[RASMB] Viscometer

Thu Jun 6 05:43:42 PDT 2013

Good morning Richard,
    Wyatt Technology offers the ViscoStar-II (http://www.wyatt.com/solutions/hardware/viscostarii-viscometer.html) , a commercially available online differential viscometer. If you have a SEC or GPC system, integrating the ViscoStar-II is straightforward and will provide the specific viscosity of your protein samples. With typical sample volumes for analytical SEC being under 100 ul, this small sample volume requirement is advantageous.

   Coupling a concentration detector, such as our Optilab T-rEX (http://www.wyatt.com/solutions/hardware/optilab-t-rex-refractive-index-detector.html) will allow for calculations of the intrinsic viscosity as well. I'd be happy to discuss our ViscoStar-II or any of our detectors with you. Please let me know if you have any questions.

Best Regards,
Will

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From: rasmb-bounces at list.rasmb.org [mailto:rasmb-bounces at list.rasmb.org] On Behalf Of Arthur Rowe
Sent: Thursday, June 06, 2013 6:23 AM
To: Richard Kingston
Cc: rasmb at rasmb.org
Subject: Re: [RASMB] Viscometer

Hi Richard

If by 'protein solutions' you solutions of proteins which are 9more or less) 'globular', then you have a serious problem on your hands. The 'signal' with which you are dealing (difference in flow or roll time of a ball in a capillary or narrow tube) is very small, and is not readily measurable in solutions of low (<~5 mg/ml) concentration. You might want to consider reading through Steve Harding's 1997 review of this area - old, but the basic physical facts have not changed. As regards using commercially available equipment, our own experience in the NCMH is that even with the AMVn rolling ball viscometer, no longer marketed but as good as has ever been made, we struggle to cope with globular proteins. Even with careful pre-treatment of the lining of the tubes to minimise protein-surface interactions.

A possible way forward is to follow the method published by Szuchet-Derechin and Johnson (1966) and add a small (few %) amount of glycerol to both solution and reference solvent. This increases the level of the 'signal', without - hopefully - any specific glycerol-induced effects.

However, in the case of your own proposed work, there is a ray of hope. The repeatability of the (time) measurements for a given tube (or capillary) is normally much better than the reproducibility (experiment to experiment) of e.g. one concentration level to another. If it is the temperature dependence of the viscosity you are looking to asses, then by starting at a low temperature and working up (e.g. 5º at a time) you just might have enough precision, as you will be working in relative not absolute mode.

Hope this is helpful.

Regards to you, and all colleagues

Arthur

S.E.Harding (1997) Prog. Biophys. molec. Biol 68 207-262 (pdf available)
S. Szuchet-Derechin & P. Johnson (1966) Euro. Polymer J. 2 115-128

Professor Arthur J Rowe
NCMH/Food Sciences
University of Nottingham
Sutton Bonington
Leics LE12 5RD UK

Tel: +44 115 9516156
arthur.rowe at nottingham.ac.uk<mailto:arthur.rowe at nottingham.ac.uk>

On 6 Jun 2013, at 05:14, Richard Kingston wrote:

Dear all,

I've become interested in measuring the viscosity of protein solutions at varying temperature,  and wondered if anyone on the list could advise on the best way to do this using commercially available instrumentation. While there are many  ways to measure viscosity, for protein applications minimizing the required sample volume is pretty critical. I note that  Anton Paar sell an instrument that measures both dynamic viscosity and density  (SVM 3000 Stabinger viscometer). If you skip the density measurement, the sample requirements look almost "manageable". Cambridge also sell a micro-sample viscometer (Viscolab 5000) which uses microlitre volumes.

I'm having difficulty tracking down people that might have used these or similar instruments, and could comment on the practicalities for protein work. If anyone can offer advice, either on- or off-list, it would be appreciated.

Many thanks,

Richard

Richard Kingston, PhD.
School of Biological Sciences
The University of Auckland
New Zealand

website: http://persephone.sbs.auckland.ac.nz/richard/lab/

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