Bradford Assay Experimental Observations & FAQs

If you need a brief refresher on the Bradford assay, review the assay itself or our data processing eForm. We'll add some common questions and answers pertaining to this experiment here. This complements our Knowledge Base, so be sure to search it, too. The Knowledge Base retains the most current and thorough reviews.

Experimental Design

How many samples are required to create a valid standard curve?

Technically, an absolute minimum of three different points are required to produce a "curve" from which to derive an equation. In reality this is clearly inadequate. A better series from which to derive a valid curve should include between five and ten different sample points. Obviously, the more points along the curve, the more accurate its derived equation and subsequently calculated data.

Experimental Procedure

Why do I need to "warm up" the spectrophotometer?

This is important to stabilize the experimental environment and ensure that the light source is uniform throughout the sample-reading process.

Experimental Results

Why are absorbance values below zero?

If an experimental sample's absorbance measure returns a value less than zero, then that sample had an amount of protein small enough that it fell out of the protein range predicted by the linear progression curve. If this happens with any samples created to establish the standard curve (not the experimental samples), then your spectrophotometer has either a) not reached a stable operating temperature, b) not been properly calibrated and is operating out of "spec", or c) has some source of light "noise".

Experimental Conclusions