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Biomedical subjects

Xia Zhang

Publications and source records attributed to Xia Zhang.

At least 55 records · Page 3Linked to original sources
PubMed2005

ERK activation following macrophage FcgammaR ligation leads to chromatin modifications at the IL-10 locus.

We have previously demonstrated that macrophages stimulated in the presence of immune complexes produce high levels of IL-10. We now examine the mechanism of IL-10 superinduction. We report that the enhanced production of IL-10 correlates with a rapid and enhanced activation of two MAPKs, ERK and p38. The inhibition of either ERK or p38 prevented IL-10 induction, indicating that both MAPKs were required for IL-10 synthesis. By chromatin immunoprecipitation assay, we demonstrate that activation of ERK leads to the phosphorylation of serine 10 on histone H3 at the il-10 gene, making the promoter more accessible to transcription factors generated in response to p38 activation. Inhibition of ERK activation prevented histone modifications, and decreased the binding of Sp1 and STAT3 to the IL-10 promoter. We conclude that the activation of ERK following FcgammaR ligation leads to a remodeling of the chromatin at the il-10 locus, making it more accessible to transcription factors. The rapid and transient regulation of transcription factor accessibility to the IL-10 promoter by MAPK activation represents a novel way that the production of this cytokine is regulated.

Animals↗
PubMed2005

Formylpeptide receptor FPR and the rapid growth of malignant human gliomas.

BACKGROUND: The formylpeptide receptor (FPR) is a G-protein-coupled receptor (GPCR) that mediates chemotaxis of phagocytic leukocytes induced by bacterial peptide N-formyl-methionyl-leucyl-phenylalanine (fMLF). We previously showed that selected human glioma cell lines also express functional FPR. We therefore investigated the relationship between FPR expression and the biologic behavior of glioma cells. METHODS: Expression and function of FPR in the human glioblastoma cell line U-87 were examined by reverse transcription-polymerase chain reaction (RT-PCR) and chemotaxis assays, respectively. FPR protein expression was detected in specimens from 33 human primary gliomas by immunohistochemistry. FPR short interfering (si) RNA was used to block FPR expression in U-87 cells. Cell proliferation was assessed by measuring DNA synthesis. Xenograft tumor formation and growth were measured in nude mice. Endogenous FPR agonist activity released by necrotic tumor cells was assessed by measuring FPR activation in an FPR-transfected basophil leukemia cell line and live U-87 cells. Vascular endothelial growth factor (VEGF) mRNA was assessed by RT-PCR, and VEGF protein was assessed by enzyme-linked immunosorbent assay. All statistical tests were two-sided. RESULTS: FPR was selectively expressed by the highly malignant human glioblastoma cell line U-87 and most primary grade IV glioblastomas multiforme and grade III anaplastic astrocytomas. U-87 cells responded to the FPR agonist fMLF by chemotaxis (i.e., increased motility), increased cell proliferation, and increased production of VEGF protein. FPR siRNA substantially reduced the tumorigenicity of U-87 cells in nude mice (38 days after implantation, mean tumor volume from wild-type U-87 cells = 842 mm3, 95% confidence interval [CI] = 721 to 963 mm3; and from FPR-siRNA transfected U-87 cells = 225 mm3, 95% CI = 194 to 256 mm3; P = .001). Necrotic glioblastoma cells released a factor(s) that activated FPR in live U-87 cells. CONCLUSIONS: FPR is expressed by highly malignant human glioma cells and appears to mediate motility, growth, and angiogenesis of human glioblastoma by interacting with host-derived agonists. Thus, FPR may represent a molecular target for the development of novel antiglioma therapeutics.

Animals↗
PubMed2005

Parthenogenetic activation of mouse oocytes by strontium chloride: a search for the best conditions.

Strontium has been successfully used to induce activation of mouse oocytes in nuclear transfer and other experiments, but the optimum treatment conditions have not been studied systematically. When cumulus-free oocytes were treated with 10mM SrCl(2) for 0.5-5h, activation rates (88.4+/-4.1 to 91.2+/-2.7%) did not differ (mean+/-S.E.; P>0.2), but rate of blastulation (57.3+/-3.5%) and cell number per blastocyst (45.0+/-2.4) were the highest after treatment for 2.5h. When treated with 1-20mM SrCl(2) for 2.5h, the activation rate and cell number per blastocyst were higher (P<0.02) after 10mM SrCl(2) treatment than other treatments. The best activation and development were obtained with Ca(2+)-free Sr(2+) medium, but the activation rate was low (37.7+/-1.6%) in Ca(2+)-containing medium. Activation rates were the same, regardless of the presence or absence of cytochalasin B (CB) in the activating medium, but the blastulation rate was higher (P<0.001) in the presence of CB. Only 70% of the cumulus-enclosed oocytes were activated and 10% blastulated after a 10 min exposure to 1.6mM SrCl(2), and many lysed, with increased intensity of Sr(2+) treatment. The presence of CB in SrCl(2) medium markedly reduced lysis of cumulus-enclosed oocytes. Media M16 and CZB did not differ when used as activating media. Only 10.5% of the oocytes collected 13 h post hCG were activated by Sr(2+) treatment alone, with 34% blastulating, but rates of activation and blastulation increased (P<0.001) to 94 and 60%, respectively, when they were further treated with 6-dimethylaminopurine (6-DMAP). The total and ICM cell numbers were less (P<0.001) in parthenotes than in the in vivo fertilized embryos. In conclusion, the concentration and duration of SrCl(2) treatment and the presence or absence of CB in activating medium and cumulus cells had marked effects on mouse oocyte activation and development. To obtain the best activation and development, cumulus-free oocytes collected 18 h post hCG should be treated for 2.5h with 10mM SrCl(2) in Ca(2+)-free medium supplemented with 5 microg/mL of CB.

Adenine↗
PubMed2005

Coactivators and corepressors of NF-kappaB in IkappaB alpha gene promoter.

In this study, we investigated recruitment of coactivators (SRC-1, SRC-2, and SRC-3) and corepressors (HDAC1, HDAC2, HDAC3, SMRT, and NCoR) to the IkappaB alpha gene promoter after NF-kappaB activation by tumor necrosis factor-alpha. Our data from chromatin immunoprecipitation assay suggest that coactivators and corepressors are simultaneously recruited to the promoter, and their binding to the promoter DNA is oscillated in HEK293 cells. SRC-1, SRC-2, and SRC-3 all enhanced IkappaB alpha transcription. However, the interaction of each coactivator with the promoter exhibited different patterns. After tumor necrosis factor-alpha treatment, SRC-1 signal was increased gradually, but SRC-2 signal was reduced immediately, suggesting replacement of SRC-2 by SRC-1. SRC-3 signal was increased at 30 min, reduced at 60 min, and then increased again at 120 min, suggesting an oscillation of SRC-3. The corepressors were recruited to the promoter together with the coactivators. The binding pattern suggests that the corepressor proteins formed two types of corepressor complexes, SMRT-HDAC1 and NCoR-HDAC3. The two complexes exhibited a switch at 30 and 60 min. The functions of cofactors were confirmed by gene overexpression and RNA interference-mediated gene knockdown. These data suggest that gene transactivation by the transcription factor NF-kappaB is subject to the regulation of a dynamic balance between the coactivators and corepressors. This model may represent a mechanism for integration of extracellular signals into a precise control of gene transcription.

Animals↗
PubMed2005

TIP30 regulates apoptosis-related genes in its apoptotic signal transduction pathway.

AIM: To investigate the role of TIP30 in apoptotic signal pathway in hepatoblastoma cells and to provide a basis for TIP30 as a gene therapy candidate in the regression of hepatoblastoma cells. METHODS: Apoptosis of human hepatoblastoma cell lines HepG2 (p53 wild), Hep3B (p53 null) and PLC/RPF/5 (p53 mutant) infected with Ad-TIP30 (bearing a wild type human Tip30 gene) were analyzed and p53, Bax and Bcl-xl expression levels were compared among these cells. MTT assay, DNA fragmentation, in situ 3' end labeling of DNA, annexin-V FITC staining were used to detect cell death and apoptosis in cells at various time intervals subsequent to infection, and to determine whether TIP30 had an effect on the expression levels of some apoptosis-related gene products such as Bax, p53 and Bcl-xl. A similar time course experiment was performed by Western blotting. RESULTS: In MTT assay, the viability of HepG2 cells decreased significantly from 99.7% to 10% and displayed more massive cell death within 5-8 d than Hep3B and PLC/RPF/5 cells, with their viability decreased from 97.8% to 44.3% and 98.1% to 50.4%, respectively. In annexin-V FITC assay, the percentage of apoptosis cells in HepG2 cells was two to three-fold higher than that in control cells (infected with Ad-GFP), two-fold higher than that in Hep3B cells and 1.4-fold higher than that in PLC/RPF/5 cells 36 h after infection, respectively. Moreover, in HepG2 cells, the p53 began to increase 6-8 h after infection, reaching a maximum level between 8 and 12 h after infection and then dropped. Bax showed a similar increase in the cells as p53 reached the maximum at 8-12 h and subsequently decreased. Interestingly, Bcl-xl protein levels were down regulated during 24 to 36 h after Ad-TIP30 infection. In contrast, ectopic expression of TIP30 in Hep3B and PLC/RPF/5 cells had no effect on the regulation of Bax expression, but had an effect on Bcl-xl levels. In comparison with HepG2 cells, these data suggested that up-regulation of p53 levels by TIP30 might be a pre-requisite for Bax and Bax/Bcl-xl ratio increase. We hypothesized that TIP30 might regulate Bax gene partly through p53, which sensitizes cells to apoptosis by involving a p53 apoptosis signal transduction pathway. CONCLUSION: TIP30 plays an important role in predisposing hepatoblastoma cells to apoptosis through regulating expression levels of these genes. Ad-TIP30 carrying exogenous TIP30-anti-tumor genes may be regarded as a potential candidate for the treatment of hepatocellular carcinoma.

Acetyltransferases↗
PubMed2005

Olanzapine attenuates the okadaic acid-induced spatial memory impairment and hippocampal cell death in rats.

It is hypothesized that olanzapine, an atypical antipsychotic drug, has beneficial effects on cognitive impairment and neuropathological changes in treating neurodegenerative diseases. In the present study, we investigated the effects of chronic administration of olanzapine on the spatial memory impairment and hippocampal cell death induced by the direct injection of okadaic acid (OA), a potent neurotoxin, into the rat hippocampus. After being pretreated with olanzapine (0.5 or 2 mg/kg/day, i.p.) for 2 weeks, the rats were unilaterally microinjected with OA (100 ng) into the hippocampus, and then were continuously administrated with olanzapine for an additional week The rats were trained on a spatial memory task in an eight-arm radial maze before OA administration, and tested on the same task 18 h after the last olanzapine injection. After the behavioral test, the rats were killed for Nissl staining and terminal deoxynucleutidyl transferase-mediated biotinylated UTP nick end labeling staining. OA significantly induced spatial memory impairment, and caused pyramidal cell loss in the CAI and apoptotic cell death in the hippocampus. Olanzapine significantly attenuated OA-induced spatial memory impairment and the OA-induced neuropathological changes in the hippocampus. These findings suggest that olanzapine may have therapeutic effects in treatment of cognitive impairment and neuropathological changes of schizophrenia and other neurodegenerative diseases.

Analysis of Variance↗
PubMed2005

[Effects of tumor suppressing gene TIP30/CC3 on the growth of tumor cells].

OBJECTIVE: To introduce the newly found gene TIP30/CC3 into a hepatoma cell line PLC/PRF/5 and select the stable expression clones. The growth and cell cycles were studied with the clones stably expressing TIP30/CC3 or anti-TIP30/CC3, and the effects of TIP30/CC3 gene on hepatoma cells were analyzed. METHODS: The internal expression of TIP30/CC3 protein was detected with Western blot, then TIP30/CC3 or anti-TIP30/CC3 cDNA was subcloned into a constitutive vector pcDNA3 followed by transfection into PLC/PRF/5. Stable expression clones were selected. The cell growth curve was made and cell cycles detected using flow cytometry. To confirm the results in vitro, stable-expressing cells were implanted subcutaneously into nude mice and time of tumor formation recorded and tumor volume measured. RESULTS: PLC-anti-TIP30 grew faster than the others. Three days after transfection, live cells of PLC-anti-TIP30 were 14.0*10(4), in comparison with the control PLC-DNA3 and PLC/PRF/5, the differences were statistically significant. Live cells of PLC-TIP30 were 4.9*10(4), significantly less than the two control groups. Six days after transfection, live cells of PLC-anti-TIP30 were 25.0*10(4), significantly more than the controls PLC-DNA3 and PLC/PRF/5. Live cells of PLC-TIP30 were 12.4*10(4), significantly less than the two control groups. Cell cycle analysis showed that PLC-anti-TIP30 proliferated faster, 22.4% cells were in G0/G1 (gap) phases and 58.6% cells in S (DNA synthesis) phase. The growth of the PLC-anti-TIP30 cell was retarded and many cells were arrested from G1 to S phases. Cells in G0/G1 and S phase were 44.2% and 33.3% respectively. Furthermore, the average time of tumor formation was shorter in anti-TIP30 group and longer in TIP30/CC3 group, and times were 6.0 d (with control groups) and 15.6 d (with control groups) respectively. Tumors in the nude mice grew faster in PLC-anti-TIP30 group and slower in PLC-TIP30 group. CONCLUSION: Tumor suppressor gene TIP30/CC3 can inhibit the proliferation of tumor cells and interfere in its cell cycles. It can be used as a valuable tool for hepatoma biotherapy including gene therapy.

Acetyltransferases↗
PubMed2005

[Construction of recombinant Escherichia coli strains producing poly (4-hydroxybutyric acid) homopolyester from glucose].

The aim of this study is to construct recombinant Escherichia coli strains capable of producing poly(4-hydroxybutyric acid) homopolyester from glucose as sole carbon source. A glutamate: succinate semialdehyde transaminase gene from Escherichia coli, a glutamate decarboxylase gene from E. coli, and a 4-hydroxybutyrate dehydrogenase gene from Ralstonia eutropha were cloned by PCR and assembled onto the plasmid pKSSE5.3 which haboured the PHA synthase gene from Ralstonia eutropha and 4-hydroxybutyrate: CoA transferase from Clostridium kluyveri. The resulting plasmids were transformed into E. coli and the pathway for biosynthesis of poly(4-hydroxybutyric acid) from glucose via alpha-ketoglutarate, an intermediate in TCA cycle was established in recombinant E. coli strains. Recombinant strains synthesized the homopolyester P(4HB), when cells were cultivated in Luria-Bertani broth with glucose as carbon source. P(4HB) accumulation was enhanced up to 30% of cell dry weight, when cells were cultivated in mineral salts M9 medium plus glucose as sole carbon source with addition of yeast extract, tryptone, casein hydrolate into medium respectively.

Cloning, Molecular↗
PubMed2005

[Clinical observation of microwave endometrial ablation for treatment of abnormal uterine bleeding].

OBJECTIVE: To evaluate the efficacy, indication, and complication of microwave endometrial ablation (MEA) in treating abnormal uterine bleeding (AUB). METHODS: One hundred and sixty-eight women with AUB due to benign causes received MEA treatment. Pre-operative endometrial thinning was carried out using uterine curettage. Then, the applicator radiating microwaves was moved by progressive withdrawal as well as "W" shape motion inside uterine cavity. All the patients were followed-up. The change of menstrual cycle, the amount of flow, dysmenorrhoea, anemia after treatment at 1, 3, 6, 12 and 24 months was recorded. RESULTS: The mean operating time was (286 +/- 75) seconds. Average follow-up time was (22 +/- 6, range 6-36) months. Of these patients, 156 women (92.9%) were premenopausal, 97 cases (62.2%) were amenorrhea, 56 cases (35.9%) were hypomenorrhoea or eumenorroea, and 3 cases (1.9%) had irregular bleeding. The overall satisfaction of this treatment reached 98.1% (153/156). The follow-up of 119 cases was up to 24 months after operation. The concentration of hemoglobin in 107 women with anemia increased significantly from (83 +/- 24) g/L to (117 +/- 18) g/L 3 months after operation (P < 0.01). Dysmenorrhoea was relieved in 74.5% (35/47) patients. No bleeding occurred in any one of 12 postmenopausal patients after MEA. There was no intraoperative complication in any case. The procedure was successful in all of 47 patients with severe medical disorders. After operation, 12 cases were complicated with endometritis, 2 with hematometra, and one case was performed with hysterectomy due to postablation tubal sterilization syndrome. CONCLUSIONS: MEA is a simple, safe and effective treatment of patients with abnormal uterine bleeding, especially suitable for those women associated with severe medical complications. Complete endometrial ablation is one of the most important determinants of treatment success. Stringent selection of patients may reduce the rate of complications.

Endometrial Ablation Techniques↗
PubMed2005

Present status and changes of the phytoplankton community after invasion of Neosalanx taihuensis since 1982 in a deep oligotrophic plateau lake, Lake Fuxian in the subtropical China.

Phytoplankton assemblages in the subtrophical oligotrophic Lake Fuxian, the second deepest lake in China, were investigated monthly from September 2002 to August 2003. A total of 113 species belonging to seven phyla were identified, among them, a filamentous green alga, Mougeotia sp., dominated almost throughout the study period and comprised most of the total phytoplankton biomass. Mougeotia sp. has made a substantial development during the past decades: it was absent in 1957, only occasionally present in 1983, increased substantially in 1993, and became predominant in 2002-2003. It is likely that natural invasion of the Taihu Lake noodlefish (Neosalanx taihuensis) has led to a change of dominant herbivorous zooplankton from small to large calanoid, which has increased grazing pressure on small edible algae, and thus has indirectly favored the development of the inedible filamentous Mougeotia sp.

Animals↗
PubMed2005

[Flow cytometry-pathology combined study of breast cancer].

OBJECTIVE: To study the relation between histopathologic grading and some of the cytogenetic and molecular biology characteristics of breast cancer. METHODS: On the basis of estrogen receptor (ER) expression, DNA content, S-phase fraction (SPF), bcl-2 and mutant p53 protein (mtp53) expression were examined by FCM in 121 breast cancer patients. In 66 patients with invasive ductal breast cancer, histopathologic grading was also examined. RESULTS: The aneuploidy rate and DNA index (DI) were significantly different in grade I, II and III breast cancer. SPF and mtp53 expression significantly increased with increase in histopathologic grading (P < 0.05), but bcl-2 did not show this trend. SPF and mtp53 expression were significantly more in breast cancer with negative ER than in those with positive ER (P < 0.05). Again, no such differences in bcl-2 regardless of ER expression. Correlations existed between DI vs SPF, DI vs mtp53, and SPF vs mtp53 expressions (P < 0.01) but bcl-2 did not correlate with any one of them. CONCLUSION: Cytogenetic and molecular biology studies on the basis of histopathologic grading may provide more information in prognostic prediction of breast cancer.

Adolescent↗
PubMed2005

[Study of the characterization of beta-cyclodextrin-acetylferrocene-thiosemicarbazone inclusion complex and micro-environmental effects].

Inclusion complex of acetylferrocene-thiosemicarbazone(TAF) with beta-cyclodextrin(beta-CD) has been prepared by using kneading method. Elemental analysis and the solubility determination proved that 1:1 inclusion complex has been formed. Characterization of the inclusion complex was studied by UV, FTIR, and X-ray diffractometry. The association constant was calculated to be 227 L x mol(-1) from the straight portion of the phase-solubility diagram. Furthermore, the influence of different solvents and pH on UV spectrum of acetylferrocene-thiosemicarbazone and beta-CD -TAF was discussed respectively. The results show that different micro-environment has apparently different effects on electric spectra of guest and inclusion complexes.

Ferrous Compounds↗
PubMed2005

[Immunohistochemical study of RET protein in Hirschsprung's disease and allied Hirschsprung's disorder].

OBJECTIVE: Hirschsprung's Disease (HD) and allied Hirschsprung's disorder (HAD) have very similar clinical manifestations, but there are many different theories about the two diseases. The present study was designed to understand the expression of Ret protein in HD and HAD, and to explore the role of Ret protein in the pathogenesis of HD and HAD. METHODS: Colon specimens from patients with confirmed HD and HAD, including 15 cases of HD (male 12, female 3) and 11 cases of HAD (male 8, female 3) were collected for this study. At the same time normal colon specimens from 10 individuals with other diseases were used as control. The expression of Ret protein in the intestinal tissue was detected by using immunohistochemical SABC technique with mouse anti-Ret monoclonal antibody. RESULTS: In the colon specimens from normal controls and the dilated segments of colon from HD and HAD patients, moderate to large number of Ret-positive cells were observed among the ganglion cells of myenteric plexuses and submucosal plexuses (P > 0.05). On the contrary, Ret-positive cells were not seen in the stenotic segment of colon from HD patients. But there was positive staining in the stenotic segment of the colon from HAD. Moreover, giant ganglion cells showing strongly positive staining could be seen. There were also displastic cells, small cells, and cells with irregular shape. Statistical analysis showed significant differences in Ret cells positivity between the stenotic segment of colon of HD and the normal control (P < 0.001) as well as between HD and HAD (P < 0.001). CONCLUSION: Ret protein may play an important role in the pathogenesis of HD and could not have definite relationship with HAD.

Case-Control Studies↗
PubMed2004

Chronic administration of quetiapine alleviates the anxiety-like behavioural changes induced by a neurotoxic regimen of dl-amphetamine in rats.

We have demonstrated that the atypical antipsychotic drugs prevent cell death in PC12 cells induced by various cytotoxins and have protective effects on methamphetamine-induced neurotoxcity in rats. The present study was designed to examine the possible effects of chronic administration of quetiapine, an atypical antipsychotic drug, on the anxiety-like behavioural consequences of a neurotoxic regimen of dl-amphetamine. Rats were treated with quetiapine (10 mg/kg/day; i.p.) for 33 days. During days 15-19 of this period, the animals were given dl-amphetamine (20 mg/kg/day; s.c.) 1 h after the administration of quetiapine. The repeated administration of dl-amphetamine resulted in a decrease of tyrosine hydroxylase (TH) immunostaining in the caudate putamen, hyperthermia, and anxiety-like behavioural changes. The behavioural changes were indicated by a significant increase in the time spent in the light box in the light/dark box test, an increase in the ratios of ambulation distance inside the inner circle over the total ambulation distance and rearings inside the inner circle over the total rearings in the open field test, and an increase in the time spent in open arms in the elevated plus-maze test. Chronic administration of quetiapine significantly attenuated the dl-amphetamine-induced hyperthermia, and the anxiety-like behavioural changes in the light/dark box and in the open field tests. These results suggest that quetiapine can normalize the dl-amphetamine-induced anxiety-like behavioural changes, and might be helpful in the treatment for amphetamine-induced emotional changes.

Amphetamine↗
PubMed2004

Increased levels of interleukin-10 in serum from patients with hepatocellular carcinoma correlate with profound numerical deficiencies and immature phenotype of circulating dendritic cell subsets.

Increased levels of interleukin (IL)-10 have been described as a negative prognostic indicator for survival in patients with various types of cancer. IL-10 exerts tolerogenic and immunosuppressive effects on dendritic cells, which are crucial for the induction of an antitumor immune response. Blood dendritic cell antigen (BDCA)-2 and BDCA-4 are specifically expressed by CD123(bright) CD11c- plasmacytoid dendritic cells; whereas BDCA-1 and BDCA-3 define 2 distinct subsets of CD11c+ myeloid dendritic cells. In this study, the T-helper cell (Th)1/Th2 cytokine serum profile of 65 hepatocellular carcinoma patients was assessed. We found that serum levels of IL-10 were substantially increased in hepatocellular carcinoma patients as compared with controls. Peripheral blood mononuclear cells from healthy volunteers were exposed to recombinant human (rh)IL-10 in vitro to additionally characterize its impact on distinct blood dendritic cell subsets. A dramatic decrease of all myeloid dendritic cell (MDC) and plasmacytoid dendritic cell (PDC) subsets was detectable after 24 hours of continuous rhIL-10 exposure. Moreover, the expression of HLA-DR, CD80 and CD86, was significantly reduced on rhIL-10-treated dendritic cell subsets. Direct ex vivo flow cytometric analysis of various dendritic cell subpopulations in peripheral blood from hepatocellular carcinoma patients revealed an immature phenotype and a substantial reduction of circulating dendritic cells that was associated with increased IL-10 concentrations in serum and with tumor progression. These findings confirm a predominantly immunosuppressive role of IL-10 for circulating dendritic cells in patients with hepatocellular carcinoma and, thus, may indicate novel aspects of tumor immune evasion.

Adult↗
PubMed2004

Online CE-MALDI-TOF MS using a rotating ball interface.

We report on the construction and performance of a rotating ball interface for online coupling of capillary electrophoresis (CE) to matrix-assisted laser desorption ionization (MALDI) mass spectrometry with a time-of-flight (TOF) mass analyzer. The interface is based on a rotating stainless steel ball that transports samples from atmospheric pressure to the high vacuum of the mass spectrometer for desorption and ionization. The sample is deposited directly from a 50-microm-i.d. separation capillary onto the 19-mm ball that is rotating at 0.03 to 0.3 rpm. The sample is mixed online with matrix flowing from a separate 50-microm-i.d. capillary. The sample deposit dries before it is rotated past a polymer gasket and into the laser ionization region. Cleaning of the interface is accomplished using solvent-saturated felt, which cleans the ball surface after it rotates out of the ionization chamber. On-line CE-MALDI is demonstrated, and the performance is evaluated with the analysis of a mixture of three peptides: [Lsy8] vasopressin, substance P, and neurotensin. The rotating ball interface to MALDI-TOF MS demonstrated mass detection limit in the high femtomole range. The interface has negligible memory effect and shows no significant electrophoretic peak broadening when operated under optimized conditions.

Electrochemistry↗