D. Rithesh Raj

Exploring the interaction of L-cysteine capped CuS nanoparticles with bovine serum albumin (BSA): a spectroscopic study

The interactions between nanoparticles and proteins have prime importance in nanomedicine and nanotoxicology. L-Cysteine capped copper sulfide (Cy-CuS) nanoparticles having average particle size of 6 nm have been synthesized using chemical coprecipitation method and their interactions with Bovine Serum Albumin (BSA) were explored using various spectroscopic techniques. A ground state complex is formed between BSA and Cy-CuS nanoparticles in solution. The number of binding sites, binding constant, quenching constant and the binding distance between Cy-CuS nanoparticles and BSA were determined. The overall conformation of BSA in the complex was unaltered, however the α-helical content of BSA was marginally reduced.

A systematic investigation on the interaction of L-cysteine functionalised Mn3O4 nanoparticles with lysozyme

Biological interactions of magnetic nanoparticles have attracted enormous interest because of their wide applications in medical diagnostics, imaging, and biosensors. Mn3O4 nanoparticles are potentially significant among magnetic nanoparticles and have not yet been investigated for their interactions with proteins. Here we report a systematic investigation of the interactions between hen egg white lysozyme and L-cysteine functionalised Mn3O4 nanoparticles using calorimetric and spectrophotometric techniques. The L-cysteine functionalised nanoparticles were synthesized by a simple chemical precipitation method and characterized by X-ray diffraction, FTIR, HRTEM, UV-Vis absorption and fluorescence spectroscopy. Mn3O4 nanoparticles are in the tetragonal phase with an average size of 10 nm. Thermodynamic parameters, the binding constant and the number of binding sites associated with the interactions were studied using Isothermal Titration Calorimetry (ITC). Quenching of lysozyme fluorescence is observed upon complex formation with Mn3O4 nanoparticle and the time resolved fluorescence measurements confirm static quenching. The Circular Dichroism (CD) spectra reveal minor alterations in the secondary structure of lysozyme in the complex indicating that Mn3O4 nanoparticles are potential candidates for therapeutic applications.

Optical nonlinearities of iron doped zinc sulphide quantum dots

Polyethylene glycol (PEG) capped pure and Fe doped ZnS nanoparticles were successfully synthesized by chemical precipitation method. Cubic zinc blende phase of the samples was confirmed from X-ray diffraction. The average grain size was found to be in the range of 2-3 nm and was confirmed with TEM. The undoped and doped ZnS samples show blue emission with emission wavelength at 360 nm. A rapid luminescence quenching with increasing dopant concentration was observed. The nonlinear absorption coefficients of the doped and undoped samples were calculated using Z-scan technique.