Liquid Chromatography Electrospray Ionization Mass Spectrometry (liquid + chromatography_electrospray_ionization_mass_spectrometry)

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Selected Abstracts

Determination and fate of oxytetracycline and related compounds in oxytetracycline production wastewater and the receiving river,

Dong Li
Abstract This study investigated the occurrence and fate of oxytetracycline (OTC) and its related substances, 4-epi-oxytetracycline (EOTC), ,-apo-oxytetracycline (,-apo-OTC), and ,-apo-oxytetracycline (,-apo-OTC), in a wastewater treatment plant (WWTP) treating OTC production wastewater and a river receiving the effluent from the WWTP using liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS). The percent removal of OTC in the WWTP was 38.0 10.5%, and the concentration of OTC was still up to 19.5 2.9 mg/L in the treated outflow. The concentration slightly decreased along the river, from 641 118 ,g/L at site R2 (discharging point) to 377 142 ,g/L at site R4 (,20 km from site R2), which was still higher than the minimal inhibition concentration of OTC reported (,250 ,g/L). On the other hand, the total amount of its related substances in the treated effluent was less than 5% of OTC. Concentrations of ,-apo-OTC and ,-apo-OTC increased along the river, from 5.76 0.63 and 2.08 0.30 ,g/L at site R2 to 11.9 4.9 and 12.0 4.6 ,g/L at R4, respectively, although EOTC decreased from 31.5 3.8 to 12.9 1.1 ,g/L, respectively. The mean concentration of ,-apo-OTC in river sediments was 20.8 7.8 mg/kg, and its ratio to OTC was approximately 0.11, nearly twice the ratio of ,-apo-OTC and EOTC to OTC (0.058 0.014 and 0.061 0.015, respectively). [source]

Compounds from rose (Rosa rugosa) flowers with human immunodeficiency virus type 1 reverse transcriptase inhibitory activity

M. Fu
The aqueous extracts and ethanol precipitates of aqueous extracts of 18 medicinal herbs traditionally used in China were screened for their ability to inhibit human immunodeficiency virus type-1 reverse transcriptase (HIV-1 RT) in-vitro. Among the samples screened at a concentration of 500 ,g mL,1, dried rose (Rosa rugosa) flowers showed the strongest inhibition. The ethanol precipitate of the aqueous extract of R. rugosa was processed and two components (P1 and P2) were obtained after ion exchange chromatography on DEAE-cellulose. Then, P1-a (Mr 150 kDa) and P1-b (Mr 8 kDa) were isolated from P1 by gel filtration on Sephadex G-200. They inhibited the activity of HIV-1 RT with an IC50 of 158 nm and 148.16 ,g mL,1 (18.5 ,m), respectively. Further structural analyses revealed that P1-a was a polysaccharide-peptide complex, and P1-b was a polymer consisting of acteoside and acteoside derivatives identified by Fourier transform infrared spectroscopy, nuclear magnetic resonance, assays of carbohydrate and protein contents and high-performance liquid chromatography electrospray ionization mass spectrometry. [source]

Identification of the human salivary cystatin complex by the coupling of high-performance liquid chromatography and ion-trap mass spectrometry

Alessandro Lupi
Abstract Human salivary cystatins, five major (S, S1, S2, SA, SN) and two minor (C and D), are multifunctional proteins playing a different role in the oral environment. Salivary cystatin SN is able to effectively inhibit lysosomal cathepsins B, C, H and L and cystatin SA inhibits cathepsins C and L in vitro. These activities suggest, particularly for cystatin SN, an important role in the control of proteolytic events in vivo. Differently, cystatins S are involved, together with statherin, in the mineral balance of the tooth. Due to their distinct role, a reliable method for identification and quantification of the different cystatins, as well as of possible truncated and derived forms, could be helpful for the assessment of the status of the oral cavity. To this purpose high-performance liquid chromatography electrospray ionization mass spectrometry (HPLC-ESI MS) was applied to the analysis of human saliva obtained from healthy subjects. All known salivary cystatins, with the exception of cystatin C, were detected. Strong evidence was also obtained for the presence in saliva of post-translational modified isoforms of cystatins, which may be related to donor habits. Cystatin SN and cystatins S, S1 and S2 were well separated by HPLC-ESI MS coupling from other components and thus this approach can be successfully applied to their quantification. [source]

Quantitative determination of alkylated quaternary amines and their n -hydroxylated metabolites in an enzyme incubation matrix by liquid chromatography electrospray ionization mass spectrometry

Victoria E. Holmes
Abstract A simple, rapid and sensitive reversed-phase liquid chromatography method coupled to electrospray ionization mass spectrometry has been developed for studying the in vitro metabolism of the long-chain quaternary ammonium compounds dodecyltrimethylamine, tetradecyltrimethylamine and hexadecyltrimethylamine. Samples were prepared from the biological matrix by a simple protein precipitation stage. The separation was performed using a BDS Hypersil C8 3 m particle size (100 3 mm i.d.) column with a fast gradient separation (60% B to 100% B) using a mobile phase of 10 mm aqueous ammonium acetate (pH 4.0, with 0.06% triethylamine; (A),acetonitrile (B) at 0.7 mL min,1. To minimize contamination of the MS source a switching value was used to divert the solvent front to waste. Decylammonium bromide was used as the internal standard and analytes were identified and quantified by positive ion electrospray selected ion monitoring of their intact molecular cations. The assay had a limit of quantitation of 0.25 m (6.25 pmol on column) and was linear over the range 0.25,100 m assay concentration for this series of long-chain quaternary amines. The precision of intra- and inter-day assays was better than 19% and the accuracy was between 93 and 109%. The method was used to assess the in vitro metabolism of the quaternary amines by wild-type cytochrome P450 enzyme CYP4A1 and mutants in an artifical membrane system. Copyright 2005 John Wiley & Sons, Ltd. [source]