[ccp4bb] is there any DNA?

Dear all, We all know that for purified protein, A260/A280=0.5, and for purified DNA, A260/A280=1.8. Now my protein A260/A280=0.75, So I wonder if there is DNA mixed with protein? Is there any way I can use to test if there is DNA? Thanks~

[ccp4bb] Can I add PEG or Li2SO4 into protein sample for new screen?

Hi everyone, I wonder if I can add PEG or Li2SO4 into protein sample for new screen? Because optimization seems no good result, initial crystal was got in Bis-Tris, PEG8000, Li2SO4. If it is OK, then what's the concentration of PEG or Li2SO4? Best regards, Shiqing