Mass Spec. Applications
Mass spectrometry was originally invented to determine elemental atomic weight. Now, scientists can use mass spectrometry for a broad range of applications, the key of which is its ability to sort ions within molecules. From determining the ion signal as a function of its mass-to-charge ratio, scientists can determine particle mass, isotopic signature, and chemical structure. Given this functionality, researchers use mass spectrometers for a broad range of applications in drug discovery, clinical testing, genomics, environmental sciences, and proteomics.
In particular, scientists can now use mass spectrometers for proteomics, allowing for more research into protein detection, identification, and quantitation, with the ability to read samples ranging from 50 – 300,000 daltons.
All mass spectrometers contain three parts: the ion source, the mass analyzer, and the detector. The ion source transforms the sample into ions, regardless whether the sample is a solid, liquid, or gaseous state (depending on the mass spectrometer used). The analyzer of a mass spectrometer is the section in which the ions are organized based on their mass-to-charge ratio. Lastly, as the name implies, the detector detects and records the ions based upon their characteristics.
At the beginning of a mass spectrometer run, the sample is inserted into the ion source. Once the sample has been converted into ions, the ion source then accelerates these molecules into the mass analyzer. There, the sample ions are exposed to electric or magnetic fields which sort the ions based on their mass-to-charge ratio. From there, the ions then encounter the detector, which emits a cascade of electrons, the amount of which depends on the ions. This emission is then read by various software which prints out a graph depicting the emission, which can then be used to determine the identity of the sample.
Proteomics is a difficult field of study, as most proteins undergo modifications after the translational process. That is why with the advancements of ionization techniques of mass spectrometers, proteins are now able to be detected and analyzed thanks to peptide ‘fingerprints’ that can be used to identify proteins within a database.
Peptide Mass Fingerprinting involves taking an unknown protein, cleaving them into smaller peptides, then transferring them to a mass spectrometer for measurement. In such cases, distinct mass spectrometers must be used; the most common forms are MALDI or ESI. These assist in the ionization of peptides with low fragmentation, thus ensuring peptides remained intact when ionized. With such experiments, scientists can now identify proteins, determine their structure and function, quantitate, and determine post-translational modifications.