At 17:59 20.01.00 -0600, you wrote:
>What is the best way to quantitate the amount of H2O and counter-ion in
>a sample of lyophilized peptide?
>
>Are esters stable to HF cleavage?
>
Dear Joseph,
probably the easiest way to get an answer to your first question (if the
peptides contain any aromatic residues) is to dissolve a small, weighed
amount of your peptide and to measure the UV absorption at 280 nm. The
difference between UV-estimated amount (from calculated epsilon(280nm)) and
weighed amount is most likely water, salt and counter ions (to my
experience up to 20% water, acetate salts are common as well).
Hope this helps. Yours sincerely,
Marcus
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Dr. Marcus Macht
Universit”t K–ln
Zentrum f¸r molekulare Medizin
Zentrales Servicelabor
Joseph-Stelzmann-Str. 52
50931 Koeln
Tel.: +49 221 478-6995
Fax: +49 221 478-6977
e-mail: Marcus.Macht@uni-koeln.de
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