For some time we have used "slickseal" tubes from National
Scientific (sold in the US by VWR as their Cat. #20172-958), which are
siliconized to prevent binding of very small amounts of purified peptides
or proteins. These tubes have generally resulted in higher recoveries from
low level enzyme digests, and have in the past seemed to tolerate moderate
levels of CH3CN from gradients without bleeding much impurities. However,
recently we got a bad batch that contained huge amounts of contaminants-
peptides collected in these 0.6 mm tubes and then diluted with H2O and
reseparated on a 1 mm column were giving off-scale impurities which stayed
off scale for 25 minutes in a 1%/min gradient! This caused gross
contamination of several peptides we were isolating on a very small scale
which were nearly pure: VERY costly of time and precious samples.
This has pointed out the wisdom of washing tubes with organic
before using them- one of my questions is whether anyone knows of
availability of an apparatus for vapor-phase degreasing of tubes and
pipette tips with an organic solvent such as methanol, making this an
easier job than manual washing?
SECONDLY, does anyone have any experience with tubes from
Continental Lab products- Biological Brand, 0.6 ml, claimed to be lower
retention of proteins/peptides than polypropylene? We are trying these
out, and a grad student, Joe Hull, finds they contain some amount of
impurities that leach SLOWLY into acetonitrile. My concern here is not
just cleanliness of the tube, but whether or not the claims of reduced
binding are true. The represntative plays secretive and won't tell what
the platic is, only that it is not polypropylene.
David
David A. Schooley
Dept. of Biochemistry/330
Univ. of Nevada
Reno, NV 89557
schooley@med.unr.edu
tel: (702) 784-4136; fax (702) 784-1419