Qiu-Ying Chen

Interaction of a novel red-region fluorescent probe, Nile Blue, with DNA and its application to nucleic acids assay

A novel fluorimetric method was developed for the rapid determination of DNA and RNA based on their quenching effect on the cationic red-region fluorescent dye Nile Blue (NB). In the investigation of the interaction of NB with DNA by steady-state polarization measurements, thermal denaturing study, determination of absorption and fluorescence characteristics, salt effect study and electrophoresis experiments, the results supported the suggestion that NB served as an intercalator to the stack base pairs of nucleic acids. Further evidence showed that the quenching could be ascribed to the static quenching mode. A binding constant of about 10(6) M-1 and a binding site size of about three base pairs were obtained by spectral methods. Under optimum conditions, the calibration curves for the determination of calf thymus DNA (CT DNA) and yeast RNA were linear over the ranges 3.0 ng mL-1-2.0 micrograms mL-1 and 27 ng mL-1-10 micrograms mL-1, respectively. The detection limits were 3.0 ng mL-1 for CT DNA and 27 ng mL-1 for RNA. The relative standard deviation (n = 6) was within 2.1% in the middle of the linear range. Interferences from some interesting co-existing substances in the determination of DNA were also examined.

Novel spectrofluorimetric method for the determination of thiamine with iron(III) tetrasulfonatophthalocyanine as a catalyst

A sensitive, selective and rapid spectrofluorimetric method is proposed for the determination of thiamine by using mimetic enzyme iron(III) tetrasulfonatophthalocyanine (FeTSPc) as a catalyst for the oxidation reaction between thiamine and hydrogen peroxide. It is based on the oxidation of thiamine in alkaline medium to give an intensively fluorescent compound, which has an excitation wavelength of 375 nm and an emission wavelength of 440 nm. The determination was found to be activated by fluorogenic substrates with a p-hydroxyphenyl structure such as L-tyrosine, tyramine and p-hydroxyphenylpropionic acid. Under optimum conditions, the responses for thiamine were linear from 1.0 × 10–8 to 1.0 × 10–4 mol L–1, with a detection limit of 4.3 × 10–9 mol L–1. The relative standard deviation was 2.2% for 2.0 × 10–7 mol L–1 thiamine (n = 6). The activation of the p-hydroxyphenyl substrates, the effects of some experimental conditions and the influence of foreign substances were investigated. The potential application of the method was tested by selectively determining thiamine in commercial vitamin B1, vitamin B complex and rice.

Brilliant cresyl blue as a new red region fluorescent probe for determination of nucleic acids

Abstract A fluorescence quenching method was developed for determination of microamounts of nucleic acids by using brilliant cresyl blue (BCB) as a new red region fluorescent probe. In aqueous hexylmethylene tetramine solution, BCB showed maximum excitation and emission wavelengths at 626 and 670 nm, respectively, and the fluorescence of BCB could be greatly quenched by DNA (or RNA). Under optimal conditions, the calibration graphs are linear over the range of 0.02–0.80 μg/ml for SM DNA and 0.25–1.5 μg/ml for yeast RNA. The corresponding detection limits are 7 ng/ml for SM DNA and 25 ng/ml for yeast RNA, respectively. SM DNA can be determinated in the presence of 40% (w/w) RNA, and the relative standard deviation of six measurements is 2.5% for 500 ng/ml SM DNA. The result of the determination of golden staphylococcus DNA by this method was satisfactory.

Study on fluorometric determination of hydrogen peroxide catalyzed by iron(III)-tetrasulfonato-phthalocyanine with thiamine hydrochloride as a substrate

ABSTRACT Iron(III)-tetrasulfonatophthalocyanine(FeTSPc) has been used as a mimetic enzyme in the determination of hydrogen peroxide with thiamine hydrochloride as a fluorogenic substrate. The determinations were carried out in both acidic and basic environments, with different limits of detection and linear ranges. In acidic condition, the linear calibration graph was obtained from 5.0x10−8 mol/L to 8.0x10−6 mol/L, with a detection limit of 2.1x10−8 mol/L H2O2 when Na2HPO4-citric buffer solution (pH 2.8) was used as the reaction medium. It was also found that using one of the three polybasic carboxylic acids such as citric acid, tartaric acid and malonic acid as the catalytic reaction medium can lead to particularly sensitive systems, permitting a detection limit as low as 3.5x10−9 mol/L H2O2; whereas in basic reaction medium (Na2CO3-NaHCO3 buffer solution, pH = 10.0), the linear range of the calibration graph was from 5.0x10−8 mol/L to 2.0x10−6 mol/L H2O2 with a detection limit of 1.4x10−8mol/L. The appl...

Determination of gaseous acidic compounds by measuring fluorescence after their reaction with tetra-substituted amino aluminum phthalocyanine

Based on the fluorescence enhancement of a red-region fluorescent dye, tetrasubstituted amino aluminum phthalocyanine (TAAlPc), in strongly acidic medium, a new method was developed for the detection of four strong acids (HCl, HBr, HNO(3) and H(2)SO(4)). Under optimal conditions the linear ranges of the calibration curves were 0.04-0.67 mol/l (HCl), 0.04-0.67 mol/l (HBr), 0.04-0.80 mol/l (HNO(3)) and 0.02-0.80 mol/l (H(2)SO(4)), respectively. The detection limits were 0.007 mol/l for HCl, 0.006 mol/l for HBr, 0.005 mol/l for HNO(3) and 0.007 mol/l H(2)SO(4.) This method has been applied to the analyses of four artificial samples with satisfactory results.

Temperature modulated solubility and activity alteration for oligo-(N-isopropylacrylamide)-iron tetrasulfonatophthalocyanine conjugates as a new mimetic peroxidase

Iron tetrasulfonatophthalocyanine (FeTSPc) was covalently bound to the terminus of a temperature sensitive oligomer, oligo-N-isopropylacrylamide (ONIPAAm), to form a new mimetic enzyme (ONIPAAm–FeTSPc) to mimic the peroxidase activity of horseradish peroxidase. This FeTSPc-based mimetic enzyme exhibits a lower critical solution temperature (LCST) of 32 °C in neutral solution. It precipitates from water above the LCST and redissolves when the solution temperature is lowered below the LCST. The peroxidase activity of this mimetic enzyme was studied based on its catalytic effect on the reaction of p-hydroxyphenylpropionic acid and H2O2. The results show that the peroxidase activity of the new mimetic enzyme is higher than that of the free FeTSPc. The possibility of its application in the analytical field was also tested by the determination of H2O2 and ONIPAAm–FeTSPc; the detection limits are 8.2 × 10−9 and 1.7 × 10−9 mol L−1, respectively.