A biomarker, or biological marker, is in general a substance used as an indicator of a biological state.
It is a characteristic that is objectively measured and evaluated as an indicator of normal biological processes, pathogenic processes, or pharmacologic responses to a therapeutic intervention. Biomarker discovery has been accelerated by proteomics, which study to entire protein expression at any given time in cell or tissue. If a certain protein is the functional molecule in cells, measurement of the differential expression of proteins could indicate disease-specific changes in tissues or organs.
Mass spectrometry (MS) is an analytical technique that measures the molecular weight of molecules based upon the motion of a charged particle in an electric or magnetic field. It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and other chemical compounds. This technique is performed by a mass spectrometer. The MS principle consists of ionizing chemical compounds to generate charged molecules or molecule fragments and measuring their mass-to-charge ratios (m/z).