Yuqin Wu

Determination of nucleic acids with tetra-(N-hexadecylpyridiniumyl) porphyrin sensitized by cetyltrimethylammonium bromide (CTMAB) using a Rayleigh light-scattering technique

Using a common spectrofluorometer to measure the intensity of Rayleigh light-scattering (RLS), a method for determination of nucleic acids has been developed. At pH 10.24 and ionic strength 0.01 mol l-1 (NaCl), the Rayleigh light-scattering of the tetra-(N-hexadecylpyridiniumyl) porphyrin (TC16PyP) is greatly enhanced by nucleic acids in the presence of cetyltrimethylammonium bromide (CTMAB), with the scattering peak located at 311.8 nm. The enhanced RLS intensity is in proportion to the concentration of calf thymus DNA (ctDNA) in the range 0.2-6.0 microg ml-1 and to that of fish sperm DNA (fsDNA) in the range 0.05-3.0microg ml-1. The limits of detection are 0.016 microg ml-1 for calf thymus DNA and 0.023 microg ml-1 for fish sperm DNA when the concentration of TPP was chosen 2.0 x 10(-6) mol l-1. Four synthetic samples were determined satisfactorily.

Near-infrared fluorimetric determination of nucleic acids by shifting the ion-association equilibrium between tetracarboxy aluminum phthalocyanine and tetra-N-hexadecylpyridiniumyl porphyrin

A new method was developed for determination of micro amounts of nucleic acids based on near-infrared (near-IR) fluorescence recovery, employing a two-reagent system which is composed of an anionic tetracarboxy aluminum phthalocyanine (AlC(4)Pc) and a cationic tetra-N-hexadecylpyridiniumyl porphyrin (TC(16)PyP). The fluorescence of the AlC(4)Pc, with the maximum emission wavelength at 701nm, could be quenched by TC(16)PyP at its proper concentration, but recovered by adding nucleic acids. Under optimal conditions, the recovered fluorescence is proportional to the concentration of nucleic acids. The calibration graphs are linear over the range of 1-200ngmL(-1) for fish sperm DNA (FS DNA) and 2-400ngmL(-1) for calf thymus DNA (CT DNA). The corresponding detection limits are 0.59ngmL(-1) for FS DNA and 0.82ngmL(-1) for CT DNA, respectively. Four synthetic and three real nucleic acid samples were determined with satisfactory results.

Near‐Infrared Fluorometric Determination of Protein by Shifting the Ion‐Association Equilibrium Between Cationic Heptamethylene Cyanine and Poly‐glutamate

Abstract A new method based on near‐infrared (near‐IR) fluorescence recovery, employing a two‐reagent system, which is composed of a cationic heptamethylene cyanine and poly‐glutamate, is presented for the determination of protein. The fluorescence of cationic heptamethylene cyanine, with the maximum excitation and emission wavelengths at 800 and 815 nm, respectively, was quenched by poly‐glutamate with a proper concentration, but recovered by adding proteins at pH 3.5. Under optimum conditions, the recovered fluorescence was in proportional to the concentration of proteins. The linear ranges of the calibration curves were 50–1000, 100–1500 and 100–1000 ng/mL with the detection limit of 37, 40, 43 ng/mL for BSA, HSA, and γ‐IgG, respectively. The relative standard deviation (n = 8) was 1.7% for 400 ng/mL bovine serum albumin (BSA). The proposed method was applied to the determination of proteins in real serum samples with satisfactory results.

Spectrophotometric Method for the Direct Determination of Anionic Surfactant Sodium Dodecyl Benzenesulfonate (SDBS) Using a Hydrophobic Near‐Infrared (NIR) Cationic Cyanine Dye Without Solvent Extraction

Abstract A new hydrophobic near‐infrared (NIR) cationic cyanine dye was synthesized and evaluated as a new reagent for the determination of anionic surfactant sodium dodecyl benzenesulfonate (SDBS). The cyanine dye with an absorption maximum at 770 nm reacted with SDBS, causing significant hypochromism. Under the optimal conditions, the decreased absorption is proportional to the concentration of SDBS over the range 2.9 × 10−7–1 × 10−5 mol/L. The detection limit was 1.9 × 10−7 mol/L. The relative standard deviation for 1.43 × 10−6 mol/L SDBS was 1.3% (n = 9). The proposed method was applied to determination of anionic surfactant in the river with 93–106% recovery levels. Preliminary research shows that the hypochromism is due to the formation of dye aggregate facilitated by SDBS.