From: Michael Jacobsen <jacobsen@biosci.uq.oz.au>
  To  : rasmb@bbri.eri.harvard.edu
  Date: Thu, 09 Jun 1994 13:23:17 +1000

analysis of associating systems and effects of molecular crowding

I wish to put out a call for information that could lead to the appropriate 
selection of candidate solutes to function as "large-inert" space-fillers. 
Candidate solutes will be used in model studies on the contributing effects 
of nonideality and self-association of associating solutes as a result of 
molecular crowding. These studies will be carried out in an XL-A 
ultracentrifuge (possessing only absorption optics). As a result, candidate 
space fillers need to satisfy certain obvious and some less obvious criteria of

1. purity,

2. stability over a moderate range of pH, temperature and ionic strength,

3. availability in relatively large quantities

4. known or suspected as behaving as an inert non self-associating solute 
(i.e inert and monodisperse),

and

5. possess an absorption characteristic in order to measure both its 
distribution and affect on the self-association and nonideality of an 
associating solute in the same solution,

or

6. lack an absorption characteristic (eg. an A280) whilst possessing a much 
lower molecular weight than the associating solute so as to measure its 
affect on the self-association and nonideality in the same solution.

7. ???

I have looked at the possibility of using metallothionein (which apparently 
lacks the characteristic A280 of most proteins due to few if any aromatic 
residues) but the cost would prohibitive due to the relatively large amounts 
required. I have also enquired as to the suitability of synthetic "polymers" 
that are monodisperse and soluble in buffered solvents without immediate 
success. Perhaps there are some small proteins (large peptides) that could 
satisfy some if not most of the criteria above that someone has access to or 
knows of??

Any feedback or ideas on this would be most appreciated.







Michael P. Jacobsen
Centre for Protein Structure, Function and Engineering
Biochemistry Department
University of Queensland
St. Lucia 4067
Australia.


Phone:      (07) 3653348
voice-mail: (07) 3653348
Fax:        (07) 3654699
e-mail:<jacobsen@biosci.uq.oz.au>