Evaluation of defect induced surface heterogeneity in Metal-Organic Framework materials with alkali dopants employing adsorption isotherm modelling

In this article, an assessment of surface structural heterogeneity in porous metal organic framework (MOF) structure has been demonstrated by employing the methane and carbon-dioxide adsorption isotherms data. The virgin MIL-101-(Cr) MOF was synthesized by the hydrothermal method and defects were induced in the MOF structure by doping with various alkali (K, Na, Li) cations. The synthesized MOFs were characterized by XRD, SEM, EDX and BET measurement techniques. In order to understand the defect induced surface heterogeneity by alkali cation dopants, the surface energy distributions for CH₄ and CO₂ adsorptions on MOFs were measured by Dubinin – Astakhov model equation. The surface heterogeneity is mainly controlled by the limiting uptakes of adsorbates, the polarizability of adsorbates and the adsorbate-adsorbent interaction energy.     

The Correlations Between TCA-Glyoxalate Metabolite and Antibiotic Production of <Emphasis Type="Italic">Streptomyces</Emphasis> sp. M4018 Grown in Glycerol,Glucose, and Starch Mediums

The alterations of organic acids citrate, α-ketoglutarate, succinate, fumarate, malate production together with isocitrate lyase activity as a glyoxalate shunt enzyme, and antibiotic production of Streptomyces sp M4018 were investigated in relation to changes in the glucose, glycerol and starch concentrations (5–20 g/L) after identification as a strain of Streptomyces hiroshimensis based on phenotypic and genotypic characteristics. The highest intracellular citrate and α-ketoglutarate levels in 20 g/l of glucose, glycerol, and starch mediums were 399.47 ± 4.78, 426.93 ± 6.40, 355.84 ± 5.38 ppm and 444.81 ± 5.12, 192.96 ± 2.26, 115.20 ± 2.87 ppm, respectively. The highest succinate, malate, and fumarate levels were also determined in 20 g/l of glucose medium as 548.9 ± 11.21, 596.15 ± 8.26, and 406.42 ± 6.59 ppm and the levels were significantly higher than the levels in glycerol and starch. Extracellular organic acid levels measured also showed significant correlation with carbon source concentrations by showing negative correlation with pH levels of the growth medium. The antibiotic production of Streptomyces sp. M4018 was also higher in glucose medium as was the case also for organic acids when compared with glycerol. On the other hand, there is no production in starch.     

Bis[hydrotris(pyrazol-1-yl)borato]titanium(II): a stable Tp2M complex of singular reactivity

Tp2Ti [Tp = hydrotris(pyrazol-1-yl)borate] is a stable hard donor complex of divalent titanium that shows controlled reaction chemistry with simple chalcogen oxidants.     

A search for Na atom in CsI:Na crystal

The presence of a Na atom in CsI: Na after X-ray irradiation is searched by ESR (35 GHz microwave) detected through the magnetic circular dichroism of a related optical absorption band. The results are discussed with the model of Na atom in the crystal where either 3s or 3 p_z orbit is the ground state depending on its site.     

Conformational Study of Spectrin in Presence of Submolar Concentrations of Denaturants

The presence of very low concentrations of the commonly used chemical denaturants, guanidinium chloride (GdmCl) and urea brought about conformational changes in the erythrocyte membrane skeletal protein, spectrin. Evidences in support of changes in the quaternary structure of spectrin have been put forward from quenching study of tryptophan fluorescence, by both steady state and time-resolved measurements, using acrylamide as the quencher. It revealed significant differences between the Stern–Volmer quenching constants (K_SV) and the fraction of accessible tryptophans (f_e) observed in absence and presence of GdmCl and urea concentrations below 1 M at which the association of the two subunits remains intact. The steady state anisotropy of both the spectrin tryptophans and the spectrin-bound fluorescence probe, Prodan also indicate changes in the overall flexibility of the spectrin dimer, originating from changes in the quaternary structure of spectrin. Studies on the binding of Prodan, further indicate that conformational changes also occur in spectrin near the Prodan-binding site at the terminal domain of the protein which is reflected in 3–4 fold decrease in the affinity of binding of Prodan to spectrin in the presence of GdmCl and urea compared to that observed in the absence of the denaturants. The dissociation constant (K_d) of Prodan to spectrin is 0.43 M at 25°C.     

Polarity Estimate of the Hydrophobic Binding Sites in Erythroid Spectrin: A Study by Pyrene Fluorescence

The apparent dielectric constant, , of the hydrophobic pyrene binding sites in erythroid spectrin and human serum albumin (HSA) were estimated using the linear relationship [Turro, N.J., Kuo, P.L., Somasundaran, P. and Wong, K. (1986). J. Phys. Chem. 90, 288–291] between the ratio of the first (373 nm) and the third (384 nm) vibronic peak intensities (l₁/l₃) and the dielectric constant of the bulk medium. Binding of the hydrophobic fluorescent probe, pyrene, to erythroid spectrin and HSA was determined from concentration dependent change in the ratio l₁/l₃ from the emission spectra. Pyrene binds to spectrin (K_app = 6.2 × 10⁶ M^–1) with a higher affinity than that of HSA (K_app = 3.7 × 10⁴ M^–1) and the binding in both cases are saturable. The for spectrin and HSA was estimated to be 7 ± 2.1 and 5.4 ± 1.6 respectively. A case study with spectrin, covalently labeled with pyrene maleimide, have been presented for aging of pyrene-labelled spectrin showing the potential of the use of vibrational peak ratios (l₁/l₃) in the study of polarity of microenvironments in the neighborhood of cysteine residues of a protein. Large changes in the pyrene spectral components indicated conformational changes in the cysteine microenvironment of the protein upon storage at 4°C.     

An efficient route to coumarin derivatives under dual catalysis,an organo- and a Lewis acid catalyst

An efficient reaction of dialkyl acetylenedicarboxylate with various o-hydroxy aromatic aldehydes under dual catalysis with piperidine and FeCl₃ in refluxing toluene afforded alkyl 2-oxo-2-(2-oxo-2H-chromen-3-yl) acetates in good to excellent yield. The advantages of this reaction include the use of easily available starting materials, one-pot reaction, mild reaction conditions and operational simplicity.     

Copper oxide catalyzed domino process for the synthesis of substituted 2H-pyran-2-ones and polyhydroxy coumarin derivatives

An efficient method for the synthesis of substituted 2H-pyran-2-ones and polyhydroxy coumarin derivatives has been developed via CuO-catalyzed C–C bond formation followed by intramolecular cyclization reaction by reacting electron-deficient alkynes with 1,3-diketones and polyhydroxy benzenes, respectively. The domino reaction proceeded smoothly by using commercially available catalysts under reflux in toluene with very good yield.     

Quantifying uncertainty in the measurement of arsenic in suspended particulate matter by Atomic Absorption Spectrometry with hydride generator

Arsenic is the toxic element, which creates several problems in human being specially when inhaled through air. So the accurate and precise measurement of arsenic in suspended particulate matter (SPM) is of prime importance as it gives information about the level of toxicity in the environment, and preventive measures could be taken in the effective areas. Quality assurance is equally important in the measurement of arsenic in SPM samples before making any decision. The quality and reliability of the data of such volatile elements depends upon the measurement of uncertainty of each step involved from sampling to analysis. The analytical results quantifying uncertainty gives a measure of the confidence level of the concerned laboratory. So the main objective of this study was to determine arsenic content in SPM samples with uncertainty budget and to find out various potential sources of uncertainty, which affects the results. Keeping these facts, we have selected seven diverse sites of Delhi (National Capital of India) for quantification of arsenic content in SPM samples with uncertainty budget following sampling by HVS to analysis by Atomic Absorption Spectrometer-Hydride Generator (AAS-HG). In the measurement of arsenic in SPM samples so many steps are involved from sampling to final result and we have considered various potential sources of uncertainties. The calculation of uncertainty is based on ISO/IEC17025: 2005 document and EURACHEM guideline. It has been found that the final results mostly depend on the uncertainty in measurement mainly due to repeatability, final volume prepared for analysis, weighing balance and sampling by HVS. After the analysis of data of seven diverse sites of Delhi, it has been concluded that during the period from 31^st Jan. 2008 to 7^th Feb. 2008 the arsenic concentration varies from 1.44 ± 0.25 to 5.58 ± 0.55 ng/m³ with 95% confidence level (k = 2).     

Some results on a doubly truncated generalized discrimination measure

Doubly truncated data appear in some applications with survival and astrological data. Analogous to the doubly truncated discrimination measure defined by Misagh and Yari (2012), a generalized discrimination measure between two doubly truncated non-negative random variables is proposed. Several bounds are obtained. It is remarked that the proposed measure can never be equal to a nonzero constant which is independent of the left and right truncated points. The effect of monotone transformations on the proposed measure is discussed. Finally, a simulation study is added to provide the estimates of the proposed discrimination measure.