Application of aluminium(III) complex with salicylidene-o-aminophenol to the fluorometric determination of nucleic acids

Study on naringenin-CTMAB-DNA system by resonance light scattering technique and its analytical application

A new high-sensitivity determination method of deoxyribonucleic acid (DNA) with detection limit at nanogram levels was proposed. Based on the measurement of resonance light scattering (RLS), it was found DNA could combine with naringenin and cetyltrimethylammonium bromide (CTMAB) in basic Tris-HCl buffer and produce enhanced RLS signal. The optimum conditions for this system were studied in detail. The enhanced intensity of RLS of naringenin-CTMAB at 353 nm was directly proportional to the concentration of DNA in the range of 0.017-1.7 μg mL(-1). The detection limit was 5.06 ng mL(-1). Using the proposed method, the synthetic samples were analyzed with satisfactory results, the recovery was 99.3-105.0% and RSD was 0.7-3.7%.

Fluorescence determination of DNA using the gatifloxacin-europium(III) complex

A method for the determination of DNA based on the fluorescence intensity of the gatifloxacin-europium(III) (GFLX-Eu(3+)) complex that could be enhanced by DNA was developed. The GFLX-Eu(3+) complex showed an up to 6-fold enhancement of luminescence intensity after adding DNA. Under the optimized experimental conditions, the system exhibited a linear relationship between the enhanced fluorescence intensity and the concentration of calf thymus DNA (ctDNA) over the range from 1.0 × 10(-8) to 1.5 × 10(-6) g mL(-1), with a correlation coefficient (R) of 0.997, and the detection limit (3σ) of the method was determined as 6.0 × 10(-9) g mL(-1). The mechanism of the fluorescence enhancement effect was also discussed.

Spectroscopic studies on the interaction of pazufloxacin with calf thymus DNA

Fluorescence spectra, absorption spectra, DNA viscosity titrations, competition experiment, and iodide quenching experiment were used to study the interaction of DNA with pazufloxacin. DNA quenches the fluorescence of pazufloxacin significantly. No red shift and isobestic points are observed in UV titration experiment. DNA viscosity and iodide quenching results suggest that pazufloxacin does not intercalate into DNA. SsDNA has a stronger quenching effect on pazufloxacin than dsDNA has. Pazufloxacin interacts with DNA in a different mode from ethidium bromide, which is a typical intercalator of DNA. All these results indicate that pazufloxacin interacts with calf thymus DNA in the mode of groove binding. The quenching constant and thermodynamic constants have also been determined.

Fluorescence enhancement effect for the determination of DNA with calcein-cetyl trimethyl ammonium bromide system

A new spectrofluorimetric method was developed for the determination of trace amounts of DNA using the calcein as a fluorescent probe. In the presence of appropriate amounts of the cationic surfactant cetyl trimethyl ammonium bromide (CTAB), the anionic dye calcein dimerizes. The weak fluorescence intensity of the dimer was enhanced by adding DNA at pH 6-7. The interaction between calcein-CTAB and DNA was studied on the basis of this behavior and a new method was developed for determining DNA. Under the optimal conditions, the enhanced fluorescence intensity was in proportion to the concentration of DNA in the range of 4.0x10(-6) to 8.0x10(-5) g L(-1) for fsDNA and thermally denatured ctDNA (4.5x10(-6) to 9.0x10(-5) g L(-1)). The detection limits (S/N=3) were 2.0x10(-6) and 2.2x10(-6) g L(-1), respectively. This method was used for determining the concentration of DNA in synthetic samples with satisfactory results.

1-[4-(Diamino-methyl-eneamino-sulfon-yl)phenyl-iminiometh-yl]-2-naphtholate N,N-dimethyl-formamide disolvate

The asymmetric unit the title compound, C₁₈H₁₆N₄O₃S·2C₃H₇NO, contains a mol­ecule in a zwitterionic form with a deprotonated hydroxyl group and an iminium group, and two dimethyl­formamide solvent mol­ecules. The dihedral angles of the guanidine group and the naphthyl ring system with respect to the central benzene ring are 76.04 (7) and 3.45 (9)°, respectively. The conformation of the mol­ecule may be influenced, in part, by two intra­molecular hydrogen bonds, while in the crystal structure, inter­molecular hydrogen bonds form one-dimensional chains along [010].

Synchronous fluorescence determination of DNA based on the interaction between methylene blue and DNA

The fluorescence intensity of methylene blue (MB) quenched by DNA in the pH range of 6.5-8.0 was studied with synchronous fluorescence technology. A novel method for detecting single-stranded and double-stranded DNA was developed. The decreased fluorescence intensity at 664 nm is in proportion to the concentration of DNA in the range of 0.28-11.0 micromol L(-1) for ctDNA, 0.14-8.25 micromol L(-1) for thermally denatured ctDNA and 0.28-8.25 micromol L(-1) for hsDNA. The detection limits (S/N=3) are 0.11, 0.04 and 0.04 micromol L(-1), respectively. The method is rapid, selective, and the reagents are lower toxic. It has been used for the determination of DNA in synthetic samples with good satisfaction. In addition, the interaction modes between MB and ctDNA and the mechanism of the fluorescence quenching were also discussed in detail. The experimental results from absorption spectra and fluorescence polarization indicate that the possible interaction modes between MB and DNA are the electrostatic binding and the intercalation binding.

Fluorimetric determinations of nucleic acids using iron, osmium and samarium complexes of 4,7-diphenyl-1,10-phenanthroline

New sensitive, reliable and reproducible fluorimetric methods for determining microgram amounts of nucleic acids based on their reactions with Fe(II), Os(III) or Sm(III) complexes of 4,7-diphenyl-1,10-phenanthroline are proposed. Two complementary single stranded synthetic DNA sequences based on calf thymus as well as their hybridized double stranded were used. Nucleic acids were found to react instantaneously at room temperature in Tris-Cl buffer pH 7, with the investigated complexes resulting in decreasing their fluorescence emission. Two fluorescence peaks around 388 and 567 nm were obtained for the three complexes using excitation lambda(max) of 280 nm and were used for this investigation. Linear calibration graphs in the range 1-6 microg/ml were obtained. Detection limits of 0.35-0.98 microg/ml were obtained. Using the calibration graphs for the synthetic dsDNA, relative standard deviations of 2.0-5.0% were obtained for analyzing DNA in the extraction products from calf thymus and human blood. Corresponding Recovery% of 80-114 were obtained. Student's t-values at 95% confidence level showed insignificant difference between the real and measured values. Results obtained by these methods were compared with the ethidium bromide method using the F-test and satisfactory results were obtained. The association constants and number of binding sites of synthetic ssDNA and dsDNA with the three complexes were estimated using Rosenthanl graphic method. The interaction mechanism was discussed and an intercalation mechanism was suggested for the binding reaction between nucleic acids and the three complexes.

High sensitive fluorophotometric determination of nucleic acids with Pyronine G sensitized by N,N-dimethylformamide

In Tris-HCl buffer (pH 8.0), the fluorescence of Pyronine G emitted at 552 nm was quenched by nucleic acids when excited at 525 nm. Adding N, N-dimethylformamide (DMF) as a sensitive media can enhance the sensitivity greatly. Based on the fluorescence reactions sensitive fluorimetric methods for nucleic acids at nanogram levels were proposed. Under the optimum conditions, the calibration curves were linear in the range of 0.0032 - 2.5 microg mL(-1) for ct DNA and 0.0024 - 2.5 microg mL(-1) for hs DNA. The limits of determination were 3.2 ng mL(-1) and 2.4 ng mL(-1) respectively. This method has good selectivity and high sensitivity. It has been applied to the determination of DNA in the synthetic samples and real samples with satisfactory results.

Spectrofluorimetric determination of trace heparin using lomefloxacin-terbium probe

A new spectrofluorimetric method was developed for determination of trace amount of heparin (Hep). Using lomefloxacin (LOM)-terbium ion (Tb3+) as a fluorescent probe, in the buffer solution of pH 8.70, Hep can remarkably enhance the fluorescence intensity of the LOM-Tb3+ complex at lambda = 545 nm and the enhanced fluorescence intensity of Tb3+ ion is in proportion to the concentration of Hep. Optimum conditions for the determination of Hep were also investigated. The linear range for the determination of Hep was 0.6-2.0 microg/ml and the detection limit was 45.22 ng/ml. This method is simple, practical and relatively free of interference from coexisting substances and can be successfully applied to assess Hep in biological samples. By the Rosenthanl graphic method, the association constant of Hep with the probe is 4.56 x 10(4) l/mol and binding numbers is 18.2. Moreover, the enhancement mechanism of the fluorescence intensity in the LOM-Tb3+ system and the LOM-Tb3+-Hep system have also been discussed.

Determination of heparin using ciprofloxacin-Tb3+ as a fluorescence probe

A new spectrofluorometric method was developed for the determination of trace amounts of heparin (Hep). Using ciprofloxacin (CIP)-terbium (Tb3+) as a fluorescent probe, in a buffer solution of pH 7.20, Hep can remarkably enhance the fluorescence intensity of the CIP-Tb3+ complex at lambda = 545 nm; also, the enhanced fluorescence intensity the Tb3+ ion is proportional to the concentration of Hep. The optimum conditions for the determination of Hep were also investigated. The dynamic range for the determination of Hep is 0.1 - 1.2 microg ml(-1) with a detection limit of 6.89 ng ml(-1). This method is simple, practical and relatively free of interference from coexisting substances, and can be successfully applied to assess Hep in biological samples. By the Rosenthanl graphic method, the association constant and binding numbers of heparin with the probe are 2.44 x 10(5) l mol(-1) and 19.7. Moreover, the enhancement mechanisms of the fluorescence intensity in the CIP-Tb3+ system and the CIP-Tb3+-Hep system have also been considered.

Nucleic Acids Analysis with Nano-Ag-Tb(III) by a Resonance Light Scattering Technique

The nano-Ag-terbium(III)-mucleic acids system was observed by a resonance light scattering (RLS) technique for the first time, and the quantitative analysis of nucleic acids at nanogram levels was established. Studies showed that the RLS intensity of the nano-Ag-terbium(III) system can be obviously enhanced by nucleic acid, which was characterized by the RLS spectrum and the UV-Vis spectrum. In this system, the nanoparticles were only of a definite size and in a limited particle concentration region. Further research indicated that under the optimum conditions, the enhanced intensity of RLS is in proportion to the concentration of nucleic acids in the ranges of 7.0 x 10(-9) g ml(-1) to 8.0 x 10(-6) g ml(-1) for calf thymus DNA (ctDNA), 2.0 x 10(-8) g ml(-1) to 1.0 x 10(-6) g ml(-1) for fish sperm DNA (fsDNA) and 1.0 x 10(-9) g ml(-1) to 1.0 x 10(-7) g ml(-1) for yeast RNA (yRNA). The detection limits were 1.4 ng ml(-1) for ctDNA, 1.2 ng ml(-1) for fsDNA and 0.85 ng ml(-1) for yRNA, respectively. Synthetic and real samples were determined satisfactorily.

Sensitive determination of nucleic acids using organic nanoparticle fluorescence probes

This paper describes the preparation of organic nanoparticles by reprecipitation method under sonication and vigorous stirring. Transmission electron microscopy (TEM) was used to characterize the size and size distribution of the luminescent nanoparticles. Their average diameter was about 25 nm with a size variation of +/-18%. The fluorescence decay lifetime of the nanoparticles also was determined on a self-equipped fluorospectrometer with laser light source. The lifetime (approximately 0.09 micros) of nanoparticles is about three times long as that of the monomer. The nanoparticles were in abundant of hydrophilic groups, which increased their miscibility in aqueous solution. These organic nanoparticles have high photochemical stability, excellent resistance to chemical degradation and photodegradation, and a good fluorescence quantum yield (25%). The fluorescence can be efficiently quenched by nucleic acids. Based on the fluorescence quenching of nanoparticles, a fluorescence quenching method was developed for determination of microamounts of nucleic acids by using the nanoparticles as a new fluorescent probe. Under optimal conditions, maximum fluorescence quenching is produced, with maximum excitation and emission wavelengths of 345 and 402 nm, respectively. Under optimal conditions, the calibration graphs are linear over the range 0.4-19.0 microgml(-1) for calf thymus DNA (ct-DNA) and 0.3-19.0 microgml(-1) for fish sperm DNA (fs-DNA). The corresponding detection limits are 0.25 microgml(-1) for ct-DNA and 0.17 microgml(-1) for fs-DNA. The relative standard deviation of six replicate measurements is 1.3-2.1%. The method is simple, rapid and sensitive with wide linear range. The recovery and relative standard deviation are very satisfactory.

Spectrofluorimetric determination of heparin using a tetracycline–europium probe

A new spectrofluorimetric method was developed for the determination of trace amounts of heparin (Hep). Using tetracycline (TC)-europium ion (Eu3+) as a fluorescent probe, in the buffer solution at pH 8.8, Hep can remarkably enhance the fluorescence intensity of the TC-Eu3+ complex at lambda=612 nm and the enhanced fluorescence intensity of Eu3+ is in proportion to the concentration of Hep. Optimal conditions for the determination of Hep were also investigated. The linear range and detection limit for the determination of Hep were 0.02 to 1.6 microg/ml and 4.45 ng/ml, respectively. This method is simple, practical, and relatively free of interference from coexisting substances, and it can be applied successfully to assess Hep in biological samples. By the Rosenthal graphic method, the association constant and binding numbers of Hep with the probe were 4.46 x 10(4) L/mol and 16.2, respectively. Moreover, the enhancement mechanism of the fluorescence intensity in the TC-Eu3+ system, the TC-Eu(3+)-Hep system, and the TC-Eu(3+)-Hep-CTMAB system is also discussed.

Spectroscopic studies of fluorescent dye N, N'- bis(2-hydroxy-5-methyl-benzylidene)-1,2-ethanediamine and its DNA complex in solution

Absorption and fluorescence emission properties of an N-salicylideneamine fluorescent dye molecule N, N'-bis(2-hydroxy-5-methylbenzylidene)-1,2-ethanediamine (1) have been studied in three typical solvents--2-methylbutane, ethanol, dimethyl sulphoxide (DMSO), and its DNA complex in methanol/H2O mixed solvent. The normal absorption band of 1 is observed in both aprotic and protic solvents and has been assigned to the l --> a(pi) transition in the enol form of 1. The long-wavelength absorption band of 1, which is caused by the formation of a cis-keto species in the ground state, is absent in aprotic solvents, but is observable in protic ones. Normal fluorescence emission from the excited enol state of 1 is obtained only when the normal absorption band is excited, while the excited-state intramolecular proton transfer (ESIPT) emissions from both cis- and trans-keto species are recorded in all cases, being acceptable for the variation of the relative emission intensities. A preliminary spectroscopic study of the 1-DNA complex indicates an intercalation-binding mode, the convincing supporting evidence being the enhanced ESIPT fluorescence intensity of 1 when complexed with DNA. Finally, a universal energy-state diagram is given to interpret the experimental results.