You-Nian Liu

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Organization: Central South University

Department: College of Chemistry and Chemical Engineering

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Chemicals
References

Spectrofluorimetric determination of total free thiols based on formation of complexes of Ce(III) with disulfide bonds

Co-reporter:Guo-Cheng Han, Yong Peng, Yuan-Qiang Hao, You-Nian Liu, Feimeng Zhou

Analytica Chimica Acta 2010 Volume 659(1–2) pp:238-242

Publication Date(Web):5 February 2010

DOI:10.1016/j.aca.2009.11.057

A simple, rapid, and sensitive determination of total free thiol groups in biological samples using cerium (IV) as a fluorescence probe is reported. The protocol is based on the oxidation of thiols by Ce(IV) and the formation the Ce(III) disulfide complex, which gives a fluorescence enhancement of Ce(III) at 352 nm. Using glutathione (GSH) and cysteine as model compounds, incubation with Ce(IV) at 25 °C for 6 min results in fluorescence, whose intensity is proportional to the thiol concentration in the range of 1.00–160 nM. The detection limits for GSH and cysteine are 0.05 and 0.08 nM, respectively. Other common metal ions and amino acids have little interference to the thiol detection. Cu(II) was used as a fluorescence quencher to eliminate potential interference from tryptophan. The method has been successfully applied to assays of free thiol contents in pig liver tissue samples, with a RSD lower than 2.5% and recovery between 100.6% and 102.3%.

Binding of α-synuclein with Fe(III) and with Fe(II) and biological implications of the resultant complexes

Co-reporter:Yong Peng, Chengshan Wang, Howard H. Xu, You-Nian Liu, Feimeng Zhou

Journal of Inorganic Biochemistry 2010 Volume 104(Issue 4) pp:365-370

Publication Date(Web):April 2010

DOI:10.1016/j.jinorgbio.2009.11.005

Parkinson’s disease (PD) is hallmarked by the abnormal intracellular inclusions (Lewy bodies or LBs) in dopaminergic cells. Amyloidogenic protein α-synuclein (α-syn) and iron (including both Fe(III) and Fe(II)) are both found to be present in LBs. The interaction between iron and α-syn might have important biological relevance to PD etiology. Previously, a moderate binding affinity between α-syn and Fe(II) (5.8 × 103 M−1) has been measured, but studies on the binding between α-syn and Fe(III) have not been reported. In this work, electrospray mass spectrometry (ES-MS), cyclic voltammetry (CV), and fluorescence spectroscopy were used to study the binding between α-syn and Fe(II) and the redox property of the resultant α-syn–Fe(II) complex. The complex is of a 1:1 stoichiometry and can be readily oxidized electrochemically and chemically (by O2) to the putative α-syn–Fe(III) complex, with H2O2 as a co-product. The reduction potential was estimated to be 0.025 V vs. Ag/AgCl, which represents a shift by −0.550 V vs. the standard reduction potential of the free Fe(III)/Fe(II) couple. Such a shift allows a binding constant between α-syn and Fe(III), 1.2 × 1013 M−1, to be deduced. Despite the relatively high binding affinity, α-syn–Fe(III) generated from the oxidation of α-syn–Fe(II) still dissociates due to the stronger tendency of Fe(III) to hydrolyze to Fe(OH)3 and/or ferrihydrite gel. The roles of α-syn and its interaction with Fe(III) and/or Fe(II) are discussed in the context of oxidative stress, metal-catalyzed α-syn aggregation, and iron transfer processes.

(CarboxymethylDextran)-Modified Magnetic Nanoparticles Conjugated to Octreotide for MRI Applications

Co-reporter:Guo-Cheng Han;Yang Ouyang;Xue-Ying Long;Yu Zhou;Meng Li;Heinz-Bernhard Kraatz

European Journal of Inorganic Chemistry 2010 Volume 2010( Issue 34) pp:5455-5461

Publication Date(Web):

DOI:10.1002/ejic.201000715

Abstract

The synthesis of (octreotide–carboxymethyl–dextran)-modified magnetic nanoparticles (CMD-MNPs), which were characterized by FT-IR, AFM, TEM and XRD, and magnetic hysteresis, is described. Magnetic Resonance Imaging (MRI) experiments were performed on a 1.5 Tesla Magnetom Vision machine. The internalization of CMD-MNPs-OC into pancreatic cancer cells Bx-PC3 and colon cancer cells HCT-116 were investigated by transmission electron microscopy (TEM) and magnetic resonance imaging (MRI). The nanoparticles can be recognized specifically, via the somatostatin receptor, and which can be used as a T₂ MRI contrast agent. TEM and MRI results show that somatostatin receptor can deliver OC-modified MNPs into the cytoplasm of a cancer cell line.

Synthesis, characterization and fluorescent properties of cerium(III) glutathione complex

Co-reporter:Guo-Cheng Han

Luminescence 2010 Volume 25( Issue 5) pp:389-393

Publication Date(Web):

DOI:10.1002/bio.1165

Abstract

The cerium (III) glutathione complex was synthesized by the redox reaction of cerium (IV) with glutathione reduced (GSH) in aqueous solution. The Job-plots indicate an ML (L = GSSG) stoichiometry of the complex. The fluorescent properties of the compound were investigated. The as-prepared complex showed the characteristic maximum emission spectra of Ce(III) at 350 nm (λ_ex = 255 nm). The fluorescence results show that the Ce(IV) ions are first reduced to Ce(III), and then form Ce(III) complex after reacting with GSH. The complex was characterized by element analysis and FT-IR spectra; the stability of the complex was analyzed by cyclic voltammeters and DSC-TG as well. Finally, Ce(IV) was successfully employed to determine the concentrations of GSH in the presence of GSSG, in which the fluorescence intensities are proportional to the concentrations of GSH in the range of 1–100 nM with the detection limit of 0.05 nM of GSH, without interference from the presence of GSSG. Copyright © 2009 John Wiley & Sons, Ltd.

Mixed Monolayers of Ferrocenylalkanethiol and Encapsulated Horseradish Peroxidase for Sensitive and Durable Electrochemical Detection of Hydrogen Peroxide

Co-reporter:Yong Peng, Dianlu Jiang, Lei Su, Lin Zhang, Ming Yan, Juanjuan Du, Yunfeng Lu, You-Nian Liu and Feimeng Zhou

Analytical Chemistry 2009 Volume 81(Issue 24) pp:9985

Publication Date(Web):November 20, 2009

DOI:10.1021/ac901833s

This paper describes the construction of a mixed monolayer of ferrocenylalkanethiol and encapsulated horseradish peroxidase (HRP) at a gold electrode for amperometric detection of H2O2 at trace levels. By tuning the alkanethiol chain lengths that tether the HRP enzyme and the ferrocenylalkanethiol (FcC11SH) mediator, facile electron transfer between FcC11SH and HRP can be achieved. Unlike most HRP-based electrochemical sensors, which rely on HRP-facilitated H2O2 reduction (to H2O), the electrocatalytic current is resulted from an HRP-catalyzed oxidation reaction of H2O2 (to O2). Upon optimizing other experimental conditions (surface coverage ratio, pH, and flow rate), the electrocatalytic reaction proceeding at the electrode was used to attain a low amperometric detection level (0.64 nM) and a dynamic range spanning over 3 orders of magnitude. Not only does the thin hydrophilic porous HRP capsule allow facile electron transfer, it also enables H2O2 to permeate. More significantly, the enzymatic activity of the encapsulated HRP is retained for a considerably longer period (>3 weeks) than naked HRP molecules attached to an electrode or those wired to a redox polymer thin film. By comparing to electrodes modified with denatured HRP that are subsequently encapsulated or embedded in a poly-l-lysine matrix, it is concluded that the encapsulation has significantly preserved the native structure of HRP and therefore its enzymatic activity. The electrode covered with FcC11SH and encapsulated HRP is shown to be capable of rapidly and reproducibly detecting H2O2 present in complex sample media.