The chloride requirement for photosynthetic oxygen evolution. Analysis of the effects of chloride and other anions on amine inhibition of the oxygen-evolving complex

In the presence of Cl^?, the severity of ammonia-induced inhibition of photosynthetic oxygen evolution is attenuated in spinach thylakoid membranes (Sandusky, P.O. and Yocum, C.F. (1983) FEBS Lett. 162, 339–343). A further examination of this phenomenon using steady-state kinetic analysis suggests that there are two sites of ammonia attack, only one of which is protected by the presence of Cl^?. In the case of Tris-induced inhibition of oxygen evolution only the Cl^? protected site is evident. In both cases the mechanism of Cl^? protection involves the binding of Cl^? in competition with the inhibitory amine. Anions (Br^? and NO^?₃) known to reactive oxygen evolution in Cl^?-depleted membranes also protect against Tris-induced inhibition, and reactivation of Cl^?-depleted membranes by Cl^? is competitively inhibited by ammonia. Inactivation of the oxygen-evolving complex by NH₂OH is impeded by Cl^?, whereas Cl^? does not affect the inhibition induced by so-called ADRY reagents. We propose that Cl^? functions in the oxygen-evolving complex as a ligand bridging manganese atoms to mediate electron transfer. This model accounts both for the well known Cl^? requirement of oxygen evolution, and for the inhibitory effects of amines on this reaction.     

Population dynamics in variable environments. IV. Weak ergodicity in the Lotka equation

The Hilbert projective metric is applied to the continuous-time Lotka equation in demography to establish weak ergodicity: populations with the same time-varying fecundity and mortality schedules ultimately have the same age composition. The analysis displays clearly the dynamic content of Lotka's equation and identifies a contraction operator which forces convergence of birth sequences over time. The relationship between primitivity in the discrete (Leslie) and continuous (Lotka) demographic models is made clear.     

The N protein of bacteriophage lambda, defined by its DNA sequence, is highly basic.

Nucleotide sequence has been determined for the restriction fragments and cloned DNA from the pL-N-tL1 region of bacteriophage lambda. A unique reading frame for the N gene is defined by the absence of natural nonsense codons and by the presence of seven nonsense codons generated by mutations in N. This reading frame is initiated at two alternative ATG codons, the second of which is probably the in vivo translation start. Reading is stopped at a single TAG codon. The protein coded is therefore 133 or, more probably, 107 amino acids long, rich in lysine, arginine and proline.     

Acceleration Workspace of Cooperating Multi-Finger Robot Systems

We present a mathematical method for acceleration workspace analysis of cooperating multi-finger robot systems using a model of point-contact with friction. A new unified formulation from dynamic equations of cooperating multi-finger robots is derived considering the force and acceleration relationships between the fingers and the object to be handled. From the dynamic equation, maximum translational and rotational acceleration bounds of an object are calculated under given constraints of contact conditions, configurations of fingers, and bounds on the torques of joint actuators for each finger. Here, the rotational acceleration bounds can be applied as an important manipulability index when the multi-finger robot grasps an object. To verify the proposed method, we used a set of case studies with a simple multi-finger mechanism system. The achievable acceleration boundary in task space can be obtained successfully with the proposed method and the acceleration boundary depends on the configurations of fingers.     

Comparison of sequences from the malB regions of Salmonella typhimurium and Enterobacter aerogenes with Escherichia coli K12: A potential new regulatory site in the interoperonic region

Summary The malE and malK genes from Salmonella typhimurium, and the MalEFG operon and a portion of malK from Enterobacter aerogenes were cloned and sequenced. Plasmid-borne malE genes from both species and the malF and malG genes from E. aerogenes were expressed normally in Escherichia coli, and their products function in maltose transport. This shows that the malB products from the three species are interchangeable, at least in the combinations tested. The general genetic organization of the malB region is conserved. Potential binding sites and distances between them are highly conserved in the regulatory intervals. An unexpected conserved region was detected, which we call the U box, and which could be another target for a regulatory protein. This hypothesis is supported by the presence of the U box in the regulatory, region of the pulA-malX operon in Klebsiella pneumoniae. The intergenic region between malE and malF from S. typhimurium and E. aerogenes, contains inverted repeats similar to the palindromic units (PU or REP) found at the same location in E. coli. The predicted amino acid sequence of the encoded proteins showed 90% or more identity in every pairwise comparison of species.     

Cotton rat<Emphasis Type="Italic"> Sihi-</Emphasis>M3 is a minimally oligomorphic<Emphasis Type="Italic"> Mhc</Emphasis> I-b molecule that binds the chemotactic peptide fMLF under stringent conditions

The leading model for class I-b evolution suggests non-polymorphic I-b genes evolve by gene duplication from polymorphic I-a genes. We recently found N-formyl peptide-specific orthologs of the class I-b gene H2-M3 in the rodent subfamily Sigmodontinae. To test if sigmodont M3 is a I-b gene, we sequenced M3 from wild cotton rats (Sigmodon hispidus) diverse at the class II locus, Sihi-DQA. These haplotypes carry a single allele of M3 that closely resembles H2-M3. However, peptide-binding assays showed that cotton rat M3 bound the chemotactic N-formylpeptide fMLF better than did rat or mouse M3. The Ala116Lys substitution in cotton rat M3 might enhance binding of fMLF and is one of eight residues of M3 that interact with ligand residues P3 and P4 and that are positively selected, with a d_N/d_S ratio of 1.8. Thus, M3 is a class I-b gene in both sigmodontine and murine murids, but positive selection operates on a small subset of residues in the traditionally defined antigen recognition site.Electronic Supplementary Material Supplementary material is available in the online version of this article at     

Phylogenetic relationships and remarkable radiation in Parartemia (Crustacea: Anostraca), the endemic brine shrimp of Australia: evidence from mitochondrial DNA sequences

The Australian continent is notable for the faunal radiations which have occurred in its saline inland waters. The endemic brine shrimp genus Parartemia inhabits many of these habitats. The complex pattern of morphological variation in parartemiids has impeded the establishment of a sound scheme of species relationships. The present study provides an explicit hypothesis of relationships for the genus based on nucleotide sequence data from a segment of mitochondrial DNA coding for the large subunit rRNA gene. Phylogenetic analyses indicated that the eight known species are genetically distinct, and revealed the existence of at least two new species. The molecular data support certain morphology-based relationships among species, but are inconsistent with other hypotheses. There is evidence that most members of the genus arose in a short interval, followed by remarkable genetic divergence. Comparisons of levels of mt DNA sequence divergence between lineages from saline inland waters and freshwaters using representative crustacean groups from Australia that included parartemiids indicated profound differences in rates of evolution, with halophiles exhibiting greater rates of change than their counterparts from freshwaters.     

革兰阴性菌引起的血培养阳性标本直接细菌鉴定和药敏的应用

目的 评估血培养阳性标本直接细菌鉴定和药敏可行性.方法 将血培养瓶放入Bact/Alert 3D 60血培养系统进行培养筛选.选取78份含革兰阴性杆菌的阳性血培养瓶进行试验.抽取培养液,用BD真空分离管离心血细胞.在收集到足量菌液后,用VITEK-32革兰阴性菌鉴定药敏卡做直接鉴定药敏试验.用标准方法及亚培养后的鉴定药敏试验对直接鉴定药敏试验进行评估.结果 VITEK-32直接鉴定试验,78株中的74株(94.9％)准确鉴定,直接药敏试验标准符合率95.6％.KB法血标本直接药敏试验标准符合率96.2％,但微小错误率高于VITEK-32直接药敏法.结论 Bact/Alert血培养阳性标本直接VITEK-32细菌鉴定和药敏对革兰阴性菌是切实可行的,可大幅度缩短时间,为临床及时修正用药提供依据,具有较高的应用价值.