Determination of DNA using sodium 9,10-anthraquinone-2-sulfonate as an in situ photochemical fluorescence probe

In vitro studies on the behavior of salmeterol xinafoate and its interaction with calf thymus DNA by multi-spectroscopic techniques

The salmeterol xinafoate (SX) binding to calf thymus DNA in vitro was explored by fluorescence, resonance light scattering (RLS), UV-vis absorption, as well as viscometry, ionic strength effect and DNA melting techniques. It was found that SX could bind to DNA weakly, and the binding constants (Ka) were determined as 8.52×10(3), 8.31×10(3) and 6.14×10(3) L mol(-1) at 18, 28 and 38°C respectively. When bound to DNA, SX showed fluorescence quenching in the fluorescence spectra and hyperchromic effect in the absorption spectra. Stern-Volmer plots revealed that the quenching of fluorescence of SX by DNA was a static quenching. Furthermore, the relative viscosity and melting temperature of DNA solution were hardly influenced by SX, while the fluorescence intensity of SX-DNA was observed to decrease with the increasing ionic strength of system. Also, the binding constant between SX and double stranded DNA (dsDNA) was much weaker than that between SX and single stranded DNA (ssDNA). All these results suggested that the binding mode of SX to DNA should be groove binding. The obtained thermodynamic parameters indicated that electrostatic force might play a predominant role in SX binding to DNA. The quantum yield (φ) of SX was measured as 0.13 using comparative method. Based on the Förster resonance energy transfer theory (FRET), the binding distance (r0) between the acceptor and donor was calculated as 4.10 nm.

The interaction of taurine-salicylaldehyde Schiff base copper(II) complex with DNA and the determination of DNA using the complex as a fluorescence probe

The interaction of taurine-salicylaldehyde Schiff base copper(II) (Cu(TSSB)2(2+)) complex with DNA was explored by using UV-vis, fluorescence spectrophotometry, and voltammetry. In pH 7.4 Tris-HCl buffer solution, the binding constant of the Cu(TSSB)2(2+) complex interaction with DNA was 3.49 x 10(4) L mol(-1). Moreover, due to the fluorescence enhancing of Cu(TSSB)2(2+) complex in the presence of DNA, a method for determination of DNA with Cu(TSSB)2(2+) complex as a fluorescence probe was developed. The fluorescence spectra indicated that the maximum excitation and emission wavelength were 389 nm and 512 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range of 0.03-9.03 microg mL(-1) for calf thymus DNA (CT-DNA), 0.10-36 microg mL(-1) for yeast DNA and 0.01-10.01 microg mL(-1) for salmon DNA (SM-DNA), respectively. The corresponding detection limits are 7 ng mL(-1) for CT-DNA, 3 ng mL(-1) for yeast DNA and 3 ng mL(-1) for SM-DNA. Using this method, DNA in synthetic samples was determined with satisfactory results.

Kinetics of Photochemical Reactions under Restricted Geometry Conditions

Kinetics of ground state reactions under restricted geometry conditions have been rationalized generally taking as a basis the Pseudophase Model, whose basic hypothesis is: The distribution of the reactants between the pseudophases is at equilibrium, that is, the rate of the reaction is slow in relation to the rates of entry and exit of the reactant to and from the receptor. However, photochemical reactions are generally very rapid, so the following question emerges: is the Pseudophase Model still applicable to photochemical reactions? To answer this question has been the primary objective of this work in which photochemical reactions in micelles, polymers and cyclodextrins have been reviewed. The lifetime of the fluorophore and the distributions of the quencher and the probe are crucial properties; they must be taken into account to obtain a proper description of the behaviour of a given system. The models of Infelta, Almgren and Quina visualise different scenarios with varied combinations of these properties. It is shown that, in some cases, the Pseudophase Model holds at least formally.

Study of interactions of anthraquinones with DNA using ethidium bromide as a fluorescence probe

The interactions of fish sperm deoxyribonucleic acid (DNA) with anthraquinones, such as chrysophanol, physcion and 1,8-dihydroxy anthraquinone, were investigated by using ethidium bromide (EB) as fluorescence probe. The binding constants of anthraquinones and DNA were obtained by the fluorescence quenching technique. Further, the binding mechanisms on the reaction of the three anthraquinones with DNA and effect of ionic strength on the fluorescence property of the system have also been investigated. The results of the assay indicate that the binding modes of chrysophanol, physcion and 1,8-dihydroxy anthraquinone with DNA were evaluated to be groove binding. And the binding constants of chrysophanol, physcion and 1,8-dihydroxy anthraquinone with DNA-EB complex were 1.64x10(4), 3.04x10(4) and 2.88x10(5) l mol(-1), respectively.

Studies of interaction of emodin and DNA in the presence of ethidium bromide by spectroscopic method

Emodin interacting with deoxyribonucleic acid (DNA) has been studied by different spectroscopic techniques, such as fluorescence, ultraviolet and visible (UV-vis), and fourier transform infared (FT-IR) spectroscopies, using ethidium bromide (EB) as a fluorescence probe of DNA. The decrease in the fluorescence of DNA-EB system on addition of emodin shows that the fluorescence quenching of DNA-EB complex by emodin occurs. The binding constants of emodin with DNA in the presence of EB are 6.02x10(4), 9.20x10(4) and 1.17x10(5)Lmol(-1) at 20, 35 and 50 degrees C, respectively. FT-IR spectrum further suggests that both the phosphate groups and the bases of DNA react with emodin. The reaction of DNA with emodin in the presence of EB is affected by ionic strength and temperature. The values of melting temperature (T(m)) of DNA-EB complex and emodin-DNA-EB complexes were determined, respectively. From the experiment evidences, the major binding mode of emodin with DNA should be the groove binding.

A novel spectrofluorimetric method for the determination of DNA

A new simple, selective and sensitive fluorescence quenching method was developed to determine nucleic acids (DNA) with the 9-anthracenecarboxylic acid (ACA)-cetyl trimethyl-ammonium bromide (CTAB) system. The fluorescence intensity of ACA was decreased by the addition (CTAB). However, the fluorescence intensity of the system increased dramatically when DNA was added to the solution. The fluorescence enhancement is probably based on the DNA interaction with CTAB. Under the optimum conditions, the changes of fluorescence intensity in the absence and presence of nucleic acids was proportional to the concentration of nucleic acids over the range 0.08-1.0 microg mL(-1) for CT (calf thymus) DNA or FS (fish sperm) DNA. Its detection limits are 0.02 microg mL(-1) for CT DNA and 0.019 microg mL(-1) for FS DNA. Based on this approach, a new quantitative method for DNA assay is presented in this paper.

Studies on interaction of an intramolecular charge transfer fluorescence probe: 4′-Dimethylamino-2,5-dihydroxychalcone with DNA

The interaction of a new intramolecular charge transfer probe, namely 4'-dimethylamino-2,5-dihydroxychalcone (DMADHC), with calf thymus DNA has been studied. Compared to the spectral characteristics of the free form in aqueous solution, the fluorescence of DMADHC enhanced dramatically accompanying a blueshift of the emission maxima in the presence of DNA. The absorption and fluorescence spectra, salt concentration effect, KI quenching, fluorescence polarization, and DNA denaturation experiments were given. These results give evidence that the DMADHC molecule is inserted into the base-stacking domain of the DNA double helix. The intrinsic binding constant and the binding site number were estimated. The analytical characteristics were also given.

Study on the interaction between nucleic acids and acetamiprid

The interaction between deoxyribonucleic acid (DNA) and acetamiprid was studied. It was found that the fluorescence of acetamiprid could be enhanced in the presence of DNA in sulfuric acid solution. The excitation and emission wavelength of acetamiprid was 291 nm and 587 nm, respectively. Under optimal conditions, the calibration graph is over the range of 0.1-10 micromL(-1). The calibration limit is 0.06 microg mL(-1) (S/N = 3). The determination results of DNA in yeast cell and golden staphylococcus samples by this method were satisfactory. The mechanism of the reaction is discussed.