Reversibly soluble macroaffinity ligand in aqueous two-phase separation of enzymes

Use of alginate as a free bioligand incorporated in an aqueous two-phase system of polyethylene glycol 6000-salt resulted in considerable purification of wheat germ alpha-amylase and sweet potato beta-amylase from their crude extracts. The elution of the enzyme from the free bioligand was facilitated by exploiting the fact that alginate can be reversibly precipitated in the presence of Ca2+. alpha-Amylase could be purified 42-fold with 92% activity recovery. beta-Amylase on the other hand could be purified 43-fold with 90% recovery. Both purified enzymes showed a single band on sodium dodecylsulfate-polyacrylamide gel electrophoresis.     

Complexes of divalent oxovanadium,manganese, iron,cobalt, nickel and copper with the ligand derived from the reaction of 2-aminopyridine and acetylacetone

Summary 2-Aminopyridine reacts with acetylacetone in the presence of VO^II, Mn^II, Fe^II, Co^II, Ni^II, and Cu^II metal salts to give complexes of the type [VO(Ap₂ac)₂X]X and [M(Ap₂ac)₂X₂] where (Ap₂ac) is the ligand formedin situ. The complexes are characterised as distorted octahedral by analyses, conductance, molecular weight, magnetic, electronic and i.r. spectral studies. The i.r. studies reveal that two molecules of aminopyridine are joined by a molecule of acetylacetone through a three carbon atom bridge and that the ligand coordinates through the azomethine and imino nitrogen atoms, whereas pyridine does not take part in coordination. The electronic spectra have been interpreted and tentative assignments are made. In the far i.r. spectra, various metal ligand vibrations are observed and discussed. Attempts to carry out electrophilic substitutions in the complexes failed.     

Chitosan as a macroaffinity ligand purification of chitinases by affinity precipitation and aqueous two-phase extractions

(1) Chitosan was found to be a suitable macroaffinity ligand for affinity precipitation of chitinase from Neurospora crassa, cabbage and puffballs. (2) The activity recoveries of 85, 82 and 90% with concomitant fold purifications in terms of specific activities were 27, 15 and 30 with N. crassa, cabbage and puffballs and were obtained with affinity precipitation. These results were obtained with clarified extracts/homogenates as the starting materials. (3) The incorporation of chitosan in poly(ethylene glycol) (PEG)-salt aqueous two-phase system allowed purification of chitinases from these sources directly from unclarified extracts/homogenates. (4) The 96% (w/v) chitosan (of initially introduced into the aqueous two-phase system) partitioned into PEG-phase and this enhanced the partitioning of chitinases into PEG-phase. The chitosan, free as well as bound to chitinases, could be separated from PEG-phase by increasing the pH to 7. (5) By the process of desorption with 2.0 M MgCl2, 86, 80 and 88% activity recoveries (% expressed in terms of total units of enzyme activities in the crude extract) were obtained in the case of N. crassa, cabbage and puffballs, respectively. The corresponding fold purifications in terms of specific activities were 34, 20 and 38. (6) The purified preparations gave single bands on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and the estimated molecular masses agreed with the reported values in the literature.     

Coumarine–imino–C2-glucosyl conjugate as receptor for Cu in blood serum milieu,on silica gel sheet and in Hep G2 cells and the characterization of the species of recognition

A coumarine–imino–C2-glucosyl conjugate (L) was synthesized and characterized. The conjugate L is found to recognize Cu²⁺ in aqueous HEPES buffer by exhibiting a 95% fluorescence quenching in pH range 7–10 even in the presence of several biologically and ecologically relevant metal ions. Fluorescence on–off behavior has been clearly demonstrated on the basis of the binding variability of Cu²⁺ to L. The binding has been elicited through the changes observed in fluorescence, absorption, ESI-MS and ¹H NMR titrations. All the other thirteen metal ions studied did not show any change in the fluorescence emission. These ions do not interfere with the recognition of Cu²⁺ by L. The structural features of [CuL]₂ complex in both the isomeric forms were established by DFT computational calculations. The utility of L has been demonstrated by showing its sensitivity toward Cu²⁺ on a thin layer of silica gel. The L gives sensitive fluorescence signals for Cu²⁺ even in blood serum and exhibits appropriate fluorescence responses in living cells.     

Gold‐Nanoparticle‐Decorated Boron Nitride Nanosheets: Structure and Optical Properties

Synergetic cooperation of individual components of the nanocomposites (NCs) is responsible for their novel properties that lead to various technological applications. A simple chemical process depicting the deposition of functionalized gold nanoparticles on the surface of boron nitride nanosheets (BNNSs) in solution is reported. The structure, chemical composition, and optical properties of nanosheets are systematically studied. The deposition of Au nanoparticles on BNNS (BNNS_Au) results in plasmonic band modulation, thus altering the optoelectronic properties of BNNSs. The intense surface plasmon absorption band of BNNS_Au is narrowed and red‐shifted relative to the absorption band of as synthesized monometallic BNNSs. The observations reflect the strong interfacial interaction between BNNS and Au nanoparticles. This approach constitutes a basis for a simple process leading to the preparation of functionalized BNNSs and their utilization as nanoscale templates for assembly and integration with other nanoscale materials for futuristic optoelectronic devices.     

Photocured characteristics of fast photocurable acrylic formulations and investigations by differential photo calorimeter

Nanofluids are obtained by suspending metallic or non-metallic nanoparticles in conventional base liquids and can be employed to increase heat transfer rate in various applications. In this study, the effects of adding three types of nanofluids on turbulent convective heat transfer at the entrance region of a constant wall heat flux tube were experimentally studied. The nanofluids were mixtures of aluminium oxide, copper oxide, and silicon carbide at various nanoparticle volume fractions ranging from 0.0002 to 0.002 in water. The convective heat transfer coefficient was measured at different Reynolds numbers of 10,000–50,000. At these concentrations and Reynolds numbers, a maximum of 11–18% of convection heat transfer coefficient was observed as compared to the base fluid, showing a 6–9% increase on average. In this study, it was observed that changes in the nanoparticle type had no considerable effect on heat transfer coefficient increase. According to the model proposed here, the dimensionless thickness of laminar sub-layer is specified as a functional equation of the volume fraction of nanoparticles for each material.

     

Purification of α-amylases using magnetic alginate beads

Magnetic alginate beads were used to purify alpha-amylases from porcine pancreas, starchzyme, BAN 240L (a commercial purification from Bacillus subtilis), and wheat germ. The beads bound a significant level of alpha-amylase activity from porcine pancreas, BAN 240L, and wheat germ. In each case, the enzyme activity could be eluted by using 1.0 M maltose, a known competitive inhibitor of alpha-amylase. In the case of BAN 240L, 3.6-fold purification with 72% recovery of activity was observed. In the case of wheat germ enzyme, starting from the crude extract, 48-fold purification with 70% activity recovery was observed. Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis also indicated considerable purification in the latter case.     

Divalent nickel,cobalt and copper complexes of a tetradentate N6 macrocyclic ligand

Summary Divalent nickel, cobalt and copper salts react with 2,6-diaminopyridine and acetylacetone to form complexes containing a 16-membered N₆ tetradentate macrocyclic ligand. The complexes are characterised as distorted octahedra of the M(TML)X₂ type where M=nickel(II), cobalt(II) and copper(II); TML=tetradentate macrocyclic ligand and X=Cl, Br, NO₃ or NCS. The ligand coordinates through all the four azomethine nitrogen atoms which are bridged by acetylacetone moieties. Pyridine nitrogen does not participate in coordination, a fact supported by far i.r. studies. The magnetic, electronic and i.r. spectral studies indicate that the complexes have lower symmetries and the amounts of distortion calculated in terms of DT/DQ applying normalised spherical harmonic Hamiltonian theory indicate that these complexes are moderately distored.     

Simulation of FTTH at 10 Gbit/s for 8 OTU by GE-PON Architecture

In this paper a fiber communication system is employed using Giga Ethernet Passive Optical Network (GE-PON) architecture. In this architecture an optical fiber is employed directly from a Central Office to the home. A 1:8 splitter is used as a PON element which establishes communication between a Central Office to different users. In this paper GE-PON architecture has investigated for different lengths from a Central Office to the PON in the terms of BER. For 10 Gbit/s system the plots between the BER and transmission distance is plotted and it is seen that as the distance increases beyond the 15 km the BER is increased very sharply. Results in the form of Voice and Data spectrum for different users of FTTH with GE-PON architecture are shown.     

Trivalent chromium,manganese, iron and cobalt chelates of a tetradentate N6 macrocyclie ligand

Summary Trivalent chromium, manganese, iron and cobalt salts reactin situ with 2,6-diaminopyridine and acetylacetone to form complexes of the 16-membered N₆ tetradentate macrocyclic ligand. The chelates are characterised as distorted square-pyramidal of [M(TML)X] type, where M = chromium(III), manganese(III), iron(III) and cobalt(III); X=Cl, Br, NO₃ or NCS for chromium(III) and iron(III) and X=(OAc) for manganese(III) and (OH) for cobalt(III). The ligand coordinates through all the nitrogen atoms through deprotonation of two of them, however, the pyridine nitrogens do not take part in coordination. The chelates incorporate one anion or hydroxyl group in the coordination sphere. The magnetic, electronic and i.r. spectral studies indicate lower symmetries for these chelates. The amount of distortion is calculated in terms of DT/DQ by applying NSH theory. X-ray measurements on powder form of the complexes show their isomorphic nature and also support the proposed structures.