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ß - GAL Filter Assay

• streak yeasts to single colony
• replica plate onto NC-filter (leave 10 sec.)
• use tweezers to lift filter and slowly submerge in liquid Nitrogen for 1 min
• place on back side of a petri dish to thaw (caution filter is very brittle !)
• take new petri dish lid, add 2 ml Z-buffer
• add 35 µl X-GAL solution directly into the Z-buffer, mix well
• set Whatman filter disk (9 cm) into lid to absorb buffer
• lay thawed filter on top, avoid bubbles
• place in 30 °C incubator
• incubate 10 - 60 min

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Buffers:

 Z-buffer:
60 mM Na2HPO4 (anhyd.); 60 mM NaH2PO4; 10 mM KCl; 1 mM MgSO4
[for 500 ml: 4.26 g Na2HPO4 (anhyd.); 2.40 g NaH2PO4; 373 mg KCl; 123 mg MgSO4; adjust to pH 7.0]

 X-GAL solution:
40 mg/ml in DMF (dimethylformamide)

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