Determination on the binding of chlortetracycline to bovine serum albumin using spectroscopic methods

In this work, the interaction of chlortetracycline with bovine serum albumin (BSA) was investigated by fluorescence spectroscopy, circular dichroism (CD) spectroscopy, and molecular docking. Results indicated that chlortetracycline quenches BSA fluorescence mainly by a static quenching mechanism. The quenching constants (K_SV) were obtained as 5.64 × 10⁴, 4.49 × 10^4/, and 3.44 × 10^4/ M_?1 at 283, 295, and 307 K, respectively. The thermodynamic parameters of enthalpy change Δ H°, entropy change Δ S°, and free energy change Δ G° were ?5.12 × 10^4/ J mol?1, ?97.6 J mol?1 K?1, and ?2.24 × 10^4/ J mol?1 (295 K), respectively. The association constant (K_A) and the number of binding sites (n) were 9.41 × 10^3/ M?1 and 0.86, respectively. The analysis results suggested that the interaction was spontaneous, and van der Waals force and hydrogen‐bonding interactions played key roles in the reaction process. In addition, CD spectra proved secondary structure alteration of BSA in the presence of chlortetracycline. © 2012 Wiley Periodicals, Inc. J Biochem Mol Toxicol 26:331–336, 2012; View this article online at wileyonlinelibrary.com . DOI 10:1002/jbt.21424     

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.     

Study of fluorescence interaction and conformational changes of bovine serum albumin with histamine H1‐receptor–drug epinastine hydrochloride by spectroscopic and time‐resolved fluorescence methods

The fluorescence, ultraviolet (UV) absorption, time resolved techniques, circular dichroism (CD), and infrared spectral methods were explored as tools to investigate the interaction between histamine H₁ drug, epinastine hydrochloride (EPN), and bovine serum albumin (BSA) under simulated physiological conditions. The experimental results showed that the quenching of the BSA by EPN was static quenching mechanism and also confirmed by lifetime measurements. The value of n close to unity indicated that one molecule of EPN was bound to protein molecule. The binding constants (K) at three different temperatures were calculated (7.1 × 10⁴, 5.5 × 10⁴, and 3.9 × 10⁴M⁻¹). Based on the thermodynamic parameters (ΔH⁰, ΔG⁰, and ΔS⁰), the nature of binding forces operating between drug and protein was proposed. The site of binding of EPN in the protein was proposed to be Sudlow's site I based on displacement experiments using site markers viz, warfarin, ibuprofen, and digitoxin. Based on the Förster's theory of non‐radiation energy transfer, the binding average distance, r between the donor (BSA) and acceptor (EPN) was evaluated and found to be 4.48 nm. The UV–visible, synchronous fluorescence, CD, and three‐dimensional fluorescence spectral results revealed the changes in secondary structure of the protein upon its interaction with EPN. © 2015 Wiley Periodicals, Inc. Biopolymers 103: 646–657, 2015.     

Spectroscopic Studies on the Interaction of Fluorine Containing Triazole with Bovine Serum Albumin

The binding of one fluorine including triazole (C₁₀H₉FN₄S, FTZ) to bovine serum albumin (BSA) was studied by spectroscopic techniques including fluorescence spectroscopy, UV–Vis absorption, and circular dichroism (CD) spectroscopy under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by FTZ was the result of forming a complex of BSA–FTZ, and the binding constants (K _a) at three different temperatures (298, 304, and 310 K) were 1.516?×?10⁴, 1.627?×?10⁴, and 1.711?×?10⁴?mol L^?1, respectively, according to the modified Stern–Volmer equation. The thermodynamic parameters ΔH and ΔS were estimated to be 7.752 kJ mol^?1 and 125.217 J?mol^?1?K^?1, respectively, indicating that hydrophobic interaction played a major role in stabilizing the BSA–FTZ complex. It was observed that site I was the main binding site for FTZ to BSA from the competitive experiments. The distance r between donor (BSA) and acceptor (FTZ) was calculated to be 7.42 nm based on the Förster theory of non-radioactive energy transfer. Furthermore, the analysis of fluorescence data and CD data revealed that the conformation of BSA changed upon the interaction with FTZ.     

Study on the interactions of mapenterol with serum albumins using multi‐spectroscopy and molecular docking

The interactions of mapenterol with bovine serum albumin (BSA) and human serum albumin (HSA) have been investigated systematically using fluorescence spectroscopy, absorption spectroscopy, circular dichroism (CD) and molecular docking techniques. Mapenterol has a strong ability to quench the intrinsic fluorescence of BSA and HSA through static quenching procedures. At 291 K, the binding constants, K_a, were 1.93 × 10³ and 2.73 × 10³ L/mol for mapenterol–BSA and mapenterol–HAS, respectively. Electrostatic forces and hydrophobic interactions played important roles in stabilizing the mapenterol–BSA/has complex. Using site marker competitive studies, mapenterol was found to bind at Sudlow site I on BSA/HSA. There was little effect of K⁺, Ca²⁺, Cu²⁺, Zn²⁺ and Fe³⁺ on the binding. The conformation of BSA/HSA was changed by mapenterol, as seen from the synchronous fluorescence spectra. The CD spectra showed that the binding of mapenterol to BSA/HSA changed the secondary structure of BSA/HSA. Molecular docking further confirmed that mapenterol could bind to Sudlow site I of BSA/HSA. According to Förster non‐radiative energy transfer theory (FRET), the distances r₀ between the donor and acceptor were calculated as 3.18 and 2.75 nm for mapenterol–BSA and mapenterol–HAS, respectively. Copyright © 2015 John Wiley & Sons, Ltd.     

Chemico-biological interaction of Etravirine and its β-Cyclodextrin complex with macromolecular targets

The interaction of etravirine with β-cyclodextrin is analyzed by UV–visible absorption, infrared, fluorescence, nuclear magnetic resonance, two-dimensional rotational frame nuclear Overhauser effect spectroscopy, and molecular modeling studies. The 4-hydroxy-3, 5-dimethylbenzonitrile moiety is found to take part in the binding. The stoichiometry of the inclusion complex of ET with β-CD is 1:1 with the binding constant of 2.03 × 10³ mol^?1 dm³. The binding of ET with calf thymus DNA (ctDNA) and bovine serum albumin (BSA) protein is investigated in the presence and the absence of β-CD. Fluorescence enhancement is observed during the binding of ET with ctDNA in the absence of β-CD, whereas in the presence of β-CD, fluorescence quenching is observed. The binding constants of the binding of ET and ET–β-CD to ctDNA are 7.84 × 10⁴ and 4.38 × 10⁴ mol^?1 dm³, respectively. The binding constant of the binding of ET and ET–β-CD to BSA are 3.14 × 10⁴ and 1.6396 × 10⁴ mol^?1 dm³, respectively. The apparent binding constants between ET–β-CD complex and ctDNA or BSA protein decreases significantly. The numbers of binding sites of interaction of ET with BSA protein and the binding distance between BSA protein and ET the absence and the presence of β-CD differ. β-CD modulates the binding of ET with the macromolecular targets.     

A study on the interaction between 3‐spiro‐piperidones and bovine serum albumin using spectroscopic approaches

The interaction between 3‐spiro‐2′‐pyrrolidine‐3′‐spiro‐3″‐piperidine‐2,3″‐dione (PPD) and bovine serum albumin (BSA) in aqueous solution was studied using fluorescence and UV–vis spectroscopy. Fluorescence emission data revealed that BSA (1.00 × 10^‐5 mol/L) fluorescence was statically quenched by PPD at various concentrations, which implies that a PPD–BSA complex was formed. The binding constant (K_A), the number of binding sites (n) and the specific binding site of the PPD with BSA were determined. Energy‐transfer efficiency parameters were determined and the mechanism of the interaction discussed. The thermodynamic parameters, ΔG, ΔH and ΔS, were obtained according to van't Hoff's equation, showing the involvement of hydrophobic forces in these interactions. The effect of PPD acting on the BSA conformation was detected by synchronous fluorescence. Copyright © 2012 John Wiley & Sons, Ltd.     

Investigations on the interactions of DiAmsar with serum albumins: Insights from spectroscopic and molecular docking techniques

Diamine‐sarcophagine (DiAmsar) binding to human serum albumin (HSA) and bovine serum albumin (BSA) was investigated under simulative physiological conditions. Fluorescence spectra in combination with Fourier transform infrared (FT‐IR), UV‐visible (UV–vis) spectroscopy, cyclic voltammetry (CV), and molecular docking method were used in the present work. Experimental results revealed that DiAmsar had an ability to quench the HSA and BSA intrinsic fluorescence through a static quenching mechanism. The Stern–Volmer quenching rate constant (K_sv) was calculated as 0.372 × 10³ M^‐1 and 0.640 × 10³ M^‐1 for HSA and BSA, respectively. Moreover, binding constants (K_a), number of binding sites (n) at different temperatures, binding distance (r), and thermodynamic parameters (?H°, ?S°, and ?G°) between DiAmsar and HSA (or BSA) were calculated. DiAmsar exhibited good binding propensity to HSA and BSA with relatively high binding constant values. The positive ?H° and ?S° values indicated that the hydrophobic interaction is main force in the binding of the DiAmsar to HSA (or BSA). Furthermore, molecular docking results revealed the possible binding site and the microenvironment around the bond. Copyright © 2014 John Wiley & Sons, Ltd.     

Combined spectroscopies and molecular docking approach to characterizing the binding interaction between lisinopril and bovine serum albumin

To further understand the mode of action and pharmacokinetics of lisinopril, the binding interaction of lisinopril with bovine serum albumin (BSA) under imitated physiological conditions (pH 7.4) was investigated using fluorescence emission spectroscopy, synchronous fluorescence spectroscopy, Fourier transform infrared spectroscopy (FTIR), circular dichroism (CD) and molecular docking methods. The results showed that the fluorescence quenching of BSA near 338 nm resulted from the formation of a lisinopril–BSA complex. The number of binding sites (n) for lisinopril binding on subdomain IIIA (site II) of BSA and the binding constant were ~ 1 and 2.04 × 10⁴ M^–1, respectively, at 310 K. The binding of lisinopril to BSA induced a slight change in the conformation of BSA, which retained its α‐helical structure. However, the binding of lisinopril with BSA was spontaneous and the main interaction forces involved were van der Waal's force and hydrogen bonding interaction as shown by the negative values of ΔG⁰, ΔH⁰ and ΔS⁰ for the binding of lisinopril with BSA. It was concluded from the molecular docking results that the flexibility of lisinopril also played an important role in increasing the stability of the lisinopril–BSA complex. Copyright © 2015 John Wiley & Sons, Ltd.     

Fluorescence spectrometric study on the interaction of tamibarotene with bovine serum albumin

The interaction between tamibarotene and bovine serum albumin (BSA) was studied using fluorescence quenching technique and ultraviolet–visible spectrophotometry. The results of experiments showed that tamibarotene could strongly quench the intrinsic fluorescence of BSA by a dynamic quenching mechanism. The apparent binding constant, number of binding site and corresponding thermodynamic parameters at different temperatures were calculated respectively, and the main interaction force between tamibarotene and BSA was proved to be hydrophobic force. Synchronous fluorescence spectra showed that tamibarotene changed the molecular conformation of BSA. When BSA concentration was 1.00 × 10^?6 mol L^?1, the quenched fluorescence ΔF had a good linear relationship with the concentration of tamibarotene in the range 1.00 × 10^?6 to 12.00 × 10^?6 mol L^?1 with the detection limit of 6.52 × 10^?7 mol L^?1. Copyright © 2010 John Wiley & Sons, Ltd.     

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.     

Molecular docking and experimental investigation of new indole derivative cyclooxygenase inhibitor to probe its binding mechanism with bovine serum albumin

The indole derivative 2-(5-methoxy-2-methyl-1H-indol-3-yl)-N'-[(E)-(3-nitrophenyl) methylidene]acetohydrazide (IND) was synthesized for its therapeutic potential to inhibit cyclooxygenase (COX)-II. Binding if IND to bovine serum albumin (BSA) was investigated was because most drugs bind to serum albumin in-vivo. Fluorescence, UV–vis spectrophotometry and molecular modeling methodologies were employed for studying the interaction mechanism. The intrinsic fluorescence of BSA was quenched by BSA and the quenching mechanism involved was static quenching. The binding constants between IND and BSA at the three studied temperatures (298, 301 and 306 K) were 1.09 × 10⁵, 4.36 × 10⁴ and 1.23 × 10⁴ L mol⁻¹ respectively. The most likely site for binding IND to BSA was Site I (subdomain IIA). The analysis of thermodynamic parameter revealed the involvement of hydrogen bonding and van der Waals forces in the IND-BSA interaction. Synchronous fluorescence spectroscopic (SFS) and UV–vis spectrophotometric studies suggested conformational change in BSA molecule post interaction to IND. Molecular docking and the experimental results corroborated one another. The study can prove as an insight for future IND drug development.     

Effects of N‐Acetyl‐L‐Cysteine‐Capped CdTe Quantum Dots on Bovine Serum Albumin and Bovine Hemoglobin: Isothermal Titration Calorimetry and Spectroscopic Investigations

The interactions of N‐acetyl‐L‐cysteine‐capped CdTe quantum dots (QDs) with bovine serum albumin (BSA) and bovine hemoglobin (BHb) were investigated by isothermal titration calorimetry (ITC), fluorescence, synchronous fluorescence, fluorescence lifetime, ultraviolet–visible absorption, and circular dichroism techniques. Fluorescence data of BSA–QDs and BHb–QDs revealed that the quenching was static in every system. While CdTe QDs changed the microenvironment of tryptophan in BHb, the microenvironment of BSA kept unchanged. Adding CdTe QDs affected the skeleton and secondary structure of the protein (BSA and BHb). The ITC results indicated that the interaction between the protein (BSA and BHb) and QDs‐612 was spontaneous and the predominant force was hydrophobic interaction. In addition, the binding constants were determined to be 1.19 × 10⁵ L mol^?1 (BSA–QDs) and 2.19 × 10⁵ L mol^?1 (BHb–QDs) at 298 K. From these results, we conclude that CdTe QDs have a larger impact on the structure of BHb than BSA.     

Probing into the binding interaction between medroxyprogesterone acetate and bovine serum albumin (BSA): spectroscopic and molecular docking methods

To further understand the mechanism of action and pharmacokinetics of medroxyprogesterone acetate (MPA), the binding interaction of MPA with bovine serum albumin (BSA) under simulated physiological conditions (pH 7.4) was studied using fluorescence emission spectroscopy, synchronous fluorescence spectroscopy, circular dichroism and molecular docking methods. The experimental results reveal that the fluorescence of BSA quenches due to the formation of MPA–BSA complex. The number of binding sites (n) and the binding constant for MPA–BSA complex are ~1 and 4.6 × 10³ M^?1 at 310 K, respectively. However, it can be concluded that the binding process of MPA with BSA is spontaneous and the main interaction forces between MPA and BSA are van der Waals force and hydrogen bonding interaction due to the negative values of ΔG⁰, ΔH⁰ and ΔS⁰ in the binding process of MPA with BSA. MPA prefers binding on the hydrophobic cavity in subdomain IIIA (site II′′) of BSA resulting in a slight change in the conformation of BSA, but BSA retaining the α‐helix structure. Copyright © 2016 John Wiley & Sons, Ltd.     

Exploring the interaction of the photodynamic therapeutic agent thionine with bovine serum albumin: multispectroscopic and molecular docking studies

This study explores the binding interaction of thionine (TH) with bovine serum albumin (BSA) under physiological conditions (pH 7.40) using absorption, emission, synchronous emission, circular dichroism (CD) and three‐dimensional (3D) emission spectral studies. The results of emission titration experiments revealed that TH strongly quenches the intrinsic emission of BSA via a static quenching mechanism. The apparent binding constant (K) and number of binding sites (n) were calculated as 2.09 × 10⁵ dm³/mol and n~1, respectively. The negative free energy change value for the BSA–TH system suggested that the binding interaction was spontaneous and energetically favourable. The results from absorption, synchronous emission, CD and 3D emission spectral studies demonstrated that TH induces changes in the microenvironment and secondary structure in BSA. Site marker competitive binding experiments revealed that the binding site of TH was located in subdomain IIA (Sudlow site I) of BSA. The molecular docking study further substantiates Sudlow site I as the preferable binding site of TH in BSA. Copyright © 2014 John Wiley & Sons, Ltd.     

Principal component analysis of chemical shift perturbation data of a multiple‐ligand‐binding system for elucidation of respective binding mechanism

Chemical shift perturbations (CSPs) in NMR spectra provide useful information about the interaction of a protein with its ligands. However, in a multiple‐ligand‐binding system, determining quantitative parameters such as a dissociation constant (K_d) is difficult. Here, we used a method we named CS‐PCA, a principal component analysis (PCA) of chemical shift (CS) data, to analyze the interaction between bovine β‐lactoglobulin (βLG) and 1‐anilinonaphthalene‐8‐sulfonate (ANS), which is a multiple‐ligand‐binding system. The CSP on the binding of ANS involved contributions from two distinct binding sites. PCA of the titration data successfully separated the CSP pattern into contributions from each site. Docking simulations based on the separated CSP patterns provided the structures of βLG–ANS complexes for each binding site. In addition, we determined the K_d values as 3.42 × 10⁻⁴M² and 2.51 × 10⁻³M for Sites 1 and 2, respectively. In contrast, it was difficult to obtain reliable K_d values for respective sites from the isothermal titration calorimetry experiments. Two ANS molecules were found to bind at Site 1 simultaneously, suggesting that the binding occurs cooperatively with a partial unfolding of the βLG structure. On the other hand, the binding of ANS to Site 2 was a simple attachment without a significant conformational change. From the present results, CS‐PCA was confirmed to provide not only the positions and the K_d values of binding sites but also information about the binding mechanism. Thus, it is anticipated to be a general method to investigate protein–ligand interactions. Proteins 2013. © 2012 Wiley Periodicals, Inc.     

Binding of a chromen-4-one Schiff’s base with bovine serum albumin: capping with β-cyclodextrin influences the binding

This work deals with the synthesis of 6-methyl-3-[(4′-methylphenyl)imino]methyl-4H-chromen-4-one (MMPIMC), its binding to β-cyclodextrin, and the influence of the cyclodextrin complexation on the compound’s binding to bovine serum albumin (BSA). The 1:2 stoichiometry for the complexation of MMPIMC with β-cyclodextrin is determined with the binding constant of 1.90 × 10⁴ M^?2. The structure of host–guest complex plays a role in protein binding of MMPIMC. One- and two-dimensional NMR spectra are used to determine the mode of binding of the guest to β-cyclodextrin cavity and the structure of the inclusion complex is proposed. The binding of MMPIMC with BSA in the absence and the presence of β-cyclodextrin is studied. The binding strengths of MMPIMC–BSA (1.73 × 10⁵ M^?1) and β-cyclodextrin-complexed MMPIMC–BSA (9.0 × 10⁴ M^?1) show difference in magnitude. The Förster Resonance Energy Transfer efficiency and the proximity of the donor and acceptor molecules, are modulated by β-cyclodextrin. Molecular modeling is used to optimize the sites and mode of binding of MMPIMC with bovine serum albumin.     

Detection of interaction between lysionotin and bovine serum albumin using spectroscopic techniques combined with molecular modeling

A combination of fluorescence, UV–Vis absorption, circular dichroism (CD), Fourier transform infrared (FT-IR) and molecular modeling approaches were employed to determine the interaction between lysionotin and bovine serum albumin (BSA) at physiological pH. The fluorescence titration suggested that the fluorescence quenching of BSA by lysionotin was a static procedure. The binding constant at 298 K was in the order of 10⁵ L mol^?1, indicating that a high affinity existed between lysionotin and BSA. The thermodynamic parameters obtained at different temperatures (292, 298, 304 and 310 K) showed that the binding process was primarily driven by hydrogen bond and van der Waals forces, as the values of the enthalpy change (ΔH°) and entropy change (ΔS°) were found to be ?40.81 ± 0.08 kJ mol^?1 and ?35.93 ± 0.27 J mol^?1 K^?1, respectively. The surface hydrophobicity of BSA increased upon interaction with lysionotin. The site markers competitive experiments revealed that the binding site of lysionotin was in the sub-domain IIA (site I) of BSA. Furthermore, the molecular docking results corroborated the binding site and clarified the specific binding mode. The results of UV–Vis absorption, CD and FT-IR spectra demonstrated that the secondary structure of BSA was altered in the presence of lysionotin.     

Intermolecular interaction of fosinopril with bovine serum albumin (BSA): The multi‐spectroscopic and computational investigation

The intermolecular interaction of fosinopril, an angiotensin converting enzyme inhibitor with bovine serum albumin (BSA), has been investigated in physiological buffer (pH 7.4) by multi‐spectroscopic methods and molecular docking technique. The results obtained from fluorescence and UV absorption spectroscopy revealed that the fluorescence quenching mechanism of BSA induced by fosinopril was mediated by the combined dynamic and static quenching, and the static quenching was dominant in this system. The binding constant, K_b, value was found to lie between 2.69 × 10³ and 9.55 × 10³ M^?1 at experimental temperatures (293, 298, 303, and 308 K), implying the low or intermediate binding affinity between fosinopril and BSA. Competitive binding experiments with site markers (phenylbutazone and diazepam) suggested that fosinopril preferentially bound to the site I in sub‐domain IIA on BSA, as evidenced by molecular docking analysis. The negative sign for enthalpy change (ΔH⁰) and entropy change (ΔS⁰) indicated that van der Waals force and hydrogen bonds played important roles in the fosinopril‐BSA interaction, and 8‐anilino‐1‐naphthalenesulfonate binding assay experiments offered evidence of the involvements of hydrophobic interactions. Moreover, spectroscopic results (synchronous fluorescence, 3‐dimensional fluorescence, and Fourier transform infrared spectroscopy) indicated a slight conformational change in BSA upon fosinopril interaction.     

Biological evaluations of newly-designed Pt(II) and Pd(II) complexes using spectroscopic and molecular docking approaches

To perform biological evaluations of newly-designed Pt(II) and Pd(II) complexes, the present study was conducted with targeted protein human serum albumin (HSA) and HCT116 cell line as model of human colorectal carcinoma. The binding of Pt(II) and Pd(II) complexes to HSA was analyzed using fluorescence spectroscopy and molecular docking. The thermal stability and alterations in the secondary structure of HSA in the presence of Pt(II) and Pd(II) complexes were investigated using the thermal denaturation method and circular dichroism (CD) spectroscopy. The cytotoxicity of the Pt(II) and Pd(II) complexes was studied against the HCT116 cell line using MTT assay. The binding analysis revealed that the fluorescence findings were well in agreement with docking results such that there is only one binding site for each complex on HSA. Binding constants of 8.7?×?10³ M^?1, 2.65?×?10³ M^?1, 0.3?×?10³ M^?1, and 4.4?×?10³ M^?1 were determined for Pd(II) and Pt(II) complexes (I–IV) at temperature of 25?°C, respectively. Also, binding constants of 1.9?×?10³ M^?1, 15.17?×?10³ M^?1, 1.9?×?10³ M^?1, and 13.1?×?10³ M^?1 were determined for Pd(II) and Pt(II) complexes (I–IV) at temperature of 37?°C, respectively. The results of CD and thermal denaturation showed that the molecular structure of HSA affected by interaction with Pt(II) and Pd(II) complexes is stable. Cytotoxicity studies represented the growth suppression effect of the Pt(II) and Pd(II) complexes toward the human colorectal carcinoma cell line. Therefore, the results suggest that the new designed Pt(II) and Pd(II) complexes are well promising candidates for use in cancer treatment, particularly for human colorectal cancer.

Communicated by Ramaswamy H. Sarma