Fellow Fellow Isotopists,
Over many years, I have been measuring S-isotope compositions in a variety
of biological tissues/minerals including hair, nails, tusks, baleen, teeth,
and feathers. The data can be qualitatively related to the isotopic
composition of diet and in turn, environments but it would be desirable to
know more about uptake/conversion processes. My understanding is that
assimilatory conversion of sulfate to organic-S  resides in the plant and
bacteria domains and is not present in the biochemistry of higher members of
food chains. The latter can inter-convert S-amino acids and such reactions
are described in biochemistry textbooks. There are also articles in medical
journals on topics such as the formation of cystine kidney stones because
enzymatic scission to two more soluble cysteine molecules is flawed. I have
also learned from our measurements of S- and O-isotope composition of
sulfate that most sulfate in fluids and minerals of animals is derived from
oxidation of organic-S.

I am trying to find information on the quantities and incorporation of
different S-amino acids into biological tissues. Feathers are of particular
interest because of a recent collaborative study with Darren Grocke on
sulfur in cockatoo feathers.  Does anyone know of data for amino acid
analyses of feathers? Have there been studies whereby birds/animals have
been fed a specific S-amino acid to see how this alters the S-amino acid
distribution in different components of the consumer...either by chemical
analyses and perhaps isotopic labelling techniques?

Thank You;
Roy Krouse