Spectroscopic determination of binding between human serum albumin and a platinum(II) dimethylsulfoxide complex

We have used electronic absorption and fluorescence spectroscopy to study binding between a platinum(II) dimethylsulfoxide complex (cis-[Pt(DMSO)₂Cl₂]) and human serum albumin (HSA), and the effect of complexation on the structure of the protein. We have calculated the binding parameters for binding between cis-[Pt(DMSO)₂Cl₂] and HSA. We have determined the binding constant K_B = (1.2 ± 0.1)·10³ M⁻¹ and the Hill coefficient h = 1.03 ± 0.1. We have determined that binding between cis-[Pt(DMSO)₂Cl₂] and the protein leads to a change in the internal packing of the macromolecule. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 573–576, July–August, 2008.     

Dielectric relaxation study of ascorbic acid solutions in pure dimethylsulfoxide (or diethylsulfoxide) and in dimethylsulfoxide (or diethylsulfoxide)/water mixtures

The complex dielectric spectra of ascorbic acid solutions in pure dimethylsulfoxide (or diethylsulfoxide) and in dimethylsulfoxide (or diethylsulfoxide)/water mixtures have been measured at frequencies between 100 MHz and 20 GHz at 298.15 K.Two kinds of dielectric relaxation processes were observed in each solution. The low frequency relaxation (Debye term) is assigned to solute. The high frequency relaxation (Cole-Davidson term) is ascribed to practically unaffected solvent.From the results obtained it follows that relaxation time and relaxation strength in DESO containing solutions (i.e. binary AA/DESO and ternary AA/DESO/water systems) are greater than those in DMSO containing solutions.     

Interaction of gold nanoparticles with bovine serum albumin

The interaction between gold nanoparticles and bovine serum albumin (BSA) in aqueous solutions was studied. The formation of nanoparticle—BSA associates was demonstrated, which is expressed in a bathochromic shift of the surface plasmon resonance band by 5–6 nm in the absorption spectrum. The results were approximated using the Drude model for metal spheres. The thickness of the dielectric (protein) shell of the nanoparticle and its permittivity (refractive index) were calculated.     

Interaction between varenicline tartrate and bovine serum albumin

This paper mainly investigated the interaction between varenicline tartrate and bovine serum albumin. The Stern–Volmer quenching constant and bimolecular quenching rate constant were determined; furthermore, the fluorescence quenching mechanism between varenicline tartrate and bovine serum albumin was clarified. The binding constants and the number of binding sites were deduced from the double logarithm regression curve. Thermodynamic parameters were calculated, which indicated that the binding process was spontaneous and the acting force were mainly hydrophobic forces. The binding distance was calculated to be 4.80 nm, which means that there was nonradiative energy transfer from varenicline tartrate to bovine serum albumin during the process. And the bovine serum albumin conformation affected by varenicline tartrate was analyzed through ultraviolet–visible and synchronous fluorescence spectroscopy.     

Interaction of different thiol-capped CdTe quantum dots with bovine serum albumin

Due to their unique optical properties, quantum dots (QDs) are rapidly revolutionizing many areas of medicine and biology. Despite the remarkable speed of development of nanoscience, relatively little is known about the interaction of nanoscale objects with organism. In this work, interaction of CdTe QDs coated with mercaptopropanoic acid (MPA), L-cysteine (L-cys), and glutathione (GSH) with bovine serum albumin (BSA) was investigated. Fluorescence (FL), UV–vis absorption, and circular dichroism (CD) spectra methods were used. The Stern-Volmer quenching constant (K_sv) at different temperatures, corresponding thermodynamic parameters (ΔH, ΔG and ΔS), and information of the structural features of BSA were gained. We found that QDs can effectively quench the FL of BSA in a ligand-dependent manner, electrostatic interactions play a major role in the binding reaction, and the nature of quenching is static, resulting in forming QDs-BSA complexes. The CD spectra showed that the secondary and tertiary structure of BSA was changed. This study contributes to a better understanding of the ligand effects on QDs-proteins interactions, which is a critical issue for the applications in vivo.     

Interaction of the flavonoid hesperidin with bovine serum albumin: A fluorescence quenching study

The interaction between the flavonoid hesperidin and bovine serum albumin (BSA) was investigated by fluorescence and UV/Vis absorption spectroscopy. The results revealed that hesperidin caused the fluorescence quenching of BSA through a static quenching procedure. The hydrophobic and electrostatic interactions play a major role in stabilizing the complex. The binding site number n, and apparent binding constant K_A, corresponding thermodynamic parameters ΔG^o, ΔH^o, ΔS^o at different temperatures were calculated. The distance r between donor (BSA) and acceptor (hesperidin) was obtained according to fluorescence resonance energy transfer. The effect of Cu²⁺, Zn²⁺, Ni²⁺, Co²⁺, and Mn²⁺ on the binding constants between hesperidin and BSA were studied. The effect of hesperidin on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy and UV/Vis absorption spectroscopy.     

Interaction of aconitine with bovine serum albumin and effect of atropine sulphate and glycyrrhizic acid on the binding

The interaction of aconitine with bovine serum albumin (BSA) and effect of atropine sulphate and glycyrrhizic acid on binding constant, binding sites, and conformation were studied in an aqueous buffer solution (pH 7.40) by ultraviolet absorption and fluorescence spectroscopy. The study results show that aconitine quenched the endogenous fluorescence of BSA via a dynamic quenching procedure. Predominant intermolecular forces between aconitine and BSA were hydrophobic interactions, which stabilized the complex of aconitine–BSA. The distance between the donor and acceptor was 2.62 nm. The conformation of BSA was investigated by synchronous fluorescence techniques, indicating that the microenvironment around tryptophan (Trp) residues was changed. Furthermore, with the addition of atropine sulphate or glycyrrhizic acid, binding constant and the number of binding sites of aconitine to BSA were decreased, and the conformation had no change, which provide an important theoretical support for aconitine detoxification by atropine sulphate and glycyrrhizic acid.     

Adsorption of bovine serum albumin (BSA) on polystyrene (PS) and its acid copolymer

The effect of surface polarity on the adsorption of bovine serum albumin (BSA) on polystyrene (PS), 7% polystyrene-co-maleic anhydride (7%PSMAn) and 50% polystyrene-co-maleic acid (50%PSMA), at pH 7.4, was investigated. Polystyrene represented the non-polar surface while 7%PSMAn and 50%PSMA represented a low and high acid content copolymer. The amount of the adsorbed BSA depended on the amount of the acid content in the copolymer. BSA formed a monolayer with a side-on orientation on the low polarity PS surface, a mixed side-on and end-on orientation on 7%PSMAn and a predominantly side-on orientation on 50%PSMA. The thickness of adsorbed BSA, measured with an atomic force microscope (AFM), varied from 3 nm to 5 nm for the side-on orientation and from 10 nm to 15 nm for the end-on orientation. The average area occupied per BSA molecule was consistent with the proposed orientation, and was 34.8 nm², 27.8 nm² and 18.0 nm² for PS, 7%PSMAn and 50%PSMA, respectively. The adsorption showed a concentration dependency following the Freundlich isotherm, which indicated the interactions among adsorbed BSA molecules on the polymer surface. The adsorption took place as an island-like morphology and started to fuse into a patch-like morphology at higher concentrations before achieving a complete monolayer formation. A non-uniform surface coverage and defects were observed in all cases. It is recommended that for an effective blocking of PS, 7%PSMAn and 50%PSMA, the BSA concentration should be higher than 3 mg/mL.     

Interaction mechanisms of ionic liquids [Cnmim]Br (n=4, 6, 8, 10) with bovine serum albumin

It is important to study the interaction of ionic liquids (ILs) with protein for the applications of ILs in biochemical process, and help the researchers to choose and design the better ILs to serve as a solvent. In this work, the interaction between 1-alkyl-3-methylimidazolium bromide [C_nmim]Br (n=4, 6, 8, 10) and bovine serum albumin (BSA) was systematically investigated for the first time by multi-spectroscopic approach (fluorescence, UV–vis and FT-IR spectroscopy) and density functional theory (DFT). [C_nmim]Br (n=4, 6, 8, 10) can bind to BSA by H-bond interaction between their cationic headgroups and Asp/Glu amino acid residue at the surface of BSA, and hydrophobic interaction between their hydrocarbon chains and the hydrophobic amino acid residues in the interior of BSA. On the basis of thermodynamic parameters and the similar structure of [C_nmim]Br (n=4, 6, 8, 10), it can be inferred that the hydrophobic interaction plays a major role in the interaction of [C₁₀mim]Br with BSA, while the hydrogen bond and van der Waals force play a major role in the interaction of [C_nmim]Br (n=4, 6, 8) with BSA. Synchronous fluorescence and FT-IR spectra indicate that [C₁₀mim]Br could markedly change the secondary structure of BSA, while [C_nmim]Br (n=4, 6, 8) could slightly change the secondary structure of BSA. The results allowed us to understand (i) the effect of the alkyl chain length of the cation on the mechanism of ILs–protein interaction and (ii) the effect of the alkyl chain length of the cation on the protein secondary structure.     

Luminescence properties of some platinum (II) complexes. Counter-ion and molecular geometry effects

Reflectance and luminescence spectra, and emission lifetimes of 14 charged and neutral Pt (II) complexes in the solid crystalline state are reported. The lifetimes (in the range of some tens of microseconds) indicate that the emissions are due to a spin-forbidden process. On the basis of spectral correlations, the phosphorescence is tentatively identified as due to the lowest d-d ligand field transition when the bonding of the ligand is essentially σ in character, and to a π1 → d charge-transfer transition for those complexes in which the ligands themselves have π orbital systems. Both the radiative (k_r) and non-radiative (k_n) rate constants are sensitive to changes in molecular geometry (cis, trans isomers) and counter-ions. Assuming unitary efficiency for the intersystem crossing to the emitting state, the counter-ion appears to predominantly affect k_n through vibrational coupling of the chromophore with the lattice. For the cis forms, both k_r and k_n are affected in a complex manner, with metal-metal interactions playing an important role. For the trans forms, however, the constancy of the quantum yield with respect to temperature suggests that k_n is negligible in comparison to k_r, and therefore the trans chromophores behave as isolated systems within the crystalline lattice.     

Interactions of ferrimagnetic glass/glass-ceramics with bovine serum albumin

Glasses/glass-ceramics with nominal composition 34 SiO₂-(45 − x)CaO-16P₂O₅-4.5MgO-0.5CaF₂ − xFe₂O₃ (where x = 10, 15, 20 wt%) have been prepared by melt quenching technique. These are characterized for structural and micro structural properties by using XRD and Raman spectroscopy. Interaction of glass-ceramics samples with bovine serum albumin (BSA) has been studied using SEM and TOF-SIMS. The formation of magnetite, apatite and wollastonite phases are observed. Typical sizes of crystallites as seen from SEM measurement are 30-50 nm. The progressive addition of iron oxide to glass leads to increase in number of non-bridging oxygen, which in turn affects the response of glass-ceramics when immersed in BSA. The samples with 15 and 20 wt% Fe₂O₃ have shown nearly full surface coverage with BSA, while the sample with 10 wt% Fe₂O₃ shows poor adhesion.     

Fluorescent analysis of interaction of flavonols with hemoglobin and bovine serum albumin

We have studied the fluorescent properties of flavonols (quercetin, fisetin, morin, rutin) with the aim of studying possible interaction with hemoglobin and bovine serum albumin (BSA). We observed an increase in the intensity of intrinsic fluorescence for all the flavonols except rutin in the presence of BSA. From the changes in the fluorescence spectra, we concluded that tautomeric forms are formed on interaction with hemoglobin. We determined the interconnection between the structure of related flavonols and their fluorescent properties on interaction with proteins, and we determined the binding constants for binding with BSA and hemoglobin. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 659–664, September–October, 2007.     

Spectroscopic investigation on the sonodynamic activity of amsacrine (AMSA) to bovine serum albumin (BSA) damage

The sonodynamic damage of bovine serum albumin (BSA) under ultrasonic irradiation in the presence of amsacrine (AMSA) was studied by hyperchromic effect of UV-vis spectra and quenching effect of intrinsic fluorescence. In addition, several influencing factors such as ultrasonic irradiation time, AMSA concentration, system acidity and ionic strength about the damage of BSA molecules were reviewed. The results showed that the damage degree was obviously enhanced with the increase of ultrasonic irradiation time and AMSA concentration, but it was only slightly increased with the increase of solution pH value and ionic strength. Furthermore, the binding and damaging sites to BSA molecules were estimated by synchronous fluorescence spectra. The different chances to damage tryptophan (Trp) and tyrosine (Tyr) residues were found through the ratios of synchronous fluorescence quenching (R_SFQ). At last, the generation of reactive oxygen species (ROS) in sonodynamic process was estimated by the method of oxidation-extraction Spectrometry (OES). And then, several radical scavengers were used to determine the kind of ROS, which includes singlet oxygen (¹O₂) and hydroxyl radicals (·OH). Perhaps, the result would bring a certain guiding significance to use sonosensitive drugs in the fields of tumor treatment.     

Spectroscopic analyses on interaction of bovine serum albumin (BSA) with toluidine blue (TB) and its sonodynamic damage under ultrasonic irradiation

In this paper, the toluidine blue (TB) with tricyclic quinone imide plane structure is used as sonosensitizer to study the interaction and sonodynamic damage to bovine serum albumin (BSA) by UV-vis and fluorescence spectroscopy. The results show that the TB can bind to BSA molecules, obviously, and the synergetic effects of TB and ultrasonic irradiation can efficiently damage the BSA molecules. Otherwise, some influencing factors such as ultrasonic irradiation time, TB concentration, pH value and ionic strength on the damage of BSA molecules were also considered by the numbers. Synchronous fluorescence spectroscopy indicates that the tyrosine (Tyr) residues of BSA molecules are damaged more seriously than the tryptophan (Trp) residues under ultrasonic irradiation.     

Spectroscopic studies on the interaction and sonodynamic damage of neutral red (NR) to bovine serum albumin (BSA)

In this paper, the interaction of neutral red (NR) with bovine serum albumin (BSA) and the sonodynamic damage to BSA under ultrasonic irradiation was studied by means of ultraviolet-visible (UV-vis) and fluorescence spectra. The quenching constant (K_SV=5.749×10⁴ L/mol), binding constant (K_A=3.19×10⁴ L/mol) and binding site number (n=0.9462) were measured. The binding distance (r=2.47 nm) between NR and BSA was obtained according to Föster’s non-radiative energy transfer theory. The damage process of BSA molecules was detected by the hyperchromic effect of UV-vis spectra and quenching of intrinsic fluorescence spectra. In addition, the influencing factors such as ultrasonic irradiation time and NR concentration on the damage to BSA molecules were also considered. The results showed that the damage degree is enhanced with the increase of ultrasonic irradiation time and NR concentration. The possible mechanism of sonodynamic damage to BSA molecules was mainly mediated by singlet oxygen (¹O₂). Otherwise, the binding and damaging sites to BSA molecules were also estimated by synchronous fluorescence. The results indicated that the NR is more vicinal to tryptophan (Trp) residue than to tyrosine (Tyr) residue and the damage site is also mainly at Trp residues. The research result will bring a certain significance to use sonosensitive drugs in the fields of tumor treatment.     

Mixed-ligand complexes of Pt(II) and Pd(II) with 2-phenylbenzothiazole

The mixed-ligand cyclometalated [M(Bt)(μ-Cl)]₂ and [(M(N∧N))(Bt)]⁺ complexes (M = Pd(II), Pt(II); Bt^? is the deprotonated form of 2-phenylbenzothiazole; and ( N∧N) is ethylenediamine (En) and orthophenanthroline (Phen)) are studied and described by ¹H NMR spectroscopy, electronic absorption and emission spectroscopy, and voltammetry. The one-electron reduction of complexes is attributed to the electron transfer to the π * orbitals of both diimine and cyclometalated ligands. The long-wavelength absorption bands and vibrationally structured luminescence bands are assigned to optical transitions that are localized mainly on the M(Bt) metal-complex fragment.     

Mn（Ⅱ）,Co（Ⅱ）与HSA相互作用的荧光光谱研究

用荧光光谱法研究了生理ｐＨ和等离子点（ｐＨ＝５．３０）时Ｍｎ（Ⅱ）、Ｃｏ（Ⅱ）与ＨＳＡ的相互作用。根据Ｆｏｒｓｔｅ非辐射能量转移理论,得到了不同ｐＨ时Ｍｎ（Ⅱ）、Ｃｏ（Ⅱ）在ＨＳＡ中的第一强结合位置与Ｔｒｐ－２１４残基间的距离。这一结果远大于文献报道值,根据Ｍｎ（Ⅱ）、Ｃｏ（Ⅱ）在ＨＳＡ中的结合部位及ＨＳＡ的畴结构对这一显著差异进行了讨论。     

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(NO₃)₂(CH₃OH)](NO₃) and [NdL(NO₃)₂(CH₃OH)](NO₃) 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 (ΔH=−14.52 kJ mol⁻¹, ΔS=56.54 J mol⁻¹ K⁻¹ for [PrL(NO₃)₂(CH₃OH)](NO₃) and ΔH=−24.63 kJ mol⁻¹, ΔS=22.07 J mol⁻¹ K⁻¹ for [NdL(NO₃)₂(CH₃OH)](NO₃)) 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.     

CdSe-ZnS quantum dots as temperature sensors during thermal coagulation of bovine serum albumin (BSA) solder

Laser tissue soldering (LTS) has variously interesting applications such as wound closure, anastomosis of blood vessels, and sealing corneal wounds. Since tissue properties such as optical absorption or thermal conductivity may differ, temperature control is essential to obtain full coagulation and to minimize thermal side effects. In this article, a non-invasive technique is proposed for temperature sensing by using CdSe-ZnS quantum dots (QDs) dissolved in protein solder, namely bovine serum albumin (BSA). The temperature measurement is conducted by monitoring the change in the photoluminescence spectra of the QDs. It is shown that the peak emission wavelength of about 653 nm of CdSe-ZnS QDs shifts linearly in a temperature range from 30 °C to 70 °C, with a coefficient of 0.153 nm?°C^?1 with increasing temperature. The wavelength shift can be determined by applying a small spectrometer with a CCD-array detector. The uncertainty associated with this method is estimated to be less than 6 °C in temperature. As the temperature increases, the measured signal strength initially remains constant and then falls off abruptly when exceeding 55 °C. The signal drop correlates with a phase change from a clear, low-scattering protein solution to strong-scattering solid material.