exclusive to Brazilian samples. Four of the 59 shared bands showed very discrepant findings with regard to prevalence in the two locations. Cluster analysis of DGGE banding profiles showed a great variability in the bacterial populations associated with teeth with abscesses regardless of the geographical location. Two big clusters, one for each location, were observed. Other clusters contained a mixture of samples from the two locations. The results of the present study demonstrated a great variability in the bacterial community profiles among samples. This indicates that the bacterial communities of abscesses are unique for each individual in terms of diversity. The composition of the microbiota in some samples showed a geography-related pattern. Furthermore, several bands were exclusive for each location and others were shared by the two locations and showed great differences in prevalence. [source]

Different hydrogen-bonding modes in two closely related oximes

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 6 2010
Grzegorz Dutkiewicz
Two closely related oximes, namely 1-chloroacetyl-3-ethyl-2,6-diphenylpiperidin-4-one oxime, C21H23ClN2O2, (I), and 1-chloroacetyl-2,6-diphenyl-3-(propan-2-yl)piperidin-4-one oxime, C22H25ClN2O2, (II), despite their identical sets of hydrogen-bond donors and acceptors, display basically different hydrogen-bonding patterns in their crystal structures. While the molecules of (I) are organized into typical centrosymmetric dimers, created by oxime,oxime O,H...N hydrogen bonds, in the structure of (II) there are infinite chains of molecules connected by O,H...O hydrogen bonds, in which the carbonyl O atom from the chloroacetyl group acts as the hydrogen-bond acceptor. Despite the differences in the hydrogen-bond schemes, the ,OH groups are always in typical anti positions (C,N,O,H torsion angles of ca 180°). The oxime group in (I) is disordered, with the hydroxy groups occupying two distinct positions and C,C,N,O torsion angles of approximately 0 and 180° for the two alternatives. This disorder, even though the site-occupancy factor of the less occupied position is as low as ca 0.06, is also observed at lower temperatures, which seems to favour the statistical and not the dynamic nature of this phenomenon. [source]

1,4,8,11-Tetraazacyclotetradecane antimony(III) sulfide

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 1 2007
Rachel J. E. Lees
Poly[1,4,8,11-tetraazacyclotetradecane(2+) [hepta-,-sulfido-trisulfidohexaantimony(III)]], {(C10H26N4)[Sb6S10]}n, consists of novel [Sb6S10]2, layers containing Sb2S2, Sb4S4 and Sb7S7 hetero-rings, which are separated by macrocyclic amine molecules. The macrocyclic amine molecules are disordered over two crystallographically distinct positions and are diprotonated in order to balance the charge of the anionic layers. [source]