Binding of chloroquine-conjugated gold nanoparticles with bovine serum albumin

We have conjugated chloroquine, an anti-malarial, antiviral and anti-tumor drug, with thiol-functionalized gold nanoparticles and studied their binding interaction with bovine serum albumin (BSA) protein. Gold nanoparticles have been synthesized using sodium borohydride as reducing agent and 11-mercaptoundecanoic acid as thiol functionalizing ligand in aqueous medium. The formation of gold nanoparticles was confirmed from the characteristic surface plasmon absorption band at 522 nm and transmission electron microscopy revealed the average particle size to be ~7 nm. Chloroquine was conjugated to thiolated gold nanoparticles by using EDC/NHS chemistry and the binding was analyzed using optical density measurement and Fourier transform infrared spectroscopy. The chloroquine-conjugated gold nanoparticles (GNP-Chl) were found to interact efficiently with BSA. Thermodynamic parameters suggest that the binding is driven by both enthalpy and entropy, accompanied with only a minor alteration in protein's structure. Competitive drug binding assay revealed that the GNP-Chl bind at warfarin binding site I in subdomain IIA of BSA and was further supported by Trp212 fluorescence quenching measurements. Unraveling the nature of interactions of GNP-Chl with BSA would pave the way for the design of nanotherapeutic agents with improved functionality, enriching the field of nanomedicine.     

The use of ECD/ETD to identify the site of electrostatic interaction in noncovalent complexes

Electrostatic interactions play an important role in the formation of noncovalent complexes. Our previous work has highlighted the role of certain amino acid residues, such as arginine, glutamate, aspartate, and phosphorylated/sulfated residues, in the formation of salt bridges resulting in noncovalent complexes between peptides. Tandem mass spectrometry (MS) studies of these complexes using collision-induced dissociation (CID) have provided information on their relative stability. However, product-ion spectra produced by CID have been unable to assign specifically the site of interaction for the complex. In this work, tandem MS experiments were conducted on noncovalent complexes using both electron capture dissociation (ECD) and electron-transfer dissociation (ETD). The resulting spectra were dominated by intramolecular fragments of the complex with the electrostatic interaction site intact. Based upon these data, we were able to assign the binding site for the peptides forming the noncovalent complex.     

An Organocatalytic Azide–Aldehyde [3+2] Cycloaddition: High‐Yielding Regioselective Synthesis of 1,4‐Disubstituted 1,2,3‐Triazoles

An organocatalytic azide–aldehyde [3+2] cycloaddition (organo‐click) reaction of a variety of enolizable aldehydes is reported. The organo‐click reaction is characterized by a high rate and regioselectivity, mild reaction conditions, easily available substrates with simple operation, and excellent yields with a broad spectrum of substrates. It constitutes an alternative to the previously known CuAAC, RuAAC, and IrAAC click reactions.     

Synthesis of LaB6 micro/nano structures using picosecond (Nd:YAG) laser and its field emission investigations

Micro/nano structures have been obtained by laser surface treatment on sintered LaB₆ pellets employing a picosecond pulsed Nd:YAG laser at a pressure of ∼1×10⁻³ mbar. The X-ray diffraction pattern of the laser treated pellet shows a set of well defined diffraction peaks, indexed to the cubic phase of LaB₆ only. The scanning electron microscope studies reveal formation of micro and nano structures upon laser treatment and the resultant surface morphology is found to be strongly influenced by the laser fluence. Field electron emission studies made on the LaB₆ pellet, treated with optimized laser fluence, have been performed in a planar diode configuration under ultra high vacuum conditions. The threshold field required to draw an emission current density of ∼10 μA/cm² has been found to be ∼2.3 V/μm and a current density of ∼530 μA/cm² has been drawn at an applied field of 5.2 V/μm. The Fowler-Nordheim plot is found to be linear in accordance with the quantum mechanical tunneling phenomenon, confirming the metallic nature of the emitter. The emission current at the pre-set value ∼10 μA shows very good stability over a period of more than 3 hours. The present results emphasize the effectiveness of a picosecond laser treatment towards fabrication of a nano metric LaB₆ emitter for high current density applications.     

Laser etching of Thoria pellets for microstructural investigations

Metallographic investigation of the microstructure of sintered Thoria pellets necessitates appropriate surface preparation of these pellets. Conventional etching methods involving either chemical or thermal etching techniques being unsuitable for surface etching of irradiated Thoria fuel, laser-based surface treatment was envisaged as a potential alternative technique. Thoria pellets were subjected to laser surface treatment using a pulsed Nd:YAG laser.Our preliminary studies have successfully demonstrated laser etching of sintered Thoria pellets with good reproducibility, clearly revealing grain structures and well-defined grain boundaries. Detailed parametric investigations determining optimum laser parameters for the process, are presented. Our results on ultra-short laser-based etching of sintered Thoria pellets are also discussed.     

Artificial intelligence based modelling and multi-objective optimization of vinyl chloride monomer (VCM) plant to strike a balance between profit,energy utilization and environmental degradation

The current research focuses on the creation of a general technique that solves the key issue of any operational chemical plant, namely, how to strike a delicate balance between profit and environmental impact. As a case study, a commercial vinyl chloride monomer (VCM) production unit was used. This research produced a new modelling and optimization tool that commercial chemical plants can use to measure their environmental impact and strike a careful balance between profit and environmental damage. This paper demonstrates how to model commercial complex reactors using Aspen and ANN in an easy-to-use manner. The current study used a multi-objective hybrid ANN and genetic algorithm to find a delicate balance between profit and environmental damage. A case study of a commercial VCM manufacturing process demonstrates the efficacy of the proposed methodology. The suggested methodology creates optimal VCM reactor operating parameters, which can be used in commercial plants to increase profit. Furthermore, the suggested methodology creates a set of Pareto optimal solutions platform to acquire insight into the profit-environmental impact balance. These insights could be extremely beneficial to plant management in making educated decisions about plant operations.     

Characterization of heparin–protein interaction by saturation transfer difference (STD) NMR

The binding affinity and specificity of heparin to proteins is widely recognized to be sulfation-pattern dependent. However, for the majority of heparin-binding proteins (HBPs), it still remains unclear what moieties are involved in the specific binding interaction. Here, we report our study using saturation transfer difference (STD) nuclear magnetic resonance (NMR) to map out the interactions of synthetic heparin oligosaccharides with HBPs, such as basic fibroblast growth factor (FGF2) and fibroblast growth factor 10 (FGF10), to provide insight into the critical epitopes of heparin ligands involved. The irradiation frequency of STD NMR was carefully chosen to excite the methylene protons so that enhanced sensitivity was obtained for the heparin–protein complex. We believe this approach opens up additional application avenues to further investigate heparin–protein interactions.