Performance Liquid Chromatography-electrospray Mass Spectrometry Research Articles

Particulate organic nitrates at Mount Tai in winter and spring: Variation characteristics and effects of mountain-valley breezes and elevated emission sources

Particulate organic nitrates, among the major components of secondary organic aerosols and fine particles, play important roles in regional nitrogen cycle, ozone budget, and cloud condensation nuclei formation. However, the pollution characteristics of particulate organic nitrates at mountain areas and the effects of anthropogenic pollutant transport remain poorly understood. In this study, field sampling and measurements were conducted at a high-elevation mountain site over North China Plain in winter and spring. Total five kinds of particulate organic nitrates in fine particles were determined by ultra-high performance liquid chromatography-electrospray mass spectrometry. The average total concentrations of particulate organic nitrates were 330 ± 121 ng m-3 and 247 ± 63 ng m-3 in winter and spring. The monoterpene-derived organic nitrates were the dominant components in both seasons with their contribution higher than 70%, accounting for 1.2 ± 0.8% and 2.0 ± 1.0% in organic aerosols in winter and spring, respectively. The significantly higher levels of particulate organic nitrates in winter than spring was ascribed to the strong effects of mountain-valley breezes and coal combustion plumes. The increasing concentrations of NOx and particulate matters brought by the valley breeze at daytime facilitated the formation of MHN215, OAKN359, and OAHN361, while the rising SO2 abundance and the sulfate aerosols transported by elevated emission sources affected the formation of MDCN247 at nighttime.

Coelomic fluid of Echinometra mathaei: The new prospects for medicinal antioxidants

Echinoid pigments have various biological properties such as antioxidant, cytotoxic, and antibacterial activities. We aimed to evaluate the extraction of cell-free coelomic fluid (CFCF) and coelomocyte lysate (CL) as well as qualitatively and quantitatively identify the coelomic fluid of Echinometra mathaei as a new source of polyhydroxylatednaphthoquinone (PHNQ) antioxidant pigments. Based on the High Performance liquid chromatography–electrospray mass spectrometry (HPLC-MS) analysis in negative mode, the main quinonoid (PHNQ) pigments were identified and quantified. This study also illustrated the total ion current chromatograms and related mass spectra of Spinochrome A, Spinochrome B, Spinochrome C, and Echinochrome A in CL and SpinochromeC in CFCF samples. The ions at 221, 279, 265 and 263 m/z correspond to the pseudo-molecular [M − H] ions of Spinochrome B, Spinochrome C, Echinochrome A, and Spinochrome A, respectively. These components have previously been noted from the shells and spines of sea urchins but identification of PHNQs pigments in CL and CFCF of E. mathaei using LC-MS was introduced for the first time. The results also showed that, the highest DPPH radical scavenging activity of CFCF (88.12 DPPH% scavenging at 70 μg/mL, IC50 = <10 μg/mL). The findings clearly suggest that the coelomic fluid of E. mathaei could be served as the promising as well as potential natural antioxidants in the medical and pharmaceutical industries and could replace the increasing prices of the commercial antioxidants products.

The correlation of serum GGT with glucose level in patients with type 2 diabetes

Objective To explore the association between serum gamma glutamyl transpeptidase (GGT) and fasting blood-glucose, evaluating the modification effects of body mass index (BMI), age, sex, and lipids. Methods The normal control group (120 cases), the hospitalized patients with three times of the average fasting blood glucose (6.0~7.0 mg/dl) (128 cases), and the hospitalized patients with three times of the average fasting blood glucose (>7.0 mg/dl) (124 cases) were selected in this study. Immune turbidimetry was used to test the serum of GGT, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), total cholesterol (TC), and triglycerides (TG). Enzymatic method was used to test glucose (GLU). High performance liquid chromatography-electrospray mass spectrometry was used to measure glycosylated hemoglobin A1c (HbA1c) in the blood. Results ⑴ The value of GGT was significantly higher in the patients with type 2 diabetes, but the fasting blood glucose was above of 7.0 compared to the other two groups (P<0.05). ⑵ After adjustment of many confounders, the significance of the highest GGT quartile band compared to the lowest was obviously among three groups (P<0.05). Conclusions GGT is expected to predict the development of disease in the process of treatment of type 2 diabetes. Key words: Diabetes mellitus, type 2/ME; Gamma-glutamyltransferase/ME; Blood glucose

Photodegradation of dimethenamid-P in deionised and ground water

The study of photodegradation of dimethenamid-P herbicide was performed in deionised and ground water using TiO2 as a catalyst under UV light. The effect of electron acceptor (H2O2), scavenger of ?OH radicals (C2H5OH) and scavenger of holes (NaCl and Na2SO4) as well as solution pH was analyzed. The photodegradation of dimethenamid-P was followed by HPLC. The formation of transformation products was followed using high performance liquid chromatography-electrospray mass spectrometry. Ion chromatography and total organic carbon measurements were used for the determination of the mineralization level. HPLC analysis showed the almost complete removal of herbicide after 90 min in deionised and ground water, while total organic carbon analysis showed that dimethenamid-P was mineralized 64 and 50 % in deionised and ground water, respectively. The ion chromatography results showed that the mineralization process leads to the formation of chloride, sulphate and nitrate anions during the process. Transformation products were identified and the degradation mechanism was proposed.

Biosynthesis of arsenolipids by the cyanobacterium Synechocystis sp. PCC 6803

Environmental context Arsenic biotransformation processes play a key role in the cycling of arsenic in aquatic systems. We show that a freshwater cyanobacterium can convert inorganic arsenic into arsenolipids, and the conversion efficiency depends on the arsenic concentration. The role of these novel arsenic compounds remains to be elucidated. Abstract Although methylated arsenic and arsenosugars have been verified in various freshwater organisms, lipid-soluble arsenic compounds have not been identified. Here, we report investigations with the model organism cyanobacterium Synechocystis sp. PCC 6803 wild type and ΔarsM (arsenic(III) S-adenosylmethionine methyltransferase) mutant strain, which lacks the enzymes for arsenic methylation cultured in various concentrations of arsenate (AsV). Although Synechocystis accumulated higher arsenic concentrations at the higher exposure levels, the bioaccumulation factor decreased with increasing AsV. The accumulated arsenic in the cells was partitioned into water-soluble and lipid-soluble fractions; lipid-soluble arsenic was found in Synechocystis wild type cells (3–35% of the total depending on the level of arsenic exposure), but was not detected in Synechocystis ΔarsM mutant strain showing that ArsM was required for arsenolipid biosynthesis. The arsenolipids present in Synechocystis sp. PCC 6803 were analysed by high performance liquid chromatography–inductively coupled plasma–mass spectrometry, high performance liquid chromatography–electrospray mass spectrometry, and high resolution tandem mass spectrometry. The two major arsenolipids were characterised as arsenosugar phospholipids based on their assigned molecular formulas C47H88O14AsP and C47H90O14AsP, and tandem mass spectrometric data demonstrated the presence of the phosphate arsenosugar and acylated glycerol groups.

Improved separation and detection of picolinic acid and quinolinic acid by capillary electrophoresis-mass spectrometry: Application to analysis of human cerebrospinal fluid

“Quinolinic acid (QA)”, a metabolite of the kynurenine pathway (KP), is implicated as a major neurological biomarker, which causes inflammatory disorders, whereas there is an increase evidence of the role of picolinic acid (PA) in neuroinflammation. Therefore, there is an urgent need to develop new clinical test for early diagnosis of neuroinflammatory disorders. A comparison is made between three different platforms such as high performance liquid chromatography–electrospray mass spectrometry (HPLC–ESI-MS/MS), nano LC–Chip/ESI-MS/MS, as well as the use of cationic (quaternary ammonium) and anionic (sulfonated) coated capillaries in capillary electrophoresis (CE)-ESI-MS/MS. The comparison revealed that CE-ESI-MS/MS method using a quaternary ammonium coated capillary is the best method for analysis of PA and QA. A simple stacking procedure by the inclusion of acetonitrile in the artificial cerebrospinal fluid (CSF) sample was employed to improve the peak shape and sensitivity of KP metabolites in CE-ESI-MS/MS. The developed CE-ESI-MS/MS assay provided high resolution, high specificity and high sensitivity with a total analysis time including sample preparation of nearly 12min. In addition, excellent intra-day and inter-day repeatability of migration times and peak areas of the metabolites were observed with respective relative standard deviation (RSD) of less than 2.0% and 2.5%. Somewhat broader variations in repeatability for a 3 independently prepared coated capillary (total 35 runs each) with % RSD up to 3.8% and 5.8% was observed for migration time and peak areas, respectively. Artificial CSF was used as a surrogate matrix to simultaneously generate calibration curves over a concentration range of 0.02–10μM for PA and 0.4–40μM for QA. The method was then successfully applied to analyze PA and QA in human CSF, demonstrating the potential of this CE-ESI-MS/MS method to accurately quantitate with high specificity and sensitivity.

Antidepressant-like effects of an alkaloid extract of the aerial parts of Annona cherimolia in mice

Ethnopharmacological relevanceSeveral species of Annona (Annonaceae) are used in traditional Mexican medicine by their anti-anxiety, anticonvulsant and tranquilizing properties. It has been reported that the alkaloids isolated from some species of the Annona have affinity to serotonergic 5-HT1A receptors and modulate dopaminergic transmission, which is involved in depressive disorders. Aim of the studyTo investigate the antidepressant-like effect of an alkaloid extract from the aerial parts of Annona cherimola (TA) in mice. Materials and methodsThe antidepressant-like effect was evaluated in the forced swimming test. To elucidate a possible mechanism of action, experiments of synergism with antidepressant drugs, such as imipramine (IMI), clomipramine (CLIMI), and fluoxetine (FLX), were carried out. The neurotransmitter content (DA: dopamine, 5HT: serotonin and its metabolites, HVA: homovanillic acid and 5HIAA: 5-hydroxyindoleacetic) in the whole brain of mice were also determined by HPLC method. TA chemical composition was determined using high performance liquid chromatography–electrospray mass spectrometry. ResultsThe results showed that repeated treatment with TA produced antidepressant-like effects in mice. This effect was not related to an increase in locomotor activity. Administration of TA facilitated the antidepressant effect of IMI and CLIMI as well as increased the turnover of DA and 5-HT. The alkaloids: 1,2-dimethoxy-5,6,6a,7-tetrahydro-4H-dibenzoquinoline-3,8,9,10-tetraol, anonaine, liriodenine, and nornuciferine were the main constituents of TA. ConclusionsResults showed that TA produces an antidepressant-like action from a generalized increase in monominergic turnover, supporting the use in tradicional medicine of Annona cherimolia, and strongly suggest its therapeutic potency as an antidepressant agent.

Metabonomics and phospholipid metabolic profiling of abnormal glucose metabolism based on high performance liquid chromatography-electrospray mass spectrometry

Abnormal glucose metabolism (AGM) has received more and more attention since its incidence is increasing. Metabonomics and phospholipid metabolic profiling methods based on high performance liquid chromatography-electrospray mass spectrometry (HPLC/ESI-MS) have been applied in the study of AGM. The two different stages of AGM, including impaired fasting glucose (IFG) and newly-diagnosed diabetes (NDD), were investigated. The raw data of both metabonomics and phospholipid metabolic profiling collected from HPLC/ESI-MS were transformed and the peak lists were gained through commercial software. The differentiations among the three groups of NDD, IFG and normal fasting glucose (N) were found through the peak lists were performed with orthogonal signal correction and partial least-squares (OSC-PLS). The metabolic differentiation compounds were selected when their variable importance values were more than 1, and p < 0.05 in phospholipid metabolic profiling data. There were more changes in the NDD group than those in the IFG group. The metabolic differentiation compounds were free fatty acids, lysophosphatidylcholine, phosphatidylethanolamine, sphingomyelin and phosphatidylcholine. This research provided some new information of what had happened in the people with AGM.

Factors affecting atrazine concentration and quantitative determination in chlorinated water

Although the herbicide atrazine has been reported to not react measurably with free chlorine during drinking water treatment, this work demonstrates that at contact times consistent with drinking water distribution system residence times, a transformation of atrazine can be observed. Some transformation products detected through the use of high performance liquid chromatography–electrospray mass spectrometry are consistent with the formation of N-chloro atrazine. The effects of applied chlorine, pH, and reaction time on the transformation reaction were studied to help understand the practical implications of the transformation on the accurate determination of atrazine in drinking waters. The errors in the determination of atrazine are a function of the type of dechlorinating agent applied during sample preparation and the analytical instrumentation utilized. When a reductive dechlorinating agent, such as sodium sulfite or ascorbic acid is used, the quantification of the atrazine can be inaccurate, ranging from 2-fold at pH 7.5 to 30-fold at pH 6.0. The results suggest HPLC/UV and ammonium chloride quenching may be best for accurate quantification. Hence, the results also appear to have implications for both compliance monitoring and health effects studies that utilize gas chromatography analysis with sodium sulfite or ascorbic acid as the quenching agent.

Effect of bifendate on the pharmacokinetics of cyclosporine in relation to the CYP3A4*18B genotype in healthy subjects

To evaluate the potential drug-drug interactions between bifendate and cyclosporine, a substrate of CYP3A4, in relation to different CYP3A4*18B genotype groups. Eighteen unrelated healthy subjects (six CYP3A4*1*1, six CYP3A4*1/*18B, and six CYP3A4*18/*18B) were selected for this study. After repeated oral administration of a placebo or bifendate (three times daily for 14 d), the whole-blood level of cyclosporine was measured using high performance liquid chromatography-electrospray mass spectrometry (HPLC/ESI-MS). This study was carried out in a two-phase randomized crossover manner. After the treatment with bifendate, the areas under the curve (AUC(0-24) and AUC(0-infinity)) decreased significantly by 9.7%+/-3.7% (P=0.01) and 19.2%+/-16.8% (P=0.001) in CYP3A4*1/*1 subjects, 11.3%+/-9.4% (P=0.03) and 10.5%+/-9.6% (P=0.043) in CYP3A4*1/*18B subjects, and 40.2%+/-14.7% (P=0.02) and 37.5%+/-15.8% (P=0.003) in CYP3A4*18B/*18B subjects. Meanwhile, the decreases in the AUC(0-24) and AUC(0-infinity) values in the three groups were significantly different (using one-way analysis of variance, P=0.001 and P=0.001), and the change in the CYP3A4*18B/*18B group was greater than that in the other two groups. The oral clearance of cyclosporine was altered in all the subjects, with substantial increases by 10.2%+/-4.4% (P=0.004) in CYP3A4*1/*1 subjects, 14.0%+/-12.0% (P=0.048) in CYP3A4*1/*18B subjects, and 32.4%+/-21.7% (P=0.013) in CYP3A4*18B/*18B subjects. These results suggest that bifendate decreases the plasma concentration of cyclosporine in a CYP3A4 genotype-dependent manner.

Analysis of flavonol glycoside isomers from leaves of Maytenus ilicifolia by offline and online high performance liquid chromatography–electrospray mass spectrometry

Flavonol glycosides present in leaves of Maytenus ilicifolia, were examined after fractionation on silica-gel column. Flavonol mono-, di-, tri-, and tetraglycosides, containing kaempferol, quercetin or myricetin were identified by offline electrospray mass spectrometry. Increasing the cone energy induced to adducts variation, from H + to Na +. Protonated ions were characteristically fragmented by sequentially removing the monosaccharide residues, whereas in the sodiated ions, the aglycone was firstly removed. Online high performance liquid chromatography–mass spectrometry, with simple gradients of water, acetonitrile and acetic acid indicated the presence of several isomers, which were further identified by gas chromatography–mass spectrometry as containing galactose or glucose.

Chemical markers of human waste contamination: Analysis of urobilin and pharmaceuticals in source waters

Giving public water authorities another tool to monitor and measure levels of human waste contamination of waters simply and rapidly would enhance public protection. Most of the methods used today detect such contamination by quantifying microbes occurring in feces in high enough densities that they can be measured easily. However, most of these microbes, for example E. coli, do not serve as specific markers for any one host species and many can have origins other than feces. As an alternative, chemicals shed in feces and urine might be used to detect human waste contamination of environmental waters. One potential chemical marker of human waste is the compound urobilin. Urobilin is one of the final by-products of hemoglobin breakdown. Urobilin is excreted in both the urine and feces from many mammals, particularly humans. Source waters from 21 sites in New England, Nevada, and Michigan were extracted using hydrophilic-lipophilic balance (HLB) cartridges and then analyzed by high performance liquid chromatography-electrospray mass spectrometry (HPLC-ES-MS). As a marker of human waste, urobilin was detected in many of the source waters at concentrations ranging from not detectable to 300 ng L(-1). Besides urobilin, azithromycin, an antibiotic widely prescribed for human use only in the US, was also detected in many of these waters, with concentrations ranging from not detectable to 77 ng L(-1). This methodology, using both urobilin and azithromycin (or any other human-use pharmaceutical) could be used to give public water authorities a definitive method for tracing the sources of human waste contamination. The analysis and detection of urobilin in surface waters by HPLC-ES-MS has not been previously reported in the peer-reviewed literature.

Analysis of corticosteroids by high performance liquid chromatography-electrospray mass spectrometry.

A high performance liquid chromatography electrospray mass spectrometry (HPLC-ESI-MS) method, for the detection of corticosteroids in cosmetics has been developed. A water-acetonitrile linear gradient on a C-18 reversed-phase column was found to be suitable in separating triamcinolone and its main derivatives, which greatly differ in lipophilicity. Detection was performed in negative electrospray ionisation mode. Good correlation between peaks areas and solutions concentration was found in the range 0.05-10.0 micro g ml(-1) and the detection limits resulted in the range of 20-45 pg injected. The method was successfully applied to the analysis of real samples of shampoo.

Multiresidue screening of neutral pesticides in water samples by high performance liquid chromatography–electrospray mass spectrometry

A multiresidue method to screen ultra traces of neutral pesticides from water samples in compliance with European Union regulations is presented, using solid-phase extraction (SPE) followed by high performance liquid chromatography coupled to atmospheric pressure electrospray ionisation (ESI) mass spectrometry, SPE/LC–MS(ESI). Calibration conditions of LC–MS(ESI) in the SIM mode, showed excellent linear response for the 12 pesticides studied (carbaryl, carbofuran, methomyl, oxamyl, pirimicarb, chlortoluron, diuron, isoproturon, linuron, atrazine, propazine and simazine) in the range from 1 to 50 μg/l and precisions having a relative standard deviation (R.S.D.) below 4.9% (chlortoluron) was achieved. Instrumental limits of detection of 0.10 μg/l were found with the exception of chlortoluron, diuron and methomyl, for which 0.25 and 0.50 μg/l were measured. The SPE assays using octadecilsilica cartridges are relatively simple and highly reproducible, requiring low volume of water sample (50 ml). For laboratory-spiked water samples having 0.10 μg/l of individual pesticides, good average recoveries were obtained, within 65.0 and 97.8% with a relative standard deviation lower than 12.6% (methomyl). For real matrices, laboratory-spiked drinking and surface water samples at the 0.05 μg/l level, reasonable average recoveries were also achieved, ranging from 75.3 to 96.8% and 67.7 to 105.2%, respectively. The present work establishes a suitable protocol as a guideline for research and routine laboratories, to screen simultaneously carbamates, phenylureas and triazines from water samples. The methodology evidences very good reproducibility and is shown to be a suitable alternative to replace the currently dedicated analytical systems. The limits of detection reached (0.5–3.0 ng/l) clearly cover the maximum concentration admissible for pesticides in water samples, established by the European Union directive.

Sensitivity of β-casein phosphopeptide-iron complex to digestive enzymes in ligated segment of rat duodenum

Binding iron to the phosphorylated β(1-25) peptide derived from β-casein improves iron bioavailability in the rat. The aim of the present work was to learn how injected β(1-25) and iron-β(1-25) complex behave in the duodenum of rats using the technique of intestinal ligation in situ and reversed-phase (RP)-high performance liquid chromatography-electrospray mass spectrometry analysis of the lumen contents. The results demonstrate that β(1-25) is sensitive to digestive enzymes including proteases/peptidases and phosphatases during duodenal transit. The lumen contents of rats perfused with iron free β(1-25) contained all peptidic sequences derived from β(1-25). In contrast, the phosphorylated part of β(1-25) [i.e., β(15-24)] was not detected in lumen of rats perfused with iron-β(1-25) complex.

Determination of residues of the plant growth regulator chlormequat in pears by ion-exchange high performance liquid chromatography-electrospray mass spectrometry†

We report a method which we have used routinely for the determination of chlormequat residues in pears. After extraction with methanol, determination was performed, without clean-up, by ion-exchange HPLC using an SCX column eluted with aqueous ammonium formate-methanol, and HPLC-MS with an electrospray interface. MS and MS-MS were employed concurrently, using selected ion monitoring and selected reaction monitoring, respectively, of the 35Cl and 37Cl isotopes of the chlormequat cation and the CID transitions of each of these precursors to the common product ion at m/z 58. The method was suitable for determinations at concentrations of chlormequat cation of 0.04 mg kg-1. Concentrations determined using the four signals were in good agreement (mean RSD 3%). The mean recovery of chlormequat cation at 0.16 mg kg-1, measured using the m/z 122-->58 signal, was 86% (RSD 7%) under repeatability conditions and 88% (RSD 15%) in routine application of the method over a 3 month period. Analysis of an in-house reference sample of pears, similarly analysed over the 3 month period, gave an RSD of 10% with a mean of 0.14 mg kg-1. Mean recovery at 0.016 mg kg-1, under repeatability conditions on two occasions, was 101% (RSD 6%) and 56% (RSD 12%).

The Inactivation Mechanism of Low Molecular Weight Phosphotyrosine-protein Phosphatase by H2O2

Low molecular weight phosphotyrosine-protein phosphatase (LMW-PTP) shares no general sequence homology with other PTPs, although it has an active site sequence motif CXXXXXR and a reaction mechanism identical to those of all PTPs. The main function of this enzyme is the down-regulation of platelet-derived growth factor and insulin receptors. Both human LMW-PTP isoenzymes are inactivated by H2O2. The enzymes are protected from inactivation by Pi, a competitive inhibitor, suggesting that the H2O2 reaction is directed to active site. Analysis of free thiols performed on the inactivated enzymes demonstrates that only two out of the eight LMW-PTP cysteines are modified. Time-course high performance liquid chromatography-electrospray mass spectrometry, together with specific radiolabeling and tryptic fingerprint analyses, enables us to demonstrate that H2O2 causes the oxidation of Cys-12 and Cys-17 to form a disulfide bond. Because both residues are localized into the active site region, this modification inactivates the enzyme. Fluorescence spectroscopy experiments suggest that the fold of the enzyme is modified during oxidation by H2O2. Because a physiological concentration of H2O2 produces enzyme inactivation and considering that the activity is restored by reduction with low molecular weight thiols, we suggest that oxidative stress conditions and other processes producing hydrogen peroxide regulate the LMW-PTP in the cell.

Site localization of sialyl Lewis(x) antigen on alpha1-acid glycoprotein by high performance liquid chromatography-electrospray mass spectrometry.

A simple, fast and sensitive method was developed to verify the presence of the sialyl Lewis(x) antigen on an N-linked glycoprotein. High performance liquid chromatography-electrospray mass spectrometry (HPLC-ESI/MS) was used to identify which of the five N-linked glycosylation sites of human plasma alpha1-acid-glycoprotein (orosomucoid, OMD) contain the sialyl Lewis(x) antigen. OMD was digested with proteolytic enzymes and analyzed by reversed phase chromatography coupled with on-line ESI/MS. A tandem mass spectrometry experiment was designed to detect the presence of the sialyl Lewis(x) antigen based on the observation of an 803 mass to charge ratio ( m/z ) ion produced in the intermediate pressure region of the ESI interface. The ESI/MS signal at m/z 803 is consistent with an oxonium ion for a glycan structure containing NeuAc, Gal, GlcNAc, and Fuc. The identity of the m/z 803 ion was confirmed by ESI/MS/MS analysis of the m/z 803 fragment ion and comparison with a sialyl Lewis(x) standard. The stereochemistry and linkage positions were assigned using previous NMR analysis but could be determined with permethylation analysis if necessary. The analysis of OMD gave a pattern showing signal for the sialyl Lewis(x) antigen coeluting with each of the five N-linked glycopeptides. The ability to monitor sialyl Lewis(x) expression at each of the five sites is of interest in the study of OMD's role in inflammatory diseases.

Proteins of rat serum: I. Establishing a reference two-dimensional electrophoresis map by immunodetection and microbore high performance liquid chromatography-electrospray mass spectrometry.

In the present investigation, we have identified 56 major spots, or spot rows, corresponding to 22 proteins, in the 2-DE pattern of adult male rats. This was done mainly by applying two complementary techniques, namely immunoblotting and high performance liquid chromatography-mass spectrometry (HPLC-MS) peptide mapping. Glycoproteins were characterized by affinity blotting with six lectins. We have also detailed how rat serum differs from human serum in two main respects: (i) relative abundance of individual proteins, which amounts in some cases to a complete absence in either sample, and (ii) varying molecular parameters for homologous proteins. It was thus possible to establish a first-generation reference map of rat serum proteins, which can be accessed through http://weber.u.washington.edu/ruedilab/aebersold++ +.html. We hope the present database will be a useful reference for the evaluation of changes in serum protein distribution in the course of pharmacological and toxicological studies. The recognition of species-specific proteins appears of special relevance in this respect.

A general method for the dereplication of flavonoid glycosides utilizing high performance liquid chromatography/mass spectrometric analysis

Using high performance liquid chromatography–electrospray mass spectrometry a method was developed to separate flavonoids and flavonoid glycosides and to obtain molecular weight information. Collision-induced dissociation was then used to obtain the molecular masses of the flavonoid aglycones. Thus, the mass of a flavonoid glycoside and its aglycone can now be determined in a mixture, and it is not necessary to isolate the components. An aqueous extract of Eugenia jambos L. was used to demonstrate the utility of the technique in analysing extracts for flavonoid glycosides. © 1997 John Wiley & Sons, Ltd.