Evolution of Transformation Texture in a Metastable B - Titanium Alloy

Texture evolution in h. c. p. (alpha) phase derived from aging of a differently processed metastable b.c.c. (beta) titanium alloy was investigated. The study was aimed at examining (i) the effect of different b. c. c. cold rolling textures and (ii) the effect of different defect structures on the h. c. p transformation texture. The alloy metastable beta alloy Ti-10V-4.5Fe-1.5Al was rolled at room temperature by unidirectional (UDR) and multi-step cross rolling (MSCR). A piece of the as-rolled materials were subjected to aging in order to derive the h. c. p. (alpha) phase. In the other route, the as-rolled materials were recrystallized and then aged. Textures were measured using X-ray as well as Electron Back Scatter Diffraction. Rolling texture of beta phase, as characterized by the presence of a strong gamma fibre, was found stronger in M S C R compared to UDR, although they were qualitatively similar. The stronger texture of MSCR sample could be attributed to the inhomogeneous deformation taking place in the sample that might contribute to weakening of texture. Upon recrystallization in beta phase field close to beta-transus. the textures qualitatively resembled the corresponding beta deformation textures; however, they got strengthed. The aging of differently beta rolled samples resulted in the product alpha-phase with different textures. The (UDR + Aged) sample had a stronger texture than (MSCR + Aged) sample, which could be due to continuation of defect accumulation in UDR sample, thus providing more potential sites for the nucleation of alpha phase. The trend was reversed in samples recrystallized prior to aging. The (MSCR + Recrystallized + Aged) sample showed stronger texture of alpha phase than the (UDR + Recrystallized + Aged) sample. This could be attributed to extensive defect annihilation in the UDR sample on recrystallization prior to aging. The (MSCR + Aged) sample exhibited more alpha variants when compared to (MSCR + Recrystallized + Aged) sample. This has been attributed to the availability of more potential sites for nucleation of alpha phase in the former. It could be concluded that alpha transformation texture depends mainly on the defect structure of the parent phase.

Transformation of 16-dehydroprogesterone and 17?-hydroxyprogesterone by Mucor piriformis

Mucor piriformis was used to study the mode of transformation of 16-dehydroprogesterone (I, pregna-4, 16-diene-3, 20-dione) and 17 alpha-hydroxyprogesterone (II, 17 alpha-hydroxypregn-4-ene-3, 20-dione). Biotransformation products formed from I were 14 alpha-hydroxypregna-4, 16-diene-3, 20-dione (Ia), 7 alpha, 14 alpha-dihydroxypregna-4 16-diene-3, 20-dione (Ib), 3 beta, 7 alpha, 14 alpha-trihydroxy-5 alpha-pregn-16-en-20-one (Ic), and 3 alpha, 7 alpha, 14 alpha-trihydroxy-5 alpha-pregn-16-en-20-one (Id). Metabolites Ic and Id appear to be hitherto unknown. Timecourse studies suggested that the transformation is initiated by hydroxylation at the 14 alpha-position (Ia) followed by hydroxylation at the 7 alpha-position (Ib). Microsomes (105,000 g sediment) prepared from 16-dehydroprogesterone-induced cells hydroxylate I to its 14 alpha-hydroxy derivative (Ia) in the presence of NADPH. Incubation of Ia with the organism resulted in the formation of Ib, Ic and Id. Biotransformation products formed from compound II were 17 alpha, 20 alpha-dihydroxypregn-4-en-3-one (IIa), 7 alpha, 17 alpha-dihydroxypregn-4-ene-3, 20-dione (IIb), 6 beta, 17 alpha, 20 alpha-trihydroxypregn-4-en-3-one (IIc) and 11 alpha, 17 alpha, 20 alpha-trihydroxypregn-4-en-3-one (IId). Time-course studies indicated that IIa is the initial product formed, which is further hydroxylated either at the 6 beta or 11 alpha position. Incubation of IIa with the organism resulted in the formation of IIc and IId. Reduction of the 4-en-3-one system and 20-keto group has not been observed before in organisms of the order Mucorales. In addition, M. piriformis has been shown to carry out hydroxylation at the C-6, C-7, C-11 and C-14 positions in the steroid molecules tested.

Tri-n-butylin hydride mediated dehalogenation in water

A new methodology has been developed to reduce water soluble and water insoluble organohalides in aqueous medium in high yields using TBTH.

Thickness-dependent fcc-hcp phase transformation in polycrystalline titanium thin films

Polycrystalline Ti thin films are shown to gradually transform from face-centered cubic (fcc) to hexagonal close-packed structure (hcp) with increasing film thickness. Diffraction stress analysis revealed that the fcc phase is formed in a highly compressive hcp matrix (>= 2 GPa), the magnitude of which decreases with increasing film thickness. A correlation between stress and crystallographic texture vis-a-vis the fcc-hcp phase transformation has been established. The total free energy change of the system upon phase transformation calculated using the experimental results shows that the fcc-hcp transformation is theoretically possible in the investigated film thickness regime (144-720 nm) and the hcp structure is stable for films thicker than 720 nm, whereas the fcc structure can be stabilized in Ti films much thinner than 144 nm. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Antigenic determinants at the carboxy terminus of chicken egg white riboflavin carrier protein (RCP): Epitope mapping and antibody-mediated pregnancy curtailment in rodents

The epitopic core sequences recognized by three monoclonal antibodies raised to chicken riboflavin carrier protein (RCP) were mapped to the C-terminal tail-end of the protein using the pepscan method A 21-residue synthetic peptide corresponding to residues 200-219 of the protein and comprising the regions corresponding to the antibodies was synthesized. Administration of polyclonal antibodies specific to this peptide led to termination of early pregnancy in mice. Also, active immunization of rats with the peptide-purified protein derivative conjugate inhibited establishment of pregnancy. These results demonstrate the functional importance of the C-terminal 200-219 region of chicken RCP. Copyright (C) 1996 Elsevier Science Ltd.

Design of some 2-D filters through the transformation technique

The transformation technique is a tool FIR designing 2-D filters, useful for the design of specially shaped filters with passband/stopband regions not centred around the origin. The authors extend this technique to design two types or filters. A notch filter has a stopband centred about a small region in the 2-D frequency plane. The authors propose an extension to the transformation technique with the windowing concept to achieve the design of notch filters. A directional filter has a passband extending fully along: a straight line pacing through the origin. The transformation technique is: further extended to yield such directional filters. Design and application examples for both these fillers are also presented.

Baculovirus mediated high-level expression of luciferase in silkworm cells and larvae

Bombyx mori nuclear polyhedrosis virus (BmNPV)-based baculovirus expression system exploits silkworm larvae as an economical alternative to large-scale cell cultures for production of biomolecules. To generate recombinant BmNPV at high efficiency, we have achieved high efficiency transfection of B. mori cells, BmN, through lipofection. Optimal conditions for lipofection were standardized by quantification of the transient expression level of firefly luciferase (luc) reporter gene under control of an immediate early gene promoter of BmNPV Lipofection was 50-fold and 100-fold more efficient than the calcium phosphate method for transfecting BmN and Sf9 cells, respectively. Lipofection enabled us to generate a recombinant BmNPV (vBmluc), harboring luc under control of the strong polyhedrin promoter On infection with vBmluc, luciferase was expressed at very high levels, 170 mu g/10(6) BmN cells or 13 mg/larva. Expression of luciferase in vBmluc-infected larvae was visualized by luminescence emission instantaneously following luciferin injection generating ''glowing silkworms''.

Realtime kinetic analysis of antigen-antibody interaction using solid phase binding: Transformation of hCG-monoclonal antibody complex

Kinetic constants of MAb-hCG interactions have been determined using solid phase binding of I-125[hCG] to immobilized MAb. While association has been shown to follow the expected pattern, dissociation consists of at least two reversible steps, one with a rate constant of 0.0025 min(-1), and a second with a rate constant of 0.00023 min(-1). Validity of affinity constant measurements in the light of the complex reaction kinetics is discussed, A comparison between the method of surface plasmon resonance technology (BIAcore) and solid phase binding (SPB) for determination of kinetic parameters shows that SPB provides not only a cost-effective approach for determination of realtime kinetic parameters of macromolecular ligand-ligate interaction but also a method with several advantages over the BIAcore system in investigating the mechanism of antigen-antibody interaction.

Effect of beta-lactamase-catalyzed hydrolysis of cephalosporins on peroxynitrite-mediated nitration of serum albumin and cytochrome c

The hydrolysis of beta-lactam antibiotics by beta-lactamases is one of the major bacterial defense systems. These enzymes generally hydrolyze a variety of antibiotics including the latest generation of cephalosporins, cephamycins and imipenem. In this paper, the effect of cephalosporins-based antibiotics on the peroxynitrite-mediated nitration of protein tyrosine is described. Although some of the antibiotics have weak inhibitory effect on the nitration reactions in the absence of beta-lactamase, they exhibit very strong inhibition in the presence of beta-lactamase. This is due to the elimination of heterocyclic thiol/thione moieties from cephalosporins by beta-lactamase-mediated hydrolysis. After the elimination, the thiols/thiones effectively scavenge peroxynitrite, leading to the inhibition of the nitration reactions.

Observation of Water-Mediated Helix-Terminating Conformation in a Dehydrophenylalanine Peptide: Crystal and Solution Structure of the Octapeptide Ac-.DELTA.Phe-Val-.DELTA.Phe-Phe-Ala-Val-.DELTA.Phe-Gly-OMe

We have synthesised and determined the solution conformation and X-ray crystal structure of the octapeptide Ac-Delta Phe(1)-Val(2)-Delta Phe(3)-Phe(4)-Ala(5)-Val(6)-Delta Phe(7)-Gly(8)-OCH3 (Delta Phe = alpha,beta-dehydrophenylalanine) containing three Delta Phe residues as conformation constraining residues. In the solid state, the peptide folds into (i) an N-terminal (3)10(R)-helical pentapeptide segment, (ii) a middle non-helical segment, and (iii) a C-terminal incipient (3)10(L)-helical segment. The results of H-1 NMR data also suggest that a similar multiple-turn conformation for the peptide is largely maintained in solution. Though the C-terminal helix is incipient, the overall conformation of the octapeptide matches well with the conformation of the hairpins reported. Comparison of the pi-turn seen in the octapeptide molecule with those observed in proteins at the C-terminal end of helixes shows the structural similarity among them. A water molecule mediates the 5 --> 2 hydrogen bond in the pi-turn region. This is the first example of a water-inserted pi-turn in oligopeptides reported so far. Comparison between the present octapeptide and another (3)10(R)-helical dehydro nonapeptide Boc-Val-Delta Phe-Phe-Ala-Phe-Delta Phe-Val-Delta Phe-Gly-OCH3 solved by us recently, demonstrates the possible sequence-dependent conformational variations in alpha,beta-dehydrophenylalanine-containing oligopeptides.

Organic Additive-Mediated Synthesis of Novel Cobalt(II) Hydroxides

Electrochemical precipitation of cobalt(II) hydroxide from nitrate solutions containing organic molecules, such as glucose, fructose, lactose, glycerol, and citric acid, yields a new modification of cobalt (II) hydroxide (a = 3.09 +/- 0.03 Angstrom, c = 23.34 +/- 0.36 Angstrom) that is isostructural with cu-nickel hydroxide; precipitation in the absence of organic additives gives the stable, brucite-like, beta-CO (OH)(2). (C) 1995 Academic Press, Inc.

Reductive dimerization of organic thiocyanates to disulfides mediated by tetrathiomolybdate

An interesting reductive dimerization of organic thiocyanates assisted by benzyltriethylammonium tetrathiomolybdate, [(PhCH(2)NEt(3))(2)MoS4], 1, leads to the formation of the corresponding disulfides in high yields.

Transformation of dehydroepiandrosterone and pregnenolone by Mucor piriformis

The mode of transformation of dehydroepiandrosterone (I, 3 beta-hydroxyandrost-5-en-17-one) and pregnenolone (II, 3 beta-hydroxypregn-5-en-20-one) was studied using Mucor piriformis. Biotransformation products formed from I were 3 beta,17 beta-dihydroxyandrost-5-ene (Ia), 3 beta-hydroxyandrost-5-ene-7,17-dione (Ib), 3 beta,17 beta-dihydroxyandrost-5-en-7-one (Ic), 3 beta,7 alpha-dihydroxyandrost-5-en-17-one (Id) and 3 beta,7 alpha,17 beta-trihydroxyandrost-5-ene (Ie). Biotransformation products formed from compound II were 3 beta,7 alpha-dihydroxypregn-5-en-20-one (IIa) and 3 beta,7 alpha,11 alpha-trihydroxypregn-5-en-20-one (IIb). The organism did not carry out isomerization of the 5-en-3 beta-ol to a 4-en-3-one system in the steroid molecules tested. In addition, it failed to carry out 14 alpha-hydroxylation possibly because of the lack of a 4-en-3-one system in I and II, and stereospecific hydroxylation at the C-7 position in I and II.

7Li and 23Na NMR studies of transmembrane cation transport mediated by ionophore lasalocid A

Ion transport across phospholipid vesicles was studied by 7Li and 23Na-NMR using an aqueous anionic paramagnetic shift reagent, dysprosium nitrilotriacetate [Dy(NTA)2]3?, mediated by ionophores, lasalocid A and A23187. The intra- and extracellular 7Li and 23Na-NMR signals were well separated (20?Hz) at mM concentration of the shift reagent. The observed data on the rate constant for lithium transport across DPPC vesicles at various concentrations of the ionophores indicated that lasalocid A is a more efficient carrier for lithium ion compared with the sodium ion transport by this ionophore, while A23187 was not specific to either of the ions (Li or Na). ©1998 European Peptide Society and John Wiley & Sons, Ltd.

Estimating the Threshold Surface Density of Gp120-CCR5 Complexes Necessary for HIV-1 Envelope-Mediated Cell-Cell Fusion

Reduced expression of CCR5 on target CD4(+) cells lowers their susceptibility to infection by R5-tropic HIV-1, potentially preventing transmission of infection and delaying disease progression. Binding of the HIV-1 envelope (Env) protein gp120 with CCR5 is essential for the entry of R5 viruses into target cells. The threshold surface density of gp120-CCR5 complexes that enables HIV-1 entry remains poorly estimated. We constructed a mathematical model that mimics Env-mediated cell-cell fusion assays, where target CD4(+)CCR5(+) cells are exposed to effector cells expressing Env in the presence of a coreceptor antagonist and the fraction of target cells fused with effector cells is measured. Our model employs a reaction network-based approach to describe protein interactions that precede viral entry coupled with the ternary complex model to quantify the allosteric interactions of the coreceptor antagonist and predicts the fraction of target cells fused. By fitting model predictions to published data of cell-cell fusion in the presence of the CCR5 antagonist vicriviroc, we estimated the threshold surface density of gp120-CCR5 complexes for cell-cell fusion as similar to 20 mu m(-2). Model predictions with this threshold captured data from independent cell-cell fusion assays in the presence of vicriviroc and rapamycin, a drug that modulates CCR5 expression, as well as assays in the presence of maraviroc, another CCR5 antagonist, using sixteen different Env clones derived from transmitted or early founder viruses. Our estimate of the threshold surface density of gp120-CCR5 complexes necessary for HIV-1 entry thus appears robust and may have implications for optimizing treatment with coreceptor antagonists, understanding the non-pathogenic infection of non-human primates, and designing vaccines that suppress the availability of target CD4(+)CCR5(+) cells.