Competitive Assay for the Ultrasensitive Detection of Organophosphate Pesticides Based on a Fiber-Optic Particle Plasmon Resonance Biosensor and an Acetylcholinesterase Binding Peptide.

An acetylcholinesterase (AChE) binding-based biosensor was developed for the ultrasensitive detection of organophosphate (OP) pesticides. The biosensor integrates the technique based on fiber-optic particle plasmon resonance detection and a synthetic AChE binding peptide conjugated with gold nanoparticles on the optical fiber surface via an AChE competitive binding assay. The OP pesticides present in the solution hinder the binding of AChE to the peptide on the biosensor by competing for the binding sites present in AChE.

Determination of cyclic GMP concentration using a gold nanoparticle-modified optical fiber.

Guanosine 3',5'-cyclic monophosphate (cGMP) produced from guanosine triphosphate (GTP) via soluble or particulate guanylyl cyclase (GC) is an important second messenger for signal transduction within cells. The currently used methods of measuring cGMP including radioimmunoassay and enzyme immunoassay involve the use of radioisotopes or tracers. To develop a cGMP assay that is label-free, non-radioactive, able to detect cGMP directly, and highly specific and sensitive, we used a gold nanoparticle-modified optical fiber (GNOF) conjugated with anti-cGMP antiserum to determine cGMP concentration based on localized surface plasmon resonance (LSPR).

Comparison of nitric oxide-induced oxidation of recombinant oxyhemoglobin subunits using a competition experiment.

A low reaction rate with nitric oxide (NO) is one of the important characteristics of hemoglobin (Hb)-based oxygen carriers. The reaction rate between oxyHb and NO is usually measured by stopped-flow spectrophotometry. However, the reported rates vary due to the difficulty of accurately determining the NO concentration and the limit of the instrument dead time.

Hemoglobin conjugated with a Band 3 N-terminus derived peptide as an oxygen carrier.

A peptide composed of 9 amino acids, 7 residues from N-terminus of human erythrocytic Band 3 protein (AcMEELQDD) followed by cysteine and glutamic acids, was conjugated to hemoglobin (Hb) serving as an allosteric effector for oxygen release. The activated polyethylene glycol (PEG), maleimide-PEG-N-hydroxysuccinimidyl, was used to crosslink Hb with the peptide. The putative conjugation site on Hb for effective enhancement of oxygen release was characterized as Lys-beta95 by liquid chromatography-tandem mass spectrometry.

Superoxide counteracts low-density lipoprotein-induced human aortic smooth muscle cell proliferation.

Previously, we demonstrated that the level of intracellular O(2)(-) is increased by low-density lipoprotein (LDL) in human aortic smooth muscle cells (HASMCs). The exact role of O(2)(-) in the LDL-induced proliferation of HASMCs, however, has not been determined. In this study, we found that the increase in the concentrations of intracellular O(2)(-) induced by native and oxidized LDL increased SMC-nitric oxide (NO) uptake rate.

H2O2 but not O2- elevated by oxidized LDL enhances human aortic smooth muscle cell proliferation.

The oxidation of low density lipoprotein (LDL) as a key event in atherosclerosis suggests that antioxidant interventions may reduce the risk of atherosclerosis. However, the better strategies among antioxidant remedies for atherosclerosis remains difficult to be determined. Here, we show that oxidized LDL increases the steady-state level of intracellular hydrogen peroxide through stimulating the protein expressions of Nox1 and Cu/Zn superoxide dismutase (SOD) in human aortic smooth muscle cells (SMCs).

Determination of organophosphorous pesticides by a novel biosensor based on localized surface plasmon resonance.

Liquid and gas chromatography are commonly used to measure organophosphorus pesticides. However, these methods are relatively time consuming and require a tedious sample pretreatment. Here, we applied the localized surface plasmon resonance (LSPR) of gold nanoparticles covalently coupled with acetylcholinesterase (AChE) to create a biosensor for detecting an example of serial signals responding to paraoxon in the range of 1-100 ppb by an AChE modified LSPR sensor immersing in a 0.

Superoxide determines nitric oxide uptake rate by vascular smooth muscle cells.

Nitric oxide (NO) is generated in endothelial cells, which diffuses to vascular smooth muscle cells (SMCs), activates soluble guanylyl cyclase, and leads to blood vessel dilation. However, this scenario does not explain how SMCs are capable of competing with erythrocytic hemoglobin for NO in vivo. Here, we have developed a competition experiment to determine the NO uptake rate by SMCs and demonstrated that the SMC-NO uptake rate is positively dependent on intracellular superoxide levels.