Yanxiu Zhou

A potentiometric protein sensor built with surface molecular imprinting method.

Surface molecular imprinting, as compared to molecular imprinted bulk polymers, has the advantages of higher re-occupation percentage of the reception sites, fast response, integration of sensing element and transducer, etc. In this study, a potentiometric protein sensor was developed based on the surface molecular imprinting technique. Using the self-assembled monolayers of alkanethiol with hydroxyl terminal groups as the matrix material, and target protein molecules as the template, the sensing layer was created on the surface of the gold-coated silicon chip-an electrochemical transducer. Potentiometric measurement demonstrated that the sensor could selectively detect myoglobin or hemoglobin molecules, either with or without the presence of other protein molecules in the same solution.

Potentiometric monitoring DNA hybridization

The usual procedure to monitor the ion exchange of small ions utilizes a potentiometer with a selective membrane as part of the working electrode. As the next step, we have applied polyaniline electrodes to the monitoring the activity macromolecular ions during DNA hybridization. Single-strand oligonucleotide (ssODN) probes were immobilized using a nucleophilic substitution reaction of the thiolated ssODN molecules with polyaniline. The anionic phosphate groups of the probe molecules also interacted with the cationic-doped polyaniline surface. Three useful findings were observed with the potentiometric experiments. First, the binding of the complimentary target molecules with the immobilized probes revealed a substantial potential change. Further, potential change was observed neither with the non-complimentary targets nor with the samples with a mutation in the sequence. The last two experiments were important for the future evaluation of the impact of medium and potential interfering compounds: anionic groups and hydrogen bonding groups in the non-complimentary samples did not cause any interactions.

Chiral Ligand Exchange Potentiometric Aspartic Acid Sensors with Polysiloxane Films Containing a Chiral Ligand N-Carbobenzoxy-Aspartic Acid

An enantioselective molecular sensor was fabricated by inserting a chiral ligand, N-carbobenzoxy-L-aspartic acid (N-CBZ-L-Asp) or N-CBZ-D-Asp, into an octadecylsiloxane (ODS) monolayer by polysiloxane film immobilization (PFI). The resulting system can recognize one enantiomer of aspartic acids (Asps) due to the chiral ligand exchange reaction at the N-CBZ-L-/D-Asp modified indium-tin oxide (ITO)-coated electrode. The enantioselective formation of diastereoisomeric complexes of Cu(II) with target enantiomers, in here L-/D-Asps, and N-CBZ-L-/D-Asp immobilized by PFI on the ITO electrode. Those diastereoisomeric complexes have different thermodynamic stabilities and Nernst factors and thus enable the sensors to convert the enantioselective recognition event into potential changes by detecting Asp enantiomers in a concentration range of (4.0 x 10(-8))-(8.9 x 10(-5)) M without any pre- or postseparation process. The enantiomeric selectivity coefficients of the sensors for the counterisomers were in the range of (4.0 x 10(-5))-(5.0 x 10(-5)).

Effect of alkyl group length on the conductivity in the 2,3,7,8,12,13,17,18-octakis(alkyl-thio)tetraazaporphyrins and redox properties of the metallooctakis(hexyl-thio)tetraazaporphyrins

A series of 2,3,7,8,12,13,17,18-octakis(alkyl-thio)tetraazaporphyrins (H2OATTAP) with different alkyl chain lengths have been synthesized. Cyclic voltammetry and differential pulse voltammetry have been used to investigate the effect of the controlled lengths of the eight peripheral thioether tails on the redox behavior of the molecules. The electrochemical reduction of octakis(hexyl-thio)tetraazaporphyrins, MOHTTAP (where M = Cu, Ni), was studied in 1,2-dichloroethane at a platinum electrode. The Cu derivative was oxidized in one single-electron-transfer step to yield a π-cation radical and reduced in three single-electron-transfer steps to yield a π-anion radical, dianion and trianion, respectively. For the Ni derivative, electron transfer reactions involving both the central metal atom and the macrocyclic ring were observed. Electron transfer pathways are proposed based upon voltammetric and in situ spectroelectrochemical results.