[RASMB] counterbalance functions
John Philo
jphilo at mailway.com
Fri Jan 7 11:11:08 PST 2011
Xin,
What Virgil said is mostly correct, but it is only part of the story. The
counterbalance is also required for "delay" calibration of the absorbance
optics (to set the timing of the lamp pulses). This calibration happens
every time you start a run or when the rotor speed is changed by more than
2000 rpm.
Radial calibration needs only to be done intermittently (I recommend doing
it only when the service tech has done something to the instrument). Since
the optical components are entirely independent of which rotor is used the
radial calibration is independent of the rotor, so I have to disagree with
what Virgil said about needing to recalibrate for each rotor.
If the counterbalances are machined accurately then they all should give the
same radial calibration also. Again, remember the optical components do not
move or change when you change counterbalances. If different counterbalances
give different calibrations then it is impossible to say which one is more
accurate. In that situation I would recommend adopting one of them as
'correct' and sticking to its calibration. Otherwise your results are
potentially different from one experiment to another depending on which
counterbalance you used for radial calibration.
If you are not using the absorbance optics then in fact the counterbalance
is not required and an additional interference or fluorescence sample can be
run in that hole.
John
-----Original Message-----
From: rasmb-bounces at rasmb.bbri.org [mailto:rasmb-bounces at rasmb.bbri.org] On
Behalf Of Virgil Schirf
Sent: Friday, January 07, 2011 9:55 AM
To: Xin-Ping Xu/FS/VCU
Cc: rasmb at rasmb.bbri.org
Subject: Re: [RASMB] RASMB Digest, Vol 16, Issue 1
Hi Xin,
The counterbalance is used to calibrate the AUC radially. There are masks,
held in place by set screws, inside the counterbalance which have an edge of
5.85 cm on the inside and 7.15 cm on the outside. You should also notice
that there is an offset of the mask on the inside edge between the
'reference' side and the 'sample side'. The counterbalance is placed in hole
4 of the An60 Ti or in hole 8 of An50 Ti rotor. You will need to perform
radial calibrations periodically if you are using the same rotor and every
time you change rotors/counterbalances.
You can go to http://cauma.uthscsa.edu and under the Home Links is an AUC
Hardware User Guide put together by Dr. Karel Planken and myself where there
is more of a description of the counterbalance and other hardware
information about the AUC.
Best regards,
Virgil
Xin-Ping Xu/FS/VCU wrote:
> Hi, everyone,
> I am also a beginner in AUC, could someone tell me what are the
> functions of counter balance? If it is just as a balance, we can use
> other cell as balance.
> Thanks.
> Xin Xu
>
>
> -----rasmb-bounces at rasmb.bbri.org wrote: -----
>
> To: rasmb at rasmb.bbri.org
> From: rasmb-request at rasmb.bbri.org
> Sent by: rasmb-bounces at rasmb.bbri.org
> Date: 01/07/2011 12:00PM
> Subject: RASMB Digest, Vol 16, Issue 1
>
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> Today's Topics:
>
> 1. question about counter balance (Jia Bei Lin)
> 2. Re: question about counter balance (Walter Stafford)
> 3. Re: question about counter balance (Leech, AP)
>
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 6 Jan 2011 17:29:37 -0600
> From: Jia Bei Lin <jiabei at uab.edu>
> To: "rasmb at rasmb.bbri.org" <rasmb at rasmb.bbri.org>
> Subject: [RASMB] question about counter balance
> Message-ID:
> <2A5095E179BC5F4F87BF7B8DBAEBD320333AA6B752 at UABEXMBS1.ad.uab.edu>
> Content-Type: text/plain; charset="us-ascii"
>
> Dear professors and colleagues,
>
> I'm in the learning process of using the Beckman XL-A
analytical ultracentrifuge. There are two counter balances in the lab, one
of them is 33.6 grams and the other is 31.7 g just by themselves (no weight
inside). Why are they made in different weight? They look identical from
outside, what's inside made the difference?
>
>
> Thank you very much. Happy new year.
>
> Jiabei Lin
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> Message: 2
> Date: Thu, 06 Jan 2011 18:45:21 -0500
> From: Walter Stafford <stafford at bbri.org>
> To: Jia Bei Lin <jiabei at uab.edu>
> Cc: "rasmb at rasmb.bbri.org" <rasmb at rasmb.bbri.org>
> Subject: Re: [RASMB] question about counter balance
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> Message: 3
> Date: Fri, 07 Jan 2011 10:55:20 +0000
> From: "Leech, AP" <apl3 at york.ac.uk>
> To: Jia Bei Lin <jiabei at uab.edu>
> Cc: "rasmb at rasmb.bbri.org" <rasmb at rasmb.bbri.org>
> Subject: Re: [RASMB] question about counter balance
> Message-ID: <4D26F118.40102 at york.ac.uk>
> Content-Type: text/plain; charset=UTF-8; format=flowed
>
> Hi Jia Bei, Walt,
>
> We have two centrepieces, one weighs 31.62 g and the other 31.91 g
> without weights.
>
> The weights themselves are also not quite exact, they vary up to
> about 0.05 g from the nominal marked weight.
>
> Andrew
>
> On 06/01/2011 23:45, Walter Stafford wrote:
> > Hi Jiabei;
> >
> > It's possible that one of them is missing the masks (held in by a
small
> > hex screw) that provide the reference edges for the radial
calibration.
> > Take a close look. It may not be obvious at first glance.
> >
> > Walter
> >
> > --
> >
> > ===============================================
> > Walter F. Stafford, Ph.D.
> > Senior Scientist
> > Boston Biomedical Research Institute
> > 64 Grove Street
> > Watertown, MA 02472
> > 617-658-7808
> > skype: w.stafford3
> > ----------------------
> > "Be kind, for everyone you meet is fighting a hard battle." -Plato
> > ------------------------------------
> >
> >
> >
> > Jia Bei Lin wrote:
> >>
> >> Dear professors and colleagues,
> >>
> >> I?m in the learning process of using the Beckman XL-A
> >> analytical ultracentrifuge. There are two counter balances in the
lab,
> >> one of them is 33.6 grams and the other is 31.7 g just by
themselves
> >> (no weight inside). Why are they made in different weight? They
look
> >> identical from outside, what?s inside made the difference?
> >>
> >> Thank you very much. Happy new year.
> >>
> >> Jiabei Lin
> >>
> >>
> >> _______________________________________________
> >> RASMB mailing list
> >> RASMB at rasmb.bbri.org
> >> http://rasmb.bbri.org/cgi-bin/mailman/listinfo/rasmb
> >>
> >
> >
> >
> > _______________________________________________
> > RASMB mailing list
> > RASMB at rasmb.bbri.org
> > http://rasmb.bbri.org/cgi-bin/mailman/listinfo/rasmb
>
> --
> Dr Andrew Leech * Laboratory Head
> Technology Facility * Molecular Interactions Laboratory
> Department of Biology (Area 15) * Tel : +44 (0)1904 328723
> University of York * Fax : +44 (0)1904 328804
> PO Box 373, York YO10 5YW * Email : apl3 at york.ac.uk
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--
Virgil Schirf
Technical Director, Center for Macromolecular Interactions
<http://cmmi.uthscsa.edu> Department of Biochemistry, Rm 4.523U The
University of Texas Health Science Center
7703 Floyd Curl Dr.
San Antonio TX 78229-3900
Voice mail: 210 567-6590
Fax: 210 567-6595
Email: schirfv at biochem.uthscsa.edu <mailto:schirfv at biochem.uthscsa.edu>
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