1. add 30 ml of phage stock to SS-34 Oakridge tube.
2. add 7.5 ml 20 % PEG-8000/2.5 M NaCl.
3. incubate on ice for 30 minutes or longer.
4. spin down phage @ 11K for 20 minutes.
5. respin 2-3x to remove all of PEG solution (using a micro-pipet tip facilitates removal of all solution).
6. resuspend phage in STE (500-1000 ul).
7. transfer to eppendorf and spin @ 14K for 10 minutes.
8. transfer supernatant to new eppendorf and label.
9. titer phage.
STE: for 100 ml add 1 ml 1 M Tris (pH 8), 0.2 ml 0.5 M EDTA (pH 8),
2 ml 5 M NaCl. Autoclave.
PEG: for 100 ml add 20 gm PEG-8000 and 14.6 gm NaCl, filter sterilize.