Determination of the cysteine residues in the surface-confined biomolecules by using electrochemical desorption and fluorescence detection / 药学学报

To develop a method for the detection of surface-confined peptides containing cysteine residues or oligodeoxynucleotides (ODNs) whose 3' ends modified with thiol groups, and a thiol-specific fluorescent cross-linker, N-(9-acridinyl) maleimide (NAM) was used. The peptides studied herein include both the oxidized and reduced forms of glutathione, and a hexapeptide (FT). Peptides are first attached onto the activated 11-mercaptoundecanoic acid (MUA)-terminated alkanethiol self-assembled monolayers (SAMs) and then derivatized with NAM. The cysteine residues was determined by using electrochemical desorption and fluorescence detection. GSH concentration as low as 40 pmol x L(-1) can be measured. The fluorescence intensity in the case of FT is about 3 times as high as that for GSH, which is consistent with the molar ratio of cysteine residues in these two molecules. The analytical performance of gene analysis was also evaluated through the analyses of a complementary target and targets with varying numbers of mismatching bases. The method described here is simple, sensitive, reproducible, and does not require sophisticated analytical instrumentation and separation procedures.

Polarographic behavior and determination of glimepiride / 药学学报

<p><b>AIM</b>To establish a polarographic method of parallel catalytic hydrogen wave for determination of glimepiride.</p><p><b>METHODS</b>The catalytic wave of glimepiride in the presence of K2S2O8 was used to improve the analytical sensitivity. The rapid determination of glimepiride was done by linear single sweep polarography.</p><p><b>RESULTS</b>The catalytic hydrogen wave of glimepiride was measured at ca. -1.36 (vs SCE) in 0.09 mol x L(-1) Na2B4O7-KH2PO4 (pH 6.24 +/- 0.1) supporting electrolyte. When 1.0 x 10(-2) mol x L(-1) K2S2O8 was present, the current increased by 25 times, and the peak potentioal was unchanged, producing a more sensitive parallel catalytic hydrogen wave. The peak current of the parallel catalytic hydrogen wave was rectilinear to the glimepiride concentration in the range 1.0 x 10(-7) - 4.2 x 10(-5) mol x L(-1) (r = 0.9990, n = 9). The detection limit was 5.0 x 10(-8) mol x L(-1).</p><p><b>CONCLUSION</b>The proposed method could be applied to the determination of glimepiride in pharmaceuticals without preliminary separation.</p>

Polarographic catalytic wave of clarithromycin and its applications / 药学学报

<p><b>AIM</b>To develop a new method for the determination of clarithromycin.</p><p><b>METHODS</b>The catalytic wave of clarithromycin in the presence of K2S2O8 was used for improving the analytical sensitivity. The rapid determination of clarithromycin has been carried out by linear single sweep polarography.</p><p><b>RESULTS</b>The reduction wave of clarithromycin appeared at ca. -0.79 V (vs SCE) in 0.24 mol x L(-1) KH2PO4-Na2HPO4 (pH 6.81) supporting electrolyte, which was ascribed to the reduction of carbonyl group on C-9 position. In the presence of 0.01 mol x L(-1) K2S2O8, the reduction wave was catalyzed to produce a parallel catalytic wave. The peak current of the catalytic wave was ca. Twenty times higher than that of the corresponding reduction wave. Based on the catalytic wave, a new method for the determination of clarithromycin has been proposed. The peak current of the catalytic wave was rectilinear to clarithromycin concentration in the range of 4.0 x 10(-7)-5.0 x 10(-5) mol x L(-1). The detection limit was 2.0 x 10(-7) mol x L(-1).</p><p><b>CONCLUSION</b>The proposed method could be used for the direct determination of clarithromycin in pharmaceuticals and urine without preliminary separation.</p>