Studies of interaction between colchicine and bovine serum albumin by fluorescence quenching method

Fluorescent labeling of proteins with amine-specific 1,3,2-(2H)-dioxaborine polymethine dye

A novel water-soluble amine-reactive dioxaborine trimethine dye was synthesized in a good yield and characterized. The potential of the dye as a specific reagent for protein labeling was demonstrated with bovine serum albumin and lysozyme. Its interaction with proteins was studied by fluorescence spectroscopy and gel electrophoresis. The covalent binding of this almost nonfluorescent dye to proteins results in a 75- to 78-fold increase of its emission intensity accompanied by a red shift of the fluorescence emission maximum by 27 to 45 nm, with fluorescence wavelengths of labeled biomolecules being more than 600 nm. The dye does not require activation for the labeling reaction and can be used in a variety of bioassay applications.

Binding of engeletin with bovine serum albumin: insights from spectroscopic investigations

In this paper, several spectroscopic techniques were used to investigate the interaction of engeletin (ELN) with bovine serum albumin (BSA). The analysis of UV-Vis absorption and fluorescence spectra revealed that ELN and BSA formed a static complex ELN-BSA, and ELN quenched the fluorescence of BSA effectively. According to the thermodynamic parameters ΔS(0) = 47.27 J·mol(-1)·K(-1) and ΔΗ(0) = -10.34 kJ·mol(-1), the hydrophobic and hydrogen bond interactions were suggested to be the major interaction forces between ELN and BSA. Raman spectroscopy indicated that the binding of ELN slightly changed the conformations and microenviroment of BSA and decreased the α-helix content of BSA.

Spectrofluorometric studies on the binding interaction of bioactive imidazole with bovine serum albumin: a DFT based ESIPT process

Bioactive imidazole derivatives were synthesized and characterized by NMR spectra, mass and CHN analysis. An excited state intramolecular proton transfer (ESIPT) process in hydroxy imidazole has been studied using emission spectroscopy. In hydrocarbon solvent, the tautomer emission predominates over the normal emission and in alcoholic solvent like ethanol; a dramatic enhancement of normal emission is observed which was due to increased solvation. DFT calculation on energy, charge distribution of the rotamers in the ground and excited states of the imidazole derivative were performed and discussed. PES calculation indicates that the energy barrier for the interconversion of two rotamers is too high in the excited state than in the ground state. The interaction between bioactive imidazole derivative and bovine serum albumin (BSA) was investigated.

The electrostatic interactions between nano-TiO(2) and trypsin inhibit the enzyme activity and change the secondary structure of trypsin

In this work, the interaction between nano-TiO(2) and trypsin was investigated, and the mechanisms of the interaction were explored by the methods of UV-vis detection, circular dichroism (CD), and fluorescence. The results clearly demonstrated that nano-TiO(2) had an inhibitory effect on the enzyme activity. The activity was decreased to 64% of the untreated trypsin in the presence of 300 μg/ml nano-TiO(2). UV spectrometry proved that nano-TiO(2) had a strong physical absorption effect on trypsin, and the CD spectra revealed that the secondary structure of trypsin was partly destroyed while bound together with nano-TiO(2). The ratio of α-helix increased from 7.9% to 12.8% in the presence of 100 μg/ml TiO(2) while the ratio of β-sheet decreased from 48.7% to 36.4%. Furthermore, the fluorescence spectrometry indicated that nano-TiO(2) could quench the intrinsic fluorescence of trypsin through static quenching. Meanwhile, the binding constant was calculated to be 1, and the process of binding of trypsin on nano-TiO(2) was a spontaneous molecular interaction procedure in which electrostatic interaction plays a major role. Our study was to provide a useful approach for evaluating the health risk of nanomaterials on level of proteins.

Studies of Interaction between Ergosta‐4,6,8(14),22‐tetraen‐3‐one (Ergone) and Human Serum Albumin by Molecular Spectroscopy and Modeling

Our previous experimental results have shown that ergosta‐4,6,8(14),22‐tetraen‐3‐one (ergone) is one of the main bioactive components of Polyporus umbellatus. The efficacy of ergone binding to human serum albumin (HSA) is critical for pharmacokinetic behavior of ergone. The interactions between ergone and HSA under simulative physiological conditions were investigated by the methods of fluorescence spectroscopy, absorption and circular dichroism spectroscopy. Fluorescence data revealed that the fluorescence quenching of HSA by ergone was the result of the formation of the ergone‐HSA complex. According to the modified Stern‐Volmer equation, the binding constants (Ka) between ergone and HSA were determined. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) for the reaction were calculated to be 0.989 kJ mol‐1 and 11.214 J mol‐1 K‐1, indicating that the hydrogen bonds and hydrophobic interactions played a dominant role in the binding of ergone to HSA. The conformational investigation showed that the presence of ergone decreased the α‐helical content of HSA and induced the slight unfolding of the polypeptides of protein. Furthermore, displacement experiments using warfarin and ibuprofen indicated that ergone could bind to site I of HSA, which was also in agreement with the results of the molecular modeling.

Mechanistic investigation on binding interaction of bioactive imidazole with protein bovine serum albumin--a biophysical study

The interaction between bioactive imidazole derivative (PPP) and bovine serum albumin (BSA) was investigated using fluorescence and UV-vis spectral studies. The experimental results showed that the fluorescence quenching of BSA by imidazole derivative was the result of the formation of BSA-PPP complex and the effective quenching constants (K(SV)) were 2.66×10(4), 2.56×10(4), and 2.10×10(4) at 301, 310 and 318 K, respectively. Static quenching and non-radiative energy transfer were confirmed to the result in the fluorescence quenching. The binding site number n, apparent binding constant K(A) and corresponding thermodynamic parameters (ΔG, ΔH and ΔS) were measured at different temperatures. The process of binding of PPP molecule on BSA was a spontaneous molecular interaction procedure in which entropy increased and Gibbs free energy decreased.

Synthesis and spectroscopic characterization of 4-butoxyethoxy-N-octadecyl-1,8-naphthalimide as a new fluorescent probe for the determination of proteins

A novel 4-butoxyethoxy-N-octadecyl-1,8-naphthalimide (BON) was synthesized as a fluorescent probe for the determination of proteins. The interactions between BON and bovine serum albumin (BSA) were studied by fluorescence spectroscopy and UV-vis absorption spectroscopy. Fluorescence data revealed that the fluorescence quenching of BSA by BON was likely the result of the formation of the BON-BSA complex. According to the modified Stern-Volmer equation, the binding constants of BON with BSA at four different temperatures were obtained. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) for the reaction were calculated to be -23.27 kJ mol(-1) and 10.40 J mol(-1)K(-1) according to van't Hoff equation, indicating that the hydrogen bonds and hydrophobic interactions played a dominant role in the binding of BON to BSA. Furthermore, displacement experiments using warfarin indicated that BON could bind to site I of BSA. The effect of BON on the conformation of BSA was also analyzed by synchronous fluorescence and three-dimensional fluorescence spectra. A new fluorescence quenching assay of the proteins BSA using BON in the HCl-Tris (pH 7.4) buffer solution was developed with maximum excitation and emission wavelengths of 373 and 489 nm, respectively. The linear range was 0.1-10.0×10(-5) mol L(-1) with detection limits were determined to be 1.76×10(-8) mol L(-1). The effect of metal cations on the fluorescence spectra of BON in ethanol was also investigated. Determination of protein in human serum by this method gave results which were very close to those obtained by using Coomassie Brilliant Blue G-250 colorimetry.

Study on the interaction between salvianic acid A sodium and bovine serum albumin by spectroscopic methods

The interaction between salvianic acid A sodium (SAS) and bovine serum albumin (BSA) was investigated using fluorescence and ultraviolet spectroscopy at different temperatures under imitated physiological conditions. The experimental results showed that the fluorescence of BSA was quenched by SAS through a static quenching procedure. The binding constants of SAS with BSA were 2.03, 1.17 and 0.71×10(5) L mol(-1) at 291, 298 and 305 K, respectively. Negative values of ΔG, ΔH, and ΔS indicate that the interaction between SAS and BSA is driven by hydrogen bonds and van der Waals forces. According to Förster non-radiation energy transfer theory, the binding distance between BSA and SAS was calculated to be about 2.92 nm. The effect of SAS on the conformation of BSA was analyzed using synchronous fluorescence spectroscopy. In addition, the effect of some metal ions Cu(2+), Ca(2+), Mg(2+), and Zn(2+) on the binding constant between SAS and BSA was examined.

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

The binding properties on [PrL2(NO3)](NO3)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 [PrL2(NO3)](NO3)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 [PrL2(NO3)](NO3)2 binding site. At 288, 298, 310 K, the quenching constants of BSA-[PrL2(NO3)](NO3)2 system were 5.11×10(4), 4.33×10(4) and 3.71×10(4) l M(-1). ΔH, ΔS and ΔG were obtained based on the quenching constants and thermodynamic theory (ΔH<0, ΔS>0 and ΔG<0). These results indicated that hydrophobic and electrostatic interactions are the mainly binding forces in the [PrL2(NO3)](NO3)2-BSA system. In addition, the CD spectra have proved that BSA secondary structure changed in the presence of [PrL2(NO3)](NO3)2 in aqueous solution. Moreover, the interaction between [PrL2(NO3)](NO3)2 and calf thymus DNA (CT DNA) was studied by spectroscopy and viscosity measurements, which showed that the binding mode of the [PrL2(NO3)](NO3)2 with DNA is intercalation. The DNA cleavage results show that in the absence of any reducing agent, the [PrL2(NO3)](NO3)2 can cleave plasmid pBR322 DNA and its hydrolytic mechanism was demonstrated with hydroxyl radical scavengers and singlet oxygen quenchers.

Interaction between felodipine and bovine serum albumin: fluorescence quenching study

The fluorescence quenching spectrum of bovine serum albumin (BSA) was investigated in the presence of felodipine (FLD) by spectroscopic methods including fluorescence spectroscopy and UV-Vis absorption spectroscopy. Stern-Volmer quenching was successfully applied and the corresponding thermodynamic parameters, namely enthalpy change (DeltaH), free energy change (DeltaG) and entropy change (DeltaS) at different temperatures (304, 314 and 324 K) were calculated according to the Van't Hoff relation. This revealed that the hydrophobic interaction plays a major role in stabilizing the complex. The fluorescence spectrum of BSA was studied in presence of various concentrations of SDS surfactant. The distance (r) between donor (BSA) and acceptor (FLD) was obtained according to fluorescence resonance energy transfer (FRET). The synchronous fluorescence spectroscopy was used to investigate the effect of FLD on BSA molecule. The result shows that the conformation of BSA was changed in the presence of felodipine.

Interface processes between iron containing aluminosilicate systems and simulated body fluid enriched with protein

The behaviour of iron containing aluminosilicate samples in Kokubo's simulated body fluid (SBF) and in SBF enriched with bovine serum albumin (BSA) has been investigated. Crystalline samples of (80-x)SiO2 X 20Al2O3 X Fe2O3 system, with x = 5, 10 or 15 mol%, obtained by sol-gel method and heat treated at 1200 degrees C in air for 24 h. Data on electrical conductivity, calcium, phosphorous and potassium concentrations in simulated body fluids after samples soaking in static regime at 37 degrees C, for several periods up to 14 days, were used to estimate the dynamics of these cations on the interface of aluminosilicate samples with SBF, and with SBF containing BSA. The UV-visible and fluorescence spectra recorded from the simulated body fluids after immersion of the investigated aluminosilicate samples evidence changes function on immersion time and Fe2O3 content.

Spectroscopic studies on the binding of cobalt(II) 1,10-phenanthroline complex to bovine serum albumin

The binding interaction of the cobalt(II) 1,10-phenanthroline complex (Co(phen) (3) (2+) , phen = 1,10-phenanthroline) with bovine serum albumin (BSA) was investigated by fluorescence spectroscopy combined with UV-Vis absorption and circular dichroism measurements under simulative physiological conditions. The experiment results showed that the fluorescence intensity of BSA was dramatically decreased owing to the formation of Co(phen) (3) (2+) -BSA complex. The corresponding association constants (K (a)) between Co(phen) (3) (2+) and BSA at four different temperatures were calculated according to the modified Stern-Volmer equation. The enthalpy change (DeltaH degrees ) and entropy change (DeltaS degrees ) were calculated to be -2.73 kJ mol(-1) and 82.27 J mol(-1) K(-1), respectively, which suggested that electrostatic interaction and hydrophobic force played major roles in stabilizing the Co(phen) (3) (2+) -BSA complex. Site marker competitive experiments indicated that the binding of Co(phen) (3) (2+) to BSA primarily took place in site I of BSA. A value of 4.11 nm for the average distance r between Co(phen) (3) (2+) (acceptor) and tryptophan residues of BSA (donor) was derived from Förster's energy transfer theory. The conformational investigation showed that the presence of Co(phen) (3) (2+) resulted in the change of BSA secondary structure and induced the slight unfolding of the polypeptides of protein, which confirmed the microenvironment and conformational changes of BSA molecules.

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.

Investigations on the photoinduced interaction of water soluble thioglycolic acid (TGA) capped CdTe quantum dots with certain porphyrins

The photoinduced interaction of TGA capped CdTe quantum dots (QDs) with porphyrins such as meso-tetrakis(4-sulfonatophenyl)porphyrin [TSPP], meso-tetrakis(4-carboxyphenyl)porphyrin [TCPP], meso-tetrakis (4-N-methylpyridyl)porphyrin [TMPyP] and meso-tetraphenylporphyrin [TPP] has been studied by using absorption, steady state and time resolved fluorescence spectroscopy. The QD surface was negatively charged due to thiol capping agent containing carboxylic group. Positively charged TMPyP interacts with QDs through charge transfer mechanism, negatively charged porphyrins (TCPP and TSPP) interacted through energy transfer mechanism and the neutral one (TPP) does not have any interaction. The Stern-Volmer constant, quenching rate constant, association constants, rate of electron transfer and energy transfer parameters were calculated from the fluorescence data. Effect of molecular structure has also been studied.

Spectroscopic study on interaction of bovine serum albumin with sodium magnesium chlorophyllin and its sonodynamic damage under ultrasonic irradiation

Sonodynamic therapy (SDT) is an attractive antitumor treatment for recent years. In this paper, sodium magnesium chlorophyllin (SMC) as a sonosensitizer combining with ultrasonic (US) irradiation to damage bovine serum albumin (BSA) has been investigated by fluorescence and UV-vis spectroscopy. The interaction of BSA with SMC was studied by the quenching of intrinsic fluorescence at varying temperature. The quenching constants (K(SV)), effective binding constants (K(A)), apparent association constants (K(a)) and binding site numbers were determined. The results indicated the quenching mechanism is a static procedure. Thermodynamic parameters show that the interactions involve hydrogen bonds, hydrophobic interactions, electrostatic interactions and complexations. The binding distance is 3.533 nm. The synergistic effect of SMC and ultrasound was estimated including the study of damage conditions. Synchronous fluorescence spectra indicate the damage to Trp residues is more serious. This paper may offer some valuable references for using spectroscopy method to study the application of chlorophyll derivatives in antitumor treatment.