Hi :D

I have a question.

We expressed a protein from E. coli and we got purified peptide.

But when we concentrate it with centrifuge filtration (like amicon), It became like a gel.

So when we invert it, it doesn't move from the bottom of the tube.

This protein is a tetramer protein (~33 kDa). So only monomer, there was no problem with gelation.

But when we make it tetramer, it makes a problem.

Actually, we tried to mix with Tween 20, But it doesn't work.

The sequence composition is acidic 18%, Neutral 26.5%, Basic 15.5% and Hydrophobic 40%.

The pI is 4.87.

The buffer is just DW. Actually, we don't use some strong ionic buffer. It will be conjugated with other materials or modification more. So, we are looking for addictives. But if you recommend some buffers for us, we try to do :D.

So, I have two questions:

1. How to prevent the gelation of our protein during concentration?

Is there anyone who had a similar problem with us?

2. Is there any possible way to predict or calculate the protein's solubility or gelation or etc?

We want to simulate or calculate which amino acids make a problem in the sequences.

If we can, we'll try to point mutation of the sequences.

Thank you.