Biomedical subjects

Xing-Fang Li

Publications and source records attributed to Xing-Fang Li.

22 records · Page 2Linked to original sources

PubMed2003

Studies of cisplatin and hemoglobin interactions using nanospray mass spectrometry and liquid chromatography with inductively-coupled plasma mass spectrometry.

Interactions of cisplatin with hemoglobin (Hb) were studied using both nanoelectrospray mass spectrometry (nanoESI-MS) and a combination of size exclusion high performance liquid chromatography with inductively coupled plasma mass spectrometry (HPLC-ICPMS). Size exclusion HPLC separation of free and protein-bound cisplatin followed by simultaneous monitoring of 195Pt and 57Fe demonstrated the presence of Hb-bound Pt complexes. Nanospray quadrupole time-of-flight mass spectrometry studies of the Hb-cisplatin complexes further demonstrated the specific binding of cisplatin to the alpha-chain, heme-alpha, beta-chain, and heme-beta units of hemoglobin. Accurate mass measurements and tandem mass spectrometry information confirmed the Hb-cisplatin complexes. The formation of Hb-cisplatin complexes was observed at the sub-microM to microM concentration levels of cisplatin, which are relevant to clinical levels. These findings and the techniques developed for cisplatin-Hb interaction studies are useful for understanding of drug-protein interactions.

Antineoplastic Agents↗

PubMed2002

Direct analysis of nine pharmaceuticals in culture media by use of cartridge separation with electrospray mass spectrometric detection.

A 2-cm cartridge has been used for separation before electrospray mass spectrometric analysis of pharmaceutical compounds in cell culture media, alleviating the need for sample extraction and desalting procedures. Nine representative pharmaceuticals listed in the biopharmaceutical classification system (BCS) were chosen as the candidate compounds and Hank's balanced salt solution with Hepes buffer (HBSS-Hepes buffer) was used as the cell-culture medium in an effort to study permeability of chemicals through cell monolayers. Effects of several conditions, e.g. pH and buffer concentration in the mobile phase, flow rate, and temperature on separation efficiency were examined. The nine pharmaceuticals were separated within 2 min by use of a 2-cm C(8) cartridge. Relative standard deviations (RSD) from repeated analysis within the same day or over five days were 0.03-0.2% for retention times and 0.6-5.3% for peak areas; antipyrine was used as internal standard. Calibration curves based on peak-area measurements were linear over the range 0.1-20 micro mol L(-1). The HBSS-Hepes buffer did not interfere with separation and detection; identical separation and peak intensity were obtained when the samples were separately prepared in distilled water or in the culture medium.

Adrenergic beta-Antagonists↗

PubMed2002

Liquid chromatography-electrospray mass spectrometric studies of ginkgolides and bilobalide using simultaneous monitoring of proton, ammonium and sodium adducts.

A liquid chromatographic-electrospray mass spectrometric method was developed for the determination of ginkgolides and bilobalide and was applied to the analysis of commercial products of Ginkgo biloba leaf extracts. Adducts of these compounds with ammonium, proton and sodium were detected and their relative abundance depended on the electrospray fragmentor voltage. The relative standard deviation (RSD) was improved from > 17% to < 6%, when three adduct ions of (M + H)+, (M + NH4)+ and (M + Na)+ were used for quantification compared with single ion monitoring. The characteristic mass spectra of bilobalide were different from those of ginkgolides; in particular, dimers of (2M + Na)+ were observed for bilobalide only. Analysis of 26 commercial ginkgo products revealed large variations in the composition and concentrations of ginkgolides and bilobalide in herbal products.

Chromatography, Liquid↗

PubMed2002

In situ extraction/preconcentration of PCBs and PAHs from aqueous samples using polytetrafluoroethylene tubing.

In situ extraction/preconcentration of organics from water samples was accomplished using polytetrafluoroethylene (PTFE) tubing. Polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were concentrated inside the tubing by flowing aqueous samples through it. The adsorbed PCBs and PAHs were then recovered by solvent desorption. The eluent was subsequently analyzed using gas chromatography with electron capture detection (GC-ECD) or gas chromatography with flame ionization detection (GC-FID). Multiple samples were simultaneously processed to concentrate organics onto several PTFE tubings. Analyses of seawater and surface microlayers using this technique demonstrated that organics in the surface microlayers were elevated with respect to those in the water column, consistent with previous findings.

Chromatography, Gas↗