It may be tangent to your question, but this article may be an interesting reference for you if you're not already aware:

http://dx.doi.org/10.1021/ma801382j

Thanks Jeffrey, but that paper is talking about the ionic strength effects on shear banding, and it does not mention too much about the theta condition.

But thanks anyway!

Yes, it does not deal with your question directly, but you may want to consider the effects discussed in the paper if you are looking to do rheology on DNA solutions.

While not being a biochemist, I’d throw in my two cents anyway.

I would think temperature would be a factor. The molecular weight does influence onset of phase separation (the observed phenomenon). In the limit of infinitely high molecular weight, the cloud point and theta temperature are the same, whereas they diverge at lower Mw (cloud point being higher than theta temp which is a direct consequence of the translational entropy). I would think conformational structures would influence this as the number of sites available for hydrogen bonding would depend on this as well.

Hello there,

First of all, I agree with the previous comments on temperature.

Apart from your question to achieve the theta condition,

you may be interested in my paper where I made simulation

of rheology of DNA solution, assuming the theta condition;

http://dx.doi.org/10.1063/1.3225994

Since my prediction and the data are in good agreement,

I suppose the experiment (made by Prof. Shaqfeh's group) may be

in vicinity of the theta condition. You may take a look on the experimental

paper;

http://dx.doi.org/10.1021/ma062932e

Good luck.