Hello,
I would like to work with the second virial coefficient (A2 or B22) to determine the best conditions to formulate protein buffers and also to determine the best conditions for crystallisation tests.
If I well understood, a range between -1.10E-4 and -8.E-4 increases our chance to get crystals.
However, is there a range or a rule of thumb for the aggregation value with A2 and for the best conditions for formulation.
Best,
Sébastien
Wilson's paper covers the crystallization slot. Wilson "Light scattering as a diagnostic for protein crystal growth - a practical approach", Journal of Structural Biology, 2003 (142), 56-65.
As for an aggregation rule of thumb, I've never heard of one - nor would I expect to. B22 is representative of the chemical potential between like species. Aggregation requires not only favorable energy but also favorable kinetics. B22 = 0 defines the theta condition, where the potential for self-association is exactly balanced by the potential for solvation. For B22 > 0, the energetics favor solvation; for B22 < 0, the energetics favor self-association; with the strength of each dependent upon the magnitude of B22. So if you a system with a negative B22 value, you system is prone to self-association, once the kinetics are favorable.
Hope this helps.
You might find it easier to work with KD (diffusion interaction parameter). In comparison to B22, it is relatively easier to determine KD using DLS or other experiments that measure diffusion in protein solutions at different concentrations. There is more data available in literature on KD than B22, especially for the antibody solutions.
I hope this helps.
Thank you for your reply.
Sandeep, do you have a review or a paper talking about kD in details? I work with a Viscosizer instrument which give me kD values. In the litterature I found more data about B22 than kD that is why I talked about B22 instead of kD in this topic.
Then I wanted to convert my kD values in B22 with the next equation:
B22=(kD+8.9)/(M*1.06)
where M is the molecular mass
Thank you for your help,
Sébastien
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