From: Disher, Rose [CNTUS] <DisherR@Centocor.com>
  To  : ">"'Walter Stafford'" , RASMB@bbri.org
  Date: Tue, 29 Aug 2000 09:20:00 -0400

RE: scratches on centerpieces

This may be old news to many of you, but I thought I would share this
anyway.  We do lots of SDS-PAGE in our group, and have thin pipet tips used
for loading gels around the lab.  I have found that a round-tip gel loading
pipet tip on a 200mL pipettor works really well for loading sedimentation
velocity cells and is much less expensive than the Leur-Lok Hamiliton tubing
recommended by Beckman.  It also prevents the operator from accidentally
stabbing the centerpiece or him/herself with a syringe needle. Although
using the tips requires two pipettings to fill a standard cell, this also
has the advantage of eliminating the risk of cross contamination that comes
with the syringe/tubing method.  Another benefit is the additional reduction
in the usually low risk of the accidental introduction of metal ions from a
syringe needle into the sample.  The low level of metal ions from a needle
is usually not a real problem, but could be an additional source of
artifacts for someone looking at proteins with metal-sensitive conformations
(eg. ion channels, heme proteins, zinc finger regions, etc.) 

		-----Original Message-----
		From:	Walter Stafford [STAFFORD@bbri.org]">mailto:STAFFORD@bbri.org]
		Sent:	Monday, August 28, 2000 9:54 PM
		To:	RASMB@bbri.org
		Cc:	STAFFORD@bbri.org
		Subject:	scratches on centerpieces

		RASMBers,
			Here is the last exchange I had recently with a
colleague concerning
		potential artifacts in sedimenatation velocity runs. Thought
it might be of 
		general interest.

		- Walter

		p.s. that centerpiece (as well as several others found
later) was removed
		from service.
	
========================================================================== 
		From:	STAFFORD     "Walter Stafford" 28-AUG-2000
21:25:38.11
		To:	SMTP%"knut@bbri.org"
		CC:	STAFFORD
		Subj:	RE: question

		Well, actually, there is a potential problem that I have
experienced.
		If there is a scratch in the wall of the centerpiece on the
sample side, it 
		can cause convection. I had one cell that created a shoulder
on every sample I 
		ran. Take a look at the wall of the septum between the
sectors on the side you
		usually load the sample. If you jab the wall with the
syringe needle, it will
		create a scratch deep enough to cause his type of problem. 

	
=======================================================================
		>Walter,
		>i was just wondering if there was any experimental
problems,
		>like something with the cells that could cause asymetry of
the peak.
		>
		>--knut



	
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		Walter F. Stafford III, Ph.D.
		Senior Scientist
		Analytical Ultracentrifugation Research Laboratory
		Boston Biomedical Research Institute
		64 Grove Street
		Watertown, MA  02472-2829

		tel: (617) 658-7808
		fax: (617) 972-1753

		Telephone switchboard operator: (617) 926-8040 or (617)
658-7700

		stafford@bbri.org">mailto:stafford@bbri.org

	
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