University of North Florida
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Stuart Chalk, Ph.D.
Department of Chemistry
University of North Florida
Phone: 1-904-620-1938
Fax: 1-904-620-3535
Email: schalk@unf.edu
Website: @unf

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Fei Meng Zhou

Abbrev:
Zhou, F.M.
Other Names:
Fei-meng Zhou, Feimeng Zhou
Address:
Department of Chemistry and Biochemistry, California State University, 5151 State University Drive, Los Angeles, CA 90032, USA
Phone:
+1-323-343-2390
Fax:
+1-323-343-6490

Citations 9

"Detection Of Oligonucleotide Hybridization At Femtomolar Level And Sequence-specific Gene Analysis Of The Arabidopsis Thaliana Leaf Extract With An Ultrasensitive Surface Plasmon Resonance Spectrometer"
Nucleic Acids Res. 2002 Volume 30, Issue 14 Pages E72-11
Fayi Song, Feimeng Zhou, Jun Wang, Nongjian Tao, Jianqiao Lin, Robert L. Vellanoweth, Yvonne Morquecho, and Janel Wheeler-Laidman

Abstract: A flow injection (FI) device Is combined, through the use of a low-volume (4 µL) flow cell, with an ultra-sensitive surface plasmon resonance (SPR) spectrometer equipped with a bi-cell photodiode detector. The application of this novel FI-SPR device for sequence-specific ultratrace analysis of oligodeoxynucleotides (ODNs) and polydeoxynucleotides was demonstrated. Self-assembled monolayers of ODN probes are tethered onto Au films with a mercaptohexyl group at the 3 ends. The FI-SPR provides a detection level (less than or equal to54 fM) 2-3 orders of magnitude lower than other SPR devices and compares well with several ultrasensitive detection methods for labeled DNA targets (e.g. fluorophore-tagged and radiolabeled DNA samples). The technique is also highly selective, since a 47 mer ODN target with a single-base mismatch yielded a much smaller SPR signal, and a specific Interaction was detected when the complementary target was present at 0.001% of the total DNA. The FI-SPR was extended to the measurement of two Individual genes In a cDNA mixture transcribed from an Arabidopsis thaliana leaf mRNA pool. The greatly enhanced sensitivity not only obviates the necessity of DNA labeling, but also significantly reduces sample consumption allowing direct quantification of low abundance mRNAs in cellular samples without amplification.

"Surface Structure And Coverage Of An Oligonucleotide Probe Tethered Onto A Gold Substrate And Its Hybridization Efficiency For A Polynucleotide Target"
Langmuir 2001 Volume 17, Issue 4 Pages 1215-1224
Eva Huang, Munlika Satjapipat, Shubo Han, and Feimeng Zhou

Abstract: A single-stranded oligonucleotide whose 5 end is derivatized with a mercaptohexyl tether group was either directly anchored onto a gold surface or attached to a gold surface as part of a mixed self-assembled monolayer that contains mercaptohexanol. The application of these surface-confined DNA oligomers as heterogeneous probes for the detection of polynucleotides (e.g., M13 phage DNA) is considered, with an emphasis on the elucidation of the relationship between the hybridization efficiency and the surface coverage and orientation of the probe molecules. Atomic force microscopy (AFM) and flow injection quartz crystal microbalance (FI-QCM) were used in tandem to study the immobilization of the probe, to estimate the extent and efficiency of the hybridization of M13 phage DNA (7249 bases), and to examine the effect of using a different alkanethiol to reorient the preformed film for a higher hybridization efficiency. The surface density and the resultant hybridization efficiency were found to be highly dependent on the morphology and surface structure of the gold substrate as well as on the concentration of the solution used for the probe fabrication but much less dependent on the probe immobilization time. The lower limit of the hybridization efficiency was estimated to be about 1.1% which is an underestimate because only the resolvable circular features were included in the estimation. Although the duplex formed at the gold surface covered with only the thiolated DNA probe adopts exclusively the orientation in which the target loop is parallel with respect to the substrate surface, the predominant duplex orientation at the gold substrate modified with mixed self-assembled monolayers is tethered to the surface with a small tilt angle versus the surface normal. Visualization of the duplex orientation allows one to understand whether the Sauerbrey equation is valid for the interpretation of certain FI-QCM results. Although it is probably valid to use the Sauerbrey equation to calculate the amount of a polynucleotide at a surface covered only by the thiolated DNA probe, the practice might be questionable for that at the surface with the DNA/alkanethiol mixed SAM on the basis of our AFM images of the target orientations.

"Quantification Of Metals Released By Metallothionein Adsorbates At Mercury Film Electrodes By Electrochemical ICP-atomic Emission Spectrometry"
J. Electroanal. Chem. 2001 Volume 513, Issue 1 Pages 25-35
Alfred J. Baca, Yajaira Garcia, Alejandro L. Briseno and Feimeng Zhou

Abstract: Electrochemistry combined on-line with inductively coupled plasma-atomic emission spectrometry (EC/ICP-AES) was used to study the electrode reactions of rabbit liver metallothionein (MT) adsorbates at thin mercury films (TMFs). Three major oxidation peaks, with peak potentials at -1.20, -0.75 and -0.32 V, were observed. Through the correlation of the DPV characteristics to the elution of the Zn2+ and Cd2+ ions monitored by time-resolved ICP-AES responses, the peak at -1.20 V was assigned to the anodic stripping of Zn(Hg). For the first time, both Zn2+ and Cd2+ were found to be associated with the initial oxidation at -0.75 V by EC/ICP-AES. In the subsequent voltammetric scans, the peak at -0.75 V decreased but remained steady and did not result in the elution of additional metals. The initial decrease in current is suggested to originate from the anodic stripping of the Cd(Hg) amalgam and the Zn-Cd intermetallic compound in the TMF. The anodic peak remaining at -0.75 V was attributed to the formation of the cystine analog from the electrodimerization of the uncomplexed cysteine residues in MT molecules. The quantities of Cd2+ and Zn2+ under the oxidation peaks were measured by EC/ICP-AES. Our work demonstrates that EC/ICP-AES is a viable technique for elucidating relatively complicated electrode reactions that involve metal release and transfer.

"Studies Of Potential-dependent Metallothionein Adsorptions Using A Low-volume Electrochemical Quartz Crystal Microbalance Flow Cell"
J. Electroanal. Chem. 2001 Volume 513, Issue 1 Pages 16-24
Alejandro L. Briseno, Fayi Song, Alfred J. Baca and Feimeng Zhou

Abstract: Adsorptions of metallothioneins (MTs) onto thin mercury films (TMFs) at potentials more negative or positive than the point of zero charge (pzc) of mercury were quantified for the first time, using a novel electrochemical quartz crystal microbalance (EQCM) flow cell in conjunction with a simple flow injection system (FI-EQCM). The EQCM flow cell has a low internal volume (ca. 50 µL) designed for the investigation of biomolecular attachment to surfaces. Such a cell facilitates in-situ gravimetric measurements of MT adsorption processes at different potentials. The amount of the MT adsorption at - 0.9 V, a potential more negative than the pzc of the TMF, was found to be greater than that attached via simple chemisorption (in an open-circuit configuration). The quantity of metals released by the MT adsorbates, measured by electrochemical inductively coupled plasma-atomic emission spectrometry (EC/ICP-AES), was found to constitute similar to 3.8% of the total mass measured by FI-EQCM. The average number of cysteines per MT molecule involved in the Hg-cysteine thiolate formation was found to be 4.2±1.8. Thus, it appears that about 1-2 metal ions (Cd2+) per MT molecule have been released off the TMF electrode since the stoichiometric, ratio between the Cd2+ and the cysteines in a MT molecule is known to be 1/3. The quantitative measurements by the two hybrid electrochemical methods (FI-EQCM and EC/ICP-AES) help elucidate the electrode reactions of MT adsorbates at TMF surfaces and the MT metal transfer processes. (C) 2001 Elsevier Science BN. All rights reserved.
Adsorption

"Nafion-Coated Bismuth Film And Nafion-Coated Mercury Film Electrodes For Anodic Stripping Voltammetry Combined On-Line With ICP-Mass Spectrometry"
J. Am. Soc. Mass Spectrom. 2006 Volume 17, Issue 7 Pages 945-952
Grace X. Cao, Omar Jimenez, Feimeng Zhou and Maotian Xu

Abstract: Nafion-coated bismuth film electrodes (NCBFEs) and Nafion-coated mercury film electrodes (NCMFEs) were used to electrochemically pre-concentrate metal analytes for subsequent analysis by inductively coupled plasma-mass spectrometry (ICP-MS). Either type of electrodes is part of a thin-layer electrochemical flow cell that is positioned upstream of a microconcentric nebulizer for the ICP-MS. Performances of these electrodes were compared in terms of the analytical "figures of merit" (e.g., dynamic ranges, reproducibility, hydrodynamic stability, and elimination of matrix effects detrimental to ICP-MS). The coupled technique (ASV-ICP-MS) is found to possess a wide dynamic range (at least 4 to 5 orders of magnitude) and to be reproducible. Both electrodes are much more stable than the thin mercury film electrode (TMFE) traditionally used for ASV-ICP-MS, with the lifetime of the NCBFE exceeding 8 h. Adopting these electrodes for ASV-ICP-MS overcomes the problems associated with a TMFE, the erosion of which decreases the sample throughput, affects the analysis precision, and contaminates conventional glass nebulizers and spray chambers of the spectrometer. The medium exchange procedure inherent in ASV is successfully implemented with a two-valve flow injection system for the accumulation of trace Cd2+ into the electrode from a certified seawater sample, followed by stripping Cd into a solution that is compatible to the ICP-MS operation.

"Selective Determination Of Methylmercury By Flow Injection Fast-scan Voltammetry"
Electroanalysis 1998 Volume 10, Issue 13 Pages 926-930
Rebecca Lai, Eva L. Huang, Feimeng Zhou *, David O. Wipf

Abstract: A simple flow injection system, suitable for solution flow rates at microliters-per-minute, was combined with fast-scan voltammetry for selective determination of MeHg+. A thin Hg film was formed at a Pt microelectrode prior to the measurement. Detection of MeHg+ is carried out by measuring the oxidation of MeHg radicals that were generated at the Hg microelectrode. At slow scan rates, the electrogenerated MeHg radicals undergo a follow-up dimerization reaction to form M2Hg2 (ErCi2 mechanism). At fast scan rates, MeHg radicals can be quantitatively reoxidized (reversible electron-transfer). Optimization of the experimental conditions of the system was performed based on studies of the relationship between the scan rate and the dimerization rate of the MeHg radical. Under optimized conditions, detection level of sub-nanomole was obtained with a sample consumption <10 µL, and the concentration. detection limit for MeHg+ at 50 V/s was estimated to be ~0.56 µM. To demonstrate the applicability of this method to automatic analysis, repetitive fast-scan cyclic voltammetry was conducted in conjunction with multiple sample injections. Determination of MeHg+ in the presence of excess inorganic Hg was also conducted. This approach to MeHg+ determination was successfully applied to the analysis of elevated dogfish muscle samples.
Methylmercury ion Dogfish Fish Tissue Voltammetry Electrode Electrode Speciation Optimization Apparatus

"Anodic Stripping Voltammetry Combined On-Line With Inductively Coupled Plasma-MS Via A Direct-Injection High-Efficiency Nebulizer"
Anal. Chem. 2003 Volume 75, Issue 10 Pages 2507-2511
Alfred J. Baca, Ana B. De La Ree, Feimeng Zhou and Andrew Z. Mason

Abstract: A direct-injection high-efficiency nebulizer (DIHEN) is used to couple a thin-layer electrochemical flow cell on-line with an ICP-mass spectrometer to perform anodic stripping voltammetry (ASV) at a thin mercury film followed by subsequent ICPMS measurements for the stripped metal analytes. The resultant hyphenated technique (ASV-DIHEN-ICPMS) is capable of analyzing select heavy metals present at ultratrace levels (down to low-ppt to sub-ppt levels) that are lower than the detection limits obtained by conventional ICPMS. In addition to its good analytical performance, the technique offers other attractive features such as the ability to eliminate detrimental matrix effects that can compromise ICPMS analyzes and the possibility of probing electrode reactions involving trace amounts metal species with ICPMS. For conducting ASV on-line with ICPMS, the DIHEN was found to be more advantageous than the microconcentric nebulizer in terms of minimizing memory effects and potential artifacts caused by the erosion of the Hg film into the flowing solution stream. Compared to a direct injection nebulizer (DIN), the DIHEN was easier to operate. Moreover, its simpler design and the lack of back pressure from the DIHEN capillary made it more compatible with coupling to the thin-layer electrochemical cell than a DIN system.

"Quantification Of Dopant Ions In Polypyrrole Films With Electrochemical ICP-atomic Emission Spectrometry And Comparison To Electrochemical Quartz Crystal Microbalance Studies"
Anal. Chim. Acta 2001 Volume 441, Issue 1 Pages 123-134
Alejandro L. Briseno, Alfred Baca, Qizhi Zhou, Rebecca Lai and Feimeng Zhou

Abstract: Quantification of electroinactive dopants in conductive polypyrrole (PPY) films was performed with electrochemistry combined on-line with inductively coupled plasma-atomic emission spectrometry (EC/ICP-AES). Anion (HSO4-) ejection out of a PPY film was first chosen as a model system and the results obtained with EC/ICP-AES were found to be comparable with values deduced by electrochemical quartz crystal microbalance (EQCM). The EC/ICP-AES approach was then extended to cases where EQCM findings become difficult to interpret (i.e. simultaneous insertion of Na+ into and ejection of HSO4- out of PPY film). It is demonstrated that EC/ICP-AES can simultaneously quantify both cationic and anionic species involved in the PPY redox switching. This is in contrast with EQCM studies that can only detect the net mass change from the two competing processes. This study shows that EC/ICP-AES is a viable technique for providing accurate information concerning the doping/dedoping processes without the necessity of removing the polymer-modified electrode from the electrochemical flow cell. More importantly, the species investigated do not need to be electroactive. It is clear that the comparative study between the two techniques can be powerful in unraveling relatively complicated redox reactions and ion-transport processes in conductive polymer films.

"Subattomole Oligonucleotide And P53 CDNA Determinations Via A High-resolution Surface Plasmon Resonance Combined With Oligonucleotide-capped Gold Nanoparticle Signal Amplification"
Anal. Biochem. 2006 Volume 354, Issue 2 Pages 220-228
Xin Yao, Xin Li, Freddy Toledo, Cecilia Zurita-Lopez, Margarita Gutova, Jamil Momand and Feimeng Zhou

Abstract: Oligonucleotide (ODN)-capped gold nanoparticles (Au-NPs) were used in a sandwich assay of ODN or polynucleotide by a flow injection surface plasmon resonance (SPR). A carboxylated dextran film was immobilized onto the SPR sensor surface to eliminate nonspecific adsorption of ODN-capped Au-NPs. The tandem use of signal amplification via the adlayer of the ODN-capped Au-NPs and the differential signal detection by the bicell detector on the SPR resulted in a remarkable DNA detection level. A 39-mer target at a quantity as low as 2.1 x 10^-20 mol, corresponding to 1.38 fM in a 15 µL solution, can be measured. To our knowledge, both the concentration and quantity detection levels are the lowest among all the gene analyzes conducted with SPR to this point. The method is shown to be reproducible (relative standard deviation values <16%) and to possess high sequence specificity. It is also demonstrated to be viable for sequence-specific p53 cDNA analysis. The successful elimination of nonspecific adsorption of, and the signal amplification by, ODN-capped Au-NPs renders the SPR attractive for cases where the DNA concentration is extremely low and the sample availability is severely limited.