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951.
Cervellati C Franzoni L Squerzanti M Bergamini CM Spinozzi F Mariani P Lanzara V Spisni A 《Amino acids》2009,36(4):633-641
Activation of tissue transglutaminase by calcium involves a conformational change which allows exposition of the active site
to the substrate via movements of domains 3 and 4 that lead to an increase of the inter-domain distance. The inhibitor GTP
counteracts these changes. Here we investigate the possible existence of non-native conformational states still compatible
with the enzyme activity produced by chemical and thermal perturbations. The results indicate that chemical denaturation is
reversible at low guanidine concentrations but irreversible at high concentrations of guanidine. Indeed, at low guanidine
concentrations tissue TG-ase exists in a non-native state which is still affected by the ligands as in the native form. In
contrast, thermal unfolding is always irreversible, with aggregation and protein self-crosslinkage in the presence of calcium.
DSC thermograms of the native protein in the absence of ligands consist of two partly overlapped transitions, which weaken
in the presence of calcium and merge together and strengthen in the presence of GTP. Overall, the present work shows, for
the first time, the reversible denaturation of a TG-ase isoenzyme and suggests the possibility that also in in vivo, the enzyme
may acquire non-native conformations relevant to its patho-physiological functions. 相似文献
952.
John A. Lowe Xinjun Hou Christopher Schmidt F. David Tingley Stan McHardy Monica Kalman Shari DeNinno Mark Sanner Karen Ward Lorraine Lebel Don Tunucci James Valentine 《Bioorganic & medicinal chemistry letters》2009,19(11):2974-2976
The type 1 glycine transporter plays an important in regulating homeostatic glycine levels in the brain that are relevant to the activation of the NMDA receptor by the excitatory neurotransmitter glutamate. We describe herein the structure–activity relationships (SAR) of a structurally novel class of GlyT1 inhibitors following on a lead derived from high throughput screening, which shows good selectivity for GlyT1 and potent activity in elevating CSF levels of glycine. 相似文献
953.
954.
955.
Monica Ruffini Castiglione M. Frediani C. Ravalli G. Venora R. Cremonini 《Protoplasma》2009,236(1-4):21-27
Vicia oroboides, a rare taxon belonging to section Atossa of subgenus Vicia, was recovered and analysed by means of cytological and karyological methods with the aim of both characterising this species and integrating our knowledge on phylogeny of subgenus Vicia. Automated karyotype analysis and nuclear DNA content have been determined after Feulgen’s reaction; chromosome banding was performed by fluorochrome staining to evidence heterochromatic blocks along the chromosome complement. The chromosome number is in line with the values of the species of section Atossa; the GC- and AT-rich sites were identified by CMA and DAPI staining. Karyomorphological parameters, based on symmetry indices, provide information about the phylogenetic position of this species inside the subgenus Vicia. DNA content is reported for the first time. 相似文献
956.
The activities of the enzymes α‐ and β‐glucosidase, and leucine aminopeptidase were measured in cultures of the dinoflagellate Prorocentrum minimum (Pavill.) J. Schiller and in field samples collected during dinoflagellate blooms occurring in tributaries of the Chesapeake Bay, Maryland, USA. Activities were measured using fluorogenic artificial substrates and partitioned among the >5 μm size fraction, small microbes fraction (0.1–5 μm), and dissolved phase (<0.1 μm). P. minimum and most other photosynthetic dinoflagellates are >5 μm in size and thus can be separated from the small microbes fraction, which contains most bacteria. Little to no glucosidase activity was detected associated with the >5 μm size fraction in cultures or in field samples, with most of the activity (67% to 93% in cultures, 54% to 100% in field samples) in the small microbes size fraction for both α and β glucosidase. In contrast, 67% to 90% of the total leucine aminopeptidase (LAP) activity in cultures was measured in the >5 μm fraction. Within a culture, LAP activity in the size fraction containing P. minimum decreased in response to ammonium and urea additions, but not in response to nitrate. In field samples, LAP activity was positively correlated with dinoflagellate abundance and chl a, and negatively correlated with ammonium concentration. During blooms, up to 34% of LAP activity was associated with the >5 μm fraction, indicating that when abundant, dinoflagellates may make a substantial contribution to ectocellular LAP activity in the water column. 相似文献
957.
958.
Reproductive success of wild Lesser Rheas (Pterocnemia -Rhea- pennata pennata) in north-western Patagonia, Argentina 总被引:1,自引:1,他引:0
We studied the reproductive success of a wild Lesser Rhea population (Pterocnemia -Rhea- pennata pennata) during two reproductive seasons (2004/2005 and 2005/2006) in north-western Patagonia, Argentina. The parameters recorded
included population and nest density, clutch size, hatching success, chick survival (up to 3 months of age) and percentage
of chicks that reached the juvenile stage after the winter. We also estimated the percentage of males that attempted to nest
and of those that were successful (those producing at least one chick), daily nest mortality rates (DNMR) at different stages
of the nesting cycle and the probability that an egg that has been recently laid will produce a chick. On average, both years
pooled, the density of this population of Lesser Rheas was 1.55 ± 0.2 individuals/km2 (SE), nest density was 0.17 ± 0.04 per km
2
, clutch size was 20.8 ± 6.4 eggs, hatching success was 74.4% ± 11.3, Mayfield’s probability of an egg that will produce a
chick was 0.64, chick survival was 65.4% ± 14.5 and percentage of chicks that reached the juvenile stage was 26.3%. Nearly
a quarter of Lesser Rhea males in the population attempted to nest during a breeding season, and the DNMR was significantly
higher during the laying stage (most nest failures were due to anthropogenic disturbances related to livestock raising activities).
Nesting success, hatching success, and chick survival of Lesser Rheas were higher than those of their most closely related
species, the Greater Rhea (Rhea americana), whereas the percentage of chicks that reached the juvenile stage was similar due to high winter mortalities of chicks.
We suggest that the increase in reproductive effort is a strategy of this species to overcome environmental constraints. 相似文献
959.
María E. Riveiro Dominick Maes Ramiro Vzquez Monica Vermeulen Sven Mangelinckx Jan Jacobs Silvia Debenedetti Carina Shayo Norbert De Kimpe Carlos Davio 《Bioorganic & medicinal chemistry》2009,17(18):6547-6559
The presumption that some coumarins might be lead compounds in the search for new differentiation agents against leukemia is based on the fact that natural coumarins, 5-(3-methyl-2-butenyloxy)-6,7-methylenedioxycoumarin (C-2) and 5-methoxy-6,7-methylenedioxycoumarin (C-1) inhibit proliferation and induce differentiation in U-937 cells [Riveiro, M. E.; Shayo, C.; Monczor, F.; Fernandez, N.; Baldi, A.; De Kimpe, N.; Rossi, J.; Debenedetti, S.; Davio, C. Cancer Lett. 2004, 210, 179–188]. These promising findings prompted us to investigate the anti-leukemia activity of a broader range of related polyoxygenated coumarins. Twenty related natural or synthetically prepared coumarins, including a range of 5-substituted ayapin derivatives which have become easy accessible via newly developed synthesis methods, were evaluated, where treatments with 5-(2,3-dihydroxy-3-methylbutoxy)-6,7-methylenedioxycoumarin (D-3) and 5-(2-hydroxy-3-methoxy-3-methylbutoxy)-6,7-methylenedioxycoumarin (D-2) were able to inhibit the cell growth and induce the differentiation of U-937 cells after 48 h treatment. These results provide insight into the correlation between some structural properties of polyoxygenated coumarins and their in vitro leukemic differentiation activity. 相似文献
960.
Lourdes Vásquez-Yeomans Eloy Sosa-Cordero Monica R. Lara Aaron J. Adams José A. Cohuo 《Ichthyological Research》2009,56(3):266-275
Overall patterns of distribution and abundance of Albula spp. leptocephali larvae offshore in the western Caribbean Sea (CAS) and Gulf of Mexico (GOM), and in coastal waters of the
Mexican Caribbean (MXC) were analyzed from: (a) cruise data available from the Academy of Natural Sciences of Philadelphia
(CAS, GOM) and (b) coastal plankton surveys (1998–2002 and January 2004) (MXC). We found striking inshore-offshore differences
in the larval catch and size structure. Offshore cruises yielded 57 leptocephali, mostly determined as early stage I (18.0 ± 8.2 mm
SL, mean ± SD). In contrast, coastal samples yielded 2,466 larvae 51.4 ± 3.6 mm SL, mostly late stage I; of these, 2,345 (95%)
were caught over 4 nights in January 2004. The relationship between the larval length (mm, SL) and the distance to the coastline
(km) was best represented by the regression model with a distinct variance for each locality. To ascertain whether the coastal inflow of leptocephali follows a regular seasonal
pattern or depends on episodic events will require further monitoring; available evidence suggests that the southern coast
of the MXC offers favorable conditions for the recruitment of Albula spp. larvae. 相似文献