求问 2Xlaemmli sample buffer 怎么配制？

1. Sample Buffer, Laemmli 2× Concentrate:Solution contains 4% SDS, 20% glycerol, 10% 2-mercaptoethanol, 0.004% bromphenol blue and 0.125 M Tris HCl, pH approx. 6.8. 2. SDS gel-loading buffer (2X) 100 mM Tris-Cl (pH 6.8), 4% (w/v) SDS (sodium dodecyl sulfate; electrophoresis grade), 0.2% (w/v) bromophenol blue, 20% (v/v) glycerol, 200 mM DTT (dithiothreitol)Store the SDS gel-loading buffer without DTT at room temperature. Add DTT from a 1 M stock just before th