M

MAb Monoclonal antibody; a highly specific, purified antibody that recognizes only a single epitope.

MAC Mammalian artificial chromosome; a vector used to clone DNA fragments larger than 100,000 base-pairs long. As suggested by the name, MACs are constructed from mammalian cell DNA.

macromolecules Very large molecules (proteins, carbohydrates, nucleic acids), often formed by two or more identical molecules in a chain configuration (polymers).

MALDI-TOF Matrix-assisted laser desorption ionization-time of flight mass spectrometry technique for determining molecular weight. Electrons become excited after laser irradiation, transferring energy into the mixture and causing molecules and ions to be ejected from its surface. Commonly used in proteomic and peptide analyses.

mannitol A sugar alcohol (found naturally in many plants, algae, and fungi) that is obtained by reducing mannose and used as a pharmaceutical excipient and in diagnostic tests of kidney function.

mannose A sugar (an aldohexose) often used as an excipient in drug formulations.

mass spectrometry Analytical method that determines a complex molecule's structure by breaking it into fragments, which are then separated by electric and magnetic fields based on the fragments' mass-to-charge ratio. Measures the difference in mass-to-charge ratio (m/z) of ionized atoms or molecules to separate them from each other.

master batch record The template that describes the step by step procedures to be followed during manufacturing, with spaces to record actual data. The master batch record is uniquely identified, under change control, pre-approved by quality assurance, and used to generate each individual batch record that is issued when a given batch is to be manufactured.

master cell banks A master cell bank is prepared by culturing a homogeneous population of cells, such as an established, cloned cell line, under defined conditions and then distributed into containers in a single operation, processed together to ensure uniformity, and stored to ensure stability. Each vial is presumed to have comparable properties, and thus the bank may be characterized by testing a representative number of individual vials. Cell cultures derived from the master cell bank are used to prepare working cell banks for manufacturing of a biopharmaceutical. Both master and working cell banks are extensively tested and characterized before use. (See working cell bank)

media Plural form of medium, a (usually sterile) preparation made for the growth, storage, maintenance, or transport of microorganisms or other cells.

Met Methionine; one of more than 20 naturally occurring amino acids.

metered dose inhaler (MDI) A device used to deliver a fixed volume or dose of an aerosol form of an active drug substance to the lungs and/or bronchi.

metabolites Chemical products of metabolism, the chemical process of life.

micelle A spherical arrangement (bubble) formed by a group of lipid molecules in an aqueous environment; hydrophobic ends of the molecules are turned inward and hydrophilic ends are turned outward. A molecular aggregate that constitutes a colloidal particle (a substance consisting of particles dispersed throughout another substance with particles too small for resolution with an ordinary light microscope, but that can pass through a semipermeable membrane).

microassays Assays usually run on very small samples, often using "micro-plates," and often automated. Microplates can have room for 96, 384, or even 1,536 tiny samples. Microassays measure small quantities of components even when the sample size is large.

microbial fermentation Processes involving the use of microorganisms, such as E. coli, to produce a protein or other substance.

microbial testing Analytical methods required by regulations to ensure sterility and to measure bioburden or identify microorganisms in controlled, classified environments.

microbiology The study of microscopic life such as bacteria, viruses, yeast, and protozoa.