Reduced incorporation of the influenza B virus BM2 protein in virus particles decreases infectivity

BM2 is the fourth integral membrane protein encoded by the influenza B virus genome. It is synthesized late in infection and transported to the plasma membrane from where it is subsequently incorporated into progeny virus particles. It has recently been reported that BM2 has ion channel activity and may be the functional homologue of the influenza A virus M2 protein acting as an ion channel involved in viral entry. Using a reverse genetic approach it was not possible to recover virus which lacked BM2. A recombinant influenza B virus was generated in which the BM2 AUG initiation codon was mutated to GUG. This decreased the efficiency of translation of BM2 protein such that progeny virions contained only 1/8 the amount of BM2 seen in wild-type virus. The reduction in BM2 incorporation resulted in a reduction in infectivity although there was no concomitant decrease in the numbers of virions released from the infected cells. These data imply that the incorporation of sufficient BM2 protein into influenza B virions is required for infectivity of the virus particles. (C) 2004 Elsevier Inc. All rights reserved.

Control of human immunodeficiency virus type-1 protease activity in insect cells expressing Gag-Pol rescues assembly of immature but not mature virus-like particles

Expression of human immunodeficiency virus type 1 (HIV-1) Gag protein in insect cells using baculovirus vectors leads to the abundant production of virus-like particles (VLPs) that represent the immature form of the virus. When Gag-Pol is included, however, VLP production is abolished, a result attributed to premature protease activation degrading the intracellular pool of Gag precursor before particle assembly can occur. As large-scale synthesis of mature noninfectious VLPs would be useful, we have sought to control HIV protease activity in insect cells to give a balance of Gag and Gag-Pol that is compatible with mature particle formation. We show here that intermediate levels of protease activity in insect cells can be attained through site-directed mutagenesis of the protease and through antiprotease drug treatment. However, despite Gag cleavage patterns that mimicked those seen in mammalian cells, VLP synthesis exhibited an essentially all-or-none response in which VLP synthesis occurred but was immature or failed completely. Our data are consistent with a requirement for specific cellular factors in addition to the correct ratio of Gag and Gag-Pol for assembly of mature retrovirus particles in heterologous cell types. (C) 2003 Elsevier Science (USA). All rights reserved.

A novel cation induced polymeric chain in Na-8[{Cu(gly)(2)}(2)]{H-2(H2W12O42)}] center dot 24H(2)O: hydrothermal synthesis, spectroscopic characterization and X-ray structure analysis

A novel bis(glycinato) copper(II) paradodecatungstate Na-8[{Cu(gly)(2)}(2)]-{H-2(H2W12O42)}] center dot 24H(2)O (1) has been synthesized under hydrothermal conditions. The crystal structure of 1 reveals an infinite one-dimensional chain along the [100] direction and is built from paradodecatungstate (H2W12O42)(10-) clusters joined through [Cu(gly)(2)] moieties. Parallel chains are interlinked by NaO6 octahedra to generate a two-dimensional network.

4,4 '-Dipyridyl-N,N '-dioxide complexes of metal-thiocyanate/selenocyanate: pi-stacked molecular rods as three-dimensional support for two-dimensional polymeric sheets and intra/interchain S center dot center dot center dot S interaction dependent architecture of the R-2(2)(8) synthon driven assembly of one-dimensional polymeric chains

Three supramolecular complexes of Co(II) using SCN-/SeCN- in combination with 4,4'-dipyridyl-N,N'-dioxide (dpyo), i.e., {[Co(SCN)(2)(dpyo)(2)].(dpyo)}(n) ( 1), {[Co(SCN)(2)(dpyo)(H2O)(2)].(H2O)}(n) ( 2), {[Co(SeCN)(2)(dpyo)(H2O)(2)]center dot(H2O)}(n) ( 3), have been synthesized and characterized by single-crystal X-ray analysis. Complex 1 is a rare example of a dpyo bridged two-dimensional (2D) coordination polymer, and pi-stacked dpyo supramolecular rods are generated by the lattice dpyo, passing through the rhombic grid of stacked layers, resulting in a three-dimensional (3D) superstructure. Complexes 2 and 3 are isomorphous one-dimensional (1D) coordination polymers [-Co-dpyo-Co-] that undergo self-assembly leading to a bilayer architecture derived through an R-2(2)(8) H-bonding synthon between coordinated water and dpyo oxygen. A reinvestigation of coordination polymers [Mn(SCN)(2)(dpyo)( H2O)(MeOH)](n) ( 4) and {[Fe(SCN)(2)(dpyo)(H2O)(2)]center dot(H2O)}(n) ( 5) reported recently by our group [ Manna et al. Indian J. Chem. 2006, 45A, 1813] reveals brick wall topology rather than bilayer architecture is due to the decisive role of S center dot center dot center dot S/Se center dot center dot center dot Se interactions in determining the helical nature in 4 and 5 as compared to zigzag polymeric chains in 2 and 3, although the same R-2(2)(8) synthon is responsible for supramolecular assembly in these complexes.

Interactions of an anionic surfactant with poly(oxyalkylene) copolymers in aqueous solution

The interactions of sodium dodecyl sulfate (SDS) with poly(ethylene oxide)/poly(alkylene oxide) (E/A) block copolymers are explored in this study: With respect to the specific compositional characteristics of the copolymer, introduction of SDS can induce fundamentally different effects to the self-assembly behavior of E/A copolymer solutions. In the case of the E18B10-SDS system (E = poly(ethylene oxide) and B = poly(butylene oxide)) development of large surfactant-polymer aggregates was observed. In the case of B20E610-SDS, B12E227B12-SDS, E40B10E40-SDS, E19P43E19-SDS (P = poly(propylene oxide)), the formation of smaller particles compared to pure polymeric micelles points to micellar suppression induced by the ionic surfactant. This effect can be ascribed to a physical binding between the hydrophobic block of unassociated macromolecules and the non-polar tail of the surfactant. Analysis of critical micelle concentrations (cmc*) of polymer-surfactant aqueous solutions within the framework of regular solution theory for binary surfactants revealed negative deviations from ideal behavior for E40B10E40-SDS and E19P43E19-SDS, but positive deviations for E18B10-SDS. Ultrasonic studies performed for the E19P43E19-SDS system enabled the identification of three distinct regions, corresponding to three main steps of the complexation; SDS absorption to the hydrophobic backbone of polymer, development of polymer-surfactant complexes and gradual breakdown of the mixed aggregates. (C) 2008 Elsevier Inc. All rights reserved.

Syntheses, structural analyses, and magneto-structural correlations of three polymeric Fe(II) complexes with azide ligand

Three new metal-organic polymeric complexes, [Fe(N-3)(2)(bPP)(2)] (1), [Fe(N-3)(2)(bpe)] (2), and [Fe(N-3)(2)(phen)] (3) [bpp = (1,3-bis(4-pyridyl)-propane), bpe = (1,2-bis(4-pyridyl)-ethane), phen = 1,10-phenanthroline], have been synthesized and characterized by single-crystal X-ray diffraction studies and low-temperature magnetic measurements in the range 300-2 K. Complexes 1 and 2 crystallize in the monoclinic system, space group C2/c, with the following cell parameters: a = 19.355(4) Angstrom, b = 7.076(2) Angstrom, c = 22.549(4) Angstrom, beta = 119.50(3)degrees, Z = 4, and a = 10.007(14) Angstrom, b = 13.789(18) Angstrom, c = 10.377(14) Angstrom, beta = 103.50(1)degrees, Z = 4, respectively. Complex 3 crystallizes in the triclinic system, space group P (1) over bar, with a = 7.155(12) Angstrom, b = 10.066(14) Angstrom, c = 10.508(14) Angstrom, alpha = 109.57(1)degrees, beta = 104.57(1)degrees, gamma = 105.10(1)degrees, and Z = 2. All coordination polymers exhibit octahedral Fe(II) nodes. The structural determination of 1 reveals a parallel interpenetrated structure of 2D layers of (4,4) topology, formed by Fe(II) nodes linked through bpp ligands, while mono-coordinated azide anions are pendant from the corrugated sheet. Complex 2 has a 2D arrangement constructed through 1D double end-to-end azide bridged iron(11) chains interconnected through bpe ligands. Complex 3 shows a polymeric arrangement where the metal ions are interlinked through pairs of end-on and end-to-end azide ligands exhibiting a zigzag arrangement of metals (Fe-Fe-Fe angle of 111.18degrees) and an intermetallic separation of 3.347 Angstrom (through the EO azide) and of 5.229 Angstrom (EE azide). Variable-temperature magnetic susceptibility data suggest that there is no magnetic interaction between the metal centers in 1, whereas in 2 there is an antiferromagnetic interaction through the end-to-end azide bridge. Complex 3 shows ferro- as well as anti-ferromagnetic interactions between the metal centers generated through the alternating end-on and end-to-end azide bridges. Complex I has been modeled using the D parameter (considering distorted octahedral Fe(II) geometry and with any possible J value equal to zero) and complex 2 has been modeled as a one-dimensional system with classical and/or quantum spin where we have used two possible full diagonalization processes: without and with the D parameter, considering the important distortions of the Fe(II) ions. For complex 3, the alternating coupling model impedes a mathematical solution for the modeling as classical spins. With quantum spin, the modeling has been made as in 2.

Syntheses, crystal structures and magnetic properties of carboxylato-bridged polymeric networks of Mn-II

Three new carboxylato-bridged polymeric networks of Mn-II having molecular formula [Mn(ox)(dpyo)](n) (1), {[Mn-2(mal)(2)(bpee)(H2O)(2)]center dot 0.5(bpee)center dot 0.5(CH3OH)}n, (2) and {[Mn-3(btc)(2)(2,2'-bipy)(2)(H2O)(6)]center dot 4H(2)O}(n) (3) [dpyo, 4,4'-bipyridine N,N'dioxide; bpee, trans-1,2 bis(4-pyridyl) ethylene; 2,2'-bipy, 2,2'-bipyridine; ox = oxalate dianion; mal = malonate dianion; btc = 1,3,5-benzenetricarboxylate trianion] have been synthesized and characterized by single-crystal X-ray diffraction studies and low temperature magnetic measurements. Structure determination of complex I reveals a covalent bonded 2D network containing bischelating oxalate and bridging dpyo; complex 2 is a covalent,bonded 3D polymeric architecture, formed by bridging malonate and bpee ligands, resulting in an open framework with channels filled by uncoordinated disordered bpee and methanol molecules. Whereas complex 3, comprising btc anions bound to three metal centers, is a 1D chain which further extends its dimensionality to 3D via pi-pi and H-bonding interactions. Low temperature magnetic measurements reveal the existence of weak antiferromagnetic interaction in all these complexes. ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006).

Design of mucoadhesive polymeric films based on blends of poly(acrylic acid) and (hydroxypropyl)cellulose

Mixing of aqueous solutions of poly(acrylic acid) and (hydroxypropyl) cellulose results in formation of hydrogen-bonded interpolymer complexes, which precipitate and do not allow preparation of homogeneous polymeric films by casting. In the present work the effect of pH on the complexation between poly(acrylic acid) and (hydroxypropyl)cellulose in solutions and miscibility of these polymers in solid state has been studied. The pH-induced complexation-miscibility-immiscibility transitions in the polymer mixtures have been observed. The optimal conditions for preparation of homogeneous polymeric films based on blends of these polymers have been found, and the possibility of radiation cross-linking of these materials has been demonstrated. Although the gamma-radiation treatment of solid polymeric blends was found to be inefficient, successful cross-linking was achieved by addition of N, N'- methylenebis(acrylamide). The mucoadhesive potential of both soluble and cross-linked films toward porcine buccal mucosa is evaluated. Soluble films adhered to mucosal tissues undergo dissolution within 30-110 min depending on the polymer ratio in the blend. Cross-linked films are retained on the mucosal surface for 10-40 min and then detach.

Self-immolative linkers in polymeric delivery systems

There has been significant interest in the methodologies of controlled release for a diverse range of applications spanning drug delivery, biological and chemical sensors, and diagnostics. The advancement in novel substrate-polymer coupling moieties has led to the discovery of self-immolative linkers. This new class of linker has gained popularity in recent years in polymeric release technology as a result of stable bond formation between protecting and leaving groups, which becomes labile upon activation, leading to the rapid disassembly of the parent polymer. This ability has prompted numerous studies into the design and development of self-immolative linkers and the kinetics surrounding their disassembly. This review details the main concepts that underpin self-immolative linker technologies that feature in polymeric or dendritic conjugate systems and outlines the chemistries of amplified self-immolative elimination.

Healable polymeric materials: a tutorial review

Given the extensive use of polymers in the modern age with applications ranging from aerospace components to microcircuitry, the ability to regain the mechanical and physical characteristics of complex pristine materials after damage is an attractive proposition. This tutorial review focusses upon the key chemical concepts that have been successfully utilised in the design of healable polymeric materials.

Carbon fractions associated with silt-size particles in surface and subsurface soil horizons

Information on the distribution and behavior of C fractions in soil particle sizes is crucial for understanding C dynamics in soil. At present little is known about the behavior of the C associated with silt-size particles. We quantified the concentrations, distribution, and enrichment of total C (TC), readily oxidizable C (ROC), hotwater- extractable C (HWC), and cold-water-extractable C (CWC) fractions in coarse (63–20-mm), medium (20–6.3-mm), and fine (6.3–2-mm) silt-size subfractions and in coarse (2000–250 mm) and fine (250–63 mm) sand and clay (<2-mm) soil fractions isolated from bulk soil (<2 mm), and 2- to 4-mm aggregate-size fraction of surface (0–25 cm) and subsurface (25–55 cm) soils under different land uses. All measured C fractions varied significantly across all soil particle-size fractions. The highest C concentrations were associated with the <20-mm soil fractions and peaked in the medium (20–6.3-mm) and fine (6.3–2-mm) silt subfractions in most treatments. Carbon enrichment ratios (ERC) revealed the dual behavior of the C fractions associated with the medium silt-size fraction, demonstrating the simultaneous enrichment of TC and ROC, and the depletion of HWC and CWC fractions. The medium silt (20–6.3-mm) subfraction was identified in this study as a zone where the associated C fractions exhibit transitory qualities. Our results show that investigating subfractions within the silt-size particle fraction provides better understanding of the behavior of C fractions in this soil fraction.

Assessing the impact of nano- and micro-scale zerovalent iron particles on soil microbial activities: Particle reactivity interferes with assay conditions and interpretation of genuine microbial effects

The effects of nano-scale and micro-scale zerovalent iron (nZVI and mZVI) particles on general (dehydrogenase and hydrolase) and specific (ammonia oxidation potential, AOP) activities mediated by the microbial community in an uncontaminated soil were examined. nZVI (diameter 12.5 nm; 10 mg gÿ1 soil)apparently inhibited AOP and nZVI and mZVI apparently stimulated dehydrogenase activity but had minimal influence on hydrolase activity. Sterile experiments revealed that the apparent inhibition of AOP could not be interpreted as such due to the confounding action of the particles, whereas, the nZVIenhanced dehydrogenase activity could represent the genuine response of a stimulated microbial population or an artifact of ZVI reactivity. Overall, there was no evidence for negative effects of nZVI or mZVI on the processes studied. When examining the impact of redox active particles such as ZVI on microbial oxidation–reduction reactions, potential confounding effects of the test particles on assay conditions should be considered.