326
|
Li Y, Shi L, Ma W, Li DW, Kraatz HB, Long YT. 6-Vinyl coenzyme Q0: Electropolymerization and electrocatalysis of NADH oxidation exploiting poly-p-quinone-modified electrode surfaces. Bioelectrochemistry 2010; 80:128-31. [PMID: 20678972 DOI: 10.1016/j.bioelechem.2010.07.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2010] [Revised: 06/30/2010] [Accepted: 07/10/2010] [Indexed: 11/24/2022]
Abstract
6-Vinyl coenzyme Q(0) serves as a convenient starting material for the formation of electropolymerized coenzyme Q(0) on glassy carbon electrodes and the modified electrodes displays electrocatalytic activity toward NADH (β-nicotinamide adenine dinucleotide) oxidation. The detection of NADH was measured by differential pulse voltammetry, which reveals that the peak current is linear to the concentration of NADH within the range of 10-100μM. This would be helpful for the understanding of the interaction between coenzyme Q(0) and NADH in the biological process.
Collapse
|
327
|
Song W, Zhang L, Shi L, Li DW, Li Y, Long YT. Simultaneous determination of cadmium(II), lead(II) and copper(II) by using a screen-printed electrode modified with mercury nano-droplets. Mikrochim Acta 2010. [DOI: 10.1007/s00604-010-0354-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
|
328
|
Li D, Li DW, Li Y, Fossey JS, Long YT. Cyclic electroplating and stripping of silver on Au@SiO2 core/shell nanoparticles for sensitive and recyclable substrate of surface-enhanced Raman scattering. ACTA ACUST UNITED AC 2010. [DOI: 10.1039/b924865j] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
329
|
Liu GL, Long YT, Choi Y, Kang T, Lee LP. Quantized plasmon quenching dips nanospectroscopy via plasmon resonance energy transfer. Nat Methods 2007; 4:1015-7. [DOI: 10.1038/nmeth1133] [Citation(s) in RCA: 259] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2007] [Accepted: 10/30/2007] [Indexed: 11/09/2022]
|
330
|
Dey SK, Long YT, Chowdhury S, Sutherland TC, Mandal HS, Kraatz HB. Study of electron transfer in ferrocene-labeled collagen-like peptides. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2007; 23:6475-7. [PMID: 17472402 DOI: 10.1021/la070175n] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
This study describes the electron transfer (ET) phenomenon through a series of (Pro-Hyp-Gly) repeat units containing collagen mimics. The peptides contain redox-active ferrocene (Fc) and thiol-functionalized cystein (Cys) at the N- and C-terminals, respectively. Peptide films were prepared on gold surfaces and characterized by X-ray photoelectron spectroscopy (XPS), ellipsometry, and Fourier transform-reflection absorption infrared spectroscopy (FT-RAIRS). Electrochemical investigations of the films showed a linear but weakly distance-dependent ET. The importance of H-bonding was realized, and the possibility of a conformationally gated ET mechanism has been discussed.
Collapse
|
331
|
Khan MAK, Long YT, Schatte G, Kraatz HB. Surface Studies of Aminoferrocene Derivatives on Gold: Electrochemical Sensors for Chemical Warfare Agents. Anal Chem 2007; 79:2877-84. [PMID: 17319647 DOI: 10.1021/ac061981m] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The cystamine conjugate [(BocNH)Fc(CO)CSA]2 was prepared by coupling cystamine with the N-protected ferrocene amino acid derivative BocHN-Fc-COOH and was fully characterized by spectroscopic methods and by single-crystal X-ray diffraction. The cystamine conjugate forms films on gold substrates, which upon deprotection of the amino group, react with chemical warfare agent (CWA) mimics, upon which the redox properties of the Fc group are affected significantly. Cyclic voltammetry shows 50(5) mV anodic shifts of the Fc redox potentials after exposure to EtSCH2CH2Cl, a simulant for sulfur mustard HD (MA), and (NC)(EtO)2P(O), a simulant for nerve agent Tabun (NA). Exposure to MA and NA causes an increase in 2.3 and 4.5 ng mass, respectively, in QCM which indicates ca. 70% efficiency in Boc-deprotection. Ellipsometry measured a film thickness increase from 6(+/-1) A for the deprotected film to 10(+/-4) A for the film modified with MA and to 7(+/-2) A for the film modified with NA. AFM measurements show changes in the thickness and morphology of the film after reaction with MA and NA. The surfaces were analyzed by X-ray photoelectron spectroscopy (XPS) and clearly show the attachment of the cystamine conjugate on the surface and its reaction with CWA mimics.
Collapse
|
332
|
Appoh FE, Long YT, Kraatz HB. Study of peptide dendrimers having a ferrocene core supported on mercaptoundecanoic acid. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:10515-22. [PMID: 17129024 DOI: 10.1021/la061114c] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Hydrogen-bonding interactions between the carboxylic acid groups of mercaptoundecanoic acid (MUA) coated gold substrates and the ester surface of peptide dendrimers allows the formation of glutamic acid dendrimers films. Dendrimer films were prepared for generations 1-6 (G1-G6) and analyzed by spectroscopic and electrochemical techniques. Electrochemical studies using cyclic voltammetry and differential pulse voltammetry show that all films except those of G6 were electrochemically active. Lack of activity of G6 films is rationalized by the total encapsulation of the ferrocene redox probe by the dendritic sheath and lack of ion pairing, which prevents its oxidation.
Collapse
|
333
|
Stefureac R, Long YT, Kraatz HB, Howard P, Lee JS. Transport of α-Helical Peptides through α-Hemolysin and Aerolysin Pores. Biochemistry 2006; 45:9172-9. [PMID: 16866363 DOI: 10.1021/bi0604835] [Citation(s) in RCA: 209] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A series of negatively charged alpha-helical peptides of the general formula fluorenylmethoxycarbonyl (Fmoc)-D(x)A(y)K(z) were synthesized, where x and z were 1, 2, or 3 and y was 10, 14, 18, or 22. The translocation of the peptides through single pores, which were self-assembled into lipid membranes, was analyzed by measuring the current blockade i(block) and the duration t(block). The pores were either alpha-hemolysin, which has a wide vestibule leading into the pore, or aerolysin, which has no vestibule but has a longer pore of a similar diameter. Many thousands of events were measured for each peptide with each pore, and they could be assigned to two types: bumping events (type I) have a small i(block) and long t(block), and translocation events (type II) have a larger i(block) and shorter t(block). For type-II events, both i(block) and t(block) increase with the length of the peptides on both pores tested. The dipole moment and the net charge of each peptide has a major effect on the transport characteristics. The ratio of type-II/type-I events increases as the dipole moment increases, and uncharged peptides gave mostly type-I events. The structural differences between the two nanopores were reflected in the characteristic values of i(block), and in particular, the vestibule of alpha-hemolysin helps to orient the peptides for translocation. Overall, the results demonstrate that the nanopore technology can provide useful structural information but peptide sequencing will require further improvements in the design of the pores.
Collapse
|
334
|
Abstract
Nature has specifically designed proteins, as opposed to DNA, for electron transfer. There is no doubt about the electron transfer within proteins compared with the uncertain and continuing debate about charge transfer through DNA. However, the exact mechanism of electron transfer within peptide systems has been a source of controversy. Two different mechanisms for electron transfer between a donor and an acceptor, electron hopping and bridge-assisted superexchange, have been proposed, and are supported by experimental evidence and theoretical calculations. Several factors were found to affect the kinetics of this process, including peptide chain length, secondary structure and hydrogen bonding. Electrochemical measurements of surface-supported peptides have contributed significantly to the debate. Here we summarize the current approaches to the study of electron transfer in peptides with a focus on surface measurements and comment on these results in light of the current and often controversial debate on electron transfer mechanisms in peptides.
Collapse
|
335
|
Long YT, Abu-Irhayem E, Kraatz HB. Cover Picture: Peptide Electron Transfer: More Questions than Answers (Chem. Eur. J. 18/2005). Chemistry 2005. [DOI: 10.1002/chem.200590057] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
336
|
Long YT, Li CZ, Sutherland TC, Kraatz HB, Lee JS. Electrochemical detection of single-nucleotide mismatches: application of M-DNA. Anal Chem 2005; 76:4059-65. [PMID: 15253643 DOI: 10.1021/ac049482d] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The detection of a single-nucleotide mismatch in unlabeled duplex DNA by electrochemical methods is presented. Impedance spectroscopy is used to characterize a perfect duplex monolayer and three DNA monolayers differing in the position of the mismatch. The monolayers were studied as B-DNA (normal duplex DNA) and after conversion to M-DNA (a metalated duplex). Modeling of the impedance data to an equivalent circuit provides parameters that are useful in discriminating the four monolayer configurations. The resistance to charge transfer, R(CT), was lower for all duplexes after conversion to M-DNA. Contrary to expectations, R(CT) was also found to decrease for duplexes containing a mismatch. However, R(CT) was found to be diagnostic for mismatch detection. In particular, the difference in R(CT) between B- and M-DNA (deltaR(CT)) decreased from 190(22) omega.cm(2) for a perfectly matched duplex to 95(20), 30(20), and 85(20) omega.cm(2) for a mismatch at the top (distal), middle, and bottom (proximal) positions of the monolayer with respect to the gold surface. Further, a method to form loosely packed single-stranded (ss)-DNA monolayers by duplex dehybridization that is able to rehybridize to target strands is presented. Rehybridization efficiencies were in the range of 40-70%. Under incomplete hybridization conditions, the R(CT) was the same for matched and mismatched duplexes under B-DNA conditions. However, deltaR(CT) between B- and M-DNA, under incomplete hybridization, still provided a distinction. The deltaR(CT) for a perfect duplex was 76(12) omega.cm(2), whereas a mismatch in the middle of the sequence yielded a deltaR(CT) value of 30(15) omega.cm(2). The detection limit was measured and the impedance methodology reliably detected single DNA base pair mismatches at concentrations as low as 100 pM.
Collapse
|
337
|
Orlowski GA, Chowdhury S, Long YT, Sutherland TC, Kraatz HB. Electrodeposition of ferrocenoyl peptide disulfides. Chem Commun (Camb) 2005:1330-2. [PMID: 15742068 DOI: 10.1039/b415278f] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Using electrodeposition of cyclic and acyclic Fc-peptide disulfides tightly-packed Fc-peptide monolayers were conveniently formed, which exhibit significant differences in their electron transfer kinetics.
Collapse
|
338
|
Mahmoud K, Long YT, Schatte G, Kraatz HB. Rearrangement of the Active Ester Intermediate During HOBt/EDC Amide Coupling. Eur J Inorg Chem 2005. [DOI: 10.1002/ejic.200400504] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
339
|
Long YT, Sutherland TC, Kraatz HB, Lee JS. Photoinduced production of NAD(P)H from an activated fluorescein-DNA monolayer. Chem Commun (Camb) 2004:2032-3. [PMID: 15367960 DOI: 10.1039/b406689h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A fluorescein (Fl)-labeled DNA monolayer on Au was formed such that under applied potentials of -750 mV (vs. Ag/AgCl) and incident irradiation (473 nm, 4 mW cm(-2)) a photocurrent was generated that ultimately reduced NAD(P)+ to biologically active NAD(P)H.
Collapse
|
340
|
Li CZ, Long YT, Lee JS, Kraatz HB. Protein–DNA interaction: impedance study of MutS binding to a DNA mismatch. Chem Commun (Camb) 2004:574-5. [PMID: 14973614 DOI: 10.1039/b314642a] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
MutS binding to a double-stranded DNA containing a single nucleotide mismatch can be conveniently monitored by impedance spectroscopy and represents the first step in developing an electrochemical binding essay for single nucleotide mismatch detection.
Collapse
|
341
|
Long YT, Li CZ, Sutherland TC, Chahma M, Lee JS, Kraatz HB. A comparison of electron-transfer rates of ferrocenoyl-linked DNA. J Am Chem Soc 2003; 125:8724-5. [PMID: 12862457 DOI: 10.1021/ja034684x] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electron transfer (ET) through two configurations of double-stranded (ds)-DNA was investigated by the attachment of a ferrocenoyl (Fc)-labeled and thiol-labeled DNA to Au electrodes. The first configuration positions the Fc moiety on the same strand as the thiolate, whereas the second configuration positions the Fc group on the complementary strand. The subtle difference in structure leads to a difference in E0' values (29 mV) and in ET rate constants (25 vs 115 s-1). The results have led to a further understanding of electron transfer in ds-DNA, and several models of ET are proposed.
Collapse
|
342
|
Abstract
Monolayers of thiol-labeled DNA duplexes of 15, 20, and 30 basepairs were assembled on gold electrodes. Electron transfer was investigated by electrochemical impedance spectroscopy with Fe(CN)(6)(3-/4-) as a redox probe. The spectra, in the form of Nyquist plots, were analyzed with a modified Randles circuit which included an additional component in parallel, R(x), for the resistance through the DNA. For native B-DNA R(x) and R(ct), the charge transfer resistance, both increase with increasing length. M-DNA was formed by the addition of Zn(2+) at pH 8.6 and gave rise to characteristic changes in the Nyquist plots which were not observed upon addition of Mg(2+) or at pH 7.0. R(x) and R(ct) also increased with increasing duplex length for M-DNA but both were significantly lower compared to B-DNA. Therefore, electron transfer via the metal DNA film is faster than that of the native DNA film and certain metal ions can modulate the electrochemical properties of DNA monolayers. The results are consistent with an ion-assisted long-range polaron hopping mechanism for electron transfer.
Collapse
|
343
|
Li CZ, Long YT, Kraatz HB, Lee JS. Electrochemical Investigations of M-DNA Self-Assembled Monolayers on Gold Electrodes. J Phys Chem B 2003. [DOI: 10.1021/jp026792w] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
344
|
Wettig SD, Li CZ, Long YT, Kraatz HB, Lee JS. M-DNA: a self-assembling molecular wire for nanoelectronics and biosensing. ANAL SCI 2003; 19:23-6. [PMID: 12558018 DOI: 10.2116/analsci.19.23] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
M-DNA is a complex between divalent metal ions such as Zn2+ and duplex DNA which forms at pH 8.5. Unlike B-DNA, M-DNA does not bind ethidium so that M-DNA formation can be monitored conveniently by an ethidium fluorescence assay. M-DNA was shown to be a better conductor than B-DNA by fluorometric measurements of electron transport in donor-acceptor labelled duplexes; by direct conductivity measurements of M-DNA bound between gold electrodes and by cyclic voltammetric studies on ferrocene labelled duplexes attached to gold microelectrodes. As is the case with B-DNA, M-DNA can self-assemble into a variety of structures and is anticipated to find widespread use in nanoelectronics and biosensing.
Collapse
|
345
|
Long YT, Rong HT, Buck M, Grunze M. Odd–even effects in the cyclic voltammetry of self-assembled monolayers of biphenyl based thiols. J Electroanal Chem (Lausanne) 2002. [DOI: 10.1016/s0022-0728(02)00711-8] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
346
|
Long YT, Herrwerth S, Eck W, Grunze M. Synthesis and characterization of self-assembled monolayers based on redox-active silane compounds on platinum surfaces. Phys Chem Chem Phys 2001. [DOI: 10.1039/b107091f] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
347
|
Long YT, Chen HY. Electrochemical regeneration of coenzyme NADH on a histidine modified silver electrode. J Electroanal Chem (Lausanne) 1997. [DOI: 10.1016/s0022-0728(97)80061-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
|