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Classical swine fever virus (CSFV) is the causative agent of classical swine fever. Its envelope comprises glycoproteins E(rns), E1, and E2. In this study, we showed that the unmodified CSFV glycoproteins could incorporate into the HIV core to generate an infectious CSFV pseudotyped virus. The infection was specific to several porcine cell lines, and could be neutralized by anti-E2 monoclonal antibodies (mAbs) completely and by anti-E(rns) mAbs partially, indicating that this pseudotyped virus can mimic the early infection steps of parental CSFV. To investigate the specific role of each envelope protein involved in viral entry, a series of pseudotyped viruses were generated bearing CSFV glycoproteins in various combinations. It was found that specific infectivity was also achieved with non-E(rns) pseudotyped virus carrying E1 and E2 glycoproteins. This indicated that E1 and E2 are sufficient to mediate CSFV entry, and E(rns) is not indispensable in this process.

Understanding the effects of coupling protein protonation and conformational states is critical to the development of drugs targeting pH sensors and to the rational engineering of pH switches. In this work, we address this issue by performing a comprehensive study of the pH-regulated switch from the closed to the open conformation in nitrophorin 4 (NP4) that determines its pH-dependent activity. Our calculations show that D30 is the only amino acid that has two significantly different pKas in the open and closed conformations, confirming its critical role in regulating pH-dependent behavior. In addition, we describe the free-energy landscape of the conformational change as a function of pH, obtaining accurate estimations of free-energy barriers and equilibrium constants using different methods. The underlying thermodynamic model of the switch workings suggests the possibility of tuning the observed pKa only through the conformational equilibria, keeping the same conformation-specific pKas, as evidenced by the proposed K125L mutant. Moreover, coupling between the protonation and conformational equilibria results in efficient regulation and pH-sensing around physiological pH values only for some combinations of protonation and conformational equilibrium constants, placing constraints on their possible values and leaving a narrow space for protein molecular evolution. The calculations and analysis presented here are of general applicability and provide a guide as to how more complex systems can be studied, offering insight into how pH-regulated allostery works of great value for designing drugs that target pH sensors and for rational engineering of pH switches beyond the common histidine trigger. Fil: Di Russo, Natali V.. University of Florida; Estados Unidos Fil: Marti, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina Fil: Roitberg, Adrián. University of Florida; Estados Unidos

Cataloged from PDF version of article. In this paper, a rapid and highly selective chromogenic naked eye detection of hydrogen sulfide was achieved by a 1,2-dioxetane based chemiluminescent probe in aqueous media at pH 7.4. Chemiluminescence property of the probe can be modulated depending on the pH value of medium. (C) 2014 Elsevier B.V. All rights reserved.

Poly(ß,L-malic acid) (PMLA) was made to interact with the cationic anticancer drug Doxorubicin (DOX) in aqueous solution to form ionic complexes with different compositions and an efficiency near to 100%. The PMLA/DOX complexes were characterized by spectroscopy, thermal analysis, and scanning electron microscopy. According to their composition, the PMLA/DOX complexes spontaneously self-assembled into spherical micro or nanoparticles with negative surface charge. Hydrolytic degradation of PMLA/DOX complexes took place by cleavage of the main chain ester bond and simultaneous release of the drug. In vitro drug release studies revealed that DOX delivery from the complexes was favored by acidic pH and high ionic strength Peer Reviewed Postprint (published version)

Poly(beta,L-malic acid) (PMLA) was made to interact with the cationic anticancer drug Doxorubicin (DOX) in aqueous solution to form ionic complexes with different compositions and an efficiency near to 100%. The PMLA/DOX complexes were characterized by spectroscopy, thermal analysis, and scanning electron microscopy. According to their composition, the PMLA/DOX complexes spontaneously self-assembled into spherical micro or nanoparticles with negative surface charge. Hydrolytic degradation of PMLA/ DOX complexes took place by cleavage of the main chain ester bond and simultaneous release of the drug. In vitro drug release studies revealed that DOX delivery from the complexes was favored by acidic pH and high ionic strength.

Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, Universidade de Lisboa, Faculdade de Farmácia, 2014 Submitted by Repositório FFUL (repositorio@ff.ul.pt) on 2019-06-19T11:08:18Z No. of bitstreams: 1 MICF_Andre_Riscado.pdf: 2529185 bytes, checksum: c40317832167885d20ca0253cb782b08 (MD5) Made available in DSpace on 2019-06-19T11:09:40Z (GMT). No. of bitstreams: 1 MICF_Andre_Riscado.pdf: 2529185 bytes, checksum: c40317832167885d20ca0253cb782b08 (MD5) Previous issue date: 2014

Cobalt nanowires were deposited within nanoporous alumina template by direct current electrodeposition. The effect of pH on temperature dependent hysteresis behavior and magnetic properties of Co nanowires has been analyzed and discussed in detail. The easy axis of magnetization was observed to change uniformly from parallel to perpendicular direction to the wire axis with decrease of temperature from 400 K to 5 K. The effect could be attributed to increased magnetocrystalline anisotropy at lower temperatures (e.g. 5 K). Strong pH dependence of cross-over temperature that changes from 300 K to 50 K was observed and the change was delayed with increase of pH. � 2013 Elsevier B.V.

The Gram-negative bacterium Sideroxydans lithotrophicus ES-1 (ES-1) grows on FeCO(3) or FeS at oxic-anoxic interfaces at circumneutral pH, and the ES-1-mediated Fe(II) oxidation occurs extracellularly. However, the molecular mechanisms underlying ES-1's ability to oxidize Fe(II) remain unknown. Survey of the ES-1 genome for candidate genes for microbial extracellular Fe(II) oxidation revealed that it contained a three-gene cluster encoding homologs of Shewanella oneidensis MR-1 (MR-1) MtrA, MtrB, and CymA that are involved in extracellular Fe(III) reduction. Homologs of MtrA and MtrB were also previously shown to be involved in extracellular Fe(II) oxidation by Rhodopseudomonas palustris TIE-1. To distinguish them from those found in MR-1, the identified homologs were named MtoAB and CymA(ES-1). Cloned mtoA partially complemented an MR-1 mutant without MtrA with regards to ferrihydrite reduction. Characterization of purified MtoA showed that it was a decaheme c-type cytochrome and oxidized soluble Fe(II). Oxidation of Fe(II) by MtoA was pH- and Fe(II)-complexing ligand-dependent. Under conditions tested, MtoA oxidized Fe(II) from pH 7 to pH 9 with the optimal rate at pH 9. MtoA oxidized Fe(II) complexed with different ligands at different rates. The reaction rates followed the order Fe(II)Cl(2) Fe(II)-citrate Fe(II)-NTA Fe(II)-EDTA with the second-order rate constants ranging from 6.3 × 10(-3) μM(-1) s(-1) for oxidation of Fe(II)Cl(2) to 1.0 × 10(-3) μM(-1) s(-1) for oxidation of Fe(II)-EDTA. Thermodynamic modeling showed that redox reaction rates for the different Fe(II)-complexes correlated with their respective estimated reaction-free energies. Collectively, these results demonstrate that MtoA is a functional Fe(II)-oxidizing protein that, by working in concert with MtoB and CymA(ES-1), may oxidize Fe(II) at the bacterial surface and transfer released electrons across the bacterial cell envelope to the quinone pool in the inner membrane during extracellular Fe(II) oxidation by ES-1.

The efficacy and the interface interactions of fluoride on laterite were investigated using batch methods, under various ionic strengths, pH, fluoride loading and diverse spectroscopy along with surface complexation modeling. The laterite used in this study was rich in iron (40%) and aluminum (30%). Proton binding sites were characterized by potentiometric titrations yielding pH ZPC around pH 8.72. Adsorption of fluoride on laterite is strongly pH dependent showing a maximum adsorption at pH &lt, 5, though not affected by the electrolyte concentration. Experimental data were quantified with a 2pK generalized diffused layer model considering two different surface binding sites for both protons and anions, using reaction stoichiometries. Surface complexation modeling showed that both Fe and Al sites of the laterite surface contributes to fluoride adsorption via inner-sphere complexation forming monodentate mononuclear interaction with laterite. Fluoride adsorption followed the Freundlich isotherm, indicating multi-site complexation on the laterite surface. FT-IR spectroscopic data provides an evidence for increased hydrogen bonding, indicated by the broadening of the OH stretch features around 3300cm -1. � 2012 Elsevier B.V.

Adsorption experiments were performed under batch process, using Th(IV) initial concentration, pH of solution, contact time and temperature as variables. Th(IV) uptake by calcined (C-D) and flux calcined diatomite (FC-D) was pH dependent (pH range, 3.0-6.0) and maximum sorption was observed at pH 4.0. Sorption capacities for Th(IV) were found to be 0.52 (121.22. mg Th/g) and 0.50. mmol/g (116.69. mg Th/g) for calcined diatomite (C-D) and flux calcined diatomite (FC-D), respectively. Adsorption process is well described by Freundlich and Dubinin-Radushkevich (D-R) isotherms in comparison with Langmuir, Temkin and Flory-Huggins isotherms. Thermodynamic data (δ H°, δ S°, δ G°) were calculated from the temperature-dependent sorption isotherms. Results suggested that the adsorption of Th(IV) on calcined and flux calcined diatomite was a spontaneous and endothermic process. A comparison of kinetic models applied to the adsorption of Th(IV) onto C-D and FC-D was evaluated for the pseudo-first-order, pseudo-second-order, intraparticle diffusion and film diffusion kinetic models. The experimental data fitted very well the pseudo-second-order kinetic model and also followed by intra-particle diffusion model, whereas intraparticle diffusion and film diffusion are both the rate limiting steps for Th(IV) onto calcined and flux calcined diatomite. © 2012 Elsevier B.V.

The paper presents and discusses the effect of various physicochemical parameters (e.g. pH, ionic strength, Cr(VI) initial concentration, amount of the adsorbent, temperature and contact time between metal ion and adsorbent) on the adsorption efficiency of Cr(VI) on dunite in aqueous solutions under atmospheric conditions. Evaluation of the experimental data shows that dunite presents increased affinity for Cr(VI) over a wide pH range and Cr(VI) concentration, and the experimental data are well fitted by the K d adsorption model. The relative adsorption is pH dependent and decreases slightly (about 10%) with increasing pH, because of changes in the surface charge of the solid. The effect of the ionic strength is significant (particularly at low pH), indicating the predominance of outer-sphere complexes. Moreover, adsorption experiments at various temperatures, two different pH values (pH 3 and pH 8) and three different ionic strengths (0.0, 0.1 and 1.0 M NaClO 4), indicate an endothermic but spontaneous entropy-driven processes. © IWA Publishing 2011. 63 4 818 824 Cited By :3

Structures of the first representatives of PF06684 (DUF1185) reveal a Bacillus chorismate mutase-like fold with a potential role in amino-acid synthesis., The crystal structures of BB2672 and SPO0826 were determined to resolutions of 1.7 and 2.1 Å by single-wavelength anomalous dispersion and multiple-wavelength anomalous dispersion, respectively, using the semi-automated high-throughput pipeline of the Joint Center for Structural Genomics (JCSG) as part of the NIGMS Protein Structure Initiative (PSI). These proteins are the first structural representatives of the PF06684 (DUF1185) Pfam family. Structural analysis revealed that both structures adopt a variant of the Bacillus chorismate mutase fold (BCM). The biological unit of both proteins is a hexamer and analysis of homologs indicates that the oligomer interface residues are highly conserved. The conformation of the critical regions for oligomerization appears to be dependent on pH or salt concentration, suggesting that this protein might be subject to environmental regulation. Structural similarities to BCM and genome-context analysis suggest a function in amino-acid synthesis.

The Wingless (Wnt) signaling pathway is one of the critical developmental pathways for control of cell differentiation, proliferation, and cell growth. The DEP domain, located on the C-terminus of Dishevelled (Dvl), plays a role in cytoplasm-membrane association, which branches the canonical and non-canonical Wnt signaling pathway within the cell. It has been suggested that the DEP domain requires the recruitment of ionic lipids, such as phosphatidic acid, to regulate its localization to the plasma membrane and association to the frizzle receptor. However, the physical mechanism for DEP association to the plasma membrane is still unknown. We show that mDvl2-DEP interacts with phosphatidic acid at a distinct patch on the surface formed by a positively charged surface area by NMR spectroscopy. The binding of this interaction was also found at physiologically relevant concentration using fluorescence spectroscopy. We also determined that the interaction is pH-dependent and regulated through a 'histidine switch' mechanism at His464 and His465 where there is increased association of mDvl2-DEP to the plasma membrane at higher pH values (7.5). This association is based on tertiary structure conformational changes with rearrangement of the loop regions by a change in local pH, not its interaction with phosphatidic acid. Overall, our work will contribute to elucidate how cells regulate their developmental pathways through localized molecular interactions. Master of Science

This paper describes the arsenite [As(III)] removal performance of manganese oxide-coated-alumina (MOCA) and its interaction with As(III) in drinking water. MOCA was characterized by XRD, SEM, EDAX, gas adsorption porosimetry, and point of zero charge (pHpzc) measurements. Raman spectroscopy coupled with sorption experiments were carried out to understand the As(III) interaction with MOCA. As(III) sorption onto MOCA was pH dependent and the optimum removal was observed between a pH of 4 and 7.5. The Sips isotherm model described the experimental equilibrium data well and the predicted maximum As(III) sorption capacity was 42.48 mg g-1, which is considerably higher than that of activated alumina (20.78 mg g-1). The sorption kinetics followed a pseudo-second-order equation. Based on sorption and spectroscopic measurements, the mechanism of As(III) removal by MOCA was found to be a two-step process, i.e. oxidation of As(III) to arsenate (As(V)) and retention of As(V) on MOCA surface, with As(V) forming an inner surface complex with MOCA. The results of this study indicated that MOCA is a promising alternative sorbent for As(III) removal from drinking water. � 2009 Elsevier B.V. All rights reserved.

Shiao-Wen Tsai,1 Ding-Syuan Yu,2 Shu-Wei Tsao,1 Fu-Yin Hsu2,3 1Graduate Institute of Biochemical and Biomedical Engineering, Chang Gung University, Taoyuan, Taiwan; 2Department of Life Science, 3Institute of Bioscience and Biotechnology, National Taiwan Ocean University, Keelung, Taiwan Abstract: Hyaluronan–cisplatin conjugate nanoparticles (HCNPs) were chosen as colon-targeting drug-delivery carriers due to the observation that a variety of malignant tumors overexpress hyaluronan receptors. HCNPs were prepared by mixing cisplatin with a hyaluronan solution, followed by dialysis to remove trace elements. The cells treated with HCNPs showed significantly lower viability than those treated with cisplatin alone. HCNPs were entrapped in Eudragit S100-coated pectinate/alginate microbeads (PAMs) by using an electrospray method and a polyelectrolyte multilayer-coating technique in aqueous solution. The release profile of HCNPs from Eudragit S100-coated HCNP-PAMs was pH-dependent. The percentage of 24-hour drug release was approximately 25.1% and 39.7% in pH 1.2 and pH 4.5 media, respectively. However, the percentage of drug released quickly rose to 75.6% at pH 7.4. Moreover, the result of an in vivo nephrotoxicity study demonstrated that Eudragit S100-coated HCNP-PAMs treatment could mitigate the nephrotoxicity that resulted from cisplatin. From these results, it can be concluded that Eudragit S100-coated HCNP-PAMs are promising carriers for colon-specific drug delivery. Keywords: hyaluronan, cisplatin, pectin, alginate, pH-dependent, drug delivery

Molecular gels of cetylpyridinium chloride (CPC) in binary solvent mixtures have been investigated. CPC formed a turbid gel at a critical solvent composition of 3:1 v/v CHCl 3:H 2O. The gelation ability was evaluated in various other organic solvents in the presence of water and the phase evolution was studied. The microstructure of the CPC gel was proposed based on spectroscopic, microscopic and small-angle X-ray scattering (SAXS) techniques. A detailed molecular level investigation using SAXS and molecular modelling demonstrated the gel to assemble as a lamellar organization maintaining a highly interdigitated bilayer structure with CPC molecules. Concentration dependent hierarchical self-assembly from micelles to fibrous gels was thus elucidated with highly interdigitated lamellar gel organization resulting from intense hydrophobic interactions in the tail-to-tail arranged bilayers. The stimuli responsiveness of the gel was elucidated with pH dependent entrapment of Congo Red. � 2012 The Royal Society of Chemistry.