Polymerization of Acrylonitrile with Ceric lon-2-Propanethiol as Initiator System

The kinetics of the polymerization of arylonitrile with ceric ammonium sulfate in the presence of 2-propanethiol as the redox initiator system in aqueous solution has been investigated. The rate of polymerization was found to be proportional to the square root of both ceric ion and thiol concentrations, and the monomer exponent was close to 1.5. Spectral studies indicated that there is a complex formation between ceric ion and the monomer acrylonitrile. A kinetic scheme, based on initial formation of this complex and its subsequent reaction with the thiol to produce the free radicals (RS.) responsible for initiation has been postulated to account for the observed results. The activation energy and different kinetic and transfer constants for the system have also been evaluated.     

Biophysical characterization of thermophilic laccase from the xerophytes: Cereus pterogonus and Opuntia vulgaris

Biophysical characterization of laccase enzyme isoforms from two different xerophytic plants Cereus pterogonus and Opuntia vulgaris was carried out using EPR, fluorescence and circular dichroism (CD) spectroscopy while their thermal denaturation profiles were investigated employing differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). EPR analysis revealed the presence of endogenous copper. The hyperfine splitting of EPR spectrum reduced with increase in the complexity of enzyme protein. Raise in temperature did not alter the protein fluorescence emission suggestive of high temperature stability of the enzyme, causing the tryptophan and tyrosine residues to remain buried within the protein structure. Far-UV CD spectrum revealed existence of 60 % random coils in enzyme structure even at elevated temperatures and in presence of metal ions and protein denaturants. DSC analysis provided a Tm in the range 95–121 °C for the native and 158–199 °C for the metal associated laccase isoforms. Loss in weight of the enzyme protein by 10–18 % was noted up to 100 °C when determined through TGA. The thermostable plant xerophytic laccase enzyme isoforms will be of potential use in textile, dyeing, pulping and biotechnology applications.     

Protein-assisted synthesis route of metal nanoparticles: exploration of key chemistry of the biomolecule

Abstract  

Essentially, biomolecule assisted synthesis of inorganic nanoparticles can be divided into two categories. One uses multi-domain protein cages (template) and other relies on the self-assembly of the biomolecules including small peptides, DNA, and denatured protein. Protein templated synthesis of various nanomaterials is relatively well understood as the cages of the biological macromolecules and their specific interaction with inorganic ions ultimately dictate the size and crystallinity of the nanomaterials. On the other hand formation of nanoparticles using protein in the cost of the native structural integrity for the self-assembly is not well understood till date. In the present work we report a protein-assisted synthesis route to prepare highly crystalline 3–5 nm gold nanoparticles, which relies systematic thermal denaturation of a number of proteins and protein mixture from Escherichia coli in absence of any reducing agent. By using UV–vis, circular dichroism spectroscopy, and high-resolution transmission electron microscopy we have explored details of the associated biochemistry of the proteins dictating kinetics, size, and crystallinity of the nanoparticles. The kinetics of nanoparticles formation in this route, which is sigmoidal in nature, has been modelled in a simple scheme of autocatalytic process. Interestingly, the protein-capped as prepared Au nanoparticles are found to serve as effective catalyst to activate the reduction of 4-nitrophenol in the presence of NaBH₄. The kinetic data obtained by monitoring the reduction of 4-nitrophenol by UV/vis-spectroscopy revealing the efficient catalytic activity of the nanoparticles have been explained in terms of the Langmuir–Hinshelwood model. The methodology and the details of the protein chemistry presented here may find relevance in the protein-assisted synthesis of inorganic nanostructures in general.     

A naphthyridine based macrocyclic “switching on” fluorescent receptor for cadmium

A new macrocyclic receptor 1 having [1,8]-naphthyridine fluorophore is designed and synthesized for selective fluorescence sensing of Cd²⁺. Receptor 1 selectively responds to Cd²⁺ over other tested metal ions via a large enhancement of emission intensity due to the cation-induced CHEF (chelation enhanced fluorescence) effect. Receptor 1 although exhibits some affinity towards Zn²⁺, it selectively binds Cd²⁺ over Zn²⁺. Binding and selectivity were examined by ¹H-NMR, fluorescence, UV-vis, mass and IR-spectroscopic techniques.     

Experimental investigation of vibration power flow in thin technical orthotropic plates by the method of vibration intensity

Vibration intensity technique is used to measure vibration power transmission in thin single layer technical orthotropic plates for flexural waves. Measurement of flexural wave power is carried out in far-field conditions. All measurements are undertaken in the frequency domain using the cross-spectra of acceleration signals, facilitating the use of FFT analyzer. The two-transducer technique applicable to these plates is used for these measurements. Technical orthotropic (rectangular corrugation) plates of steel are used for the measurements. One isotropic plate of steel is also considered for comparison. Method of elastic equivalence technique is used. Both input power and vibration power transmission through the plates are estimated. Far-field power is normalized with the input power for flexural wave. Influence of flexural rigidity on vibration energy transfer is also investigated.     

Synthesis and structural characterization of II–VI semiconductor nanocrystallites (quantum dots)

A methodology for the production of II–VI semiconductor nanocrystallites employing organometallic precursors has been developed. The rapid pyrolysis of reagents in a coordinating solvent provides temporally discrete nucleation. Subsequent controlled growth allows the production of macroscopic quantities of nanocrystallites with consistent structure, surface derivatization and a high degree of monodispersity. The samples produced are structurally characterized with a combination of X-ray and Electron Beam based techniques.     

Synthesis and characterisation of cobalt(III) complexes with 1,1-dimethylethylenediamine (1,1-dmen) and 1,2-propanediamine (pn)

Two stable diamine complexes [Co(1,1-dmen)₂(NCS)₂]SCN · (H₂O)_1.5 (1) and [Co(pn)₂(NCS)₂]SCN · (H₂O)_1.5 (2) have been synthesised and characterised by elemental analysis, i.r. and electronic spectra and t.g.a. The structure of (1) has been confirmed by single-crystal X-ray diffraction and reveals that the cobalt complex has octahedral geometry and consists of two crystallographically independent cations, both situated on centres of inversion. In the crystal structure of (1), free H₂O molecules and SCN^– ions form an extensive hydrogen bonding network with the cation. It is an ordered pseudo-polymorph of a previous structure determination. Both (1) and (2) are diamagnetic.     

Investigation of quark distributions in a family of pentaquarks using the Thomas-Fermi quark model

Using the Thomas-Fermi quark model,a collective,spherically symmetric density of states is created to represent a gas of interacting fermions with various degeneracies at zero temperature.Over a family of pentaquarks,uudcc,color interaction probabilities were obtained after averaging over all the possible configurations.Three different functions are developed for light,charm,and anti-charm quarks and are assumed to be linearly related by some proportionality constants.Interesting patterns of quark distributions are observed while analyzing the quark function consistency conditions for such constants.     

Aptamer based voltammetric biosensor for the detection of <Emphasis Type="Italic">Mycobacterium tuberculosis</Emphasis> antigen MPT64

The authors report an aptaelectrode based on graphene modified iron-oxide chitosan hybrid (CHIT-IO-GR) nanocomposite film deposited on fluorine tin oxide (FTO) for the detection of the Mycobacterium tuberculosis specific antigen MPT64. The biotinylated DNA aptamer sequence specific to the MPT64 was immobilized onto the CHIT-IO-GR/FTO electrode by using streptavidin-biotin interactions. XRD, FT-IR, FE-SEM and electrochemical studies were applied to monitor the steps of the fabrication. The aptaelectrode, operated best at typical voltage of 0.44 V, exhibited a limit of detection (LOD) of 0.9 fg?mL^?1 within 20 min. The biosensor retained about 80% of its initial activity after 10 uses. The potential application of the aptasensor was established by spike-in studies to obtain recoveries between 83 and 95%.

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Graphical abstract An electrochemical aptaelectrode based on nanocomposite consisting of chitosan (CHIT), iron-oxide nanoparticles (IO) and functionalized graphene (GR) has been fabricated to detect M. tb antigen MPT64 with an LOD of 0.9 fg?mL^?1 within 20 min.

     

Enantioselective access to tetrahydropyrano[2,3-c]pyrazoles via an organocatalytic domino Michael-hydroalkoxylation reaction

An asymmetric domino Michael-hydroalkoxylation reaction of trans-α-alkynyl-nitroolefins with N-arylpyrazolinones has been accomplished using a chiral bifunctional squaramide catalyst. Under the organocatalytic method, a broad range of tetrahydropyrano[2,3-c]pyrazoles with an exocyclic alkene at the C-6 position were prepared in high yields and excellent stereoselectivities. The presence of an exocyclic double bond and nitro group in the pyranopyrazoles provide a wide scope for further structural transformations.