The rapid and enormous expansion in the biotechnology revolution has caused increased interest in determining exact molecular weights of biological systems. Mass spectrometry offers a quick and convenient method for determining accurate molecular weights of biological samples including peptides, proteins, oligonucleotides, and oligosaccharides. Matrix-Assisted Laser Desorption Ionization (MALDI) and Electrospray Ionization (ESI) are the two predominant mass spectrometry techniques used for the development of biological assays. During the MALDI process singly charged analyte ions are produced after desorption/ionization from a matrix using a nitrogen laser.
For example, Dr. Bentzley's laboratory utilizes MALDI to detect amiodarone, an anti-arrhythmic drug, in biopsies of explanted human hearts from cardiac transplant recipients. In another study, MALDI is used to track the decomposition of PCR primers over various periods of time ranging from one day to 10 years. In contrast to MALDI, the ESI method ionizes an analyte to form charged species through desolvation of microscopic droplets. A resultant ESI spectrum contains a multiply protonated envelope of various mass-to-charge ratios. ESI can be used to track the activity of protein kinases as well as the modulation of the kinase activity. To demonstrate the effectiveness of using ESI-MS as a kinase assay, one of the best-characterized kinases, cyclic adenosine monophosphate (cAMP)-dependent protein kinase (PKA) is studied. ESI can also be utilized to study the conformational changes of protein structures as they undergo desolvation. It is also possible to analyze the denaturing of oligonucleotide strands as the sample enters the gaseous phase.