I've never worked with Tetrakis, but long time ago in a paper
published in 1981 we've described the use of mercarbide
(mercarbide electron-dense label - MEDL) containing a Hoffman
base as the label for SH-groups in microsomal cytochrome(s)
P450. Our goal was to use electron-dense labels for studying
cytochrome P450 localization in the membrane of endoplasmic
reticulum and in proteoliposomes. A solution of the MEDL was
added to the equimolarly titrated SH groups and incubated for 20
min at room temperature. In all cases 90-95% of SH-groups were
blocked. No precipitation was observed in any case including
solution of the pure protein.
Following are references.
<FontFamily><param>CG Times</param><bigger>Alterman, M.A. et al<bold> </bold> Study of cytochrome P-450 distribution
in endoplasmic reticulum membranes of rat liver.
<italic>Biochemistry </italic>(USSR), <bold>46</bold>:182-188, 1981.
Kalamkaov, G.R. et all, Bioorg. Khim., 3, 775-779, 1977
I hope that helps.
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M. Alterman, Ph.D.
Director,
Biochemical Research Service Laboratory
University of Kansas
Lawrence, KS 66045
Phone: (913)-864-4166
(913)-864-4247 lab
FAX: (913)-864-5396
http://www.idl.ukans.edu/anylresc/brsl/brsl.html