Polylysine‐Catalyzed Hydrogen Evolution at Mercury Electrodes

Abstract

It has been shown that peptides and proteins produce at nanomolar concentrations a structure-sensitive chronopotentiometric peak H at mercury electrodes, which is due to the catalytic hydrogen evolution reaction (HER). Herein, we use for the first time poly(amino acids) to obtain information about the role of individual amino acid residues in the HER. At pH 6 polylysine (polyLys) and polyarginine,tryptophan yield a peak H, in agreement with their ionization state, while polyglutamic acid gives no catalytic response. PolyLys catalyzes hydrogen evolution in its adsorbed state. Even at potentials negative to the potential of zero charge, hydrophobic interactions could be involved in polyLys adsorption.

Enzymatic activity and catalytic hydrogen evolution in reduced and oxidized urease at mercury surfaces

“…The presence of these peaks was tentatively explained by limited accessibility of amino acid residues involved in CHER, located in partially unfolded segments of the urease molecules. Such amino acid residues with labile protons may include lysine, arginine, Cys and histidine [25][26][27]. Our preliminary data show that CPS peak H is produced by practically all proteins, but the peak sizes and potentials are strongly influenced by the protein structures, making CPS of great potential use in biomedicine and proteomics.…”

Chronopotentiometric Analysis of Proteins at Charged Electrode Surfaces

“…In the last decade, it has been found that amino acids (AA) containing labile protons such as cysteine, lysine, arginine, and histidine can be involved in CHER of peptides , polyamino acids and proteins themselves at neutral pH. Specifically, the proton‐exchangeable groups for individual AA are imidazolium (His), ϵ‐ammonium (Lys), guanidinium (Arg) and thiol group (Cys). His residues, at neutral pH, behaved as a weaker catalyst for CHER (considering pKa values) in comparison to Arg and Lys residues .…”

Biophysical properties and cellular toxicity of covalent crosslinked oligomers of α-synuclein formed by photoinduced side-chain tyrosyl radicals

“…The specific differential capacity (C s ) of the electrode double layer is a sensitive indicator of adsorption at the electrodes [46,48]. In proteins absorbed at nearly neutral pH values, only accessible Lys, Arg and Cys residues are predominantly involved in catalytic hydrogen evolution reaction [47,49,50]. Since aS lacks Arg or Cys, only the 15 Lys residues per protein molecule can give rise to the electrocatalytic activity.…”