luciferase In luminiscent organisms (fireflies, some bacteria, and certain marine organisms), luciferase is an enzyme that acts on species-specific light-emitting substances known as luciferins. Chemiluminescent assay systems using firefly luciferin–luciferase have detected small amounts of ATP, the energy-storage compound of a cell. Such systems may serve as alternatives to radioimmunoassays and fluorescence methods.

lymphocytes White blood cells that produce antibodies.

lyophilization Freeze-drying; a procedure by which a liquid solution is frozen to a glassy state (primary drying), then slightly heated to remove the unfrozen water by sublimation.

lysed-cell slurry A mixture of the debris formed by disintegrating or breaking cells.

lysosomes Cell organelles containing enzymes, responsible for degrading proteins and other materials ingested by the cell.

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.

macrokinetics Movement of whole cells and their media within a bioreactor.

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

Microassays often use microwell plates like this one — sometimes filled and handled by robots rather than by hand.

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/e) 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)

MedDRA The Medical Dictionary for Regulatory Activities is the global standard medical terminology. Major global regulatory authorities in ICH countries are adopting MedDRA and moving toward requiring its use. FDA has implemented MedDRA within its adverse event reporting system. European authorities are beginning to use MedDRA as a key component of their electronic database systems.