[RASMB] Centerpiece question

[Walter Stafford]

Hi John,
I used a sharpened dissecting needle and a metal straight edge. And, yes you need an additional capillary at the top to allow the air to transfer to equalize the pressure between the sectors. Good point. Standard synthetic boundary cp's have both capillaries.

Walter
p.s. I don't think diamond tipped pens are very expensive.
You can get a carbide tipped pen (just as good on epon) from Sigma for  $15.60 Cat # Z225568-1EA
http://www.sigmaaldrich.com/catalog/product/aldrich/z225568?lang=en&region=US


On Dec 18, 2014, at 13:22, John Sumida <jpsumida at u.washington.edu> wrote:

> Walter,
>  
> Thanks.  What would you use to cut/scribe the channel.  I see that someone on RASMB used a diamond point pen – which sounds expensive.  Could one use an exacto blade?
>  
> I assume one would also want to cut a straight capillary channel somewhere near the top of the channel to equalize pressure?
>  
> John S.
>  
> From: Walter Stafford [mailto:wstafford3 at walterstafford.com] 
> Sent: Thursday, December 18, 2014 9:57 AM
> To: John Sumida
> Cc: rasmb at rasmb.org
> Subject: Re: [RASMB] Centerpiece question
>  
> Hi John,
>                 The synthetic boundary centerpieces generally work OK. A potential problem is that some protein may transfer from the solution side to the reference either by diffusion or by sedimentation (i.e. if the capillary is slightly "downhill" from the samples side to the reference side.)
>  
> The MM centerpieces were designed to avoid that potential problem. If you want to make your own MM centerpieces, you can scribe a capillary on the center rib with a deliberate "uphill" slant to avoid mixxing - this must be done very carefully under a dissecting microscope with a sharp, pointy object and must not be "too" deep, etc, etc... And no caffeine ...
>  
> Good luck,
> Walter
>  
>  
> On Dec 18, 2014, at 12:44, John Sumida <jpsumida at u.washington.edu> wrote:
> 
> 
> Dear RASMB,
>  
> For interference measurements where matching the sample and reference channel menisci is essential, is there a preference for either the meniscus matching centerpiece versus synthetic boundary centerpiece.  We would be interested to hear about pros and cons.
>  
> Thank you and happy holidays.
>  
> Best regards,
>  
> John Sumida, Ph.D.
> Analytical Biopharmacy Core Facility
> University of Washington
> Molecular Engineering & Sciences Institute, G22
> 3946 West Stevens Way NE
> Seattle WA 98195-1653
>  
> _______________________________________________
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>  
> 
> Walter Stafford
> wstafford3 at walterstafford.com
> 
> "We're all better off when we're all better off" –Eric Liu
>  


Walter Stafford
wstafford3 at walterstafford.com

"We're all better off when we're all better off" –Eric Liu

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