Which of the following techniques is commonly used to study protein-protein interactions?

Two hybrid screening is a powerful technique specifically designed to study protein-protein interactions within living cells. This method relies on the principle of reconstituting a functional transcription factor when two proteins of interest interact. In a typical two-hybrid experiment, a "bait" protein is fused to one part of a transcriptional activator, while a "prey" protein is attached to another part. If the bait and prey proteins interact, they bring together the two halves of the transcription factor, leading to the activation of reporter genes. This allows researchers to easily identify and analyze the interactions between proteins in a cellular context.

In contrast, although techniques like Western blotting, mass spectrometry, and fluorescence microscopy are valuable tools in the study of proteins, they serve different purposes. Western blotting is primarily used for detecting specific proteins in a sample rather than studying their interactions. Mass spectrometry can identify proteins and their modifications, and it can provide information on protein complexes, but it does not directly show interactions under physiological conditions. Fluorescence microscopy can visualize proteins in cells and, through techniques like FRET (Förster resonance energy transfer), can provide insights into interactions, yet it typically requires prior labeling and is less straightforward than the two-hybrid system for routine protein