Methods for removing suspended particles from soluble protein solutions

1. A method for removing suspended particles from a soluble protein solution comprising the steps of:

filtering the soluble protein solution through highly purified diatomaceous earth, thereby providing a clarified soluble protein solution; and,

reducing the amount of DNA and endotoxins by flocculation with polyethylencimine at a pH of between about pH 7.3 and about pH 7.7.

2. A method for removing suspended particles from a soluble protein solution comprising the steps of:

filtering the soluble protein solution through highly purified diatomaceous earth, thereby providing a clarified soluble protein solution; and,

reducing the amount of DNA and endotoxins, wherein the protein solution is a lysate, and wherein the yield of the protein is between about 95% and about 100%.

3. A method for removing suspended particles from a soluble protein solution comprising the steps of

filtering the soluble protein solution through highly purified diatomaccous earth, thereby providing a clarified soluble protein solution;

reducing the amount of DNA and endotoxins, wherein the protein solution is a lysate, wherein the lysate is a bacterial lysate containing a heterologous protein that was obtained by expression; and,

resolubilizing retractile bodies in the lysate.

4. A method for removing suspended particles from a soluble protein solution comprising the steps of

filtering the soluble protein solution through highly purified diatomaceous earth, thereby providing a clarified soluble protein solution and

reducing the amount of DNA and endotoxins, wherein the protein solution is a lysate, wherein the lysate is a bacterial lysate containing SY161, wherein SY161 has an amino acid sequence as shown in SEQ ID NO: 1.

5. The method of claim 1 , 2 , 3 , or 4 wherein the protein comprises cysteine residues and those residues are protected by treating the residues with a protecting group selected from the group consisting of disulfides, sulfenyl compounds, thiocarbamates, thioesters, and thioethers.

6. The method of one of claim 1 , 2 , 3 , or 4 wherein the protein comprises a cysteine residue and the residue is blocked by oxidation.

7. The method of claim 5 further comprising the step of removing the protecting group.

8. The method of claim 6 further comprising the step of deblocking the residue with a reducing agent.