共查询到20条相似文献,搜索用时 15 毫秒
1.
In the acridine orange–dermatan sulfate system, free and bound dye can be distinguished from each other spectroscopically. This permits the use of fluorometric methods to study the binding of acridine orange to the acid mucopolysaccharide dermatan sulfate. Experiments were conducted at 24°C in 10?3 M citrate/phosphate buffer at pH = 7.0. The binding of the dye is highly cooperative, as evidenced by considerable interaction between adjacent bound dye molecules. Analysis of the data indicates that dermatan sulfate binds 2.3 ± 0.3 mol of acridine orange per dermatan sulfate uronic acid residue with a cooperative binding constant, Kq ranging from 4.9 to 6.0 × 105 M?1 which corresponds to a free energy of 7.74 ? ΔG° ? 7.86. The cooperativity parameter q apparently increases with increasing polymer-to-dye ratio. 相似文献
2.
Soheila Kashanian Ameneh Tahmasian Ghobadi Hamideh Roshanfekr Zohreh Shariati 《Molecular biology reports》2013,40(2):1173-1179
The interaction of native calf thymus DNA (CT-DNA) with sesamol (3,4-methylenedioxyphenol) in Tris–HCl buffer at neutral pH 7.4 was monitored by absorption spectrophotometry, viscometry and spectrofluorometry. It is found that sesamol molecules could interact with DNA outside and/or groove binding modes, as are evidenced by: hyperchromism in UV absorption band, very slow decrease in specific viscosity of DNA, and small increase in the fluorescence of methylene blue (MB)-DNA solutions in the presence of increasing amounts of sesamol, which indicates that it is able to partially release the bound MB. Furthermore, the enthalpy and entropy of the reaction between sesamol and CT-DNA showed that the reaction is enthalpy-favored and entropy-disfavored (ΔH = ?174.08 kJ mol?1; ΔS = ?532.92 J mol?1 K?1). The binding constant was determined using absorption measurement and found to be 2.7 × 104 M?1; its magnitude suggests that sesamol interacts to DNA with a high affinity. 相似文献
3.
The kinetics of complex formation between fluorescein mercuric acetate and heat-denatured DNA were studied by measuring the fluorescence quenching of this reagent. This quenching process involved no immeasurably rapid phase and it was shown that this reaction follows simple second-order kinetics. The rate constant at 25°C was estimated to be 2.9 × 104M?1 sec?1 for calf-thymus DNA (42% G + C) and 1.1 × 104M?1 sec?1 for Micrococcus lysodeikticus DNA (72% G + C). Activation parameters for this reaction were calculated from the temperature dependence of the reaction rate, and the activation entropy was found to be highly negative (?27.5 cal/mol deg for calf-thymus DNA and ?25.5 cal/mol deg for M. lysodeikticus DNA). The binding of fluorescein mercuric acetate to native DNA, which requires the opening of the double-helical structure, was also followed by measuring the absorbance change of this reagent. There was a lag phase in this binding process, and the enthalpy change for the opening step corresponded roughly to that for the opening of one base pair. These findings are discussed in relation to the results of a similar study with formaldehyde. 相似文献
4.
The enthalpy change associated with the isothermal pH-induced uncharged coil-to-helix transition ΔHh° in poly(L -ornithine) in 0.1 N KCl has been determnined calorimetrically to be ?1530 ± 210 and ?1270 ± 530 cal/mol at 10° and 25°C, respectively. Titration data provided information about the state of charge of the polymer in the calorimetric experiments, and optical rotatory dispersion data about its conformation. In order to compute ΔHh°, the observed calorimetric heat was corrected for the heat of breaking the sample cell, the heat of dilution of HCl, the heat of neutralization of the OH? ion, and the heat of ionization of the δ-amino group in the random coil. The latter was obtained from similar calorimetric measurements on poly(D ,L -ornithine). Since it was discovered that poly(L -ornithine) undergoes chain cleavage at high pH, the calorimetric measurements were carried out under conditions where no degradation occurred. From the thermally induced uncharged helix–coil transition curve for poly(L -ornithine) at pH 11.68 in 0.1 N KCl in the 0°–40°C region, the transition temperature Ttr and the quantity (?θh/?T)Ttr have been obtained. From these values, together with the measured values of ΔHh°, the changes in the standard free energy ΔGh° and entropy ΔGh°, associated with the uncharged coil-to-helix transition at 10°C have been calculated to be ?33 cal/mol and ?5.3 cal/mol deg, respectively. The value of the Zimm–Bragg helix–coil stability constant σ has been calculated to be 1.4 × 10?2 and the value of s calculated to be 1.06 at 10°C, and between 0.60 and 0.92 at 25°C. 相似文献
5.
6.
Khursheed Ali Faizan Abul Qais Sourabh Dwivedi Eslam M. Abdel-Salam Sabiha M. Ansari Quaiser Saquib 《Journal of biomolecular structure & dynamics》2018,36(10):2530-2542
Titanium dioxide nanoparticles (TiO2-NPs) interaction with human serum albumin (HSA) and DNA was studied by UV–visible spectroscopy, spectrofluorescence, circular dichroism (CD), and transmission electron microscopy (TEM) to analyze the binding parameters and protein corona formation. TEM revealed protein corona formation on TiO2-NPs surface due to adsorption of HSA. Intrinsic fluorescence quenching data suggested significant binding of TiO2-NPs (avg. size 14.0 nm) with HSA. The Stern–Volmer constant (Ksv) was determined to be 7.6 × 102 M?1 (r2 = 0.98), whereas the binding constant (Ka) and number of binding sites (n) were assessed to be 5.82 × 102 M?1 and 0.97, respectively. Synchronous fluorescence revealed an apparent decrease in fluorescence intensity with a red shift of 2 nm at Δλ = 15 nm and Δλ = 60 nm. UV–visible analysis also provided the binding constant values for TiO2-NPs–HSA and TiO2-NPs-DNA complexes as 2.8 × 102 M?1 and 5.4 × 103 M?1. The CD data demonstrated loss in α-helicity of HSA and transformation into β-sheet, suggesting structural alterations by TiO2-NPs. The docking analysis of TiO2-NPs with HSA revealed its preferential binding with aromatic and non-aromatic amino acids in subdomain IIA and IB hydrophobic cavity of HSA. Also, the TiO2-NPs docking revealed the selective binding with A-T bases in minor groove of DNA. 相似文献
7.
The effects of sodium chloride concentration on the structure of chicken erythrocyte nucleosome core particles have been studied by the use of fluorescently labelled histones. Histone H3 was modified with two sulfhydryl-specific dyes and reconstituted into core nucleosomes. Between 10?4 m and 0.6 M-NaCl four different states were observed by the fluorescent techniques of collisional quenching, polarization and energy transfer. Below 5 × 10?4 m-NaCl the nucleosome is flexible, with the single cysteine residues of the two H3 species about 48 Å apart and somewhat exposed. Between 5 × 10?3 m and 10?1 m-NaCl the nucleosome is rigid and non-spherical. The cysteine residues are close together and buried. Between 10?1 m and 4 × 10?1 m-NaCl, the cysteines become slightly more exposed but remain close together. At 6 × 10?1 m-NaCl the nucleosome is very flexible. The cysteines are more than 70 Å apart and are quite exposed. The dramatic structural changes that are observed in core nucleosomes are consistent with the variety of functions in which they must participate in the cell. 相似文献
8.
Spectrophotometric binding studies were undertaken on the interaction of neutral red with native and heat-denatured, sonicated, calf thymus DNA in a 0.2M ionic strength buffer containing Tris–sodium acetate–potassium chloride at 25°C. The pKA of neutral red was found to be 6.81. At pH 5 the binding of protonated neutral red was complicated even at low concentration ratios of dye to DNA. In the pH range 7.5–8.5 the tight binding process could be studied and it was found that both protonated and free base species of neutral red significantly bind with DNA having association constants (in terms of polynucleotide phosphate) of 5.99 × 103 M?1 and 0.136 × 103 M?1, respectively, for native DNA and 7.48 × 103 M?1 and 0.938 × 103 M?1, respectively, for denatured DNA. The pKA value of the neutral red–DNA complexes were 8.46 for native DNA and 7.72 for denatured DNA. These results are discussed in terms of possible binding mechanisms. 相似文献
9.
Atmanand M. Bagoji Jayant I. Gowda Naveen M. Gokavi 《Journal of biomolecular structure & dynamics》2017,35(11):2395-2406
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 (Ksv) 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. 相似文献
10.
The helix–coil transitions of poly(Nε-methyl, Nε-carbobenzoxy-L -lysine), poly(Nδ-methyl, Nδ-carbobenzoxy-L -ornithine), and poly(Nδ-ethyl, Nδ-carbobenzoxy-L -ornithine) in chloroform–dichloroacetic acid and their corresponding decarbobenzoxylated polypeptides in alkaline solutions were followed by optical rotation measurements. The introduction of a methyl or an ethyl group to the side chains of the carbobenzoxy derivatives of poly(L -lysine) and poly(L -ornithine) appeared to weaken the helical conformation at 25°C. The thermodynamic quantities of the three water-soluble polypeptides were calculated from the data on potentiometric titrations at several temperatures. For uncharged coil-to-helix transition, ΔH = ?370 cal/mol and ΔS = ?1.1 eu/mol for poly(Nε-methyl-L -lysine), and ΔH = ?540 cal/mol and ΔS = ?1.6 eu/mol for poly(Nδ-ethyl-L -ornithine) (all on molar residue basis). The absolute values of ΔH and ΔS dropped in the region of pH-induced transition and eventually both quantities became positive. The initiation factor σ was about 2 × 10?3, which was essentially independent of temperature. For poly(Nδ-methyl-L -ornithine) the coil-to-helix transition was not complete even when the polymer was uncharged at high pH. 相似文献
11.
Zohreh Moradi Ali Reza Rezvani Meissam Noroozifar 《Journal of biomolecular structure & dynamics》2018,36(3):779-794
In order to evaluate biological potential of a novel synthesized complex [Nd(dmp)2Cl3.OH2] where dmp is 29-dimethyl 110-phenanthroline, the DNA-binding, cleavage, BSA binding, and antimicrobial activity properties of the complex are investigated by multispectroscopic techniques study in physiological buffer (pH 7.2).The intrinsic binding constant (Kb) for interaction of Nd(III) complex and FS–DNA is calculated by UV–Vis (Kb = 2.7 ± 0.07 × 105) and fluorescence spectroscopy (Kb = 1.13 ± 0.03 × 105). The Stern–Volmer constant (KSV), thermodynamic parameters including free energy change (ΔG°), enthalpy change (?H°), and entropy change (?S°), are calculated by fluorescent data and Vant’ Hoff equation. The experimental results show that the complex can bind to FS–DNA and the major binding mode is groove binding. Meanwhile, the interaction of Nd(III) complex with protein, bovine serum albumin (BSA), has also been studied by using absorption and emission spectroscopic tools. The experimental results show that the complex exhibits good binding propensity to BSA. The positive ΔH° and ?S° values indicate that the hydrophobic interaction is main force in the binding of the Nd(III) complex to BSA, and the complex can quench the intrinsic fluorescence of BSA remarkably through a static quenching process. Also, DNA cleavage was investigated by agarose gel electrophoresis that according to the results cleavage of DNA increased with increasing of concentration of the complex. Antimicrobial screening test gives good results in the presence of Nd(III) complex system. 相似文献
12.
Quasi-elastic light scattering as measured by intensity fluctuation (self-beat) spectroscopy in the time domain can be profitably used to follow both the translational diffusion D and the dominant internal flexing mode τint of DNA and its complexes with various histones in aqueous salt solutions. Without histones, DNA is found to have D = 1.6 × 10?8 cm2/sec and τint ? 5 × 10?4 sec in 0.8 M NaCl, 2 M urea at 20°C. Total histone as well as fraction F2A induce supercoiling (D = 2.6 × 10?8 cm2/sec, τint ? 2.8 × 10?4 sec) whereas fraction F1 induces uncoiling (D = 1.0 × 10?8 cm2/sec, τint ? 9.4 × 10?4 sec). Upon increasing the salt concentration to 1.5 M the DNA–histone complex dissociates (D = 1.8 × 10?8 cm2/sec). Upon decreasing the salt concentration to far below 0.8 M, the DNA–histone complex eventually precipitates as a chromatin gel. 相似文献
13.
Methods including spectroscopy, electronic chemistry and thermodynamics were used to study the inclusion effect between γ-cyclodextrin (CD) and vitamin K3(K3), as well as the interaction mode between herring-sperm DNA (hsDNA) and γ-CD-K3 inclusion complex. The results from ultraviolet spectroscopic method indicated that VK3 and γ-CD formed 1:1 inclusion complex, with the inclusion constant Kf = 1.02 × 104 L/mol, which is based on Benesi–Hildebrand's viewpoint. The outcomes from the probe method and Scatchard methods suggested that the interaction mode between γ-CD-K3 and DNA was a mixture mode, which included intercalation and electrostatic binding effects. The binding constants were K θ25°C = 2.16 × 104 L/mol, and Kθ37°C = 1.06 × 104 L/mol. The thermodynamic functions of the interaction between γ-CD-K3 and DNA were ΔrHmθ = ?2.74 × 104 J/mol, ΔrSmθ = 174.74 J·mol?1K?1, therefore, both ΔrHmθ (enthalpy) and ΔrSmθ (entropy) worked as driven forces in this action. 相似文献
14.
The binding of neomycin sulfate (NS)/paromomycin sulfate (PS) with DNA was investigated by fluorescence quenching using acridine orange (AO) as a fluorescence probe. Fluorescence lifetime, FT-IR, circular dichroism (CD), relative viscosity, ionic strength, DNA melting temperature, and molecular docking were performed to explore the binding mechanism. The binding constant of NS/PS and DNA was 6.70 × 103/1.44 × 103 L mol?1 at 291 K. The values of ΔHθ, ΔSθ, and ΔGθ suggested that van der Waals force or hydrogen bond might be the main binding force between NS/PS and DNA. The results of Stern–Volmer plots and fluorescence lifetime measurements all revealed that NS/PS quenching the fluorescence of DNA–AO was static in nature. FT-IR indicated that the interaction between DNA and NS/PS did occur. The relative viscosity and melting temperature of DNA were almost unchanged when NS/PS was introduced to the solution. The fluorescence intensity of NS/PS–DNA–AO was decreased with the increase in the ionic strength. For CD spectra of DNA, the intensity of positive band at nearly 275 nm was decreased and that of negative band at nearly 245 nm was increased with the increase in the concentration of NS/PS. The binding constant of NS/PS with double-stranded DNA (dsDNA) was larger than that of NS/PS with single-stranded DNA (ssDNA). From these studies, the binding mode of NS/PS with DNA was evaluated to be groove binding. The results of molecular docking further indicated that NS/PS could enter into the minor groove in the A–T rich region of DNA. 相似文献
15.
Weihua Zhao Mei Xiong Mingbin Liu Xiao Xian Baoping Lin 《Nucleosides, nucleotides & nucleic acids》2020,39(7):964-978
AbstractThe interaction between Tb(IV)-NR complex and herring sperm DNA in buffer solution of Tris-HCl was investigated with the use of acridine orange(AO) as a spectral probe. The binding modes and other information were provided by the UV–spectrophotometry and fluorescence spectroscopy. The thermodynamic functions expressed that the binding constants of Tb(IV)-NR complex with DNA was Kθ298.15K = 4.03?×?105?L·mol?1, Kθ310.15K =1.30?×?107?L·mol?1, and the ΔrGθ m 298.15?K=?3.20?×?104 J·mol?1. The scatchard equation suggested that the interaction mode between Tb(IV)-NR complex and herring sperm DNA is electrostatic and weak intercalation bindings. FTIR spectroscopy results also indicate that there is a specific interaction between the Tb(IV)-NR complex and the A and G bases of DNA. 相似文献
16.
Bryan B. Sauer Russell A. Flint J.B. Justice C.G. Trowbridge 《Archives of biochemistry and biophysics》1984,234(2):580-584
A liquid membrane electrode selective for ethidium ion was used to measure free ethidium in mixtures with calf thymus DNA. Electrode response was unaffected by variation in ionic strength from 1 mm to 0.5 m, and was not degraded over the temperature range studied. DNA-ethidium binding isotherms obtained with the electrode at 17.4, 25.4, 30.1, and 40.6 °C were fitted to a single class of excluded sites model for gn ranging from 0.01 to 0.16. van't Hoff analysis of these data yielded ΔH = ?8300 cal/mol ethidium bound (in 0.5 m KCl, 10 mm Tris buffer, pH 10, 1 mm EDTA). Direct calorimetric measurements of the heat of complex formation led to a value of ?7600 cal/mol at 25 °C in the same medium; the two results were not significantly different at the 95% confidence level. The agreement supports the validity of the ethidium selective electrode, and illustrates its utility in the study of ligand binding to nucleic acids and related materials. 相似文献
17.
Yang Liu Ping Mei Ye-Zhong Zhang Xiao-Hong Sun Yi Liu 《Biological trace element research》2010,138(1-3):125-138
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. 相似文献
18.
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. 相似文献
19.
Amanda Fernandes de Medeiros Izael de Sousa Costa Fabiana Maria Coimbra de Carvalho Sumika Kiyota Beatriz Blenda Pinheiro de Souza Daniel Nogoceke Sifuentes 《Journal of enzyme inhibition and medicinal chemistry》2018,33(1):334-348
A trypsin inhibitor isolated from tamarind seed (TTI) has satietogenic effects in animals, increasing the cholecystokinin (CCK) in eutrophy and reducing leptin in obesity. We purified TTI (pTTI), characterised, and observed its effect upon CCK and leptin in obese Wistar rats. By HPLC, and after amplification of resolution, two protein fractions were observed: Fr1 and Fr2, with average mass of [M?+?14H]+?=?19,594,690?Da and [M?+?13H]+?=?19,578,266?Da, respectively. The protein fractions showed 54 and 53 amino acid residues with the same sequence. pTTI presented resistance to temperature and pH variations; IC50 was 2.7?×?10?10?mol.L?1 and Ki was 2.9?×?10?11?mol.L?1. The 2-DE revealed spots with isoelectric points between pH 5 and 6, and one near pH 8. pTTI action on leptin decrease was confirmed. We conclude that pTTI is a Kunitz trypsin inhibitor with possible biotechnological health-related application. 相似文献
20.
G. Mahalakshmi K. N. Vennila B. Selvakumar P. Lakshmana Rao Ruchi Malwade Sunny Deval 《Journal of biomolecular structure & dynamics》2020,38(12):3443-3451
AbstractTwo new 10-methoxydibenzo[b,h][1,6]naphthyridine-2-carboxamide derivatives (R1 and R2) have been synthesized and characterized using different spectral techniques. The binding of these probes with DNA was investigated using spectral (Electronic, fluorescence, 1H NMR and circular dichroism) and molecular docking studies. These probes exhibited a strong fluorescence around 440?nm upon excitation around 380?nm. Electronic and competitive fluorescence titration studies, in HEPES [(4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid)] buffer/dimethyl sulfoxide (pH 7.4) medium, suggest that these probes bind strongly to DNA, which is substantiated by 1H NMR study. The binding constants are calculated to be 5.3?×?107 and 6.8?×?106 M?1 for R1 and R2, respectively. From the results of spectral studies, it is proposed that the mechanism of binding of these probes with DNA is through minor groove binding mode, which is further confirmed by circular dichroism and molecular docking studies. Initial cell viability screening using MTT (3-[4,5-methylthiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) assay shows that normal Vero cells are viable towards these probes at nano molar concentration, which is the concentration range employed in the present study for DNA staining (IC50 in the order of 0.023?mM). The enhancement in fluorescence intensity of these probes upon binding with DNA enables the staining of DNA in agarose gel in gel electrophoresis experiment. The sensitivity of these probes is comparable with that of ethidium bromide and DNA amounts as low as 4 nano gram are detectable.Communicated by Ramaswamy H. Sarma 相似文献