[RASMB] summary of MALLS

[Joel Mackay]

hi all
Aside from John Philo's reply, which was sent to all, here are the titbits 
of information that i received:

Neil Errington said:
We had both a mini-DAWN and a 'full-size' DAWN from Wyatt when I was at the
NCMH in Nottingham. Unfortunately we didn't use them on proteins so much as
polysaccharides so I can't say anything directly about their use in that area,
but I would imagine that with 5-10kDa protein/peptides you would need quite a
high concentration to detect them by MALLS.
As for refractive index values I found it better to measure them rather than
use calculated values, you can do this fairly easily in the ASTRA software 
that
comes with the DAWN instruments. The person there who has used these
instruments the most is Conny Jumel so it may be worth asking her too.

Allen Minton said:
Joel, we have been working with a Wyatt DAWN EOS apparatus for about 9 
months now, and my strong opinion is that the technique is by no means as 
foolproof and "point-and-click" as the Wyatt folks would have you believe 
it is -- particularly for proteins. It is a sophisticated technique which 
is capable of producing reliable results, but only in the hands of those 
who understand the method thoroughly and are aware of all of the possible 
pitfalls, of which there are quite a few. In this respect the technique 
parallels analytical ultracentrifugation, which is by no means as foolproof 
and "point-and-click" as the Beckman-Coulter blurbs would have you believe. 
You could probably say the same about most other quantitative biophysical 
measurements. The manufacturers want to sell as much hardware as possible, 
and there aren't that many investigators around who are prepared to do the 
homework, so they try to "dumb it down" as much as possible. The bottom 
line is that you shouldn't have blind faith in the black box approach to 
light scattering. Scientists should be skeptics, not believers.
So if -- but only if -- you are willing to become a serious student of 
light scattering, then go for it.

Glenn King said:
Our mini-DAWN has been great. We've measured masses down to 5.6 kDa with
high accuracy.

 > *Do you use a refractometer to measure your refractive indices?
Yes, we use Wyatt's OPTILAB DSP refractometer.

cheers
joel



*****************************************************************
Dr Joel Mackay
Senior Lecturer
School of Molecular and Microbial Biosciences
Building G08
University of Sydney,
Sydney, NSW 2006
Australia
ph +61-2-9351-3906
fax +61-2-9351-4726
WWW: http://www.mmb.usyd.edu.au/mackay/
Sydney Protein Group Website:
http://www.mmb.usyd.edu.au/spg/
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