Question

What are the positive and negative controls for (a) SPSPAGE and (b) Bradford Assay.

Answer 1

Answer-

Positive control = The positive control is the sample that shows expected results that may contains standards that give sure positive results. If our test sample shows same results as positive control then we can say that test is positive.

Negative control = The negative control is the sample that is treated in same way as test samples and they will not give any positive result. If our test sample also does bot give any change and looks like negative control then we can say test is negative.

SDS-PAGE positive control = For SDS-PAGE, any standard protein whose molecular weight is known is used as positive control. After staining, these positive control protein shows bands and by comparing unknown samples we can determine molecular weight of unknown protein.

SDS-PAGE negative control= SDS-PAGE negative control is only sample loading buffer that will not give any band after staining.

Bradford assay positive control = The positive control for Bradford assay is the standard BSA which will give colour change after addition of Bradford reagent. If unknown sample also changes colour as positive control then we can say that protein is present and we can also determine its concentration.

Bradford assay negative control = for Bradford assay PBS buffer is used as negative control and it will not change colour after addition of Bradford reagent as it does not contain any protein. If test sample also does not change colour as negative control then we can conclude that protein is absent in test sample.