How does mass spectrometry aid in protein analysis?

Mass spectrometry is a powerful analytical technique used in protein analysis primarily through the measurement of peptide mass. In this process, proteins are often enzymatically digested into smaller peptides, typically using proteolytic enzymes such as trypsin. These smaller peptides are then ionized and introduced into the mass spectrometer.

Once inside the mass spectrometer, the peptides are separated based on their mass-to-charge ratio (m/z). This allows for detailed analysis of the peptide composition, relative abundance, and ultimately provides insight into the original protein's identity and structure. The mass measurements can be used for various purposes, including identifying post-translational modifications, determining sequence information, and quantifying proteins in complex mixtures.

This process does not directly identify the three-dimensional structure of the protein nor does it change the protein conformation, nor does it determine the isoelectric point (pI) of the proteins, which are the focuses of the other answer options. The ability to accurately measure the mass of peptides formed from protein digestion makes mass spectrometry an essential tool in proteomics and protein characterization.