Small peptide purification blues

Thu May 26 14:09:55 EST 1994

I have a peptide query:

	I'm trying to isolate a peptide about 1000 to 1500 Da (best guess)
and probably cyclic. Initial purification steps are: acid precipitation
(very inefficient) followed by ion exchange chromatography (which
works well). I want to make polyclonals against the peptide and need
more purification steps so I've set up a gel filtration column. Now I
need to concentrate the sample before loading the column. The sample is
about 20 ml in volume and contains approx 0.4M NaCl and 10 mM Tris buffer
pH 7.5. The peptide is reasonably easy to produce, so we can tolerate 
some loss.
	We're considering trying: 

1) Ultrafiltration (but can't find any appropriate columns)
2) Ammonium sulphate precipitation (the peptide appears to be quite soluble)
3) Phenol (will the peptide go into the phenol? and how do we get it back?)
4) ?????

Thanks for any suggestions or protocols...


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