I have been following this discussion, and I was thinking that the
TFA could be protonating the side-chains of Glu and Asp, and the
C-terminus. In the presence of acetate, Glu and Asp should deprotonate,
based on respective pKa values. Does anyone have an opinion on whether
this is, in fact, what is occurring?
Chris Halkides
>> Federico,
>> I tried to freeze-dry TFA salts from acetic acid several times measuring
>> the amount of TFA before and after and this did not work well. But an
>> ion-exchange resin in an acetate form worked fine for my peptides.
>> Trifluoroacetate was transferred to an acetate.
>> Regards,
>> Michael Breslav
>> R.W.Johnson PRI
>> Spring House, PA
>>
>> ----------
>> From: Federico Brianza[SMTP:brianza@imb-jena.de]
>> Sent: Friday, July 17, 1998 8:38 AM
>> To: Recipients of ABRF List
>> Subject: How to get rid of TFA?
>>
>> Hi everybody,
>> after purification with RPC-FPLC, using acetonitril and TFA, my synthetic
>> peptides
>> have extremely low pH, I guess due to the presence of TFA. The problem
>> persists
>> also after freeze-drying. What can I do? Is it true that freeze-dryng
>> after adding
>> acetic acid can help remove the TFA?
>> Thanks in advance
>>
>>
>>
>> --
>> Federico Brianza
>> Protein Laboratory
>> Institute of Molecular Biotechnology
>> Beutembergstr. 11, 07745 Jena / Germany
>> Tel: +49 3641 656432
>> Fax: + 49 3641 656431
>>
>>
Christopher Halkides
Dept. of Chemistry, UNCW
601 S. College Road
Wilmington, NC 28403-3297
(910) 962-7427