Biomedical subjects

Bo Zhang

Publications and source records attributed to Bo Zhang.

At least 37 records · Page 2Linked to original sources

PubMed2007

Anti-proliferative activity of fenretinide in human hepatoma cells in vitro and in vivo.

N-(4-hydroxyphenyl)-retinamide (fenretinide) is a synthetic derivative of all-trans-retinoic acid and induces apoptosis in several cancer cell lines. We determined the anti-cancer activity of fenretinide using human hepatoma cell lines, Bel-7402, HepG2 and Smmc-7721. An in-vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that fenretinide exhibited growth inhibition in these cell lines, with IC50 values ranging from 13.1 to 15.5 micromol/l. In Bel-7402 cells, apoptosis with 15 micromol/l fenretinide for 0 and 48 h was 3 and 48%, respectively. In-vivo studies using the Bel-7402 xenografted athymic mouse model showed tumor inhibition rates ranging from 37.2 to 57.2%, with fenretinide administration once per 3 days at the rate of 25-100 mg/kg. Western blot analysis further showed down-regulation of procaspase-3, X-linked inhibitor of apoptosis protein and poly(ADP-ribose) polymerase cleavage in Bel-7402 cells treated with 15 mumol/l fenretinide for 48 h. Overexpression of p53 was observed in a time-dependent manner, along with a decrease in the Bcl-2/Bax ratio. Depolarized mitochondrial membranes were found in fenretinide-induced apoptotic cells, in a time-dependent manner. We conclude that fenretinide effectively inhibits the proliferation of Bel-7402, both in vitro and in vivo. Both procaspase-3 and p53-mediated apoptotic pathways are involved in its potent anti-cancer activity.

Animals↗

PubMed2007

Do valsartan and losartan have the same effects in the treatment of coronary artery disease?

BACKGROUND: Many angiotensin II type 1 receptor blockers (ARBs) are available for clinical use, but because they do not all have the same effects, the present study investigated whether all benefits conferred by ARBs are class effects. METHODS AND RESULTS: Study 1 was a case-control study of patients with coronary artery disease, which showed that a non-depressor dose of valsartan significantly decreased the rate of target lesion revascularization at 6 months after stenting compared with the control group without ARB treatment. In Study 2, 44 patients with acute myocardial infarction who randomly received an initial lower dose of either valsartan or losartan after stenting were evaluated. The late loss and decrease in %diameter stenosis in the valsartan group were significantly lower than those in the losartan group as assessed by quantitative coronary angiography after 6 months. In addition, the valsartan group showed a significantly lower expression of intracellular adhesion molecule-1 and L-selectin. CONCLUSION: A non-depressor dose of ARB may have beneficial effects on coronary restenosis that are associated with the regulation of adhesion molecules, and these effects might not be a class effect of ARBs.

Aged↗

PubMed2006

DNA damage induces N-acetyltransferase NAT10 gene expression through transcriptional activation.

NAT10 (N-acetyltransferase 10) is a protein with histone acetylation activity and primarily identified to be involved in regulation of telomerase activity. The presented research shows its transcriptional activation by genotoxic agents and possible role in DNA damage. NAT10 mRNA could be markedly increased by using hydrogen peroxide (H2O2) or cisplatin in a dose- and time-dependent way, and the immunofluorescent staining revealed that the treatment of H2O2 or cisplatin induced focal accumulation of NAT10 protein in cellular nuclei. Both H2O2 and cisplatin could stimulate the transcriptional activity of the NAT10 promoter through the upstream sequences from -615 bp to +110 bp, with which some nuclear proteins interacted. Ectopic expression of NAT10 could enhance the number of survival cells in the presence of H2O2 or cisplatin. The above results suggested that NAT10 could be involved in DNA damage response and increased cellular resistance to genotoxicity.

Acetyltransferases↗

PubMed2006

Cloning and characterization of the genes encoding a glycine betaine ABC-type transporter in Halobacillus trueperi DSM10404T.

By using Southern blot hybridization and inverse polymerase chain reaction, a 5.5-kb DNA fragment was obtained from the genomic DNA of Halobacillus trueperi DSM10404(T). Sequence analysis revealed that it contained a potential operon with high levels of sequence similarity to the opuA operon encoding glycine betaine transporter from Bacillus subtilis, which is a member of the ATP-binding cassette (ABC) substrate binding the protein-dependent transporter superfamily. The potential operon, designated as qatA (quaternary amine transporter), consists of three structural genes, which are predicted to encode an ATP-binding protein (QatAA), a membrane-associated protein (QatAB), and an extracellular substrate-binding protein (QatAC). Moreover, the putative promoter region of the operon was found with close homology to the sigma(A)-dependent promoter of B. subtilis. Reverse transcription (RT)-PCR analysis revealed that qatAA, qatAB, and qatAC genes were transcribed in cells of H. trueperi. Cells of Escherichia coli mutant MKH13 harboring qatA on pAY41 were able to grow on selective M9 salt medium containing glycine betaine and accumulated glycine betaine in the cytoplasm, showing that qatAA, qatAB, and qatAC genes together encode a functional glycine betaine transporter.

ATP-Binding Cassette Transporters↗

PubMed2006

Ionic conductivity of the aqueous layer separating a lipid bilayer membrane and a glass support.

The in-plane ionic conductivity of the approximately 1-nm-thick aqueous layer separating a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer membrane and a glass support was investigated. The aqueous layer conductivity was measured by tip-dip deposition of a POPC bilayer onto the surface of a 20- to 75-microm-thick glass membrane containing a single conical-shaped nanopore and recording the current-voltage (i-V) behavior of the glass membrane nanopore/POPC bilayer structure. The steady-state current across the glass membrane passes through the nanopore (45-480 nm radius) and spreads radially outward within the aqueous layer between the glass support and bilayer. This aqueous layer corresponds to the dominant resistance of the glass membrane nanopore/POPC bilayer structure. Fluorescence recovery after photobleaching measurements using dye-labeled lipids verified that the POPC bilayer maintains a significant degree of fluidity on the glass membrane. The slopes of ohmic i-V curves yield an aqueous layer conductivity of (3 +/- 1) x 10(-3) Omega(-1) cm(-1) assuming a layer thickness of 1.0 nm. This conductivity is essentially independent of the concentration of KCl in the bulk solution (10-4 to 1 M) in contact with the membrane. The results indicate that the concentration and mobility of charge carriers in the aqueous layer between the glass support and bilayer are largely determined by the local structure of the glass/water/bilayer interface.

Electric Conductivity↗

PubMed2006

Flavodoxin hydroquinone reduces Azotobacter vinelandii Fe protein to the all-ferrous redox state with a S = 0 spin state.

Azotobacter vinelandii flavodoxin hydroquinone (FldHQ) is a physiological reductant to nitrogenase supporting catalysis that is twice as energy efficient (ATP/2e- = 2) as dithionite (ATP/2e- = 4). This catalytic efficiency results from reduction of Fe protein from A. vinelandii (Av2) to the all-ferrous oxidation state ([Fe4S4]0), in contrast to dithionite, which only reduces Av2 to the [Fe4S4]1+ state. Like FldHQ, Ti(III) citrate yields ATP/2e- = 2, and Ti(III)-reduced [Fe4S4]0 Av2 has a S = 4 spin state and characteristic Mossbauer spectrum, a parallel mode g = 16.4 EPR signal, and a shoulder at 520 nm in its UV-vis spectrum, each of which distinguish the S = 4 [Fe4S4]0 Av2 from other states. In this study, we demonstrate that FldHQ makes [Fe4S4]0 Av2, which is sufficiently characterized to demonstrate unique physical properties that distinguish it from the previously characterized Ti(III)-reduced [Fe4S4]0 Av2. In particular, Evans NMR magnetic susceptibility and EPR measurements indicate that FldHQ-reduced [Fe4S4]0 Av2 has an S = 0 spin state (like [Fe4S4]2+ Av2). There is no g = 16.4 EPR signal and no shoulder at 520 nm in its absorbance spectrum, which resembles that of [Fe4S4]1+ Av2. That the physiological reductant to Av2 is capable of forming [Fe4S4]0 Av2 has important implications for in vivo nitrogenase activity.

Azotobacter vinelandii↗

PubMed2006

Calcium influx through If channels in rat ventricular myocytes.

The hyperpolarization-activated, cyclic nucleotide-gated (HCN) channels, or cardiac (I(f))/neuronal (I(h)) time- and voltage-dependent inward cation current channels, are conventionally considered as monovalent-selective channels. Recently we discovered that calcium ions can permeate through HCN4 and I(h) channels in neurons. This raises the possibility of Ca(2+) permeation in I(f), the I(h) counterpart in cardiac myocytes, because of their structural homology. We performed simultaneous measurement of fura-2 Ca(2+) signals and whole cell currents produced by HCN2 and HCN4 channels (the 2 cardiac isoforms present in ventricles) expressed in HEK293 cells and by I(f) in rat ventricular myocytes. We observed Ca(2+) influx when HCN/I(f) channels were activated. Ca(2+) influx was increased with stronger hyperpolarization or longer pulse duration. Cesium, an I(f) channel blocker, inhibited I(f) and Ca(2+) influx at the same time. Quantitative analysis revealed that Ca(2+) flux contributed to approximately 0.5% of current produced by the HCN2 channel or I(f). The associated increase in Ca(2+) influx was also observed in spontaneously hypertensive rat (SHR) myocytes in which I(f) current density is higher than that of normotensive rat ventricle. In the absence of EGTA (a Ca(2+) chelator), preactivation of I(f) channels significantly reduced the action potential duration, and the effect was blocked by another selective I(f) channel blocker, ZD-7288. In the presence of EGTA, however, preactivation of I(f) channels had no effects on action potential duration. Our data extend our previous discovery of Ca(2+) influx in I(h) channels in neurons to I(f) channels in cardiac myocytes.

Animals↗

PubMed2006

Rapid and simultaneous quantification of 4 urinary proteins by piezoelectric quartz crystal microbalance immunosensor array.

BACKGROUND: Urinary proteins are predictive and prognostic markers for diabetes nephropathy. Conventional methods for the quantification of urinary proteins, however, are time-consuming, and most require radioactive labeling. We designed a label-free piezoelectric quartz crystal microbalance (QCM) immunosensor array to simultaneously quantify 4 urinary proteins. METHODS: We constructed a 2 x 5 model piezoelectric immunosensor array fabricated with disposable quartz crystals for quantification of microalbumin, alpha1-microglobulin, beta2-microglobulin, and IgG in urine. We made calibration curves after immobilization of antibodies at an optimal concentration and then evaluated the performance characteristics of the immunosensor with a series of tests. In addition, we measured 124 urine samples with both QCM immunosensor array and immunonephelometry to assess the correlation between the 2 methods. RESULTS: With the QCM immunosensor array, we were able to quantify 4 urinary proteins within 15 min. This method had an analytical interval of 0.01-60 mg/L. The intraassay and interassay imprecisions (CVs) were <10%, and the relative recovery rates were 90.3%-109.1%. Nonspecificity of the immunosensor was insignificant (frequency shifts <20 Hz). ROC analyses indicated sensitivities were > or =95.8% and, specificities were > or =76.3%. Bland-Altman difference plots showed the immunosensor array to be highly comparable to immunonephelometry. CONCLUSIONS: The QCM system we designed has the advantages of being rapid, label free, and highly sensitive and thus can be a useful supplement to commercial assay methods in clinical chemistry.

Alpha-Globulins↗

PubMed2006

Differential expression within the LOX gene family in ripening kiwifruit.

Real-time quantitative PCR was used to study lipoxygenase (LOX) gene expression patterns in kiwifruit (Actinidia deliciosa [A. Chev.] C.F. Liang et A.R. Ferguson var. deliciosa cv. Hayward) during fruit ripening, and in response to ethylene and low temperature during post-harvest storage. Six LOX genes were identified and cloned from a kiwifruit EST database. All were expressed in vegetative tissues and in the fruit. Expression of AdLox1 and AdLox5 increased markedly as fruit developed to the climacteric stage and were up-regulated by ethylene treatment, following a similar pattern to LOX enzyme activity. By contrast, AdLox2, AdLox3, and AdLox4 transcripts were negatively associated with ethylene accumulation, and ethylene application enhanced the decline in transcript levels. Transcripts of AdLox6 declined with fruit ripening. The fruit showed no ripening changes at low temperature, where transcripts of AdLox1 and AdLox6 were slightly induced about 72 h after harvest, suggesting an adaptive response to low temperature. Transient expression of the ethylene-responsive AdLox1 gene in tobacco leaves led to significant degradation of chlorophyll and promoted tissue senescence, whereas AdLox2 had no such effect. The results showed that the six LOX genes were differentially regulated during kiwifruit ripening and senescence, forming two groups, one active in ripening and responsive to ethylene and the other more constitutively expressed. The possible roles of individual LOX isoforms in kiwifruit are discussed.

Actinidia↗

PubMed2006

Effect of levothyroxine on total lipid profiles as assessed by analytical capillary isotachophoresis in a patient with hypothyroidism.

The patient was a 51-year-old Japanese female who had been diagnosed with hyperlipidemia. At the first medical examination, her serum levels of total cholesterol (TC) and triglyceride (TG) were 482 and 205 mg/dl, respectively. Since hyperlipidemia was not improved by pravastatin, atorvastatin or niceritrol, and since the levels of thyroid-stimulating hormone (TSH) and free T4 were 730 IU/ml and 0.3 ng/dl, respectively, the patient was diagnosed as secondary hyperlipidemia with hypothyroidism. A method for the charge isolation of lipoproteins using capillary isotachophoresis (cITP) is proposed as a clinical application because it allows us to quantitatively measure electronegative low-density lipoprotein cholesterol (LDL-C), a potent marker of coronary heart disease. After 5 months of treatment with levothyroxine, Serum TC and LDL-C levels drastically decreased without statin treatment and high-density lipoprotein cholesterol (HDL-C) increased. In the lipoprotein profiles as assessed by cITP after treatment with levothyroxin, all HDL-C subfractions were increased and fast-migrating LDL/electronegative LDL appeared to be greatly reduced after treatment, while the area under the non-modified LDL peak was increased. The cITP analysis was able to obtain more information about coronary risk factors and may be clinically useful for evaluating the effect of treatment with levothyroxine in patients with hypothyroidism and secondary hyperlipidemia.

Electrophoresis, Capillary↗

PubMed2006

A novel endothelial-specific heat shock protein HspA12B is required in both zebrafish development and endothelial functions in vitro.

A zebrafish transcript dubbed GA2692 was initially identified via a whole-mount in situ hybridization screen for vessel specific transcripts. Its mRNA expression during embryonic development was detected in ventral hematopoietic and vasculogenic mesoderm and later throughout the vasculature up to 48 hours post fertilization. Morpholino-mediated knockdown of GA2692 in embryos resulted in multiple defects in vasculature, particularly, at sites undergoing active capillary sprouting: the intersegmental vessels, sub-intestinal vessels and the capillary sprouts of the pectoral fin vessel. During the course of these studies, a homology search indicated that GA2692 is the zebrafish orthologue of mammalian HspA12B, a distant member of the heat shock protein 70 (Hsp70) family. By a combination of northern blot and real-time PCR analysis, we showed that HspA12B is highly expressed in human endothelial cells in vitro. Knockdown of HspA12B by small interfering RNAs (siRNAs) in human umbilical vein endothelial cells blocked wound healing, migration and tube formation, whereas overexpression of HspA12B enhanced migration and accelerated wound healing - data that are consistent with the in vivo fish phenotype obtained in the morpholino-knockdown studies. Phosphorylation of Akt was consistently reduced by siRNAs against HspA12B. Overexpression of a constitutively active form of Akt rescued the inhibitory effects of knockdown of HspA12B on migration of human umbilical vein endothelial cells. Collectively, our data suggests that HspA12B is a highly endothelial-cell-specific distant member of the Hsp70 family and plays a significant role in endothelial cells during development and angiogenesis in vitro, partially attributable to modulation of Akt phosphorylation.

Alkaline Phosphatase↗

PubMed2006

Screening for genes essential for mouse embryonic stem cell self-renewal using a subtractive RNA interference library.

The pluripotency of mouse embryonic stem (ES) cells is maintained by self-renewal. To screen for genes essential for this process, we constructed an RNA interference (RNAi) library by inserting subtracted ES cell cDNA fragments into plasmid containing two opposing cytomegalovirus promoters. ES cells were transfected with individual RNAi plasmids and levels of the pluripotency marker Oct-4 were monitored 48 hours later by real time RT-PCR. Of the first 89 RNAi plasmids characterized, 12 downregulated Oct-4 expression to less than 50% of the normal level and 7 of them upregulated Oct-4 expression to more than 150% of the normal level. To investigate their long-term effect on self-renewal, ES cells were transfected by these 19 RNAi plasmids individually and G418-resistant colonies were subjected to alkaline phosphatase (AP) staining after 7 days selection. Except for 4 plasmids that caused cell death, the ratio of AP positive colonies was repressed to less than 60% of the control group by the other 15 plasmids and even below 20% by 10 plasmids. The cDNA fragments in these 10 plasmids correspond to eight genes, including Zfp42/Rex-1, which was chosen for further functional analysis. RNAi knockdown of Zfp42 induced ES cells differentiate to endoderm and mesoderm lineages, and overexpression of Zfp42 also caused ES cells to lose the capacity of self-renewal. Our results indicate that RNAi screen is a feasible and efficient approach to identify genes involved in ES cells self-renewal. Further functional characterization of these genes will promote our understanding of the complex regulatory networks in ES cells.

Animals↗

PubMed2006

Genome-wide linkage analysis of heroin dependence in Han Chinese: results from wave one of a multi-stage study.

The contribution of genes to the etiology of heroin dependence is greater than for any other illicit drug. The specific genes mediating this effect remain unknown, despite several candidate gene association studies of the condition. Here we report the results of a genome-wide search for heroin dependence susceptibility loci using multipoint linkage analysis. In phase I, we ascertained 207 independent affected sibling pairs from 202 Han Chinese families from Yunnan Province, China (near Asia's "Golden Triangle"). After data-cleaning, 194 fully independent sibling pairs (i.e., with no overlapping individuals) from 192 families were genotyped on 404 short tandem-repeat markers spaced at an average inter-marker distance of 9 cM. Although none of our findings achieved genome-wide significance, we found two regions with non-parametric linkage (NPL) Z-scores greater than 2.0. An NPL Z-score of 2.19 (uncorrected P-value = 0.014) was observed at D4S1644, located at 143.3 cM on chromosomal region 4q31.21. The highest NPL Z-score of 2.36 (uncorrected P-value = 0.009) was observed at 53.4 cM on chromosomal region 17q11.2 at marker D17S1880. This is among the first published reports of a genome-wide linkage analysis of heroin dependence. Forthcoming results from other groups and from two additional waves of ascertainment (one planned, one currently ongoing) for our own study should be able to support or refute the putative susceptibility loci we have identified, after which positional candidate genes can be further evaluated as risk factors for the illness.

China↗

PubMed2006

Lower level of low-density lipoprotein cholesterol by statin prevents progression of coronary restenosis after successful stenting in acute myocardial infarction.

OBJECTIVE: It is unclear whether the reduction of coronary restenosis by statins is due to a decrease in low-density lipoprotein (LDL) cholesterol and/or pleiotropic effects. Therefore, we performed quantitative coronary angiography (QCA) and analyzed the lipid profile and changes in adhesion molecules and chemokines caused by statin in patients with acute myocardial infarction (AMI). METHODS: The subjects included AMI patients who had initial coronary angiograms and significant coronary stenosis and were implanted with a stent. After stent implantation, patients were treated either with (n = 36) or without (n = 14) statin. The primary end-point for this study was the absolute changes in the lipid profile, C-reactive protein (CRP), adhesion molecules, chemokines and stenosis measured by QCA between the post-stent and follow-up angiogram at 6 months after stenting. RESULTS: Treatment with statin reduced % coronary diameter stenosis (DS) and was associated with a greater reduction in LDL cholesterol at 6 months after stenting in patients with acute myocardial infarction (AMI), while there were no differences in adhesion molecules, chemokines, CC chemokine receptor or CXC chemokine receptor. Interestingly, changes in % DS between before and after statin treatment at 6 months (Delta%DS) were positively correlated with DeltaLDL cholesterol, and patients who had an LDL cholesterol level of less than 80 mg/dl had a significantly lower Delta%DS. In addition, Delta%DS was significantly related only to the reduction in LDL cholesterol as assessed by a stepwise multivariable regression analysis. CONCLUSION: These results suggest that the lower level of LDL cholesterol is the most critical factor in preventing coronary restenosis.

Aged↗

PubMed2006

Ferritin-catalyzed consumption of hydrogen peroxide by amine buffers causes the variable Fe2+ to O2 stoichiometry of iron deposition in horse spleen ferritin.

Ferritin catalyzes the oxidation of Fe2+ by O2 to form a reconstituted Fe3+ oxy-hydroxide mineral core, but extensive studies have shown that the Fe2+ to O2 stoichiometry changes with experimental conditions. At Fe2+ to horse spleen ferritin (HoSF) ratios greater than 200, an upper limit of Fe2+ to O2 of 4 is typically measured, indicating O2 is reduced to 2H2O. In contrast, a lower limit of Fe2+ to O2 of approximately 2 is measured at low Fe2+ to HoSF ratios, implicating H2O2 as a product of Fe2+ deposition. Stoichiometric amounts of H2O2 have not been measured, and H2O2 is proposed to react with an unknown system component. Evidence is presented that identifies this component as amine buffers, including 3-N-morpholinopropanesulfonic acid (MOPS), which is widely used in ferritin studies. In the presence of non-amine buffers, the Fe2+ to O2 stoichiometry was approximately 4.0, but at high concentrations of amine buffers (0.10 M) the Fe2+ to O2 stoichiometry is approximately 2.5 for iron loadings of eight to 30 Fe2+ per HoSF. Decreasing the concentration of amine buffer to zero resulted in an Fe2+ to O2 stoichiometry of approximately 4. Direct evidence for amine buffer modification during Fe2+ deposition was obtained by comparing authentic and modified buffers using mass spectrometry, NMR, and thin layer chromatography. Tris(hydroxymethyl)aminomethane, MOPS, and N-methylmorpholine (a MOPS analog) were all rapidly chemically modified during Fe2+ deposition to form N-oxides. Under identical conditions no modification was detected when amine buffer, H2O2, and O2 were combined with Fe2+ or ferritin separately. Thus, a short-lived ferritin intermediate is required for buffer modification by H2O2. Variation of the Fe2+ to O2 stoichiometry versus the Fe2+ to HoSF ratio and the amine buffer concentration are consistent with buffer modification.

Amines↗

PubMed2006

Influence of the application of three different elicitors on soybean plants on the concentrations of several isoflavones in soybean seeds.

Soybean [Glycine max (L.) Merr.] is a rich source of isoflavones that are often affected by biotic and abiotic factors. The objectives of this study were to evaluate the effect of various concentrations of three natural elicitors applied at different soybean growth stages on isoflavone content and to compare the efficiency of several solvent systems in isoflavone extraction and quantification. The isoflavones extracted from R96-3444 soybean using eight solvent systems were separated, identified, and quantified by a high-performance liquid chromatography (HPLC) procedure. The soybean plants were sprayed with salicylic acid, methyl salicylate, or ethyl acetate at 0, 10(-6), 10(-3), and 10(-1) M at R1 (blooming) or R4 (full pods) growth stage. Results showed that 10(-3) M ethyl acetate sprayed at the R1 stage significantly increased total isoflavone content and the levels of some individual isoflavones in soybean seeds. With all the elicitors that were tested, concentration was a more important factor than application time with respect to isoflavone content with lower concentrations being more effective on most isoflavones. A 53% acetonitrile solvent system was the best solvent system for extracting total isoflavone, malonyl glucosides, genistein, glycitin, genistin, acetyl-daidzin, and acetyl-genistin. The results of this study will be useful for increasing the isoflavone content in desirable soybean varieties and improving isoflavone concentration during extraction.

Acetates↗

PubMed2006

Electrostatic-gated transport in chemically modified glass nanopore electrodes.

Electrostatic-gated transport in chemically modified glass nanopore electrodes with orifice radii as small as 15 nm is reported. A single conical-shaped nanopore in glass, with a approximately 1 microm radius Pt disk located at the pore base, is prepared by etching the exposed surface of a glass-sealed Pt nanodisk. The electrochemical response of the nanopore electrode corresponds to diffusion of redox-active species through the nanopore orifice to the Pt microdisk. Silanization of the exterior glass surface with Cl(Me)(2)Si(CH(2))(3)CN and the interior pore surface with EtO(Me)(2)Si(CH(2))(3)NH(2) introduces pH-dependent ion selectivity at the pore orifice, a consequence of the electrostatic interactions between the redox ions and protonated surface amines. Nanopore electrodes with very small pore orifice radii (< approximately 50 nm) display anion permselectively at pH < 4, as demonstrated by electrochemical measurement of transport through the pore orifice. Ion selective transport vanishes at pH > 6 or when the pore radius is significantly larger than the Debye screening length, consistent with the observed ion selectivity resulting from electrostatic interactions. The ability to introduce different surface functionalities to the interior and exterior surfaces of glass nanopores is demonstrated using fluorescence microscopy to monitor the localized covalent attachment of 5- (and 6)-carboxytetramethylrhodamine succinimidyl ester to interior pore surfaces previously silanized with EtO(Me)(2)Si(CH(2))(3)NH(2).

Biosensing Techniques↗

PubMed2006

A primary sodium pump gene of the moderate halophile Halobacillus dabanensis exhibits secondary antiporter properties.

The primary sodium pump has been proved to be involved in Na(+) extrusion of bacteria. In our present study, a novel gene encoding a putative primary sodium pump was cloned from chromosomal DNA of moderate halophile Halobacillus dabanensis D-8 by functional complementation, which expression resulted in the growth of antiporter-deficient Escherichia coli strain KNabc in the presence of 0.2 M NaCl. The gene was sequenced and designated nap. The deduced amino acid sequence of Nap has 56% identity to NADH dehydrogenase of Bacillus cereus and 55% to NADH oxidase of Bacillus halodurans C-125. E. coli KNabc carrying nap exhibited resistance to uncoupler CCCP (carbonyl-cyanide m-chlorophenylhydrazone). Everted membrane vesicles prepared from E. coli KNabc carrying nap exhibited secondary Na(+)/H(+) antiporter activity, and nap also supported the growth of respiratory-deficient E. coli ANN0222 lacking NADH dehydrogenase. Based on these results, we proposed that Nap possessed both characteristics of secondary Na(+)/H(+) antiporter and primary sodium pump.

Amino Acid Sequence↗