QbD approached comparison of reaction mechanism in microwave synthesized gold nanoparticles and their superior catalytic role against hazardous nirto‐dye

Microwave irradiation (MI) process characteristically enables extremely rapid “in‐core” heating of dipoles and ions, in comparison to conventional thermal (conductance) process of heat transfer. During the process of nanoparticles synthesis, MI both modulates functionality behaviors as well as dynamic of reaction in favorable direction. So, MI providing a facile, favorable and alternative approach during nanoparticles synthesis nanoparticles with enhanced catalytic performances. Although, conventionally used reducing and capping reagents of synthetic origin, are usually environmentally hazardous and toxic for living organism. But, in absence of suitable capping agent; stability, shelf life and catalytic activity of metallic nanoparticles adversely affected. However, polymeric templates which emerged as suitable choice of agent for both reducing and capping purposes; bearing additional advantages in terms of catalyst free one step green synthesis process with high degree of biosafety and efficiency. Another aspect of current works was to understand role of process variables in growth mechanism and catalytic performances of microwave processed metallic nanoparticles, as well as comparison of these parameters with conventional heating method. However, due to poor prediction ability with previously published architect OFAT (One factor at a time) design with these nanoparticles as well as random selection of process variables with their different levels, such comparison couldn't be possible. Hence, using gum Ghatti (Anogeissus latifolia) as a model bio‐template and under simulated reaction conditions; architect of QbD design systems were integrated in microwave processed nanoparticles to establish mechanistic role these variables. Furthermore, in comparison to conventional heating; we reported well validated mathematical modeling of process variables on characteristic of nanoparticles as well as synthesized gold nanoparticles of desired and identical dimensions, in both thermal and microwave‐based processes. Interestingly, despite of identical dimension, MI processed gold nanoparticles bearing higher efficiency (kinetic rate) against remediation of hazardous nitro dye (4‐nitrophenol), into safer amino (4‐aminophenol) analogues.     

Purification of Bioactive Lipopeptides Produced by Bacillus subtilis Strain BIA

Bacillus subtilis strain BIA was used for the production of bioactive lipopeptides. Different extraction and purification methods were assayed as liquid–liquid extraction, and acid and ammonium sulfate precipitation followed by TLC, SPE, and gel filtration. Active fractions were further purified using RP-HPLC. The molecular mass of the purified product from HPLC was determined through Tris-Tricine SDS-PAGE and MALDI–TOF-MS. The results revealed that Bacillus subtilis strain BIA produced surfactin and iturin like compounds. Coproduction of surfactin and iturin like compounds by this strain is a remarkable trait for a potential biocontrol agent. This paper also includeds techniques that have been developed for the optimal and convenient extraction of bioactive lipopeptides from microbial origin.

     

Observation of an unprecedented Cu Bis-His site: crystal structure of the H129V mutant of nitrite reductase

Copper nitrite reductases contain both an electron-transfer type 1 Cu site and a catalytic type 2 Cu site. We have mutated one of the type 2 copper ligating histidines to observe the effect on catalytic turnover. This mutation has created a unique site where Cu is ligated by 2 His Nepsilon2 atoms alone.     

Luminescence excitation spectra of toluene and mesitylene in rare-gas matrices

Total luminescence yield of toluene and mesitylene, isolated in rare-gas matrices, has been measured as a function of excitation energy in the energy range covering the absorption region of both host and guest. Energy transfer from the host to the dopant is apparent. An increase in the luminescence yield is observed at the host exciton state. Luminescence excitation spectrum of pure mesitylene is presented.     

High precision delta(17)O isotope measurements of oxygen from silicates and other oxides: method and applications

The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 μm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd.     

Molecular structure of an alkyl-side-chain polymer-water interface: origins of contact angle hysteresis

A new and direct approach to verify surface heterogeneity as the microscopic origin of contact-angle hysteresis is demonstrated. IR-visible sum-frequency-generation spectroscopy (SFG) was used to selectively probe the molecules at the interface of an alkyl-side-chain polymer [poly(vinyl n-octadecyl carbamate-co-vinyl acetate)] with water. The spectra indicate that in contact with water, the polymer surface is heterogeneous (having areas of differing surface energies). This evidence of surface heterogeneity supports the hysteresis observed in the advancing and receding contact angles of the polymer surface with water. The same measurements made for the chemically and structurally similar surface of an octadecyltrichlorosilane self-assembled monolayer indicates a homogeneous surface at the water interface. In this case, contact-angle hysteresis measurements implicate surface roughness as the cause of hysteresis. Atomic force microscopy measurements of roughness for these surfaces further support our conclusions. The polymer-water interface was probed using SFG at above-ambient temperatures, and an order-to-disorder transition (ODT) of alkyl side chains at the interface was observed, which closely follows the melting of crystalline side chains in the bulk. This transition explains the increased wettability of the polymer, by water, when the temperature is raised above the bulk melting temperature. Furthermore, the irreversibility of this ODT suggests that the disordered polymer-water interface is the thermodynamic equilibrium state, whereas the before-heating structure of this interface is a kinetically hindered metastable state.     

Infrared-visible sum frequency generation spectroscopic study of molecular orientation at polystyrene/comb-polymer interfaces

Surface-sensitive infrared-visible sum frequency generation spectroscopy (SFG) in total internal reflection geometry has been used to study the structure of poly(vinyl n-octadecyl carbamate-co-vinyl acetate) (PVNODC) or poly(octadecyl acrylate) (PA-18) in contact with a deuterated or hydrogenated polystyrene (dPS or hPS) layer. SFG spectra from the PVNODC (or PA-18)/hPS interface show methyl and methylene peaks corresponding to PVNODC (or PA-18) and phenyl peaks corresponding to the PS. Analysis suggests that the methyl groups are tilted at angles less than 30 degrees with respect to the surface normal. The presence of a strong methylene peak suggests the PVNODC alkyl side chains contain more gauche defects at the PS/PVNODC interface in comparison to PVNODC (or PA-18)/air interfaces. On heating, the SFG intensity from the PS/PA-18 interface drops sharply near the bulk melting temperature (T(m)) of PA-18. Interestingly, a similar drop in SFG signal is also observed for the PS phenyl groups. This demonstrates the ability of the phenyl group at the PS/PA-18 interface to rearrange itself upon the solid-to-liquid transition of the PA-18 alkyl side chain, at a temperature well below the bulk PS glass transition temperature. For PS/PVNODC interfaces, the drop in SFG intensity is gradual and in agreement with the three broad transitions of PVNODC observed in the bulk.     

Adsorption properties of thermally stable and biologically active polyurea: its synthesis and spectral aspects

Novel polymer metal complexes were prepared by the condensation polymerization of a polymeric ligand with transition metal ions of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II). The polymeric ligand was prepared by the addition polymerization of urea with toluene 2,4‐diisocyanate in 1:1 molar ratio. The polymeric ligand and its polymer metal complexes were characterized by elemental analysis, Fourier transform infrared spectroscopy, ¹³C‐NMR, and¹H‐NMR (nuclear magnetic resonance). The geometry was determined by electronic spectra and magnetic moment measurement. Thermogravimetric analysis (TGA) was utilized to find out the degradation process of the polyurea ligand and the polymer metal complexes. The TGA data revealed that all the metal‐containing polyureas are much more thermally stable than the corresponding polyurea ligand. The surface morphology of the polyurea ligand and cobalt(II)‐containing polyureas was determined by scanning electron micrographs. The antibacterial and antifungal activities of all the synthesized polymers were investigated against Staphylococcus aureus, Escherichia coli, and Bacillus subtilis (bacteria) and Aspergillus niger, Candida albicans, and Aspergillus flavus (fungi). These compounds show remarkably good biocidal activities, which were enhanced after complexation with the metal. Batch adsorption studies of the ligand were carried out for malachite green dye, and the polyurea ligand was found to be a good adsorbent for this dye. Copyright © 2011 John Wiley & Sons, Ltd.     

A distal pocket Leu residue inhibits the binding of O2 and NO at the distal heme site of cytochrome c'

Cytochromes c' are pentacoordinate heme proteins with sterically hindered distal sites that bind NO and CO but do not form stable complexes with O(2). Removal of distal pocket steric hindrance via a Leu→Ala mutation yields favorable O(2) binding (K(d) ~49 nM) without apparent H-bond stabilization of the Fe-O(2) moiety, as well as an extremely high distal heme-NO affinity (K(d) ~70 fM). The native Leu residue inhibits distal coordination of diatomic ligands by decreasing k(on) as well as increasing k(off). The connection between distal steric constraints, k(off) values, and distal to proximal heme-NO conversion is discussed.