Synthesis of lipophilic peptides and characterisation !

[Ganesh Jawahar Swaminathan]

	I am a graduate student studying the synthesis and bioactivity of
lipophilic peptides. I am attaching long chain fatty acids like stearic acid,
palmitic acid etc to the N-terminalof peptides. Protocol involves 

a) addition of fatty acid (in DCM or DMF) to the resin-bound de-protected 
peptide in the presence of HoBt and DIPCDI. 

b)Reaction is overnight at 35C with shaking. 

Post-cleavage Rp-HPLC of the peptide indicates an increase (2times) in the
retention times as compared to the native peptides. ES-Mass, however, gives
molecular weights lower than the predicted  molecular weight  i.e 1729 instead
of expected 1905 !
I need help to answer the following problems:
a) is ES-Mass the right method to characterise lipophilic peptides.
b) any problem with the protocol followed 
c) any method to check conjugation of lipid to peptide i.e use of
lipid-specific stain in TLC or any wet tests ?
d) Can you suggest any alternative tried and tested protocol.
Any help in this regard will be highly appreciated.
Please mail your responses to this address.
cheers,
Jawahar


-- 
Jawahar Swaminathan     \ /      E-mail: jawahar at nii.ernet.in
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