1. suspend a single plaque in 1 ml PSB
2. adsorb 10 min at 37°C: 0.1 ml eluted phage*/0.1 ml MgCa/0.1 ml saturated K802 culture grown in NZY broth/0.2% maltose
3. use 10 ml of this to inoculate 2.5 ml NZY, shake ovn at 37°C or until lysed
4. cool to RT, then add 2 drops of CHCl₃
5. add 5 ml of 10 mg/ml DNase I (20 mg/ml final) and gently shake for 25 min
6. divide lysate into two Eppendorf tubes, spin 5 min
7. transfer 0.6 ml of each tube into a new tube prefilled with 200 ml of STE
8. mix and incubate 15 min at 70°C
9. cool to RT, add 150 ml 8 M KAc, mix and keep on ice for 15 min, spin for 15 min
10. save 700 ml of clear supernatant, extract 1x with phenole/chloroform (vortex 5 sec)
11. add 420 ml 2-propanol, mix and let sit at RT for 10 min
12. spin for 8 min, very carefully remove supernatant (pellet does not stick to bottom of tube very well)
13. wash pellet twice with 0.5 ml of 70% EtOH (-20°C), dry in speed vac
14. digest pellet in 50 ml each of 0.3 mg/ml panc. RNase in TE, pH 8.0 for 30 min at 37°C
15. pool to 100 ml per sample, add 40 ml of 5 M NH₄Ac and 200 ml 2-propanol
16. keep 10 min at RT, spin 10 min
17. remove supernatant, wash with 0.5 ml of 70% EtOH (-20°C), dry in speed vac
18. take up pellet in 20 ml 1x TE, usually 10 ml can be used for a restriction digest

Solutions:

STE: 1.5 % SDS, 0.3 M Tris (pH 9), 0.15 M EDTA STE   10 % SDS 7.5 ml 2 M Tris pH 9 7.5 ml 0.5 M EDTA 15.0 ml Total 50.0 ml		l-dil: 10 mM Tris-HCl pH7.5/10 mM MgSO4, autoclave before use l-dil   2 M Tris-HCl pH 7.5 5.0 ml 1 M MgSO4 10.0 ml H2O 985.0 ml Total 1 l
MgCa: 10 mM MgCl2/10 mM CaCl2, autoclave before use MgCa   1 M MgCl2 5.0 ml 1 M CaCl2 5.0 ml H2O 990.0 ml Total 1 l		PSB: 10 mM Tris-HCl pH 7.5, 0.1 M NaCl, 10 mM MgCl2, 0.05 % gelatine; store over CHCl3 PSB   2 M Tris-HCl pH 7.5 1.0 ml 5 M NaCl 4.0 ml 1 M MgCl2 2.0 ml 0.5 % gelatine 20.0 ml H20 173.0 ml Total 200.0 ml

Remarks:

*: this value holds true for genomic phages (EMBL4, Lambda DASH), if using cDNA phages (lgt10/11, Lambda ZAP) take: 1 ml of eluted phage in each of 0.1 ml l-dil, MgCa and K802. This is a tricky protocol. However, when strictly adhering to the indicated treatment times and generally experimenting carefully it should work allright.