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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H. H. Weetall

Abbrev:
Weetall, H.H.
Other Names:
Address:
Biosensor Technology Group, Biotechnology Division, National Institute of Standards and Technology,
Phone:
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Citations 2

"Detection Of Aromatic Compounds Based On DNA Intercalation Using An Evanescent Wave Biosensor"
Anal. Chem. 1995 Volume 67, Issue 5 Pages 787-792
P. C. Pandey and H. H. Weetall

Abstract: A FIA system coupled with an evanescent wave biosensor employing total internal reflection of fluorescence was used to detect compounds that intercalate with DNA. The analyte was detected by competition and displacement of intercalated ethidium bromide (excitation and emission at 499 and 592 nm, respectively). Double-stranded DNA was immobilized over the surface of a silanized optical fiber using acrylamide-methacrylamide-hydrazide prepolymer. The sample solution (20 µL) was introduced into 0.5 M phosphate buffer of pH 7.2 flowing at 24 ml/h and passed to the fluoribiosensor. A constant concentration of ethidium bromide was also pumped at the same rate and, at the steady state, the competitive intercalator was introduced. The response for 9,10-anthraquinone-2,6-disulfonic acid, remazol brilliant blue, decacyclene and 4',6-diamidino-2-phenylindole dihydrochloride at the µg/ml level was significantly higher using the modified fiber than an unmodified one, and increased with increasing concentration of immobilized DNA. A decrease in response to ethidium bromide was obtained on injection of the competing DNA intercalator, which was followed by recovery of the steady state in 6.5-12 min. This decrease in response was a linear function of analyte concentration.
Sensor Sensor Optical fiber Immobilized reagent Indirect Steady state

"Application Of Photochemical Reaction In Electrochemical Detection Of DNA Intercalation"
Anal. Chem. 1994 Volume 66, Issue 8 Pages 1236-1241
P. C. Pandey and H. H. Weetall

Abstract: Portions (20 µL) of 0.2 µM-9,10-anthraquinone-2,6-disulfonic acid (I) were injected into a carrier stream of 0.1 M phosphate buffer of pH 7.5 and 20 mM glucose which was passed over the surface of a UV lamp (λmax = 366 nm) through a network of PTFE tubing (10 m x 0.3 mm i.d.) at 30 ml/h. The reduced form of I was oxidized at the surface of a tetracyanoquinodimethane (TCNQ)-modified graphite paste electrode (preparation described) covered with a Nucleopore membrane in a flow cell. Preliminary [photo]voltammetric experiments (described) were performed with I or 9,10-anthraquinone-2-sulfonic acid (II) and glucose in 0.1 M phosphate buffer of pH 7 containing 0.1 M NaCl. A calibration graph of FIA response (µA) was linear for 0.014-0.121 µmol of I. Intercalation between DNA and I or II was established and there was a linear relation between the decrease in electrochemical response and DNA concentration at a constant substituted anthraquinone concentration. Intercalated anthraquinone molecules were completely replaced by molecules such as ethidium bromide which were more strongly intercalated within DNA. A flow injection analysis (FIA) system for the detection of the compounds that intercalate within DNA is reported. A derivative of 9,10- anthraquinone has been used as the reference compound for photoelectrochemical detection. The sodium salts of 9,10-anthraquinone- 2,6-disulfonic acid and 9,10-anthraquinone-2-sulfonic acid are photochemically activated and then reduced in the presence of an electron donor (glucose). The electrochemical signal is based on the measurement of the anodic current resulting from the oxidation of the reduced form of 9,10-anthraquinone. The reduced form of the 9,10- anthraquinone is oxidized through a mediated mechanism at the surface of a tetracyanoquinodimethane-(TCNQ)-modified graphite paste electrode covered by a Nucleopore membrane. TCNQ acts as an efficient mediator for the oxidation of reduced 9,10-anthraquinone. Cyclic voltammetry, photocyclic voltammetry, and the photoelectrochemical FIA response of 9,10-anthraquinone are reported. Experimental results show that these anthraquinones can be intercalated within the helix of double-stranded calf thymus DNA. The anthraquinone molecules that are intercalated within DNA cannot be oxidized due to their limited transport to the modified electrode surface. This results in a decrease in the anodic current at a constant concentration of anthraquinone after intercalation. There is a linear relation between the decrease in electrochemical response and the DNA concentration at a constant concentration of anthraquinone. The intercalated anthraquinone molecules can be completely replaced by another intercalating agent (i.e., ethidium bromide) that is more strongly intercalated within DNA, thereby regenerating the electrochemical response.
9,10-Anthraquinone-2,6-disulfonic acid 9,10-Anthraquinone-2-sulfonic acid Glucose Spectrophotometry Voltammetry Electrode Apparatus UV reactor Photochemistry