The interaction of Mercurochrome, a medical preparation based on the mercury organic compound merbromin, with free thiols in low molecular weight peptides and in proteins has been investigated by means of liquid chromatography (LC) and electrospray mass spectrometry (ESI-MS). Beta-lactoglobulin A (beta-LGA) from bovine milk (18.4 kDa) has been used as the model protein. It was found that, in contrast to assumptions in literature, the commercial product itself is a heterogeneous mixture of moderate chemical stability, which may contain precipitated Hg salts depending on storage time and conditions. Further variability results from different degrees of bromination of the fluorescein backbone of the compound. The formation of mercury compound-protein adducts was detected. The peptide sequence T13 containing a free thiol residue was identified as the binding site for mercury species after tryptic digestion of beta-lactoglobulin A. While fresh Mercurochrome tends to the formation of a Hg(II)-beta-LGA adducts due to excess Hg(2+) in solution, investigations after precipitation of Hg salts yield Hg(merbromin)(beta-LGA) as the major product.

Investigation of the interaction of Mercurochrome® constituents with proteins using liquid chromatography/mass spectrometry

Binary and ternary mixtures of the organic compounds of the title elements are decomposed either by wet digestion in the Kjeldahl flasks or through combustion in the oxygen flask using 1:1 HNO3 soln. as absorbent and Pt gauze as sample holder. An aliquot of 15 μl of each decomposed mixture is separated on thin layer plate, using silica gel (G 60) as stationary phase and a mixture of 100 ml benzene: 80 ml acetone : 20 ml DMF as a mobile phase in normal saturation system at 25°C. The spots areas are determined, from which the individual concentrations of the cations are calculated. Parallely the spots are scratched from the plates and are eluted with water. Their concentrations are measured in the UV-region, for Hg(II) at 205 nm, for Cu(II) at 203 and for Cd at 201 nm. Concentrations are obtained from previously constructed calibration curves which are linear for Hg(II) in the range 0.0 – 0.375 ppm, for Cu(II) in the range 0.0 – 3.811 ppm and for Cd from 0.7 – 13.48 ppm.

Oxygen Plask-TLC Microdetermination of Binary and Ternary Mixtures of Hg(II), Cu(II) and Cd in their Organic Compounds and Some Pharmaceutical Preparations

M. Lederer

Papers

The thin-layer chromatography of some organomercurial antiseptics on cellulose thin layers with aqueous solvents.