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Protein Detection


A colleague just performed a cellular extraction to analyze protein content.

She is particularly interested in detecting a multi-subunit, transmembrane protein with a molecular weight of ~ 45kDa (holoenzyme).

Whole protein complex (left, 45 kDa) is formed by a large subunit and a secondary subunit at 5 kDa (right). BY: Tarek Mohamed - Created for Copyright 2016. All rights reserved

She attempted to perform electrophoresis detection assays with a standard, commercially-sourced sample of the peptide complex on four fractions from the cellular extraction protocol.

Unfortunately, her experiment did not turn out as planned (based on a previously published research study), and she seeks your advice.

Using the data provided, why was the experiment unsuccessful?

Select ALL that apply.

PAGE (TOP panels) and Western Blots (BOTTOM panels): Colleague's results (left); results from a comparable research study (right). Std = Standard sample; 1-4 = Fraction numbers; Purple boxes in the Western blots = Anti-body positive bands. BY: Tarek Mohamed - Created for Copyright 2016. All rights reserved


She likely isolated the wrong proteins.


Results from the research study are likely based on native PAGE.


The concentration of protein in their sample was too dilute to be detected properly.


Their antibody for the western blot was old and not active so she was unable to detect the protein complex.


She likely used SDS-PAGE.


The standard sample was ineffective.