Expression of heterologous genes for wall teichoic acid in Bacillus subtilis 168

Summary A localized region of low DNA sequence homology was revealed in two strains of Bacillus subtilis by a specific 100-fold reduction in transformation by W23 DNA of the tag1 locus, a teichoic acid marker of strain 168. Fifty nine rare recombinants, hybrid at this locus, had all acquired donor-specific phage resistance characters, while losing those specific to the 168 recipient. Chemical analysis of isolated cell walls showed that these modifications are associated with major changes in the wall teichoic acids. Genetic analysis demonstrated that determinants for the ribitol phosphate polymer of strain W23 had been transferred to 168, replacing those for the glycerol phosphate polymer in the recipient. All W23 genes coding for poly(ribitol phosphate) in the hybrids and those specifying anionic wall polymers in strain 168 are clustered near hisA. In addition to tag1, the region exchanged extends just beyond gtaA in some hybrids, whereas in others it may include the more distant gtaB marker, encompassing a region sufficient to contain at least 20 average-sized genes. Surface growth, flagellation, transformability and sporulation all appeared normal in hybrids examined. Recombinants without a major wall teichoic acid from either strain were not found, suggesting that an integral transfer of genes for poly(ribitol phosphate) from W23 had occurred in all hybrids isolated. We interpret these results as indicating an essential role for anionic wall polymers in the growth of B. subtillis.     

Receptor interactions of the position 4 side chains of angiotensin II analogues: Importance of aromatic ring quadrupole

A triad of interacting group (TyrOH? His$ \underline\ominus$O₂C) in angiotensin II (ANG II) has been postulated to create the tyrosinate anion pharmacophore (tyanophore) responsible for receptor activation/triggering (Biochim. Biophys. Acta 1991, 1065, 21). In the present study we investigated the effects on bioactivity of substituting the Tyr⁴ residue in [Sar¹]ANG II with other anionic or electronegative amino acids, and with a number of aromatic amino acids lacking a hydroxyl group. [Sar¹ Nva(δ-OH)⁴]ANG II, [Sar¹ Nva(δ-OCH₃)⁴]ANG II, [Sar¹ Met⁴]ANG II, [Sar¹ Gln⁴]ANG II, [Sar¹ Glu⁴]ANG II and [Sar¹ DL -Alg⁴]ANG II had agonist activities in the rat isolated uterus assay of 4, 3, 19, 10, > 0.1 and > 0.1%, respectively, of that of ANG II. [Sar¹ Nal⁴]ANG II, [Sar¹ Pal⁴]ANG II, [Sar¹ DL -Phg(4′-F)⁴]ANG II, [Sar¹ Phe(4′-F)⁴]ANG II, [Sar¹ Phe(F₅)⁴]ANG II and [Sar¹ His⁴]ANG II had agonist activities of 4.5, 7, < 0.1, 0.2, 1 and 0.6%, respectively. All peptides investigated were devoid of measurable antagonist activity except [Sar¹] Phe(4′-F)⁴ ANG II (pA₂ = 7.7). These findings illustrate that anionic or electronegative aliphatic side chains replacing tyrosinate at position 4 can partially activate the angiotension receptor. For ANG II analogues containing an aromatic amino acid other than Tyr at position 4, ligand binding and agonist activity are not dependent on the electronegativity or dipole moment of the aromatic ring, or on the ability of the 4′ ring substituent to accept a proton. Modelling based on ab initio calculations of aromatic ring multipoles illustrate that the apparent binding affinity (PA₂) of ANG II analogues is associated with a perpendicular electrostatic interaction of the position 4 aromatic ring with a receptor-based group. In addition, intramolecular interactions providing for the conformation of the ligand as it approaches its receptor appear to have a role in determining agonist vs antagonist activity.     

“雄茭”、灰茭形成规律的初步研究

茭白栽培过程中,常会出现“雄茭”和灰茭分蘖。根据对茭白的形态学观察,认识到:“雄茭”分蘖的产生是分蘖期母茎中茭白黑粉菌菌丝未能入侵新生分蘖腋芽而导致的结果;灰茭分蘖是因其菌丝的潜育期比正常茭短,故在苗端的膨大部分较早地产生了不同程度的黑粉孢子堆。     

Community Structure and Role Analysis in Biological Networks

Abstract

Complex network analysis has received increasing interest in recent years, which provides a remarkable tool to describe complex systems of interacting entities, particular for biological systems. In this paper, we propose a methodology for identifying the significant nodes of the networks, including core nodes, bridge nodes and high-influential nodes, based on the idea of community and two new ranking measures, InterRank and IntraRank. The results show the significant nodes form a small number in biological networks, and uncover the relative small number of which has advantage for reducing the dimensions of the network and possibly help to define new biological targets.     

The importance of black-pigmented Gram-negative anaerobes in human infections

Abstract Black-pigmented Gram-negative anaerobic rods are found on mucosal surfaces as indigenous flora. With mucosal damage due to disease, trauma or surgery, these organisms may invade tissues and set up infection. Other important factors determining whether or not infection results include ‘inoculum’ size, synergy with other organisms and production of virulence factors that include capsules, lipopolysaccharide, attachment factors, proteases, collagenase, neuraminidase, and phospholipase A; also, they may have fibrinolytic and anti-phagocytic activity and may degrade complement and IgG and IgM. Pigmented anaerobes are found in all types of infections including such serious infections as bacteraemia, endocarditis, intracranial abscess, necrotizing pneumonia and necrotizing fasciitis, generally as part of a mixed infecting flora, and they play a key role in experimental mixed infections. They dominate or are prominent in infections involving organisms originating in the oropharynx, such as central nervous system, head and neck, dental and pleuropulmonary infections. Therapy of infections involving pigmented anaerobes includes surgery plus antimicrobial agents; a significant percentage of strains produce β-lactamase. Much remains to be done to determine the relative importance of the various taxa of black-pigmented Gram-negative anaerobes and of the different virulence factors produced by them.     

Mechano-electric feedback and arrhythmias

The mechanical state of the heart feeds back to modify cardiac rate and rhythm. Mechanical stretch of myocardial tissue causes immediate and chronic responses that lead to the common end point of arrhythmia. This review provides a brief summary of the author's personal choice of contributions that she considers have fostered our understanding of the role of mechano-electric feedback in arrhythmogenesis.

Acute mechanical stretch reversibly depolarises the cell membrane and shortens the action potential duration. These electrophysiological changes are related to the activation of mechano-sensitive ion channels. Several different ion channels are involved in the sensing of stretch, among them K⁺-selective, Cl⁻-selective, non-selective, and ATP-sensitive K⁺ channels. Sodium and Ca²⁺ entering the cells via non-selective ion channels are thought to contribute to the genesis of stretch-induced arrhythmia. Mechano-sensitive channels have been cloned from non-vertebrate and vertebrate species.

Chronic stress on the heart activates gene expression in cardiomyocytes and non-myocytes. The signal transduction involves atrial natriuretic peptides and growth factors that initiate remodelling processes leading to hypertrophy which in turn may contribute to the electrical instability of the heart by increasing the responsiveness of mechano-sensitive channels. Selective block of these channels could provide some new form of treatment of mechanically induced arrhythmias, although at present there are no drugs available with sufficient selectivity. Detailed understanding of how mechanical strain on myocardial cells is translated into channel activation will allow to identify new targets for putative antiarrhythmic drugs.     

Restrained molecular dynamics studies on complex of adriamycin with DNA hexamer sequence d-CGATCG

Adriamycin is an anthracycline anticancer drug used widely for solid tumors in spite of its adverse side effects. The solution structure of 2:1 adriamycin-d-(CGATCG)(2) complex has been studied by restrained molecular dynamics simulations. The restraint data set consists of several intramolecular and intermolecular nuclear Overhauser enhancement cross-peaks obtained from two-dimensional nuclear magnetic resonance spectroscopy data. The drug is found to intercalate between CG and GC base pairs at two d-CpG sites. The drug-DNA complex is stabilized via specific hydrogen bonding and van der Waal's interactions involving 4OCH(3), O5, 6OH, and NH(3)(+) moiety of daunosamine sugar, and rings A protons. The O-glycosidic bond C7-O7-C1'-C2' lies in the range 138 degrees -160 degrees during the course of simulations. The O6-H6...O5 hydrogen bond is stable while O11-H11...O12 hydrogen bond is not favored. The intercalating base pairs are buckled and minor groove is wider in the complex. The phosphate on one strand at intercalation site C1pG2 is in B(I) conformation and the phosphates directly lying on opposite strand is in B(II) conformation. The phosphorus on adjacent site G2pA3 is in B(II) conformation and hence a distinct pattern of B(I) and B(II) conformations is induced and stabilized. The role of various functional groups by which the molecular action is mediated has been discussed and correlated to the available biochemical evidence.     

Synthesis, vibrational spectra and X-ray structures of copper(I) thiourea complexes

Complex formation of thiourea with copper takes place as an intermediate step in the preparation of copper sulfide thin films by spray pyrolysis starting from aqueous solutions of copper(II) chloride and thiourea. The stoichiometry of the complex and that of the resulting thin film primarily depends on the molecular ratio of the starting materials. For comparison, the structures of all copper(I) thiourea complexes found in the Cambridge Structural Database are classified in this paper. In addition, syntheses, structural (single crystal XRD also at low temperature 193 K) and spectroscopic studies (FTIR and Raman) of six copper-thiourea complexes are now reported. The copper to thiourea stoichiometric ratio is 1:3 in four of these complexes, but their structures are basically different as dimerization or polymer formation takes place depending on whether the water of crystallisation is present or absent. The structure of bis(μ-thiourea)tetrakis(thiourea)dicopper(I) dichloride dihydrate, [Cu₂(tu)₆]Cl₂ · 2H₂O (1) was determined at room and also at low temperature. Bis(μ-thiourea)tetrakis(thiourea)dicopper(I) dibromide dihydrate, [Cu₂(tu)₆]Br₂ · 2H₂O (2) is isomorphous with 1, like the anhydrous compounds chlorotris(thiourea)copper(I), [Cu(tu)₃]Cl (3) and bromotris(thiourea)copper(I), [Cu(tu)₃]Br (4) are isomorphous. In the third isomorphous pair of complexes the copper to thiourea stoichiometric ratio is 1:1, viz. chloro(thiourea)copper(I) hemihydrate, [Cu(tu)]Cl · 0.5H₂O (5) and bromo(thiourea)copper(I) hemihydrate, [Cu(tu)]Br · 0.5H₂O (6). During the preparation of chloro(thiourea)copper(I) hemihydrate (5) a reaction by product α,α^′-dithiobisformamidinium dichloride, [SC(NH₂)₂]₂Cl₂ (7) was identified and structurally characterized which made it possible to suggest a reaction path leading to complex formation.     

Effects of NV gene knock-out recombinant viral hemorrhagic septicemia virus (VHSV) on Mx gene expression in Epithelioma papulosum cyprini (EPC) cells and olive flounder (Paralichthys olivaceus)

To determine whether the NV gene of viral hemorrhagic septicemia virus (VHSV) is related to the type I interferon response of hosts, expression of Mx gene in Epithelioma papulosum cyprini (EPC) cells and in olive flounder (Paralichthys olivaceus) in response to infection with either wild-type VHSV or recombinant VHSVs (rVHSV-ΔNV-EGFP and rVHSV-wild) was investigated. A reporter vector was constructed for measuring Mx gene expression using olive flounder Mx promoter, in which the reporter Metridia luciferase was designed to be excreted to culture medium to facilitate measurement. The highest increase of luciferase activity was detected from supernatant of cells infected with rVHSV-ΔNV-EGFP. In contrast cells infected with wild-type VHSV showed a slight increase of the luciferase activity. Interestingly, cells infected with rVHSV-wild that has artificially changed nucleotides just before and after the NV gene ORF, also showed highly increased luciferase activity, but the increased amplitude was lower than that by rVHSV-ΔNV-EGFP. These results strongly suggest that the NV protein of VHSV plays an important role in suppressing interferon response in host cells, which provides a condition for the viruses to efficiently proliferate in host cells. In an in vivo experiment, the Mx gene expression in olive flounder challenged with the rVHSV-ΔNV-EGFP was clearly higher than fish challenged with rVHSV-wild or wild-type VHSV, suggesting that lacking of the NV gene in the genome of rVHSV-ΔNV-EGFP brought to strong interferon response that subsequently inhibit viral replication in fish.