Constant Current Chronopotentiometric Stripping Analysis of Bioactive Peptides at Mercury and Carbon Electrodes

Abstract

Constant current derivative chronopotentiometric stripping analysis (CPSA) was used to study bioactive peptides [Lys 8 ]-vasopressin and angiotensin II at carbon paste electrode (CPE) and hanging mercury drop electrode (HMDE). Both peptides contain a single tyrosine residue which is oxidized at CPE close to þ0.6 V (against Ag/AgCl/3 M KCl electrode) producing peak Y; this peak was by about 15 mV more positive in vasopressin than in angiotensin II. At HMDE vasopressin yielded peak S due to the reduction of the disulfidic bond in the peptide. No peak S was observed with angiotensin II as it does not contain any cystine/cysteine residues. Vasopressin produced different catalytic hydrogen reduction signals in media with cobalt ion and in media not containing any metal ion. The signal produced in the latter media (peak H), which appeared close to ¹1.7 V, was well separated from the background. No catalytic hydrogen reduction signal was obtained with angiotensin II. The above mentioned CPSA signals can be applied for the determination of the respective peptide at nanomolar concentrations. The least sensitive peak S appears which requires at least 100 nM vasopressin concentration at moderate accumulation time. By two orders of magnitude, higher sensitivities can be obtained with peaks Y and H. In measuring these peaks CPSA shows significant advantages over the voltammetric stripping techniques.

Characterization of phytoplankton exudates and carbohydrates in relation to their complexation of copper, cadmium and iron

“…Constant-current chronopotentiometric stripping analysis (CPSA) for the determination of catalytic groups. CPSA produces a well-resolved catalytic peak (so called peak 'H') (Tomschik et al 1998) that is characteristic for peptides and proteins at nanomolar concentrations (Ostatná et al 2007). In CPSA the potential of the catalytic reaction peak (Ep) and its height (dE/dt) -1 depend primarily on the molecular structure, i.e.…”

Effect of transition metals on binding of p53 protein to supercoiled DNA and to consensus sequence in DNA fragments

“…This technique can also be applied for the analysis of DNA and proteins (Palecek et al, 1997a;Tomschik et al, 1998). Measurements were performed with an AUTOLAB (EcoChemie, Utrecht, The Netherlands) connected to a Metrohm 647 VA Stand (mercury electrode) in HMDE mode (drop surface area 0.4 mm 2 ) at a constant current of 71 mA using 0.2 M sodium phosphate as a background electrolyte.…”

Polymer thin films embedded with metal nanoparticles for electrochemical biosensors applications

“…The first label-free electrochemistry of proteins came from mercury electrodes. Peptides and proteins containing cysteine/ cystine showed specific electrochemical signals on mercury electrodes with the help of Hg-S bond formation (Havran et al, 2004;Palecek and Ostatna, 2007), reduction of disulfide groups (Tomschik et al, 1998), and the catalytic evolution of hydrogen in cobalt containing solutions (Brdicka reaction) (Brdicka, 1933;Heyrovsky, 2004). Fan et al (2011), who reported Nafion/TiO 2 / graphene/GCE electrode for response to the amino acids L-tryptophane and L-tyrosine with 0.7 and 2.3 mM LODs, and a sensitivity of 75.9 and 22.8 mA mM À 1 , respectively.…”