Changxia Sun

Fluorimetric determination of ascorbic acid with o-phenylenediamine

A simple and sensitive fluorimetric method for the determination of ascorbic acid (AA) is described. The method is based on the condensation reaction between AA and o-phenylenediamine (OPDA) in the absence of the oxidant. The fluorescence intensity is measured at excitation and emission wavelengths of 360 and 430 nm, respectively. Under optimum condition, a linear relationship is obtained between the fluorescence intensity and the concentration of AA in the range of 0.05-40 mug ml(-1). The detection limit is 0.006 mug ml(-1), which is obviously lower than that of other fluorimetric methods reported.

Study of the interaction of nucleic acids with acridine orange-CTMAB and determination of nucleic acids at nanogram levels based on the enhancement of resonance light scattering

The resonance light scattering (RLS) of acridine orange (AO) are greatly enhanced by both nucleic acid and cetyltrimethyl ammonium bromide (CTMAB). Based on this, nucleic acids can be sensitively determined. The interaction of AO with nucleic acid in the presence of CTMAB is studied by using RLS, absorption spectroscopy, zeta potential assay, transmission electron microscope (TEM) image and molecular molding. On its surface, nucleic acid acts as the template to promote the assembly of both AO and CTMAB in close proximity, which formatted large AO-nucleic acid-CTMAB association. Therefore, RLS intensity of cationic dye is greatly enhanced.

Study on the resonance light scattering spectrum of berberine–cetyltrimethylammonium bromide system and the determination of nucleic acids at nanogram levels

The interaction of berberine with nucleic acid in the presence of cetyltrimethylammonium bromide (CTMAB) in aqueous solution has been studied by spectrophotometry and resonance light scattering (RLS) spectroscopy. At pH 7.30, the RLS signals of berberine were greatly enhanced by nucleic acid in the region of 300-600 nm characterized by four peaks at 324.0, 386.5, 416.5 and 465.0 nm. The binding properties were examined by using a Scatchard plot based on the measurement of enhanced RLS data at 416.5 nm. Under optimum conditions, the increase of RLS intensity of this system at 416.5 nm is proportional to the concentration of nucleic acid. The linear range is 7.5 x 10(-9)-7.5 x 10(-5) g ml(-1) for calf thymus DNA, 7.5 x 10(-9)-2.5 x 10(-5) g ml(-1) for herring sperm DNA, and 5.0 x 10(-9)-2.5 x 10(-5) g ml(-1) for yeast RNA. The detection limits (S/N = 3) are 2.1 ng ml(-1) for calf thymus DNA, 6.5 ng ml(-1) for herring sperm DNA and 3.5 ng ml(-1) for yeast RNA, respectively. Three synthetic samples were analyzed satisfactorily.

Fluorimetric determination of nucleic acid using the enhancement of terbium/gadolinium/nucleic acid/ cetylpyridine bromide system

It is found that the fluorescence intensity of Tb-cetylpyridine bromide (CPB)-nucleic acid system can be enhanced by La(3+), Gd(3+), Lu(3+), Sc(3+) and Y(3+), of which Gd(3+) has the greatest enhancement. The experiments indicate that under the optimum condition, the fluorescence intensity of the system is in proportion to the concentration of nucleic acids in the range from 9x10(-8) to 1x10(-5) g ml(-1) for yeast RNA, from 1x10(-7) to 1x10(-5) g ml(-1) for fish sperm DNA. The detection limits are 3.2 and 4.1 ng ml(-1), respectively. This method has been used satisfactorily for the determination of both synthetic and actual samples. In comparison with most fluorescence method for the determination of nucleic acids, this method has higher sensitivity and stability.

Study on the co-luminescence effect of terbium–gadolinium–nucleic acids–cetylpyridine bromide system

Abstract In this paper, the luminescence mechanism of a new co-luminescence system (Tb–Gd–nucleic acids–cetylpyridine bromide) was studied. The experiment has shown that cetylpyridine bromide (CPB) could combine with nucleic acids through both electrostatic forces and hydrophobic forces, then Gd 3+ and Tb 3+ were bound to PO 4 3− of nucleic acid and formed Tb–nucleic acid–CPB and Gd–nucleic acid–CPB complexes, respectively. When the system was excited, the DNA–CPB absorbed light energy and then transferred it to Tb 3+ through both intramolecular energy transfer in Tb–nucleic acid–CPB complex and intermolecular energy transfer between Gd–nucleic acid–CPB and Tb–nucleic acid–CPB complexes. In addition, it was found that the gadolinium complex acted not only as the energy donor but also the energy-insulating sheath, which improved the fluorescence quantum efficiency.

Progresses of Derivatization Techniques for Analyses of Carbohydrates

Abstract Carbohydrates, one of the most important bioactive materials and information-carrying molecules, play important roles in physiological and pathological processes. Unfortunately the direct chemical analysis of carbohydrates is difficult because of their characteristics. Recently, the investigations of carbohydrates made a great development because of considerable progresses in the derivatization techniques of carbohydrates. This article summarized several derivatization techniques, including the derivatization reactions with amines and amine-like compounds, derivatizations of amino sugars, derivatizations with reducibility of carbohydrates, derivatizations by chemiluminescences and enzyme reactions, derivatization of conversion to furfurals, derivatization reactions with boronic acid derivatives. Their advantages, problems, and applications are discussed. About 95 references are cited.

Interaction of morin–cetyltrimethylammonium bromide with nucleic acids and determination of nucleic acids at nanograms per milliliter levels based on the enhancement of preresonance light scattering

A new preresonance light scattering (PRLS) assay of nucleic acids is presented. At pH 7.30, the weak PRLS of morin-cetyltrimethylammonium bromide (CTMAB) can be greatly enhanced by the addition of nucleic acids, owing to the interaction between the nucleic acid and morin-CTMAB. After the addition of morin and CTMAB to DNA, the zeta potential of DNA decreases and changes from negative to positive, which is due to the formation of an associate, the aggregation of morin on nucleic acids and the electric neutralization between DNA and the cationic surfactant CTMAB. Mechanism studies showed that the enhanced PRLS comes from the aggregation of morin in the presence of nucleic acids and CTMAB. The enhanced intensity of PRLS is in proportion to the concentration of nucleic acids in the range 7.5 x 10(-9)-1.0 x 10(-5) g ml(-1) for calf thymus DNA, 7.5 x 10(-9)-1.0 x 10(-6) g ml(-1) for salmon sperm DNA and 1.0 x 10(-8)-1.0 x 10(-6) g ml(-1) for yeast RNA. The detection limits are 3.4, 6.2 and 4.1 ng ml(-1) for calf thymus DNA, salmon sperm DNA and yeast RNA, respectively. Synthetic samples were analyzed satisfactorily.

Interaction of morin with CTMAB: aggregation and location in micellar.

The aggregation and location of morin in CTMAB micellar solution was studied by light scattering spectra, electronic absorption spectra and pulsed FT NMR techniques. The difference in the light scattering property of morin with and without CTMAB proved that a large particle of the morin-CTMAB associate formed. Morin has a self-assembly tendency, but the assembly number is not high. With the increase of morin concentration, morin changed from a monomer to dimer. The hyperchromic and bathochromic effect of morin, with the increase in pH value or

Fluorescence enhancement effect for the determination of proteins with morin–Al3+–cetyltrimethylammonium bromide

It is found that the fluorescence intensity of morin-Al(3+) complex can be greatly enhanced by proteins in the presence of cetyltrimethylammonium bromide (CTAB). It is considered that protein and CTAB provide a hydrophobic environment with low polarity and large viscosity, resulting in the fluorescence enhancement of morin-Al(3+) complex. The experiments indicate that under optimum conditions, the enhanced intensity of fluorescence is in proportion to the concentration of proteins (such as bovine serum albumin (BSA), human serum albumin (HSA) and egg albumin (EA)) in the wide range, and their detection limits (S/N=3) are 2.6 x 10(-9), 1.4 x 10(-8) and 1.6 x 10(-8) g ml(-1), respectively. This method has satisfactorily been used for the determination of protein in actual sample. In comparison with most of fluorimetric methods reported, this method is quick and simple, and has high sensitivity, wide linear range and good stability.

The fluorescence enhancement effect of Tb-Gd-adenosine triphosphate-phen system and its analytical application.

It is found that the fluorescence of Tb-adenosine triphosphate (ATP)-phenanthroline (phen) system can be enhanced by Gd(3+). The fluorescence enhancement of the Tb-Gd-ATP-phen system is considered to originate from intramolecular and intermolecular energy transfers, and the energy-insulating sheath effect of Gd-ATP-phen complex. In addition, a new energy transfer pathway in Tb-ATP-phen system is proposed. As a mediator, phen can transfer the energy absorbed by ATP to Tb(3+) through the stacking action between aromatic ring of phen and purine ring of ATP. The proposed method has been used to determine trace amount of ATP. The detection limit is 5.4 x 10(-9)mol/l, which is about 40 times lower than that of the Tb-ATP-phen system. The proposed method is one of the most sensitive fluoremetries of ATP.