When transferring supernatant into a new microcentrifuge tube, what is the suggested volume?

The correct choice of 250 µL for transferring supernatant into a new microcentrifuge tube is based on the typical volume ranges used in molecular biology protocols for handling supernatants. This volume allows for efficient processing while maximizing the yield of the target protein, in this case, green fluorescent protein (GFP), without exceeding the capacity of standard microcentrifuge tubes, which typically can hold up to 1.5 mL. Additionally, using 250 µL strikes a balance between being a sufficient amount to isolate the protein while also permitting easy mixing or further processing in subsequent steps, such as purification or analysis.

Choosing volumes that are too low, such as 150 µL or 200 µL, may not capture enough of the supernatant, potentially leading to lower yields of GFP. A volume as high as 300 µL could risk the limitations of the microcentrifuge tube's capacity, which may lead to spills or inaccurate measurements if the tube overfills during centrifugation. Thus, 250 µL is the most practical and effective choice for these procedures.