Maximum Affinity Research Articles

Magnitudes of departures from equilibrium during regional metamorphism of porphyroblastic rocks

AbstractNumerical models of diffusion‐controlled nucleation and growth of garnet crystals, which successfully replicate diverse textures in 13 porphyroblastic rocks, yield quantitative estimates of the magnitudes of departures from equilibrium during crystallization. These estimates are derived from differences in chemical potential between subvolumes containing stable product assemblages and those containing persistent but metastable reactant assemblages. The magnitude of disequilibrium is evaluated in terms of the thermal overstepping, which is commonly referenced to the garnet‐in isograd; the reaction affinity in the intergranular fluid at the site and time of each nucleation event, and on average throughout the rock, and the ‘latent energy of reaction’ per unit volume, a measure of the average unreacted capacity of the bulk rock, which describes its overall metastability. Across all of the models, the first crystals nucleate after 5–67 °C of thermal overstepping (correspondingly, 0.7–5.8 kJ mol−1 of 12‐oxygen garnet); the maximum reaction affinity averaged across the intergranular fluid is between 4.7 and 16.0 kJ mol−1 of 12‐oxygen garnet; and the maximum latent energy of reaction ranges from 7.3 to 51.7 J cm−3. These results demonstrate that impediments to crystallization significantly delay nucleation and retard reaction, with the consequence that nucleation of new crystals extends throughout nearly the entire crystallization interval. This potential for protracted reaction during prograde metamorphism, with reactions continuing to temperatures and pressures well beyond equilibrium conditions, suggests the likelihood of overstepping of multiple – possibly competing – reactions that can progress simultaneously. Isograds and ranges of stability for metamorphic assemblages along a metamorphic field gradient may therefore be significantly offset from the positions predicted from calculations based on equilibrium assumptions, which poses a substantial challenge to accurate interpretations of metamorphic conditions and processes.

Surface interaction of L-alanine on hematite: an astrobiological implication.

In the present work, surface interaction of L-alanine (L-ala) has been investigated on hematite (α-Fe2O3), an abundant mineral on Mars, as a function of time (5 min-48 h), pH (4.0 and 6.20 ± 0.10) and concentration (1 × 10(-3) M-10 × 10(-3) M) with optical absorbance and energy-dispersive spectroscopy (EDS). Adsorption parameters (XM and KL) were calculated from Langmuir adsorption isotherms. L-alanine has maximum affinity (65.31 %) in its zwitterionic form at pH 6.20, while it is only 29.86 % adsorbed at pH 4.0. Possible astrobiological implications are discussed.

A Digital Signal Processing-Based Bioinformatics Approach to Identifying the Origins of HIV-1 Non B Subtypes Infecting US Army Personnel Serving Abroad

Two HIV-1 non B isolates, 98US_MSC5007 and 98US_MSC5016, which have been identified amongst the US Army personnel serving abroad, are known to have originated from other nations. Notwithstanding, they are categorized as American strains. This is because their countries of origin are unknown. American isolates are basically B subtype. 98US_MSC5007 belongs to Circulating Recombinant Form (CRF02_AG) while 98US_MSC5016 is of the C clade. Both sub-groups are recognized to have originated from African and Asian continents. It has become necessary to properly determine the countries of origin of microbes and viruses. This is because diversity and cross-subtyping have been found to mitigate the designing and development of vaccine and therapeutic interventions. The aim of this study therefore is to identify the countries of origin of the two American isolates found amongst US Army personnel serving abroad. A Digital Signal Processing-based Bioinformatics technique called Informational Spectrum Method (ISM) has been engaged. ISM entails translating the amino acids sequences of the protein into numerical sequences (signals) by means of one biological parameter (Amino Acids Scale). The signals are then processed using Discrete Fourier Transform (DFT) in order to uncover and present the embedded biological information as Informational Spectra (IS). Spectral Position of Maximum Binding Interaction (SPMBI) is used. Several approaches including Phylogeny have preliminarily been employed in the determination of evolutionary trends of organisms and viruses. SPMBI has preliminarily been used to re-establish the semblance and common originality that exist between human and Chimpanzee, evolutionary roadmaps in the Influenza and HIV viruses. The results disclosed that 98US_MSC5007 shared same semblance and originality with a Nigeria isolate (92NG083) while 98US_MSC5016 with the Zairian isolates (ELI, MAL, and Z2/CDC-34). These results appear to demonstrate that the American soldiers harboring these strains may have been infected by isolates from Nigeria and Zaire, respectively. This is because 98US_MSC5007 and the Nigerian isolate share SPMBI at position 44. Additionally, 98US_MSC5016, which has SPMBI at position 148, may have come from Zaire as it has similar SPMBI with the Zairian isolates at 150. SPMBI is a demonstration of Bio-functionality arising from maximum affinity by the proteins from different sources to a common protein. To help validate the findings, the experiment was further repeated using ISM-based Phylogenetic technique. The outcome appears not to be in complete accord with the results obtained in this study. It is therefore recommended that the countries in which these US Army personnel are deployed be identified and where the findings made and the locations of the Army personnel appropriately correlate, this novel procedure be engaged in the identification of the nations of origins of all other such HIV isolates across all clades and nations.

Synthesis, Anticonvulsant Activity and <i>In silco</i> Studies of Schiff Bases of 2-Aminothiophenes via Guanidine- Catalyzed Gewald Reaction

Purpose: To synthesize Schiff bases of 2-aminothiophenes and evaluate their anticonvulsant activity and in silco propertiesMethods: 2-Amino-N-o-tolyl-5,6-dihydro-4H-cylcopenta[b]thiophene-3-carboxamide was synthesized using 1,1,3,3-tetramethylguanidine lactate as a basic catalyst and by microwave irradiation. 2- substitued-o-tolyl-5,6-dihyro-4H-cylcopenta[b]thiophene-3-carboxamide was prepared by reacting with different substituted aromatic aldehydes. The synthesized compounds were characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (1H NMR) and mass spectrometry (MS) while their anticonvulsant activity was screened against maximum electroshockinduced seizure (MES), and pentylenetetrazole-induced seizure (PTZ) against phenytoin and diazepam as reference standards. Molecular docking (in silico) studies were performed using 4-aminobutyrateaminotransferase in order to predict possible protein-ligand interactions.Results: Among the 21 synthesized compounds, 2b, 2d, 2f, 2k, 2m, 2n and 2o showed good to moderate activity against MES and PTZ-induced convulsions. Compounds 2b, 2d, 2f, 2k and 2m exhibited lower activity against PTZ than against MES model while compounds 2n and 2o afforded greater protection against PTZ than against MES model. In silico results also revealed maximum binding affinity to GABA-AT protein which was higher than other compoundsConclusion: The synthesized compounds showed potent anticonvulsant activity. Molecular docking results should give an insight into how further modification of lead compound can be carried out for higher inhibitory activity.Keywords: Ionic liquid, 2-Aminothiophenes, Anticonvulsant, In silco studies, Molecular docking.

Study of carbon dioxide and methane equilibrium adsorption on silicoaluminophosphate-34 zeotype and T-type zeolite as adsorbent

Carbon dioxide is known as a hazardous material with acidic property that can be found as impurity in natural gas reservoirs with a broad range of 2 up to 40 %. Therefore, many efforts have been directed to remove and separate carbon dioxide from methane to prevent corrosion problems as well as improving the nat- ural gas energy content. In this study, two molecular sieves, silicoaluminophosphate-34 (SAPO-34) zeotype and T-type zeolite, were synthesized by the hydrothermal method for the comparative study of adsorptive separation of carbon dioxide from methane. The synthesized adsorbents were characterized by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, and Brunner-Emmett-Teller techniques. These characteriza- tion tests confirmed formation of both materials with acceptable crystallinity. Both adsorbents were tested in equilibrium adsorption experiments in order to evaluate maximum capacity and adsorption affinity. Adsorption capacity of carbon dioxide and methane on SAPO-34 and zeolite T were measured in a pressure range of 0.1-2.0 MPa and temperature of 288, 298, and 308 K and fitted with the Sips and Langmuir isotherm models. The ideal selectivity of CO2/CH4 was determined for SAPO-34 and zeolite T at the studied pressures and temperatures, indicating that the molecular sieves can be properly used for CO2-CH4 separation or CO2 capturing from natural gas.

Treatment of wastewater containing high concentrations of terephthalic acid by Comamonas sp. and Rhodococcus sp.: kinetic and stoichiometric characterization

AbstractIn this work, terephthalic acid degradation was studied with two strains that were isolated and identified as closely related to Comamonas (99%) and Rhodococcus (99%) genus. A characterization of both strains was carried out during batch experiments performed at two oxygen transfer capacities (0.094 ± 0.011 and 0.538 ± 0.042 g O2/L/h) and five concentrations of terephthalic acid (2.5 to 15.0 g/L). Maximum degradation rates of 0.073 ± 0.004 and 0.062 ± 0.003 g TOC/L/h, were observed, for Comamonas sp. and Rhodococcus sp., respectively. However, a degradation rate of 0.159 ± 0.011 g TOC/L/h was reached with a mixed culture. Haldane, Aiba, Edwards and Andrews models were used to fit terephthalic acid degradation kinetics, being Haldane the model that best fitted the results. Several parameters were determined including, maximum growth rate, growth yield, substrate affinity and inhibition constant.

Development of a Novel Rapid Immunodiagnostic Kit Based on Flagellar 40 kDa Antigen Epitope for the Detection of Typhoid Fever in Indian Patients

To aid the clinical diagnosis of typhoid fever in India, where most hospitals and primary health centres have no facilities for culture, we report on the development of a novel and rapid immunodiagnostic kit for the direct detection of Salmonella Typhi—specific IgG antibodies against S. Typhi flagellar H antigen. The disease often does not show a specific clinical picture, and can be confused with other febrile illness such as malaria, dengue fever and Staphylococcus aureus. To overcome the problem of cross reactivity specific epitope of the flagellar H antigen was immobilised on the testing kit strip eliminating chances of cross reactivity and false positive results thereby increasing the specificity of the test. Since the immunodiagnostic kit, uses the flagellar H antigen from bacteria present in our country, the antibodies present in the serum of patients of our country will have maximum binding affinity, enhancing the sensitivity of our test kit. The immunodiagnostic kit on analysis gave a positive result with clinically diagnosed typhoid positive patient serum and negative results were obtained with the sera of clinically diagnosed malaria, abscess of Staphylococcus aureus and Visceral leishmaniasis (Kala-azar) patients.

Comparative Study of Bivalent Cationic Metals Adsorption Pb(II), Cd(II), Ni(II) and Cu(II) on Olive Stones Chemically Activated Carbon

In this work the ability of olive stone activated carbon (COSAC) to remove Pb(II), Cd(II), Ni(II) and Cu(II) metal ions from aqueous solutions was evaluated. The effect of initial pH, contact time and initial concentration on metal ions adsorption was investigated. The results indicated that pH 5 is the optimum value for metal removal. Adsorption kinetic rates were found to be fast; total equilibrium was achieved after 4 hours. Kinetic experimental data fitted very well the pseudo-second order equation and the values of adsorption rate constants were calculated. The equilibrium isotherms were evaluated in terms of maximum adsorption capacity and adsorption affinity by the application of Langmuir and Freundlich equations. Results indicate that the Langmuir model fits adsorption isotherm data better than the Freundlich model. The removal efficiency of heavy metal ions by COSAC decreases in the order Pb(II) >Cd(II) > Ni(II) ≥ Cu(II).

Molecular Modeling of Differentially Phosphorylated Serine 10 and Acetylated lysine 9/14 of Histone H3 Regulates their Interactions with 14-3-3ζ, MSK1, and MKP1

Histone modifications occur in precise patterns, with several modifications known to affect the binding of proteins. These interactions affect the chromatin structure, gene regulation, and cell cycle events. The dual modifications on the H3 tail, serine10 phosphorylation, and lysine14 acetylation (H3Ser10PLys14Ac) are reported to be crucial for interaction with 14-3-3ζ. However, the mechanism by which H3Ser10P along with neighboring site-specific acetylation(s) is targeted by its regulatory proteins, including kinase and phosphatase, is not fully understood. We carried out molecular modeling studies to understand the interaction of 14-3-3ζ, and its regulatory proteins, mitogen-activated protein kinase phosphatase-1 (MKP1), and mitogen- and stress-activated protein kinase-1 (MSK1) with phosphorylated H3Ser10 alone or in combination with acetylated H3Lys9 and Lys14. In silico molecular association studies suggested that acetylated Lys14 and phosphorylated Ser10 of H3 shows the highest binding affinity towards 14-3-3ζ. In addition, acetylation of H3Lys9 along with Ser10PLys14Ac favors the interaction of the phosphatase, MKP1, for dephosphorylation of H3Ser10P. Further, MAP kinase, MSK1 phosphorylates the unmodified H3Ser10 containing N-terminal tail with maximum affinity compared to the N-terminal tail with H3Lys9AcLys14Ac. The data clearly suggest that opposing enzymatic activity of MSK1 and MKP1 corroborates with non-acetylated and acetylated, H3Lys9Lys14, respectively. Our in silico data highlights that site-specific phosphorylation (H3Ser10P) and acetylation (H3Lys9 and H3Lys14) of H3 are essential for the interaction with their regulatory proteins (MKP1, MSK1, and 14-3-3ζ) and plays a major role in the regulation of chromatin structure.

Characterization of Homocysteine γ-Lyase from Submerged and Solid Cultures of Aspergillus fumigatus ASH (JX006238)

Among 25 isolates, Aspergillus fumigatus ASH (JX006238) was identified as a potent producer of homocysteine gamma- lyase. The nutritional requirements to maximize the enzyme yield were optimized under submerged (SF) and solid-state fermentation (SSF) conditions, resulting in a 5.2- and 2.3-fold increase, respectively, after the last purification step. The enzyme exhibited a single homogenous band of 50 kDa on SDS-PAGE, along with an optimum pH of 7.8 and pH stability range of 6.5 to 7.8. It also showed a pI of 5.0, as detected by pH precipitation with no glycosyl residues. The highest enzyme activity was obtained at 37-40 degrees C, with a Tm value of 70.1 degrees C. The enzyme showed clear catalytic and thermal stability below 40 degrees C, with T1/2 values of 18.1, 9.9, 5.9, 3.3, and 1.9 h at 30 degrees C, 35 degrees C, 40 degrees C, 50 degrees C, and 60 degrees C, respectively. Additionally, the enzyme Kr values were 0.002, 0.054, 0.097, 0.184, and 0.341 S-1 at 30 degrees C, 35 degrees C, 40 degrees C, 50 degrees C, and 60 degrees C, respectively. The enzyme displayed a strong affinity to homocysteine, followed by methionine and cysteine when compared with non-S amino acids, confirming its potency against homocysteinuriarelated diseases, and as an anti-cardiovascular agent and a specific biosensor for homocysteinuria. The enzyme showed its maximum affinity for homocysteine (Km 2.46 mM, Kcat 1.39 × 10(-3) s(-1)), methionine (Km 4.1 mM, Kcat 0.97 × 10(-3) s(-1)), and cysteine (Km 4.9 m M, Kcat 0.77 × 10(-3) s(-1)). The enzyme was also strongly inhibited by hydroxylamine and DDT, confirming its pyridoxal 5'-phosphate (PLP) identity, yet not inhibited by EDTA. In vivo, using Swiss Albino mice, the enzyme showed no detectable negative effects on platelet aggregation, the RBC number, aspartate aminotransferase, alanine aminotransferase, or creatinine titer when compared with negative controls.

Conformation induced discrimination between picric acid and nitro derivatives/anions with a Cu-pyrene array: the first decision making photonic device

A new pyrene based copper complex 3 is designed and synthesized. The fluorescence behaviour of the complex was studied in the presence of different nitro aromatics and anions. It was observed that the copper complex showed the maximum affinity for picric acid marked by changes in the conformation of pyrene in its excited state. Applying the principles of electronics, a decision making photonic device is proposed, which selectively determines the presence of picric acid.

High-Affinity VEGF Antagonists by Oligomerization of a Minimal Sequence VEGF-Binding Domain

Vascular endothelial growth factor (VEGF) neutralizing antagonists including antibodies or receptor extracellular domain Fc fusions have been applied clinically to control angiogenesis in cancer, wet age-related macular degeneration, and edema. We report here the generation of high-affinity VEGF-binding domains by chemical linkage of the second domain of the VEGF receptor Flt-1 (D2) in several configurations. Recombinant D2 was expressed with a 13 a.a. C-terminal tag, including a C-terminal cysteine to enable its dimerization by disulfide bond formation or by attachment to divalent PEGs and oligomerization by coupling to multivalent PEGs. Disulfide-linked dimers produced by Cu(2+) oxidation of the free-thiol form of the protein demonstrated picomolar affinity for VEGF in solution, comparable to that of a D2-Fc fusion (sFLT01) and ~50-fold higher than monomeric D2, suggesting the 26 a.a. tag length between the two D2 domains permits simultaneous interaction of both faces of the VEGF homodimer. Extending the separation between the D2 domains by short PEG spacers from 0.35 kD to 5 kD produced a modest ~2-fold increase in affinity over the disulfide, thus defining the optimal distance between the two D2 domains for maximum affinity. By surface plasmon resonance (SPR), a larger (~5-fold) increase in affinity was observed by conjugation of the D2 monomer to the termini of 4-arm PEG, and yielding a product with a larger hydrodynamic radius than sFLT01. The higher affinity displayed by these D2 PEG tetramers than either D2 dimer or sFLT01 was largely a consequence of a slower rate of dissociation, suggesting the simultaneous binding by these tetramers to neighboring surface-bound VEGF. Finally, disulfide-linked D2 dimers showed a greater resistance to autocatalytic fragmentation than sFLT01 under elevated temperature stress, indicating such minimum-sequence constructs may be better suited for sustained-release formulations. Therefore, these constructs represent novel Fc-independent VEGF antagonists with ultrahigh affinity, high stability, and a range of hydrodynamic radii for application to multiple therapeutic targets.

Removal of Cd2+ And Pb2+ from Aqueous Solutions Using Bio-Char Residues

Abstract In this paper, wheat straw and rapeseed residues before and after microwave pyrolysis during biooil production were studied as potential sorbents of heavy metals. The sorbents were characterized by elemental analysis and FTIR spectroscopy. Sorption properties of the materials were investigated using batch adsorption-equilibrium experiments and the effect of initial Cd and Pb concentration was studied. The experimental data fit Langmuir adsorption isotherm. The maximum sorption affinity of studied materials was observed in the case of rapeseed and its sorption capacity was 31.6 and 83.5 mg/g for Cd and Pb, respectively.

PharmaTrek: A Semantic Web Explorer for Open Innovation in Multitarget Drug Discovery

The realisation that vast amounts of pharmacological data for small molecules are continuously being reported in bibliographic sources has promoted in recent years the rise of initiatives aiming at collecting, organising, and storing these data together with chemical structures. Today, there are numerous databases that connect hundreds of thousands of small molecules to thousands of biological responses of their interaction with macromolecules. Some of these repositories, such as GLIDA, PDSP, BindingDB, IUPHARdb, PubChem, ChEMBL, and DrugBank, make all data available in the public domain. [1] In addition, some others, such as BioPrint, Integrity, Wombat, and GOSTAR, offer access to their data only through licensing from the respective commercial providers. [2] This wide diversity of sources does not facilitate direct access and interrogation of the entire contents covered by all of them. Integrating all these repositories into a single accessible resource is not trivial, mainly due to issues related with the use of different vocabularies and ontologies for the various domain entities which makes cross-referencing among multiple sources a challenging task. [3] But even if some degree of integration is accomplished, managing and updating such an integrated framework in an efficient manner may require significant human resources and be extremely time consuming and difficult to fully automate. [4] Managing chemical structures, for instance, involves taking into consideration a fair amount of detailed aspects such as salt formulation and isomerism (tautomerism, regioisomerism, and optical and geometrical isomerisms), and it has been reported that different molecular identifiers may actually lead to an essentially different number of unique chemical structures depending on the user criteria for defining uniqueness. [5] On the other hand, managing pharmacological data across databases is also complicated, as one may encounter different values for the same molecule – protein interaction obtained from different laboratories, from the same protein but different species, or from the same protein and species but different settings and conditions. [6] In parallel, there have been some recent initiatives to provide some conceptual meaning to the connections established between objects from different domains, so the links are stored in such a way that become more understandable to computers. This is the main goal of applying

Adsorption properties of gold onto a chitosan derivative

In order to find a material which can be used for the recovery of Au(III), a chitosan derivative was synthesized by carboxymethylation and grafting sulfur groups onto cross-linked chitosan backbone. Adsorption studies were carried out at different pH values to optimize the pH condition. Batch method was conducted to study the effects of parameters such as reaction time, initial metal concentration and temperature on Au(III) sorption. The maximum adsorption affinity for Au(III) was found to be 8.32mmol/g at pH 4.0, 25°C. The results of kinetic study showed that the adsorption reaction followed the pseudo second order model. The derivative showed high adsorption ability and reusability toward Au(III). All results suggested that the chitosan derivative had potential to be utilized in the recovery of Au(III) from aqueous medium.

Dispersion State and Humic Acids Concentration-Dependent Sorption of Pyrene to Carbon Nanotubes

Sonication and humic acids (HA) are known to disperse carbon nanotube (CNT) suspensions, but potential effects on sorption of chemicals to CNTs remain poorly understood. We applied a passive sampling method to investigate the influence of dispersion/aggregation on sorption of pyrene to CNTs. Sonication broke down CNT aggregates and increased pyrene sorption affinity by up to 1.39 orders of magnitude. Sorption surfaces newly exposed by sonication remained available to pyrene even after reaggregation occurred, suggesting an irreversible effect of sonication. The presence of HA decreased sorption of pyrene to CNTs, but at the highest HA concentration investigated (200 mg/L), sorption affinity was still 1.90 orders of magnitude larger than sorption of pyrene to HA alone. Specific interactions between pyrene and CNTs were thus still taking place, in spite of the presence of a HA coating on the CNTs' surface. A greater suppression of sorption by CNTs occurred when the HA addition was combined with a sonication pretreatment. Sorption isotherm fitting indicated that the maximum sorption capacity, sorption affinity, and heterogeneity of the CNT surface were all affected by sonication and the presence of HA at a concentration as low as 1 mg/L. The present results contribute to an improved understanding of the sorption behavior of CNTs in both natural and wastewater systems.

Bioaccumulation of mercury in the trophic chain of flatfish from the Baltic Sea

Mercury concentrations in three flatfish species – flounder (Platichtys flesus), plaice (Pleuronectes platessa), and Baltic turbot (Scophthalmus maximus), netted in the southern Baltic Sea were assessed and compared to concentrations of this metal in sediments, sea water, and flatfish food – bivalve Macoma balthica, isopod Saduria entomon, and sprat (Sprattus sprattus). Collected simultaneously with flatfish in 2009 and 2010. Different concentrations of mercury depending on species, tissue or organ, sex, individual length, kind of food, and region were determined. The muscle tissues of turbot had the highest concentrations of the metal. The bioaccumulation (BF) and biomagnification (BMF) factors has been counted showing that the muscle tissues of turbot have maximum affinity for mercury, and thus best reflected the metal contamination of the Baltic Sea environment. The data suggest that the common Baltic turbot (S. maximus) is an important model species, suitable and cost-effective to biomonitor environmental mercury pollution for ecological research.

Removal of Cd, Pb and Cu from Water Using Thiol and Humic Acid Functionalized Fe<sub>2</sub>O<sub>3</sub> Nanoparticles

Humic acid (HA) and 3-Mercaptopropyltriethoxysilane (MPTES) were successfully coated onto the surface of Fe2O3 (α and γ) nano-particles as characterized using IR and BET-N2 analysis, the potential use of the naked and functionalized nano-Fe2O3 particles as novel nano-sorbents for removal of Cd, Pb and Cu ions in solution was investigated in this study. The result indicated that the sorption of Cd, Pb and Cu ions by the nano-particles can be fitted well using langmuir isotherm; all the adsorbents exhibited definitely adsorption ability to Cd, Pb and Cu ions in solution. The sorption maximum and sorption affinity on the nano-particles for Pb (aq) were always higher than Cu (aq) and Cd (aq), the sorption maxima for the Pb, Cd and Cu followed the order Pb>Cu>Cd. Among the nano-sorbents, the Fe2O3 (α and γ) nano-particles coated with HA exhibited higher sorption ability to metal ions than the naked and thiolated Fe2O3 nano-particles, the sorption maxima of α-Fe2O3/HA for Pb(aq) reached 151.5 mg/g, which was significantly higher than the values of 116.3 and 84.0 mg/g observed for the α-Fe2O3 and α- Fe2O3/MPTES particles. However, no increased sorption maxima was observed for the thiolated Fe2O3 nano-particles (Fe2O3/MPTES) for the metal ions compared with the naked Fe2O3 nano-particles in this study. The greater capability of Fe2O3/HA to adsorb Cd(aq), Pb(aq), Cu(aq) indicates its potential use as another promising way to remediate metals-contaminated water.

Consistently modeling the combined effects of temperature and concentration on nitrate uptake in the ocean

[1] Considerable uncertainty remains about the combined effects of multiple limiting factors on oceanic phytoplankton, which constitute the base of the marine food web and mediate biogeochemical cycles of carbon and nutrients. I apply Bayesian statistical analysis to disentangle the combined effects of temperature and concentration on uptake of the important nutrient nitrate as measured by oceanic field experiments. This provides consistent estimates of temperature sensitivities for the maximum uptake rate and affinity (initial slope), the two parameters which define the shape of the uptake-concentration curve. No evidence is found that the temperature sensitivities of these two parameters differ, which implies that half-saturation constants, as commonly obtained by fits of the Michaelis-Menten (MM) equation, should be independent of temperature. This explains the robust relationship between half-saturation values and ambient nitrate concentration observed in compilations of data from diverse studies of uptake in marine and freshwater environments. Compared to the MM kinetics as applied in most large-scale models, accounting for a physiological trade-off between maximum uptake rate and affinity: (1) yields a more consistent model, which better describes observed changes in the shape of the uptake-concentration curve, and (2) implies a significantly greater inferred temperature sensitivity for nitrate uptake. These findings impact our understanding of how marine ecosystems and biogeochemical cycles will respond to climate change and anthropogenic nutrient inputs, both of which are expected to alter the relationship between nutrient concentrations and temperature in the near-surface ocean.

DNA recognition and transcriptional regulation by the WhiA sporulation factor

Sporulation in the filamentous bacteria Streptomyces coelicolor is a tightly regulated process involving aerial hyphae growth, chromosome segregation, septation and spore maturation. Genetic studies have identified numerous genes that regulate sporulation, including WhiA and the sigma factor WhiG. WhiA, which has been postulated to be a transcriptional regulator, contains two regions typically associated with DNA binding: an N-terminal domain similar to LAGLIDADG homing endonucleases, and a C-terminal helix-turn-helix domain. We characterized several in vitro activities displayed by WhiA. It binds at least two sporulation-specific promoters: its own and that of parABp2. DNA binding is primarily driven by its HTH domain, but requires full-length protein for maximum affinity. WhiA transcription is stimulated by WhiG, while the WhiA protein binds directly to WhiG (leading to inhibition of WhiG-dependent transcription). These separate activities, which resemble a possible feedback loop, may help coordinate the closely timed cessation of aerial growth and subsequent spore formation.