Gopa Mandal

Interaction of bovine serum albumin and albumin-gold nanoconjugates with l-aspartic acid. A spectroscopic approach

The interaction of an essential transport protein bovine serum albumin (BSA) and albumin-gold nanoconjugates (BSA-GNPs) with amino acid l-aspartic (ASP) are investigated by steady state and time resolved spectroscopic techniques. In both the cases, static fluorescence quenching is observed indicating that a ground state complex is formed between the donor BSA/BSA-GNP with the acceptor ASP. High values of quenching constant suggest that energy transfer also occurred from BSA and BSA-GNPs to ASP. Distance between the fluorophore in the protein and the amino acid (ASP) is evaluated. Binding constants and the number of binding sites were determined in both the cases. The observed thermodynamic parameters suggest that the key interacting forces involved in both cases are hydrophobic interactions. Circular dichroism (CD) spectrum of BSA molecule suffers marginal change in the presence of ASP both in its pure as well as bio-nanoconjugate forms. As no structural deformation is occurred, the biological activity along with the activity of immune response of protein and the biocompatibility of protein-nanoconjugate remain as such.

Steady state, time resolved, and circular dichroism spectroscopic studies to reveal the nature of interactions of zinc oxide nanoparticles with transport protein bovine serum albumin and to monitor the possible protein conformational changes

In this paper, the interaction between bovine serum albumin (BSA) and zinc oxide (ZnO) nanoparticles was investigated by fluorescence quenching spectra, circular dichroism (CD), and synchronous spectra under physiological conditions. From the analysis of the steady state and time resolved fluorescence quenching of BSA in aqueous solution in presence of ZnO it was observed that the nature of the quenching is of static-type quenching. The Stern–Volmer quenching constant KS at different temperatures were determined and the thermodynamic parameters ΔH, ΔG, and ΔS were computed. The experiment revealed that the electrostatic interaction was the predominant force in stabilizing the complex. The effect of ZnO on the conformation of BSA has been analyzed by synchronous spectra and CD spectrum. Although the observed results demonstrate some conformational changes in BSA in presence of ZnO nanoparticles, the secondary structure of BSA, predominantly of α-helix, is found to retain its identity.

Detailed spectroscopic investigations to reveal the nature of interaction of anionic porphyrin with calf thymus DNA

The interaction between anionic form of meso-tetrakis(4-carboxyphenyl) porphyrin (TCPP) and calf thymus deoxyribonucleic acid (CT DNA) is investigated by measuring UV-vis absorption, steady-state fluorescence, steady-state fluorescence anisotropy, time-resolved fluorescence, resonance light scattering (RLS), FT-IR and circular dichroism (CD) spectra along with the help of atomic force microscopy (AFM) under Tris-Borate-EDTA (TBE) buffer solution of pH 8.3. The static mode of fluorescence quenching of porphyrin by calf thymus deoxyribonucleic acid indicates the formation of a ground-state complex. The formation of ground-state complex is a spontaneous molecular interaction procedure in which outside groove binding through hydrogen bond or van der Waals force plays a major role. For biomedical application this investigation is very important as here TCPP, i.e. the anionic porphyrin does not bring any changes in the original structure of the CT DNA to selectively cleaving the nucleic acid to destroy the cancer or tumor cells whereas cationic porphyrin makes change in the protein structure significantly during the same process.

Mode of bindings of zinc oxide nanoparticles to myoglobin and horseradish peroxidase: A spectroscopic investigations

The interactions between two heme proteins myoglobin (HMb) and horseradish peroxidase (HRP) with zinc oxide (ZnO) nanoparticles are investigated by using UV–vis absorption, steady state fluorescence, synchronous fluorescence, time-resolved fluorescence, FT-IR, atomic force microscopy (AFM) and circular dichroism (CD) techniques under physiological condition of pH∼7.4. The presence of mainly static mode in fluorescence quenching mechanism of HMb and HRP by ZnO nanoparticle indicates the possibility of formation of ground state complex. The processes of bindings of ZnO nanoparticles with the two proteins are spontaneous molecular interaction procedures. In both cases hydrogen bonding plays a major role. The circular dichroism (CD) spectra reveal that a helicity of the proteins is reduced by increasing ZnO nanoparticle concentration although the α-helical structures of HMb and HRP retain their identity. On binding to the ZnO nanoparticles the secondary structure of HRP molecules (or HMb molecules) remains un...