Simple protein structure-sensitive chronopotentiometric analysis with dithiothreitol-modified Hg electrodes

We have shown that proteins produce at bare mercury electrodes a well-developed chronopotentiometric peak H. At sufficiently high current densities and low ionic strengths, this peak is sensitive to changes in protein structures. At higher ionic strengths this sensitivity can be lost but it can be restored, when instead of bare, thiol-modified Hg electrodes are used. Here we studied properties of the dithiothreitol (DTT) layer at the hanging mercury drop electrode and showed that at low concentrations (5 μM–200 μM) the DTT is adsorbed as a dithiol with both –SH groups attached to the surface. At higher DTT concentrations than 1 mM, a densely packed pinhole-free layer is formed with the DTT molecules bound to the electrode surface by a single –SH group, oriented perpendicularly to the surface. We found that, if a sufficiently high DTT concentration is used, preparation of the DTT-modified Hg electrodes can be omitted and proteins can be co-adsorbed with DTT on liquid Hg or solid amalgam electrodes without the loss of sensitivity for changes in protein structures. The newly observed properties of the DTT self assembled monolayers (SAMs) at Hg electrodes appear important for designing new types of solid amalgam electrode arrays for electrochemical analysis of proteins.

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► DTT-modified mercury and solid amalgam electrodes for protein structure-sensitive analysis.
► One step co-adsorption of DTT and protein at electrode surface.
► DTT molecules perpendicularly orientated to the surface form a densely packed pinhole-free layer.