Bovine Serum Albumin System Research Articles

Binding interaction of sorafenib with bovine serum albumin: Spectroscopic methodologies and molecular docking

The binding interaction of sorafenib with bovine serum albumin (BSA) was studied using fluorescence, circular dichrosim (CD) and molecular docking methods. The results revealed that there was a static quenching of BSA induced by sorafenib due to the formation of sorafenib–BSA complex. The binding constant and number of binding site of sorafenib with BSA under simulated physiological condition (pH=7.4) were 6.8×104M−1 and 1 at 310K, respectively. Base on the sign and magnitude of the enthalpy and entropy changes (ΔH0=−72.2kJmol−1 and ΔS0=−140.4Jmol−1K−1) and the results of molecular docking, it could be suggested that the binding process of sorafenib and BSA was spontaneous and the main interaction forces of sorafenib with BSA were van der Waals force and hydrogen bonding interaction. From the results of site marker competitive experiments and molecular docking, it could be deduced that sorafenib was inserted into the subdomain IIA (site I) of BSA and leads to a slight change of the conformation of BSA. And, the significant change of conformation of sorafenib occurred in the binding process with BSA to increase the stability of the sorafenib–BSA system, implying that the flexibility of sorafenib played an important role in the binding process.

Characteristics of selective fluoride adsorption by biocarbon-Mg/Al layered double hydroxides composites from protein solutions: Kinetics and equilibrium isotherms study

In the study, two novel applied biocarbon-Mg/Al layered double hydroxides composites (CPLDH and CPLDH-Ca) were successfully prepared and characterized by TEM, ICP-AES, XFS, EDS, FTIR, XRD, BET and pHpzc. The fluoride removal efficiency (RF) and protein recovery ratio (RP) of the adsorbents were studied in protein systems of lysozyme (LSZ) and bovine serum albumin (BSA). The results showed that the CPLDH-Ca presented remarkable performance for selective fluoride removal from protein solution. It reached the maximum RF of 92.1% and 94.8% at the CPLDH-Ca dose of 2.0g/L in LSZ and BSA system, respectively. The RP in both systems of LSZ and BSA were more than 90%. Additionally, the RP of CPLDH-Ca increased with the increase of ionic strengths, and it almost can be 100% with more than 93% RF. Fluoride adsorption by the CPLDH-Ca with different initial fluoride concentrations was found to obey the mixed surface reaction and diffusion controlled adsorption kinetic model, and the overall reaction rate is probably controlled by intra-particle diffusion, boundary layer diffusion and reaction process. The adsorption isotherms of fluoride in BSA system fit the Langmuir–Freundlich model well. The BSA has synergistic effect on fluoride adsorption and the degree increased with the increase of the initial BSA concentration.

Location and binding mechanism of an ESIPT probe 3-hydroxy-2-naphthoic acid in unsaturated fatty acid bound serum albumins

The binding site and the binding mechanism of 3-hydroxy-2-naphthoic acid (3HNA) in oleic acid (OA) bound serum albumins (bovine serum albumin (BSA) and human serum albumin (HSA)) have been determined using steady state and time resolved emission of tryptophan residues (Trp) in proteins and the ESIPT emission of 3HNA. Time resolved anisotropy of the probe 3HNA and low temperature phosphorescence of Trp residues of BSA in OA bound BSA at 77K reveals a drastic change of the binding site of 3HNA in the ternary system compared to that in the free protein. 3HNA binds near Trp213 in the ternary system whereas 3HNA binds near Trp134 in the free protein. The structure of OA bound BSA generated using docking methodology exhibits U-bend configuration of all bound OA. The docked pose of 3HNA in the free protein and in OA bound albumins (ternary systems) and the concomitant perturbation of the structure of proteins around the binding region of 3HNA corroborate the enhanced ESIPT emission of 3HNA and the energy transfer efficiency from the donor Trp213 of BSA to 3HNA acceptor in 3HNA–OA–BSA system.

Probing the interaction of a globular protein with a small fluorescent probe in the presence of silver nanoparticles: spectroscopic characterization of its domain specific association and dissociation

Photoinduced intramolecular charge transfer produces a polar excited state in the small fluorescent probe 1-anilino-8-naphthalene-sulfonate (ANS) rendering the resulting emission sensitive to the medium polarity. The binding of ANS to proteins has been well characterized in the literature. The probe binds to the less polar hydrophobic, restricted proteinous environment of bovine serum albumin (BSA) resulting in a blue shift of the emission maximum with an increase in emission intensity. However, upon addition of silver nanoparticles to the probe–BSA system, there was found to be an interaction between the nanoparticle and protein resulting in a weakening of the probe–BSA binding and an associated conformational change of the protein in order to accommodate the silver nanoparticle. This has been hitherto undeciphered. Studies using site markers of flufenamic acid and phenylbutazone coupled with other spectroscopic techniques, REES, time resolved studies, FTIR, and SEM imaging studies have shed light on the interaction of silver nanoparticles with the probe bound protein. ANS was observed to move from its binding site in the protein to accommodate the silver nanoparticle surface which involved conformational changes of the protein near the probe binding site. The association of the probe to the protein and its dissociation from the sites on introduction of silver nanoparticles has thus been investigated using spectroscopic studies.

Physicochemical characterization and sorption behavior of Mg–Ca–Al (NO3) hydrotalcite-like compounds toward removal of fluoride from protein solutions

The present study explores the potential of Mg–Ca–Al (NO3) hydrotalcite-like compounds (MgCaAlNO3-HTlcs) for the removal of fluoride from protein solutions. In this study, the Mg3−xCaxAlNO3-HTlcs (x=0–3, x is the mol.% of Ca) were synthesized and characterized by SEM, XRD, FTIR, BET, ICP-AES and pHzpc analysis. The sorption experiments were conducted in protein systems of bovine serum albumin (BSA) and lysozyme (LSZ). The batch experiment results showed that the NO3-HTlc with Mg/Ca/Al molar ratio of 2.5/0.5/1 had remarkable fluoride sorption ability with maximum sorption capacities of 82.35mg/g and 72.69mg/g at pH 5.0 and 40°C in BSA and LSZ system, respectively. Moreover, the loss of BSA of 0.71% was low and there was no loss of LSZ. It was evident that the Mg2.5Ca0.5AlNO3-HTlc could selectively adsorb fluoride from protein solutions. The equilibrium sorption data fitted well to the Langmuir model and the kinetic data conformed to the pseudo-second-order model. Thermodynamic parameters (ΔG°, ΔH° and ΔS°) were evaluated and revealed that the sorption process was spontaneous and endothermic in nature. Furthermore, the results from Antarctic krill processing wastewater study confirmed the feasibility and practicality of the Mg2.5Ca0.5AlNO3-HTlc for fluoride removal in fluoride bearing protein system.

Biophysical influence of isocarbophos on bovine serum albumin: Spectroscopic probing

Isocarbophos (ICP) is a phosphorous pesticide with high toxicity. It has been detected in several kinds of food and therefore can enter human body. In this paper, spectroscopic approaches including three-dimensional fluorescence (3D-FL) spectroscopy, UV–visible absorption spectroscopy and circular dichroism (CD) spectroscopy were employed to explore the binding of ICP to bovine serum albumin (BSA) at simulated physiological conditions. It was found that the fluorescence quenching of BSA was caused by the formation of ICP-BSA complex at ground state and belonged to static quenching mechanism. The binding constants, the number of binding sites, enthalpy change (ΔHθ), Gibbs free energy change (ΔGθ) and entropy change (ΔSθ) were calculated at four different temperatures according to Scatchard model and thermodynamic equations. To identify the binding location, fluorescence probe techniques were used. The results showed that warfarin, an acknowledged site marker for BSA, could be partially replaced by ICP when ICP was added to warfarin–BSA systems, which demonstrated that ICP primarily bound on Sudlow's site I in domain IIA of BSA molecule. The distance r (3.06nm) between donor (Trp-212) and acceptor (ICP) was obtained based on Förster's non-radiation fluorescence resonance energy transfer (FRET) theory. Furthermore, the CD spectral results indicated that the secondary structure of BSA was changed in presence of ICP. The study is helpful to evaluating the toxicology of ICP and understanding its effects on the function of protein during the blood transportation process.

Combined voltammetric and spectroscopic analysis of small molecule–biopolymer interactions: The levodopa and serum albumin system

An analytical method was researched for the simultaneous determination of reactants and products during the binding of important small molecules such as levodopa (LD) with biopolymers such as bovine serum albumin (BSA). Voltammetry and fluorescence spectroscopy were used to obtain the analytical profiles from different reactant mixtures as a function of concentration. This enabled the extraction of the equilibrium constants (KSV) which are reported for the first time. Voltammetric results supported the formation of the LD–BSA complex but not that with dopamine. Further information of the LD–BSA system was unattainable because the measured composite profiles could not be extracted.New information was obtained when the extended data matrix was resolved by the MCR–ALS method. The previously unavailable extracted voltammogram profile of LD–BSA complex indicated that the complex was electroactive; this was unexpected if the LD–BSA system was in its folded state, and hence, it was suggested that the protein must be unfolded. The observation that the drug:BSA stoichiometry was 3:1, i.e. (levodopa)3–BSA, supported this suggestion; these results were obtained from the MCR–ALS extracted concentration profiles for the three reaction components.

Probing the Binding of Rifampicin to Bovine Serum Albumin in Aqueous Solution

The binding of rifampicin (RFP), an anti-tuberculosis agent, to bovine serum albumin (BSA) was studied at physiological conditions (pH=7.40) by a spectroscopic approach. In the discussion of the quenching mechanism, it was proved that the fluorescence quenching of BSA by RFP is a result of the formation of a RFP–BSA complex. Binding parameters were determined using the modified Stern-Volmer equation and Scatchard’s equation to provide a measure of the binding affinity between RFP and BSA. The resulting thermodynamic parameters ΔG, ΔH, and ΔS at different temperatures indicate that electrostatic interactions play a major role in RFP–BSA association. Site marker competitive displacement experiments demonstrate that RFP binds with high affinity to the site I (subdomain IIA) of BSA. Furthermore, the effect of metal ions on the RFP–BSA system was studied, and the specific binding distance r (3.38 nm) between donor and acceptor (RFP) was obtained according to the fluorescence resonance energy transfer (FRET).

Mechanism and conformational studies of farrerol binding to bovine serum albumin by spectroscopic methods

The mechanism and conformational changes of farrerol binding to bovine serum albumin (BSA) were studied by spectroscopic methods including fluorescence quenching technique, UV–vis absorption, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. The results of fluorescence titration revealed that farrerol could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The thermodynamic parameters enthalpy change and entropy change for the binding were calculated to be −29.92 kJ mol −1 and 5.06 J mol −1 K −1 according to the van’t Hoff equation, which suggested that the both hydrophobic interactions and hydrogen bonds play major role in the binding of farrerol to BSA. The binding distance r deduced from the efficiency of energy transfer was 3.11 nm for farrerol–BSA system. The displacement experiments of site markers and the results of fluorescence anisotropy showed that warfarin and farrerol shared a common binding site I corresponding to the subdomain IIA of BSA. Furthermore, the studies of synchronous fluorescence, CD and FT-IR spectroscopy showed that the binding of farrerol to BSA induced conformational changes in BSA.

Binding of rare earth metal complexes with an ofloxacin derivative to bovine serum albumin and its effect on the conformation of protein

The water-soluble Pr (Ⅲ) and Nd (Ⅲ) complexes with an ofloxacin derivative have been prepared and characterized. The single-crystal X-ray diffraction showed that the Pr (III) and Nd (III) complexes have the similar molecular structure. Under physiological pH condition, the effects of [PrL(NO 3) 2(CH 3OH)](NO 3) and [NdL(NO 3) 2(CH 3OH)](NO 3) on bovine serum albumin (BSA) were examined using fluorescence spectroscopy in combination with UV–vis absorbance and circular dichroism (CD) spectra. The result reveals that the quenching mechanism of fluorescence of BSA by two complexes is a static quenching process and the number of binding sites is about 1 for both. The thermodynamic parameters (Δ H=−14.52 kJ mol −1, Δ S=56.54 J mol −1 K −1 for [PrL(NO 3) 2(CH 3OH)](NO 3) and Δ H=−24.63 kJ mol −1, Δ S=22.07 J mol −1 K −1 for [NdL(NO 3) 2(CH 3OH)](NO 3)) indicate that hydrophobic and electrostatic interactions are the main binding force in the complexes–BSA system. The binding average distance between complexes and BSA was obtained on the basis of Förster's theory. In addition, it was proved by the CD spectra that the BSA secondary structure was changed in the presence of complexes in an aqueous solution.

Interactions between Bovine Serum Albumin and Oxidized Sodium Alginate in Solution

This paper focuses on the interactions between oxidized sodium alginate (OSA) and bovine serum albumin (BSA) at the molecular level with the purpose to provide basic information for optimizing the biological utilization and pharmaceutical applications of OSA. The results revealed that OSA could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The thermodynamic parameters, enthalpy change (H) and entropy change (S), were also calculated. The process of binding was a spontaneous process in which Gibbs free energy change was negative. The distances between donor (BSA) and acceptor (OSA) were calculated to be 2.41, 2.54 and 2.84 nm for SA–BSA, 10% OSA–BSA and 30% OSA–BSA systems, based on Förster non-radiative energy transfer theory, respectively. The results of synchronous fluorescence spectra showed that binding of OSA with BSA cannot induce conformational changes in BSA. Meanwhile, the OSA with low degree of oxidization (DO% 30%) was non-cytotoxic. Therefore, OSA could be promising as a bioactive compound carrier.

Spectroscopic studies on the interaction between Pr(III) complex of an ofloxacin derivative and bovine serum albumin or DNA

The binding properties on [PrL 2(NO 3)](NO 3) 2 (L = 9-fluoro-2,3-dihydro-3-methyl-10-(4-methyl-1-piperaziny)-7-oxo-7Hpyrido[1,2,3-de]-1,4-benzoxazine-6-carbaldehyde benzoyl hydrazone) to bovine serum albumin (BSA) have been studied for the first time using fluorescence spectroscopy in combination with UV–Vis absorbance spectroscopy. The results showed that [PrL 2(NO 3)](NO 3) 2 strongly quenched the intrinsic fluorescence of BSA through a static quenching procedure, and non-radiation energy transfer happened within molecules. The number of binding site was about 1, and the efficiency of Förster energy transfer provided a distance of 4.26 nm between tryptophan and [PrL 2(NO 3)](NO 3) 2 binding site. At 288, 298, 310 K, the quenching constants of BSA–[PrL 2(NO 3)](NO 3) 2 system were 5.11 × 10 4, 4.33 × 10 4 and 3.71 × 10 4 l M −1. Δ H, Δ S and Δ G were obtained based on the quenching constants and thermodynamic theory (Δ H < 0, Δ S > 0 and Δ G < 0). These results indicated that hydrophobic and electrostatic interactions are the mainly binding forces in the [PrL 2(NO 3)](NO 3) 2–BSA system. In addition, the CD spectra have proved that BSA secondary structure changed in the presence of [PrL 2(NO 3)](NO 3) 2 in aqueous solution. Moreover, the interaction between [PrL 2(NO 3)](NO 3) 2 and calf thymus DNA (CT DNA) was studied by spectroscopy and viscosity measurements, which showed that the binding mode of the [PrL 2(NO 3)](NO 3) 2 with DNA is intercalation. The DNA cleavage results show that in the absence of any reducing agent, the [PrL 2(NO 3)](NO 3) 2 can cleave plasmid pBR322 DNA and its hydrolytic mechanism was demonstrated with hydroxyl radical scavengers and singlet oxygen quenchers.

Immunochemical and Mass Spectrometric Analysis of Nε-(Carboxymethyl)lysine Content of AGE−BSA Systems Prepared with and without Selected Antiglycation Agents

The present study was designed to compare surface plasmon resonance (SPR) biosensor, enzyme-linked immunosorbent assay (ELISA), and ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) methods for the analysis of Nε-(carboxymethyl)lysine (CML) in glucose-bovine serum albumin (BSA) model systems and to investigate the possible inhibitory effect of selected compounds (α-tocopherol, ferulic acid, rutin, thiamin, thiamin monophosphate, and thiamin pyrophosphate) on CML formation. The reported levels of CML detected were dependent upon the method of analysis employed. The highest reported concentrations were obtained with the SPR biosensor, whereas the lowest were found by ELISA. However, a high correlation was observed between these two immunochemical procedures. CML concentrations were dependent upon the type and concentration of the candidate CML inhibitor. All inhibitory compounds investigated, with the exception of α-tocopherol, decreased the level of CML formation in the glucose-BSA system.

Determination of Chondroitin Sulfate A by Resonance Rayleigh Scattering and Resonance Non-linear Scattering with Proteins as Probes

In a pH 2. 5 ～ 4. 0 Britton-Robinson( BR) buffer medium,some proteins such as bovine serum albumin( BSA) ,Chymotrypsin( Chy) and α-amylase( α-Amy) can react with chondroitin sulfate A( CS) via electrostatic force,hydrogen bond force or/and hydrophobic force to form binding products. As a result,the resonance Rayleigh scattering( RRS) ,second-order scattering( SOS) and frequency doubling scattering( FDS) were enhanced greatly with new scattering spectra appeared. The increments of scattering intensity( ΔI) were proportional to the concentration of CS in certain ranges. The detection limits( 3σ) of CS in Chy,BSA and α-Amy systems were 1. 4,2. 0 and 1. 8 μg/L( RRS method) ,2. 3,2. 9 and 2. 5 μg/L( SOS method) ,5. 8,13. 2 and 9. 6 μg/L ( FDS method) ,respectively. Among them,the RRS method exhibited the highest sensitivity and the Chy-CS system was more sensitive than others. The characteristics of the spectra and optimal conditions of RRS method were investigated. The effects of external substances were tested. The established methods have a good selectivity and can be applied to the determination of CS in eye drops with satisfactory results.

Mechanistic and conformational studies on the interaction of anti-inflammatory drugs, isoxicam and tenoxicam with bovine serum albumin

The mechanism of interaction of the non-steroidal anti-inflammatory drugs, isoxicam (IXM) and tenoxicam (TXM) with bovine serum albumin (BSA) has been studied using spectroscopic techniques, viz., spectrofluorescence, circular dichroism (CD), UV–visible absorption and FT-IR under simulative physiological conditions. Stern–Volmer analysis of fluorescence quenching data shows the presence of the static quenching mechanism. Thermodynamic parameters (negative Δ H 0 and positive Δ S 0 values obtained in the present study) revealed that the hydrophobic interactions played a major role in the interaction of these drugs with BSA. The distance, r between the donor (BSA) and acceptor (IXM/TXM) was calculated based on the Forster’s theory of non-radiation energy transfer and the values were observed to be 3.85 nm and 2.60 nm in IXM–BSA and TXM–BSA system, respectively. CD and FT-IR studies indicated that the binding of IXM/TXM to BSA induced conformational changes in BSA. The effect of common ions on the binding of IXM/TXM to BSA has been investigated.

Characterize the interaction between naringenin and bovine serum albumin using spectroscopic approach

Naringenin, a flavanone compound highly enriched in grapefruits, has been identified as a possible inhibitor of cell proliferation; and thus has the potential to act as an antitumorigenic agent. In this study, the binding of naringenin to bovine serum albumin (BSA) was studied at the physiological conditions (pH=7.40) by fluorescence and UV–vis spectroscopy. Naringenin strongly quenches the intrinsic fluorescence of BSA, and a decrease in the fluorescence quenching constant was observed together with an increase in temperature, which indicates that the fluorescence quenching of BSA by naringenin is a result of the formation of naringenin–BSA complex. Binding parameters calculating from Stern-Volmer method and Scatchard method showed that naringenin bind to BSA with the binding affinities of the order 10 4 L mol −1. Thermodynamic parameters such as Δ G, Δ H and Δ S, were calculated at different temperatures, showing that electrostatic interactions were mostly responsible for the binding of naringenin to BSA. Site marker competitive displacement experiments demonstrating that naringenin bind with high affinity to site I (subdomain IIA) of BSA. Furthermore, the effect of metal ions to naringenin–BSA system was studied, and the specific binding distance r (3.30 nm) between donor (Trp-212) and acceptor (naringenin) was obtained according to fluorescence resonance energy transfer (FRET).

Effects of Temperature and Common Ions on Binding of Puerarin to BSA

The effects of temperature and common ions on binding of puerarin to bovine serum albumin (BSA) are investigated. The binding constants (Ka) between puerarin and BSA are 1.13×104 L⋅mol−1 (20 °C) and 1.54×104 L⋅mol−1 (30 °C), and the number of binding sites (n) is (0.95±0.02). However, at a higher temperature (40 °C) the stability of the puerarin–BSA system decreases, which results in a lower binding constant (1.58×103 L⋅mol−1) and number of binding sites (n=0.73) of the puerarin–BSA system. However, the presence of Cu2+ and Fe3+ ions increases the binding constants and the number of binding sites in the puerarin–BSA complex.

The hyaluronan–protein complexes at low ionic strength: How the hyaluronidase activity is controlled by the bovine serum albumin

Hyaluronan (HA) hydrolysis catalysed by hyaluronidase (HAase) is strongly inhibited when performed at low HAase over HA concentration ratio and under low ionic strength conditions. The reason is the ability of long HA chains to form electrostatic and non-catalytic complexes with HAase. For a given HA concentration, low HAase concentrations lead to very low hydrolysis rates because all the HAase molecules are sequestered by HA, whilst high HAase concentrations lead to high hydrolysis rates because the excess of HAase molecules remains free and active. At pH 4, non-catalytic proteins like bovine serum albumin (BSA) are able to compete with HAase to form electrostatic complexes with HA, liberating HAase which recovers its catalytic activity. The general scheme for the BSA-dependency is thus characterised by four domains delimited by three noticeable points corresponding to constant BSA over HA concentration ratios. The existence of HA–protein complexes explains the atypical kinetic behaviour of the HA / HAase system. We also show that HAase recovers the Michaelis–Menten type behaviour when the HA molecule complexed with BSA in a constant complexion state, i.e. with the same BSA over HA ratio, is considered for substrate. When the ternary HA / HAase / BSA system is concerned, the stoichiometries of the HA–HAase and HA–BSA complexes are close to 10 protein molecules per HA molecule for a native HA of 1 MDa molar mass. Finally, we show that the behaviour of the system is similar at pH 5.25, although the efficiency of BSA is less.

Controlled synthesis of CdSe and CdSe/CdS core/shell nanoparticles using Gemini surfactant Py-16-10-16 and their bioconjugates with BSA

CdSe and CdSe/CdS core/shell nanoparticles (NPs) were synthesized by using Gemini surfactant, 1,10-bis(α-hexadecyl pyridine) decamethylene dibromide (abbreviated Py-16-10-16), as a soft template. Subsequent analysis revealed that the as-synthesized CdSe NPs and CdSe/CdS core/shell NPs were highly luminescent with quantum yields of 18% and 35%, respectively, compared with Rhodamine 6G (95%). Furthermore, when the nanoparticles were conjugated with bovine serum albumin (BSA) in PBS buffer solution (pH 7.40), the fluorescence intensity of the BSA system was quenched by the addition of CdSe/TGA or CdSe/CdS/TGA NPs, while the fluorescence intensities of CdSe/TGA and CdSe/CdS/TGA NPs were enhanced by the addition of BSA. This enhancement and quenching of the fluorescence intensity by conjugating with BSA could be used to determine the albumin concentration.

Spectroscopic studies on the interaction of efonidipine with bovine serum albumin

Efonidipine hydrochloride is an antihypertensive and antianginal agent with fewer side effects and is better tolerated in the treatment of hypertension with renal impairment. Its interaction with bovine serum albumin (BSA) is of great use for the understanding of the pharmacokinetic and pharmacodynamic mechanisms of the drug. The binding of efonidipine to BSA was investigated by fluorescence spectroscopy and circular dichroism. BSA fluorescence was quenched by efonidipine, due to the fact that efonidipine quenched the fluorescence of tryptophan residues mainly by the collision mode. The thermodynamic parameters DeltaH0 and DeltaS0 were 68.04 kJ/mol and 319.42 J x mol-1 x K-1, respectively, indicating that the hydrophobic interactions played a major role. The results of circular dichroism and synchronous fluorescence measurements showed that the binding of efonidipine to BSA led to a conformational change of BSA. The fraction of occupied sites (theta) for the 8-anilino-1-naphthalein-sulfonic acid (ANS)-BSA system is 85%, whereas for the NZ-105-BSA system, it is 53%, which suggests that the interaction of ANS with BSA is stronger than that of NZ-105 with BSA. Binding studies in the presence of ANS indicated that efonidipine competed with ANS for hydrophobic sites of BSA. The effects of metal ions on the binding constant of the efonidipine-BSA complex were also investigated. The presence of metal ions Zn2+, Mg2+, Al3+, K+, and Ca2+ increased the binding constant of efonidipine-BSA complex, which may prolong the storage period of NZ-105 in blood plasma and enhance its maximum effects.