You might enhance the binding of the basic peptides to your C18 by using
0.05% HFBA instead of TFA. The HFBA enhances the hydrophobicity of basic
peptides through ion pairing and is less suppressive in electrospray
ionisation.
Len
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Dr Len C. Packman
Assistant Director of Research
Protein and Nucleic Acid Chemistry Facility
Department of Biochemistry
University of Cambridge
80 Tennis Court Road
Old Addenbrookes Site
Cambridge, CB2 1GA, UK
Tel: +44 (1223) 333639 (including answerphone)
FAX: +44 (1223) 766002
e-mail: lcp2@mole.bio.cam.ac.uk
Visit my WWW page at http://www.bio.cam.ac.uk/proj/adr/PNAC/pnac.html