Thiol group determination in proteins by flameless atomic absorption spectrometry of mercury.

The flameless atomic absorption procedure for determination of minute amount of mercury has been adapted for measuring thiol-groups in native and denatured proteins. The excess ofp-hydroxymercuribenzoate is removed by gel filtration after its reaction with the protein. The protein-p-hydroxymercuribenzoate complex is digested and the mercury is determined in an atomic absorption spectrophotometer. The sensitivity of the method allows measurement of 0.05 μg protein-bound mercury with the equipment used, but can be further increased. Results are presented for five different proteins.