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991.
With the help of quantum mechanical calculations, we have examined the series of central system X(ML)3
+(X = O, S, Se; M = Au, Ag, Cu). Using a scalar–relativistic density functional approach, we studied the geometry structures, Mulliken populations and charges of the systems. Structure parameters of the experimental systems are reproduced well with Xα method. The metallophilic interaction energy is analyzed and decomposed. For the systems with different central atoms and different metal atoms, the nature of the metallophilic attraction interaction is analyzed. 相似文献
992.
In this study, we performed a molecular docking and dynamics simulation for a benzoxazinone–human oxytocin receptor system to determine the possible hydrophobic and electrostatic interaction points in the dynamic complex. After the homology modeling, the ligand was docked into the putative active using AutoDock 3.05. After the application of energetic and structural filters, the complexes obtained were further refined with a simulated annealing protocol (AMBER8) to remove steric clashes. Three complexes were selected for subjection to the molecular dynamics simulation (5 ns), and the results on the occurrence of average anchor points showed a stable complex between the benzoxazinone derivative and the receptor. The complex could be used as a good starting point for further analysis with site-directed mutagenesis, or further computational research.
Figure The location of the ligands (complex B – blue; complex E – red; and complex F –
green) in the transmembrane regions (TM1 – red; TM2 – blue; TM3 – yellow; TM4
– purple; TM5 – orange; TM6 – cyan; TM7 – pink) of the hOTR. For clarity, the EC
and IC loops are not shown
Electronic Supplementary Material Supplementary material is available at 相似文献
993.
Understanding the mechanism of the protein stability change is one of the most challenging tasks. Recently, the prediction
of protein stability change affected by single point mutations has become an interesting topic in molecular biology. However,
it is desirable to further acquire knowledge from large databases to provide new insights into the nature of them. This paper
presents an interpretable prediction tree method (named iPTREE-2) that can accurately predict changes of protein stability
upon mutations from sequence based information and analyze sequence characteristics from the viewpoint of composition and
order. Therefore, iPTREE-2 based on a regression tree algorithm exhibits the ability of finding important factors and developing
rules for the purpose of data mining. On a dataset of 1859 different single point mutations from thermodynamic database, ProTherm,
iPTREE-2 yields a correlation coefficient of 0.70 between predicted and experimental values. In the task of data mining, detailed
analysis of sequences reveals the possibility of the compositional specificity of residues in different ranges of stability
change and implies the existence of certain patterns. As building rules, we found that the mutation residues in wild type
and in mutant protein play an important role. The present study demonstrates that iPTREE-2 can serve the purpose of predicting
protein stability change, especially when one requires more understandable knowledge. 相似文献
994.
Botulinum neurotoxins type A (BoNT/A) are highly potent toxins, but are also useful in the treatment of illnesses. We studied
the properties of BoNT/A at various temperatures and pH values in order to understand its toxicity and structure variations.
The pH values of the environment of BoNT/A are obtained by changing the protonation states of certain titratable residue groups.
Our results show that certain parts of the protein are active at acidic pH environments or at high temperatures. The protein
is more stable in neutral environments at normal human body temperature, whereas, at high temperature, the protein is more
stable in acidic environments. Also, the three domains of the protein tend to have relative motion rather than within individual
domains. 相似文献
995.
996.
Different nest predator faunas and nest predation risk on ground and shrub nests at forest ecotones: an experiment and a review 总被引:1,自引:0,他引:1
This study examined predator faunas of artificial ground and shrub nests and whether nest predation risk was influenced by
nest site, proximity to forest edge, and habitat structure in 38 grassland plots in south-central Sweden. There was a clear
separation of predator faunas between shrub and ground nests as identified from marks in plasticine eggs. Corvids accounted
for almost all predation on shrub nests whereas mammals mainly depredated ground nests. Nest predation risk was significantly
greater for shrub than for ground nests at all distances (i.e. 0, 15 and 30 m) from the forest edge. However, nest predation
risk was not significantly related to distance to forest edge, but significantly increased with decreasing distance to the
nearest tree. Different corvid species robbed nests at different distances from the forest edge, with jays robbing nests closest
to edges. We conclude that the relationship between the predation risk of grassland bird nests and distance to the forest
edge mainly depends on the relative importance of different nest predator species and on the structure of the forest edge
zone. A review of published articles on artificial shrub and ground nest predation in the temperate zone corroborated the
results of our own study, namely that shrub nests experienced higher rates of depredation in open habitats close to the forest
edge and that avian predators predominantly robbed shrub nests. Furthermore, the review results showed that predation rates
on nests in general are highest <50 m inside the forest and lower in open as well as forest interior habitats (≥50 m from
the edge).
Received: 16 March 1998 / Accepted: 30 July 1998 相似文献
997.
Mutsumi Nakamura Takafumi Nagamine Chisato Harada Kiyoshi Tajima Hiroki Matsui Yoshimi Benno 《Current microbiology》2003,47(1):0071-0074
The objective of this study was to ligate the xylanase gene A (xynA) isolated from Ruminococcus albus 7 into the promoter and signal-peptide region of the lichenase [β-(1,3-1,4)-glucanase] gene of Streptococcus bovis JB1. This fusion gene was inserted into the pSBE11 vector, and the resulting recombinant, plasmid pXA, was used to transform
S. bovis 12-U-1 cells. The transformant, S. bovis 12UXA, secreted the xylanase, which was stable against freeze-thaw treatment and long-time incubation at 37°C. The introduction
of pXA and production of xylanase did not affect cell growth, and the xylanase produced degraded xylan from oat-spelt and
birchwood.
Received: 24 June 2002 / Accepted: 7 October 2002 相似文献
998.
Bacillus sphaericus LP1-G, belonging to flagellar serotype H3, has been found to have moderate toxicity against two resistant Culex quinquefasciatus colonies (RLCq1 and RLCq2) and the susceptible contrast (SLCq). With an aim of screening mosquitocidal acting factor, a partial genome library was prepared from a partial HindIII digest of the total DNA from Bacillus sphaericus LP1-G. Two thousand twenty Escherichia coli clones were screened for toxicity against susceptible SLCq, and a toxic clone, designated E-UL68, was chosen for further study. The recombinant E-UL68 performed toxicity against both susceptible and two resistant colonies, having the same level of toxicity as that of wide-type strain LP1-G. Sequence analysis revealed that the inserted fragment was composed of 3876 nucleotides and contained a complete gene, whose sequence was identical to that of the mtx gene from B. sphaericus SSII-1. Because the binary toxin produced during sporulation of strain LP1-G has no activity against the target mosquitoes, this indicates that the Mtx toxin or other active factors might perhaps be responsible for the toxicity of LP1-G against different colonies of mosquito larvae.Received: 7 October 2002 / Accepted: 4 November 2002 相似文献
999.
We investigated the mycorrhizal status of perennial xeric plant species occurring in the "matorral xerófilo" (arid tropical scrub) and the ecotone of the "selva baja caducifolia" (tropical deciduous forest) communities in the semiarid valley of Tehuacán-Cuicatlán, south-central Mexico. The perennial species examined are dominant/codominant elements within the "matorral xerófilo" and the "selva baja caducifolia", both endangered communities in the Biosphere Reserve Tehuacán-Cuicatlán Valley. Of the 50 sampled species, 45 were mycorrhizal. To our knowledge, we report arbuscular mycorrhizae (AM) for the first time in 37 species, of which 21 are endemic to Mexico and nine are endemic to the Valley. We also report AM for the first time in three genera, Buddleja, Hechtia and Zornia, and in one plant family, Buddlejaceae. Beaucarnea gracilis, a threatened species, and Mimosa purpusii, a potentially rare species, are both mycorrhizal. This is the first study of the mycorrhizal status of plant species within the Valley. 相似文献
1000.
Luis Giménez 《Helgoland Marine Research》2003,56(4):265-273
Chasmagnathus granulata is a South American crab occurring in estuarine salt marshes of the Brazilian, Uruguayan and Argentine coasts. Life history
is characterized by an export strategy of its larval stages. I reviewed information on experimental manipulation of salinity
during embryonic and larval development (pre- and posthatching salinities), and on habitat characteristics of C. granulata in order to determine potential effects of larval response to salinity in the field and to suggest consequences for the population
structure. Local populations are spread over coastal areas with different physical characteristics. Benthic phases occupy
estuaries characterized by different patterns of salinity variation, and release larvae to coastal waters characterized by
strong salinity gradients. The zoea 1 of C. granulata showed a strong acclimatory response to low salinity. This response operated only during the first weeks of development (during
zoeae 1 and 2) since subsequent larval survival at low posthatching salinities was consistently low. Larvae developing at
low salinity frequently followed a developmental pathway with five instead of four zoeal stages. The ability to acclimate
and the variability in larval development (i.e. the existence of alternative developmental pathways) could be interpreted
as a strategy to buffer environmental variability at spatial scales of local or population networks. Early survivorship and
production of larvae may be relatively high across a rather wide range of variability in salinity (5–32‰). Plastic responses
to low salinity would therefore contribute to maintain a certain degree of population connectivity and persistence regardless
of habitat heterogeneity.
Electronic Publication 相似文献