If no signal is detected in a total cell extract, it is worth to fractionate, to obtain specific chloroplast, mitochondria or nuclei enriched fraction. This procedure will allow to concentrate a target protein and lead to a detection of desired band (for non-cytoplasmic proteins), as shown in the example above - from no band in a total cell extract, to a specific band in photosystem I fraction.
This approach is especially important when working with proteins of low expression. Fractionation combined with usage of a specific organ, for example root tip, leaf at a certain developmental stage, will greatly contribute to a success with identification of a protein of interest.
Examples of protocols to fractionate can be found here.
For Agrisera Western Blot Guide and video tutorials, check here.
In case of any questions, you are always welcome to contact Agrisera Technical Support.