Investigation of binding properties of dicationic styrylimidazo[1,2‐a]pyridinium dyes to human serum albumin by spectroscopic techniques

The binding interaction between two dicationic styrylimidazo[1,2‐a]pyridinium dyes and human serum albumin (HSA) was investigated at physiological conditions using fluorescence, UV–vis absorption, and circular dichroism (CD) spectroscopies. Analysis of the fluorescence titration data at different temperatures suggested that the fluorescence quenching mechanism of HSA by these dyes was static. The calculated thermodynamic parameters (ΔG°, ΔH° and ΔS°) indicated that hydrogen bonding and van der Waals forces played a major role in the formation of the dye–HSA complex. Binding distances (r) between dyes and HSA were calculated according to Förster's non‐radiative energy transfer theory. Studies of conformational changes of HSA using CD measurements indicate that the α‐helical content of the protein decreased upon binding of the dyes. Copyright © 2016 John Wiley & Sons, Ltd.     

Mechanistic and conformational studies on the interaction of sulfamethazine with human immunoglobulin G by molecular modeling and multi‐spectroscopic approach in vitro

Binding interaction of sulfamethazine (SMZ) with human immunoglobulin G (HIgG) has been explored under physiological conditions. The interaction mechanism was firstly predicted through molecular modeling which showed that several hydrogen bonds participated in stabilizing the SMZ ? HIgG complex. Fluorescence spectroscopy, ultraviolet–visible (UV–vis) light absorption and circular dichroism (CD) spectroscopy were used to analyze the binding site, binding constants and effects of SMZ on HIgG stability and secondary structure. The binding parameters and thermodynamic parameters at different temperatures for the reaction have been calculated according to the Scatchard, Sips and Van 't Hoff equations, respectively. Experimental results showed that the quenching mechanism was a static quenching and there was one independent class of binding site on HIgG for SMZ during their interaction. The thermodynamic parameters of the reaction, namely standard enthalpy ΔH⁰ and entropy ΔS⁰, had been calculated to be ?19.12 kJ · mol^?1 and 20.22 J · mol^?1 · K^?1, respectively, which meant that the electrostatic interaction was the predominant intermolecular force in stabilizing the SMZ ? HIgG complex. Moreover, the conformational changes of HIgG in the presence of SMZ were confirmed by three‐dimensional fluorescence spectroscopy, UV–vis absorption spectroscopy and CD spectroscopy. Copyright © 2014 John Wiley & Sons, Ltd.     

Human hemoglobin adsorption onto colloidal cerium oxide nanoparticles: a new model based on zeta potential and spectroscopy measurements

The nanoparticle (NP)-induced conformational changes of protein and NP agglomeration have gained a remarkable interest in medical and biotechnological fields. Herein, the effect of human hemoglobin (Hb) on the colloidal stability of cerium oxide NP (CNP) was investigated by dynamic light scattering (DLS), zeta potential, and TEM analysis. In addition, the effect of CNP on the heme degradation and structural changes of Hb was studied using fluorescence, circular dichroism (CD), and UV–visible (UV–vis) spectroscopic methods. DLS and TEM analysis showed that the presence of Hb can increase the mean diameter of CNP. Zeta potential measurements revealed that CNP demonstrated a higher charge distribution relative to CNP/Hb complex. Besides, fluorescence studies indicated that two fluorescent heme degradation products are revealed during the interaction of CNP with Hb. Near UV-CD spectroscopy also showed that the microenvironmental changes of heme groups occur after interaction of Hb with CNP. The result of thermal behavior of Hb confirmed the structural changes of protein, which referred to decrease in the Hb stability in the presence of CNP. Indeed, the finding related to structural and functional changes of Hb induced by CNP may be crucial to obtain information regarding the side effects of NPs. Finally, this data reveal much insight into the effects of the interaction on protein structural changes and NP agglomeration, and can correlate the zeta potential of NP-protein complexes with the nature of the principle NP-protein interaction.     

Multi-spectroscopic and voltammetric evidences for binding,conformational changes of bovine serum albumin with thiamine

The interaction between thiamine hydrochloride (TA) and bovine serum albumin (BSA) was investigated by fluorescence, FTIR, UV–vis spectroscopic and cyclic voltammetric techniques under optimised physiological condition. The fluorescence intensity of BSA is gradually decreased upon addition of TA due to the formation of a BSA–TA complex. The binding parameters were evaluated and their behaviour at different temperatures was analysed. The quenching constants (K_sv) obtained were 2.6 × 10⁴, 2.2 × 10⁴ and 2.0 × 10⁴ L mol^?1 at 288, 298 and 308 K, respectively. The binding mechanism was static-type quenching. The values of ΔH° and ΔS° were found to be 26.87 kJ mol^?1 and 21.3 J K^?1 mol^?1, and indicated that electrostatic interaction was the principal intermolecular force. The changes in the secondary structure of BSA upon interaction with TA were confirmed by synchronous and 3-D spectral results. Site probe studies reveal that TA is located in site I of BSA. The effects of some common metal ions on binding of BSA–TA complex were also investigated.     

Inhibitory effects of deferasirox on the structure and function of bovine liver catalase: a spectroscopic and theoretical study

Deferasirox (DFX), as an oral chelator, is used for treatment of transfusional iron overload. In this study, we have investigated the effects of DFX as an iron chelator, on the function and structure of bovine liver catalase (BLC) by different spectroscopic methods of UV–visible, fluorescence, and circular dichroism (CD) at two temperatures of 25 and 37 °C. In vitro kinetic studies showed that DFX can inhibit the enzymatic activity in a competitive manner. K _I value was calculated 39 nM according to the Lineweaver–Burk plot indicating a high rate of inhibition of the enzyme. Intrinsic fluorescence data showed that increasing the drug concentrations leads to a significant decrease in the intrinsic emission of the enzyme indicating a significant change in the three-dimensional environment around the chromophores of the enzyme structure. By analyzing the fluorescence quenching data, it was found that the BLC has two binding sites for DFX and the values of binding constant at 25 and 37 °C were calculated 1.7 × 10⁷ and 3 × 10⁷ M^?1, respectively. The static type of quenching mechanism is involved in the quenching of intrinsic emission of enzyme. The thermodynamic data suggest that hydrophobic interactions play a major role in the binding reaction. UV–vis spectroscopy results represented the changes in tryptophan (Trp) absorption and Soret band spectra, which indicated changes in Trp and heme group position caused by the drug binding. Also, CD data represented that high concentrations of DFX lead to a significant decreasing in the content of β-sheet and random coil accompanied an increasing in α-helical content of the protein. The molecular docking results indicate that docking may be an appropriate method for prediction and confirmation of experimental results and also useful for determining the binding mechanism of proteins and drugs. According to above results, it can be concluded that the DFX can chelate the Fe(III) on the enzyme active site leading to changes in the function and structure of catalase which can be considered as a side effect of this drug and consequently has an important role in hepatic complications and fibrosis.     

Hydrogen bonding-assisted interaction between amitriptyline hydrochloride and hemoglobin: spectroscopic and molecular dynamics studies

Herein, we have explored the interaction between amitriptyline hydrochloride (AMT) and hemoglobin (Hb), using steady-state and time-resolved fluorescence spectroscopy, UV–visible spectroscopy, and circular dichroism spectroscopy, in combination with molecular docking and molecular dynamic (MD) simulation methods. The steady-state fluorescence reveals the static quenching mechanism in the interaction system, which was further confirmed by UV–visible and time-resolved fluorescence spectroscopy. The binding constant, number of binding sites, and thermodynamic parameters viz. ΔG, ΔH, ΔS are also considered; result confirms that the binding of the AMT with Hb is a spontaneous process, involving hydrogen bonding and van der Waals interactions with a single binding site, as also confirmed by molecular docking study. Synchronous fluorescence, CD data, and MD simulation results contribute toward understanding the effect of AMT on Hb to interpret the conformational change in Hb upon binding in aqueous solution.     

Characterizing the interaction between pyrogallol and human serum albumin by spectroscopic and molecular docking methods

In the present study, the interaction of Pyrogallol (PG) with human serum albumin (HSA) was investigated by UV, fluorescence, Circular dichroism (CD), and molecular docking methods. The results of fluorescence experiments showed that the quenching of intrinsic fluorescence of HSA by PG was due to a static quenching. The calculated binding constants (K) for PG-HSA at different temperatures were in the order of 10⁴?M ^?1, and the corresponding numbers of binding sites, n were approximately equal to unity. The thermodynamic parameters, ΔH and ΔS were calculated to be negative, which indicated that the interaction of PG with HSA was driven mainly by van der Waals forces and hydrogen bonds. The negative value was obtained for ΔG showed that the reaction was spontaneous. In addition, the effect of PG on the secondary structure of HSA was analyzed by performing UV–vis, synchronous fluorescence, and CD experiments. The results indicated that PG induced conformational changes in the structure of HSA. According to Förster no-radiation energy transfer theory, the binding distance of HSA to PG was calculated to be 1.93?nm. The results of molecular docking calculations clarified the binding mode and the binding sites which were in good agreement with the results of experiments.

Communicated by Ramaswamy H. Sarma     

Fluorescent bovine serum albumin interacting with the antitussive quencher dextromethorphan: a spectroscopic insight

The interaction of dextromethorphan hydrobromide (DXM) with bovine serum albumin (BSA) is studied by using fluorescence spectra, UV–vis absorption, synchronous fluorescence spectra (SFS), 3D fluorescence spectra, Fourier transform infrared (FTIR) spectroscopy and circular dichroism under simulated physiological conditions. DXM effectively quenched the intrinsic fluorescence of BSA. Values of the binding constant, K_A, are 7.159 × 10³, 9.398 × 10³ and 16.101 × 10³ L/mol; the number of binding sites, n, and the corresponding thermodynamic parameters ΔG°, ΔH° and ΔS° between DXM and BSA were calculated at different temperatures. The interaction between DXM and BSA occurs through dynamic quenching and the effect of DXM on the conformation of BSA was analyzed using SFS. The average binding distance, r, between the donor (BSA) and acceptor (DXM) was determined based on Förster's theory. The results of fluorescence spectra, UV–vis absorption spectra and SFS show that the secondary structure of the protein has been changed in the presence of DXM. Copyright © 2015 John Wiley & Sons, Ltd.     

Using resonance light scattering and UV/vis absorption spectroscopy to study the interaction between gliclazide and bovine serum albumin

At different temperatures (298, 310 and 318 K), the interaction between gliclazide and bovine serum albumin (BSA) was investigated using fluorescence quenching spectroscopy, resonance light scattering spectroscopy and UV/vis absorption spectroscopy. The first method studied changes in the fluorescence of BSA on addition of gliclazide, and the latter two methods studied the spectral change in gliclazide while BSA was being added. The results indicated that the quenching mechanism between BSA and gliclazide was static. The binding constant (K_a), number of binding sites (n), thermodynamic parameters, binding forces and Hill's coefficient were calculated at three temperatures. Values for the binding constant obtained using resonance light scattering and UV/vis absorption spectroscopy were much greater than those obtained from fluorescence quenching spectroscopy, indicating that methods monitoring gliclazide were more accurate and reasonable. In addition, the results suggest that other residues are involved in the reaction and the mode ‘point to surface’ existed in the interaction between BSA and gliclazide. Copyright © 2015 John Wiley & Sons, Ltd.     

Spectroscopic analysis on the interaction of ferulic acid and tetramethylpyrazine with trypsin

The interaction of trypsin with tetramethylpyrazine (TMP) and ferulic acid (FA) was studied using fluorescence, synchronous fluorescence, UV–vis absorption, circular dichroism (CD) and three‐dimensional (3D) fluorescence spectra techniques. Using fluorescence quenching calculations, the bimolecular quenching constant (k_q), apparent quenching constant (K_SV), effective binding constant (K_a) and binding site number (n) were obtained. The distance r between donor and acceptor was found to be 2.049 and 1.281 nm for TMP–trypsin and FA–trypsin complexes. TMP and FA can quench the fluorescence intensity of trypsin by a static quenching procedure. Thermodynamic parameters calculated on the basis of different temperatures revealed that the binding of trypsin to TMP/FA mainly depended on van der Waals' forces and hydrogen bonds. The effect of TMP and FA on the conformation of trypsin was analyzed using synchronous fluorescence, CD, 3D fluorescence spectra and molecular docking studies. Copyright © 2013 John Wiley & Sons, Ltd.     

Study on the interaction of β‐carotene and astaxanthin with trypsin and pepsin by spectroscopic techniques

β‐Carotene and astaxanthin are two carotenoids with powerful antioxidant properties, but the binding mechanisms of β‐carotene/astaxanthin to proteases remain unclear. In this study, the interaction of these two carotenoids with trypsin and pepsin was investigated using steady‐state and time‐resolved fluorescence measurements, synchronous fluorescence spectroscopy, UV–vis absorption spectroscopy and circular dichroism (CD) spectroscopy. The experimental results indicated that the quenching mechanisms of trypsin/pepsin by the two carotenoids are static processes. The binding constants of trypsin and pepsin with these two carotenoids are in the following order: astaxanthin–trypsin > astaxanthin–pepsin > β‐carotene–trypsin > β‐carotene–pepsin, respectively. Thermodynamic investigations revealed that the interaction between the two carotenoids and trypsin/pepsin is synergistically driven by enthalpy and entropy, and hydrophobic forces and electrostatic attraction have a significant role in the reactions. In addition, as shown by synchronous fluorescence spectroscopy, UV–vis absorption spectroscopy and CD, the two carotenoids may induce conformational and microenvironmental changes in trypsin/pepsin. The study provides an accurate and full basic data for clarifying the binding mechanisms of the two carotenoids with trypsin/pepsin and is helpful in understanding their effect on protein function and their biological activity in vivo. Copyright © 2015 John Wiley & Sons, Ltd.     

Study on the interaction between a water-soluble dinuclear nickel complex and bovine serum albumin by spectroscopic techniques

The interaction of a water-soluble dinuclear nickel(II) complex, [Ni₂(EGTB)(CH₃CN)₄](ClO₄)₄·4H₂O (EGTB = ethylene glycol-bis(β-aminoethyl ether) N,N,N′,N′-tetrakis(2-benzimidazoyl)) (1), and bovine serum albumin (BSA) was investigated under physiological conditions using fluorescence, synchronous fluorescence, UV–vis absorption and circular dichroism (CD). The experimental results suggested that the nickel(II) complex could bind to BSA with binding constant (K) ~ 10⁴ M^?1 and quench the intrinsic fluorescence of BSA through a static quenching mechanism. The thermodynamic parameters, ΔG°, ΔH°, and ΔS°, calculated at different temperatures, indicated that the binding reaction was spontaneous and electrostatic interactions played a major role in this association. Based on the number of binding sites, it was considered that one molecule of complex 1 could bind to a single site or two sites of the BSA molecule or the two binding modes coexisted. In view of the results of site marker competition experiments, the reactive sites of BSA to complex 1 mainly located in subdomain IIA (site I) and subdomain IIIA (site II) of BSA. Moreover, the binding distance, r, between donor (BSA) and acceptor (complex 1) was 5.13 nm according to Förster nonradiation energy transfer theory. Finally, as shown by the UV–vis absorption, synchronous fluorescence and CD, complex 1 could induce conformation and microenvironmental changes of BSA. The results obtained herein will be of biological significance in toxicology investigation and anticancer metallodrug design.     

Characterization of domain-specific interaction of synthesized dye with serum proteins by spectroscopic and docking approaches along with determination of in vitro cytotoxicity and antiviral activity

The interaction between a synthesized dye with proteins, bovine, and human serum albumin (BSA, HSA, respectively) under physiological conditions has been characterized in detail, by means of steady-state and time-resolved fluorescence, UV–vis absorption, and circular dichroism (CD) techniques. An extensive time-resolved fluorescence spectroscopic characterization of the quenching process has been undertaken in conjugation with temperature-dependent fluorescence quenching studies to divulge the actual quenching mechanism. From the thermodynamic observations, it is clear that the binding process is a spontaneous molecular interaction, in which van der Waals and hydrogen bonding interactions play the major roles. The UV–vis absorption and CD results confirm that the dye can induce conformational and micro-environmental changes of both the proteins. In addition, the dye binding provokes the functionality of the native proteins in terms of esterase-like activity. The average binding distance (r) between proteins and dye has been calculated using FRET. Cytotoxicity and antiviral effects of the dye have been found using Vero cell and HSV-1F virus by performing MTT assay. The AutoDock-based docking simulation reveals the probable binding location of dye within the sub-domain IIA of HSA and IB of BSA.     

Comparative Studies on the Interaction Between Bovine β-lacto-globulin Type A and B and a New Designed Pd(II) Complex with Anti-tumor Activity at Different Temperatures

Abstract

An new water-soluble Pd(II) complex, 2,2′-bipyridin n-butyl dithiocarbamato Pd(II) nitrate has been synthesized. The Pd(II) complex has been characterized by elemental analysis and conductivity measurements as well as spectroscopic methods such as infrared, 1H NMR, and ultraviolet-visible. The interaction between this new design Pd(II)-complex, an anti-tumor component, with carrier proteins of β-lactoglobulin-A and -B (BLG-A and -B) were studied at different temperatures of 27, 37, 42, and 47 °C by fluorescence spectroscopy and far-UV circular dichroism (CD) spectrophotometric techniques. A strong fluorescence quenching interaction of Pd(II) complex with BLG-A and -B was observed at different temperatures. The binding parameters were evaluated by fluorescence quenching method. The thermodynamic parameters, including ΔH°, ΔS°, and ΔG° were calculated by fluorescence quenching method indicated that the electrostatic and hydrophobic forces might play a major role in the interactions of Pd(II) complex with BLG-A and -B, respectively. The distances between donors (Trps of the BLG-A and -B) and acceptor (Pd(II) complex) were obtained according to the fluorescence resonance energy transfer (FRET). Far-UV CD studies showed that the Pd(II) complex did not represent any significant changes in the secondary structures of BLG- A and -B. The difference in the interaction properties observed for BLG-A and -B with Pd(II) complex is related to the difference in the amino acid sequences between these two variants.     

Binding of caffeine with caffeic acid and chlorogenic acid using fluorescence quenching,UV/vis and FTIR spectroscopic techniques

The interactions of caffeine (CF) with chlorogenic acid (CGA) and caffeic acid (CFA) were investigated by fluorescence quenching, UV/vis and Fourier transform infrared (FTIR) spectroscopic techniques. The results of the study indicated that the fluorescence quenching between caffeine and hydroxycinnamic acids could be rationalized in terms of static quenching or the formation of non‐fluorescent CF–CFA and CF–CGA complexes. From fluorescence quenching spectral analysis, the quenching constant (K_SV), quenching rate constant (k_q), number of binding sites (n), thermodynamic properties and conformational changes of the interaction were determined. The quenching constants (K_SV) between CF and CGA, CFA are 1.84 × 10⁴ and 1.04 × 10⁴ L/mol at 298 K and their binding site n is ~ 1. Thermodynamic parameters determined using the Van't Hoff equation indicated that hydrogen bonds and van der Waal's forces have a major role in the reaction of caffeine with caffeic acid and chlorogenic acid. The 3D fluorescence, UV/vis and FTIR spectra also showed that the binding of CF with CFA and CGA induces conformational changes in CFA and CGA. Copyright © 2015 John Wiley & Sons, Ltd.     

Spectroscopic and molecular modeling approaches to investigate the binding of proton pump inhibitors to human serum albumin

The interaction between two proton pump inhibitors viz., omeprazole (OME) and esomeprazole (EPZ) with human serum albumin (HSA) was studied by fluorescence, absorption, circular dichroism (CD), Fourier transform infrared spectroscopy (FT-IR), voltammetry, and molecular modeling approaches. The Stern–Volmer quenching constants (K_sv) for OME-HSA and EPZ-HSA systems obtained at different temperatures revealed that both OME and EPZ quenched the intensity of HSA through dynamic mode of quenching mechanism. The binding constants of OME-HSA and EPZ-HSA increased with temperature, indicating the increased stability of these systems at higher temperatures. Thermodynamic parameters viz., ?H^°, ?S^°, and ?G^° were determined for both systems. These values revealed that both systems were stabilized by hydrophobic forces. The competitive displacement and molecular docking studies suggested that OME/EPZ was bound to Sudlow’s site I in subdomain IIA in HSA. The extent of energy transfer from HSA to OME/EPZ and the distance of separation in tryptophan (Trp214) Trp214-OME and Trp214-EPZ was determined based on the theory of fluorescence resonance energy transfer. UV absorption, 3D fluorescence, and CD studies indicated that the binding of OME/EPZ to HSA has induced micro environmental changes around the protein which resulted changes in its secondary structure.     

Probing the conformational changes and peroxidase-like activity of cytochrome c upon interaction with iron nanoparticles

Herein, the interaction of iron nanoparticle (Fe-NP) with cytochrome c (Cyt c) was investigated, and a range of techniques such as dynamic light scattering (DLS), zeta potential measurements, static and synchronous fluorescence spectroscopy, near and far circular dichroism (CD) spectroscopy, and ultraviolet–visible (UV–vis) spectroscopy were used to analyze the interaction between Cyt c and Fe-NP. DLS and zeta potential measurements showed that the values of hydrodynamic radius and charge distribution of Fe-NP are 83.95 ± 3.7 nm and 4.5 ± .8 mV, respectively. The fluorescence spectroscopy results demonstrated that the binding of Fe-NP with Cyt c is mediated by hydrogen bonds and van der Waals interactions. Also Fe-NP induced conformational changes in Cyt c and reduced the melting temperature value of Cyt c from 79.18 to 71.33°C. CD experiments of interaction between Fe-NP and Cyt c revealed that the secondary structure of Cyt c with the dominant α-helix structures remained unchanged whereas the tertiary structure and heme position of Cyt c are subjected to remarkable changes. Absorption spectroscopy at 695 nm revealed that Fe-NP considerably disrupt the Fe…S(Met80) bond. In addition, the UV–vis experiment showed the peroxidase-like activity of Cyt c upon interaction with Fe-NP. Hence, the data indicate the Fe-NP results in unfolding of Cyt c and subsequent peroxidase-like activity of denatured species. It was concluded that a comprehensive study of the interaction of Fe-NP with biological system is a crucial step for their potential application as intracellular delivery carriers and medicinal agents.     

Investigation of the interactions of quercetin and morin with trypsin

The interactions of quercetin and morin with trypsin were investigated by UV–vis absorption, fluorescence, synchronous fluorescence and three‐dimensional fluorescence spectra techniques under physiological pH 7.40. Quercetin and morin effectively quenched the intrinsic fluorescence of trypsin via static quenching. The process of binding quercetin and morin on trypsin was a spontaneous molecular interaction procedure. The binding constants and thermodynamic parameters at two different temperatures, the binding locality and the binding power were obtained. The conformation of trypsin was discussed by synchronous and three‐dimensional fluorescence techniques. Copyright © 2009 John Wiley & Sons, Ltd.     

The investigation of the interaction between ribavirin and bovine serum albumin by spectroscopic methods

The interaction between ribavirin (RIB) with bovine serum albumin (BSA) has been investigated by fluorescence quenching technique in combination with UV–vis absorption and circular dichroism (CD) spectroscopies under the simulative physiological conditions. The quenching of BSA fluorescence by RIB was found to be a result of the formation of RIB–BSA complex. The binding constants and the number of binding sites were calculated at three different temperatures. The values of thermodynamic parameters ?H, ?S, ?G at different temperatures indicate that hydrophobic and hydrogen bonds played important roles for RIB–BSA association. The binding distance r was obtained according to the theory of FÖrster’s non–radiation energy transfer. The displacement experiments was performed for identifying the location of the binding site of RIB on BSA. The effects of common ions on the binding constant of RIB and BSA were also examined. Finally, the conformational changes of BSA in the presence of RIB were also analyzed by CD spectra and Synchronous fluorescence spectra.     

Investigation on the interaction of newly designed potential antibacterial Zn(II) complexes with CT-DNA and HSA

Two Zn(II) complexes of formula [Zn(bpy)(Gly)]NO₃ (I) and [Zn(phen)(Gly)]NO₃ (II) (where bpy = 2,2′-bipyridine, phen = 1,10-phenanthroline and Gly = glycine) were synthesized and characterized by elemental analysis, molar conductance measurements, UV–vis, FT-IR, and ¹H NMR spectra. The interaction ability of these complexes with calf thymus DNA was monitored using spectroscopic methods, including UV–vis absorption spectroscopy, ethidium bromide displacement, Fourier transform infrared, and electrophoretic mobility assay. Further, the human serum albumin interactions of complexes I and II were investigated using UV–vis absorption spectroscopy, fluorescence quenching, circular dichroism, and Fourier transform infrared. The results obtained from these analyses indicated that both complexes interact effectively with CT-DNA and HSA. The binding constant (K_b), the Stern–Volmer constant (K_sv), and the number of binding sites (n) at different temperatures were determined for CT-DNA and HSA. Also, the negative ΔH° and ΔS° values showed that both hydrogen bonds and van der Waals forces played major roles in the association of CT-DNA-Zn(II) and HSA-Zn(II) complex formation. The displacement experiments suggested that Zn(II)-complexes primarily bound to Sudlow’s site II of HSA. The distance between the donor (HSA) and the acceptor (Zn(II) complexes) was estimated on the basis of the Forster resonance energy transfer (FRET) and the alteration of HSA secondary structure induced by the compounds were confirmed by FT-IR spectroscopy. The complexes follow the binding affinity order of I > II with DNA and II > I with HSA. Finally, Antibacterial activity of complexes I and II have been screened against gram positive and gram negative bacteria.