Thiotungstates containing the syn-[W2(O/S)2(μ-S)2] (E = O, S) and cuboidal [W2Cu2(μ3-S)4] cores

Reaction of [W^VIS₄]²⁻ with ethane-1,2-dithiol edtH₂ in the presence of the sulfide scavenger Cd²⁺ yielded the dinuclear tungstate syn-[{(edt)W^V(O/S)}₂(μ-S)₂]²⁻ (1), with the terminal S/O disordered over the two tungsten sites in the ratio 0.8:02. In the presence of thiocyanate, phosphine and CuI, the anionic cuboidal clusters of composition [{(SCN)₃W^V}₂{Cu^I(PPh₃)}₂(μ₃-S)₄]²⁻ (2) and (3, diphos = 1,2-bis(o-diphenylphosphinophenyl)ethane), and possibly via an intermediate [{(SCN)₃W^VS}₂(μ-S)₂]⁴⁻. The crystal and molecular structures of [Et₄N]₂1, [Et₄N]₂2 · H₂O and [Et₄N]₂3 · H₂O have been determined.     

The use of volatile cues in recognition of kin eggs by predatory mites

1. Several animal species are known to distinguish between their own eggs and eggs of unrelated conspecifics. However, the cues involved in this discrimination are often unknown. These cues were studied using the predatory mite Gynaeseius liturivorus Ehara.
2. Adult females of these predatory mites oviposit in clusters and avoid oviposition close to eggs laid by other females, resulting in reduced cannibalism between offspring. Because predatory mites are blind, it was tested whether volatiles of eggs were used as a cue for egg recognition.
3. Adult female predatory mites were offered volatile cues of their own eggs and of unrelated conspecific eggs, and females were prevented from contacting the eggs. Predatory mites oviposited closer to their own eggs than to unrelated eggs. This preference was observed even when one own and one unrelated egg were offered as a volatile source.
4. These results suggest that adult female predatory mites can determine kinship using volatiles released from the eggs.

     

DNA sequence patterns in human,mouse, and rabbit immunoglobulin kappa-genes

Summary DNA sequences of the human, mouse, and rabbit immunoglobulin kappa-gene (J-C regions) are compared with respect to various DNA patterns, including dyad symmetry pairings, runs of nucleotides, repeat clusters, and repeats that occur with unusually high frequency. The significant dyad symmetry pairings within each of the sequences emphasize the two control-enhancer elements of the J₅-C intron. Dyad symmetry pairs between the J-C region and a number of kappa variable (V)-gene domains suggest differences in the affinities between the V and J segments. It is the consensus heptamer rather than the consensus nonamer that embodies the longest V-J dyad symmetry combinations. In the rabbit there are long runs and repeat clusters of the sequences that identify regions of high duplication; these regions are absent in the human and mouse sequences. High-frequency oligonucleotides feature the consensus nonamer 5 to the J segments, especially in the mouse sequence.     

Construction of carbon chains on ruthenium and osmium carbonyl clusters

We have used the elimination of AuX(PR₃) (X = halide, R = Ph, tol) that occurs in reactions of alkynylgold(I)-phosphine complexes with M₃(μ-H)₃ (μ₃-CBr) (CO)₉ (M = Ru, Os) to prepare the complexes M₃(μ-H)₃(μ₃-CCCR)(CO)₉ [M = Ru, R = Ph 2, CCSiMe₃3, Fc 4, CCFc 6-Ru, CC[Ru(PPh₃)₂Cp] 8; M = Os, R = CCFc 6-Os, CCCCFc 7], Fc′{(μ₃-CCC)Ru₃(μ-H)₃(CO)₉}₂5, and bis-cluster-capped carbon chain complexes {M₃(μ-H)₃(CO)₉}₂{μ₃:μ₃-C(CC)_nC} (M = Ru, n = 2 9, 3 10-Ru; M = Os, n = 3 10-Os) and {(L)(OC)₈(μ-H)₃M₃}C(CC)_nC{Co₃(μ-dppm)(CO)₇} (n = 1, M = Ru, L = CO 11, PPh₃12-Ru/P; n = 2, L = CO 12-Ru, PPh₃13; M = Os, L = CO 12-Os) in good to excellent yields. X-ray structural determinations of 2-5, 6-Ru, 6-Os, 7, 9, 11, 12-Ru, 12-Os and 12-Ru/P are reported.     

桂东北山地五列木种群结构与动态的初步研究

根据四个代表性样地的典型取样资料,运用数学分析方法,研究桂东北山地五列木种群的结构与分布格局及其动态。结果表明,五列木的重要值远高于群落中其它种类,优势度十分突出,为优势种群;分布格局呈聚集分布,其成因主要是由环境因子的影响所决定的;幼树数量大,种群的年龄结构呈发展型。     

The magnitude of local adaptation under genotype‐dependent dispersal

Dispersal moves individuals from patches where their immediate ancestors were successful to sites where their genotypes are untested. As a result, dispersal generally reduces fitness, a phenomenon known as “migration load.” The strength of migration load depends on the pattern of dispersal and can be dramatically lessened or reversed when individuals move preferentially toward patches conferring higher fitness. Evolutionary ecologists have long modeled nonrandom dispersal, focusing primarily on its effects on population density over space, the maintenance of genetic variation, and reproductive isolation. Here, we build upon previous work by calculating how the extent of local adaptation and the migration load are affected when individuals differ in their dispersal rate in a genotype‐dependent manner that alters their match to their environment. Examining a one‐locus, two‐patch model, we show that local adaptation occurs through a combination of natural selection and adaptive dispersal. For a substantial portion of parameter space, adaptive dispersal can be the predominant force generating local adaptation. Furthermore, genetic load may be largely averted with adaptive dispersal whenever individuals move before selective deaths occur. Thus, to understand the mechanisms driving local adaptation, biologists must account for the extent and nature of nonrandom, genotype‐dependent dispersal, and the potential for adaptation via spatial sorting of genotypes.     

Defect of Fe-S cluster binding by DNA polymerase δ in yeast suppresses UV-induced mutagenesis,but enhances DNA polymerase ζ – dependent spontaneous mutagenesis

Eukaryotic genomes are duplicated by a complex machinery, utilizing high fidelity replicative B-family DNA polymerases (pols) α, δ and ε. Specialized error-prone pol ζ, the fourth B-family member, is recruited when DNA synthesis by the accurate trio is impeded by replication stress or DNA damage. The damage tolerance mechanism dependent on pol ζ prevents DNA/genome instability and cell death at the expense of increased mutation rates. The pol switches occurring during this specialized replication are not fully understood. The loss of pol ζ results in the absence of induced mutagenesis and suppression of spontaneous mutagenesis. Disruption of the Fe-S cluster motif that abolish the interaction of the C-terminal domain (CTD) of the catalytic subunit of pol ζ with its accessory subunits, which are shared with pol δ, leads to a similar defect in induced mutagenesis. Intriguingly, the pol3-13 mutation that affects the Fe-S cluster in the CTD of the catalytic subunit of pol δ also leads to defective induced mutagenesis, suggesting the possibility that Fe-S clusters are essential for the pol switches during replication of damaged DNA. We confirmed that yeast strains with the pol3-13 mutation are UV-sensitive and defective in UV-induced mutagenesis. However, they have increased spontaneous mutation rates. We found that this increase is dependent on functional pol ζ. In the pol3-13 mutant strain with defective pol δ, there is a sharp increase in transversions and complex mutations, which require functional pol ζ, and an increase in the occurrence of large deletions, whose size is controlled by pol ζ. Therefore, the pol3-13 mutation abrogates pol ζ-dependent induced mutagenesis, but allows for pol ζ recruitment for the generation of spontaneous mutations and prevention of larger deletions. These results reveal differential control of the two major types of pol ζ-dependent mutagenesis by the Fe-S cluster present in replicative pol δ.     

Positioning of the mouse Hox gene clusters in the nuclei of developing embryos and differentiating embryoid bodies

Expression of Hox genes located on different chromosomes is precisely regulated and synchronized during development. In order to test the hypothesis that the Hox loci might cluster in nuclear space in order to share regulatory components, we performed 3D FISH on cryosections of developing mouse embryos and differentiating embryoid bodies. We did not observe any instances of co-localization of 4 different Hox alleles. Instances of 2 different alleles touching each other were found in 20-47% of nuclei depending on the tissue. The frequency of such “kissing” events was not significantly different in cells expressing a high proportion of the Hox clusters when compared to cells expressing none or only a few Hox genes. We found that the HoxB and HoxC clusters, which are located in gene-rich regions, were involved more frequently in gene kissing in embryonic nuclei. In the case of HoxB, this observation correlated with the positioning of the corresponding chromosome towards the interior of the nucleus. Our results indicate that co-regulation of the different Hox clusters is not associated with co-localization of the loci at a single regulatory compartment and that the chromosomal context may influence the extent to which they contact each other in the nucleus.     

Local adaptation and matching habitat choice in female barn owls with respect to melanic coloration

Local adaptation is a major mechanism underlying the maintenance of phenotypic variation in spatially heterogeneous environments. In the barn owl (Tyto alba), dark and pale reddish-pheomelanic individuals are adapted to conditions prevailing in northern and southern Europe, respectively. Using a long-term dataset from Central Europe, we report results consistent with the hypothesis that the different pheomelanic phenotypes are adapted to specific local conditions in females, but not in males. Compared to whitish females, reddish females bred in sites surrounded by more arable fields and less forests. Colour-dependent habitat choice was apparently beneficial. First, whitish females produced more fledglings when breeding in wooded areas, whereas reddish females when breeding in sites with more arable fields. Second, cross-fostering experiments showed that female nestlings grew wings more rapidly when both their foster and biological mothers were of similar colour. The latter result suggests that mothers should particularly produce daughters in environments that best match their own coloration. Accordingly, whiter females produced fewer daughters in territories with more arable fields. In conclusion, females displaying alternative melanic phenotypes bred in habitats providing them with the highest fitness benefits. Although small in magnitude, matching habitat selection and local adaptation may help maintain variation in pheomelanin coloration in the barn owl.