phosphorylation Addition of a phosphate (PO
) group to a molecule, usually enzymatically done by transferring a phosphate group from ATP (adenosine triphosphate).
physical state The form that matter takes, whether solid, liquid, gas, or plasma.
Isoelectric point, the pH at which a substance has no net charge; above which a substance acts as a base and below which it acts as an acid.
A solution of proteins or amino acids has its minimum conductivity and viscosity at the isoelectric point. The pI is a pH
value for a given substance; for example, the pI of gelatin is pH 4.7. pI can be used to identify and characterize proteins..
This scientist wears face-protection while working with the neurotoxic polyacrylamide gel used in SDS-PAGE.
An alternative yeast species proposed as a recombinant expression system. It performs posttranslational modifications that
are more similar to human protein modifications than those performed by other yeasts used in fermentation.
pilot plant A medium-scale bioprocessing facility used as an intermediate in scaling up processes from the laboratory to commercial production.
placebo A fake treatment (usually the same formulation used for the real product, but without the active ingredient) administered
to the control group in a controlled clinical trial so that the specific and nonspecific effects of the experimental treatment
can be distinguished. The experimental treatment must produce better results than the placebo to be considered effective.
plasmid Hereditary material that is not part of a chromosome. Plasmids are circular and self-replicating and found (naturally in bacteria
and some yeasts) in the cytoplasm of cells. They can be used as vectors for introducing up to 10,000 base-pairs of foreign
DNA into recipient cells.
polarized light Light waves that vibrate transversely on a single plane, in contrast to ordinary lightwaves that vibrate in all directions
polar solvent A solvent for molecules that have permanent electric dipoles.
Preparative chromatography uses large columns like these.
polishing The final purification step(s) in a biopharmaceutical manufacturing process, usually involving an affinity or other refined
chromatography method. Often this step uses the most expensive technique in the process because it handles the smallest amount
polyacrylamide A high molecular-weight polymer of acrylamide (a neurotoxin) used as a support and separations matrix in electrophoresis
and gel chromatography.
polymer A large molecule formed by the combination of at least five (and sometimes as many as 1,000) identical smaller molecules
polymerase An enzyme that catalyzes the production of nucleic acid molecules.
polymerize To undergo or subject to polymerization, a chemical reaction in which two or more molecules combine to form larger molecules that contain repeating structural units.
polysaccharide A kind of complex carbohydrate (macromolecule composed of long chains of simple sugars). Several polysaccharides from microorganisms
have important commercial uses.
polysorbate 80 A hydrophilic surfactant commonly used as a pharmaceutical excipient, among other things.
polysorbates Complex mixtures of polyoxyethylene ethers used as emulsifiers or dispersing agents in pharmaceuticals.
polyvinyl A polymer prepared from polyvinyl acetates by replacement of the acetate groups with hydroxyl groups. It is used as a pharmaceutic
aid (a substance with little or no therapeutic value that is necessary in the manufacture, compounding, or storage of pharmaceutical
preparations or drug dosage forms). Polyvinyls are used as solvents, diluting agents, suspending agents, and emulsifying agents.