What you are describing would be viewed in a biotech/pharmaceutical context
as a formulation problem, and the first approach would likely be to try to
address it via modifying solvent conditions rather than covalent
modifications.
Assuming that the aggregates represent a non-native structure, you could
minimize aggregation by choosing a solvent that enhances the intrinsic
conformational stability of the native monomer. This could be as simple as
changing pH, buffer, and salt content, or you could try some of the
'classic' protein stabilizers such as amino acids or sucrose. This is
really equivalent to searching for solvent conditions that give the highest
thermal unfolding temperature.
If for this protein you instead essentially have self-association of native
monomers, it is less clear cut how to minimize the problem with solvent
conditions. Again excipients such as sucrose or PEG or even detergents such
as Tween may reduce the aggregation (but may make it worse!). Increasing
the charge to increase electrostatic repulsion may help, but doing this
through covalent modification of course risks alteration of critical
functional residues.
John Philo
Alliance Protein Laboratories
-----Original Message-----
From: Association of Biomolecular Resource Facilities
[mailto:abrf-request@aecom.yu.edu]On Behalf Of Kenneth D. Hapner
Sent: Wednesday, July 01, 1998 2:52 PM
To: Recipients of ABRF List
Subject: protein modification
Dear abrf: We have a protein (40K) that tends to aggregate to trimers,
tetramers and above. We wish to stabilize the dimer or better, the monomer.
How to do this? I remember the succinic anhydride acetylation procedure to
replace positive lysine groups with negative succinyl groups and will
likely try this. Are there other approaches that we might try? Thanks
Ken Hapner
Montana State University
khapner@gemini.oscs.montana.edu
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Kenneth D. Hapner
Department of Chemistry and Biochemistry
Montana State University
Bozeman, MT 59717-0310
khapner@gemini.oscs.montana.edu