The type III secretion system needle,tip, and translocon

Many Gram‐negative bacteria pathogenic to plants and animals deploy the type III secretion system (T3SS) to inject virulence factors into their hosts. All bacteria that rely on the T3SS to cause infectious diseases in humans have developed antibiotic resistance. The T3SS is an attractive target for developing new antibiotics because it is essential in virulence, and part of its structural component is exposed on the bacterial surface. The structural component of the T3SS is the needle apparatus, which is assembled from over 20 different proteins and consists of a base, an extracellular needle, a tip, and a translocon. This review summarizes the current knowledge on the structure and assembly of the needle, tip, and translocon.     

Bacopaside I and II: two pseudojujubogenin glycosides from Bacopa monniera

Two saponins, designated as bacopaside I and II, have been isolated from Bacopa monniera Wettst. and their structures have been elucidated as 3-O-alpha-L-arabinofuranosyl-(1-->2)-[6-O-sulphonyl-beta-D-glucopyranosyl-(1-->3)]-alpha-L-arabinopyranosyl pseudojujubogenin (1) and 3-O-alpha-L-arabinofuranosyl-(1-->2)-[beta-D-glucopyranosyl (1-->3)]-beta-D-glucopyranosyl pseudojujubogenin (2) mainly on the basis of 2D NMR and other spectral analyses.     

A mechanistic model for the organization of microtubule asters by motor and non-motor proteins in a mammalian mitotic extract

We used computer simulation to understand the functional relationships between motor (dynein, HSET, and Eg5) and non-motor (NuMA) proteins involved in microtubule aster organization. The simulation accurately predicted microtubule organization under all combinations of motor and non-motor proteins, provided that microtubule cross-links at minus-ends were dynamic, and dynein and HSET were restricted to cross-linking microtubules in parallel orientation only. A mechanistic model was derived from these data in which a combination of two aggregate properties, Net Minus-end-directed Force and microtubule Cross-linking Orientation Bias, determine microtubule organization. This model uses motor and non-motor proteins, accounts for motor antagonism, and predicts that alterations in microtubule Cross-linking Orientation Bias should compensate for imbalances in motor force during microtubule aster formation. We tested this prediction in the mammalian mitotic extract and, consistent with the model, found that increasing the contribution of microtubule cross-linking by NuMA compensated for the loss of Eg5 motor activity. Thus, this model proposes a precise mechanism of action of each noncentrosomal protein during microtubule aster organization and suggests that microtubule organization in spindles involves both motile forces from motors and static forces from non-motor cross-linking proteins.     

Synthesis,crystal structure,and nuclease activity of planar mono-heterocyclic base copper(II) complexes

A series of mononuclear copper(II) complexes having a 1:1 molar ratio of copper and the planar heterocyclic base like 1,10-phenanthroline (phen), dipyrido[3,2-d:2',3'-f]quinoxaline (dpq) and dipyrido[3,2-a:2',3'-c]phenazine (dppz) are prepared from a reaction of copper(II) nitrate.trihydrate and the base (L) in ethanol or aqueous ethanol at different temperatures. The complexes [Cu(dpq)(NO(3))(2)] (2), [Cu(dpq)(NO(3))(H(2)O)(2)](NO(3)) (3), [Cu(dpq)(NO(3))(2)(H(2)O)(2)].2H(2)O (4.2H(2)O) and [Cu(dppz)(NO(3))(2)(H(2)O)].H(2)O (5.H(2)O) have been characterized by X-ray crystallography. The crystal structures show the presence of the heterocyclic base in the basal plane. The coordination geometries of the copper(II) centers are axially elongated square-pyramidal (4+1) in 2, 3 and 5, and octahedral (4+2) in 4. The nitrate anion in the coordination sphere displays unidentate and bidentate chelating bonding modes. The axial ligand is either H(2)O or NO(3) in these structures giving a Cu-L(ax) distance of approximately 2.4 A. The one-electron paramagnetic complexes (mu approximately 1.8 mu(B)) exhibit axial EPR spectra in DMF glass at 77 K giving g(parallel)>g( perpendicular ) with an A(parallel) value of approximately 170G indicating a [d(x)2(-y)2](1) ground state. The complexes are redox active and display a quasireversible cyclic voltammetric response for the Cu(II)/Cu(I) couple near 0.0 V vs. SCE giving an order of the E(1/2) values as 5(dppz)>2-4 (dpq)>[Cu(phen)(2)(H(2)O)](2+)>1 (phen). The complexes bind to calf thymus DNA giving an order 5 (dppz)>2 (dpq)>[Cu(phen)(2)(H(2)O)](2+)>1 (phen). An effect of the extended planar ring in dpq and dppz is observed in the DNA binding. The complexes show nuclease activity with pUC19 supercoiled DNA in DMF/Tris-HCl buffer containing NaCl in presence of mercaptopropanoic acid as a reducing agent. The extent of cleavage follows the order: [Cu(phen)(2)(H(2)O)](ClO(4))(2)>5>2 approximately 3 approximately 4>1. The bis-phen complex is a better cleaver of SC DNA than 1-5 having mono-heterocyclic base. Mechanistic investigations using distamycin reveal minor groove biding for the phen, dpq complexes, and a major groove binding for the dppz complex 5. The cleavage reactions are found to be inhibited in the presence of hydroxyl radical scavenger DMSO and the reactions are proposed to proceed via sugar hydrogen abstraction pathway. The ancillary ligand is found to have less effect in DNA binding but are of importance in DNA cleavage reactions.     

Protein stabilization through phage display

RNase S consists of two proteolytic fragments of RNase A, residues 1-20 (S20) and residues 21-124 (S pro). A 15-mer peptide (S15p) with high affinity for S pro was selected from a phage display library. Peptide residues that are buried in the structure of the wild type complex are conserved in S15p though there are several changes at other positions. Isothermal titration calorimetry studies show that the affinity of S15p is comparable to that of the wild type peptide at 25 degrees C. However, the magnitudes of DeltaH(o) and DeltaC(p) are lower for S15p, suggesting that the thermal stability of the complex is enhanced. In agreement with this prediction, at pH 6, the T(m) of the S15p complex was found to be 10 degrees C higher than that of the wild type complex. This suggests that for proteins where fragment complementation systems exist, phage display can be used to find mutations that increase protein thermal stability.     

Virological Characteristics of Acute Hepatitis B in Eastern India: Critical Differences with Chronic Infection

Hepatitis B Virus (HBV) manifests high genetic variability and is classifiable into ten genotypes (A-J). HBV infection can lead to variable clinical outcomes, ranging from self-limiting acute hepatitis to active chronic hepatitis, cirrhosis and hepatocellular carcinoma. The present study characterizes HBV strains circulating among patients with acute (AHB) and chronic HBV infection (CHB). Among a total of 653 HBsAg positive cases, 40 manifested acute infection. After sequencing the surface(S), basal core promoter/pre-core(BCP/PC) and the X gene regions, phylogenetic tree was constructed using MEGA4 by neighbor-joining method. Statistical robustness was established with bootstrap analysis. Nucleotide diversity was determined by Shannon entropy per site using the Entropy program of the Los Alamos National Laboratories. Analyses of acute patients revealed that HBV/D2 is the major circulating sub-genotype and commonly associated with sexual promiscuity and the age group between15-30 years. Comparison of AHB and CHB patients revealed that HBeAg positivity, ALT levels and genotype D were significantly high in AHB, whereas CHB patients were predominantly male, had a high viral load, and were commonly associated with genotype C. The frequencies of mutations in the S, BCP/PC, and X gene were low in AHB as compared to CHB. Drug resistant mutations were not detectable in the polymerase gene of AHB. Average nucleotide diversity in AHB was considerably low as compared to CHB. Further, the highest average ΔH (average difference in entropy between chronic and acute infection) was observed in the BCP/PC region implying that this region was most vulnerable to mutations upon HBV persistence, especially in case of genotype C. Additionally, among all substitutions, the A1762T and G1764A BCP mutations were the strongest indicators of chronicity. In conclusion, the study exhibits a general portrait of HBV strains circulating among acute hepatitis B patients in Eastern India and their intricate differences with chronic patients which should be useful from the clinical point of view.     

Discovery of a novel class of biphenyl pyrazole sodium channel blockers for treatment of neuropathic pain

A series of novel biphenyl pyrazole dicarboxamides were identified as potential sodium channel blockers for treatment of neuropathic pain. Compound 20 had outstanding efficacy in the Chung rat spinal nerve ligation (SNL) model of neuropathic pain.     

Methylene amine substituted arylindenopyrimidines as potent adenosine A2A/A1 antagonists

A novel series of arylindenopyrimidines were identified as A_2A and A₁ receptor antagonists. The series was optimized for in vitro activity by substituting the 8- and 9-positions with methylene amine substituents. The compounds show excellent activity in mouse models of Parkinson’s disease when dosed orally.     

Design and synthesis of piperazine-indole p38α MAP kinase inhibitors with improved pharmacokinetic profiles

Derivatives of the 4-fluorobenzyl dimethylpiperazine-indole class of p38α MAP kinase inhibitors are described. Biological evaluation of these compounds focused on maintaining activity while improving pharmacokinetic (PK) properties. Improved properties were observed for structures bearing substitutions on the benzylic methylene.