D

Da Dalton; the unit of molecular mass, very nearly equal to that of a hydrogen atom (precisely equal to 1 on the atomic mass scale), named after John Dalton, who developed the atomic theory of matter (kDa, kilodalton).

DEAE Diethylaminoethyl; a weak ion-exchanger that is often coupled to a resin and used in charge based separation chro-matography. It is an anion exchange resin.

Declaration of Helsinki A set of recommendations or basic principles guiding medical doctors in the conduct of biomedical research involving human subjects.

deflashing The finishing procedure by which excess plastic (flash) is removed from a molding in BFS operations.

degradants The smaller parts that are left over after a molecule or solution degrades.

degradation Loss or reduction of quality, integrity, or character; a chemical reaction that breaks down a molecule into smaller parts.

delaminate To split apart into thin layers; the act of separating a laminate into layers.

delivery matrix A heterogeneous semisolid matrix (such as a biopolymer gel) for the sustained delivery of drug substances directly to the tissues; a matrix can be modified to optimize the dosage or time period during which the drug is delivered.

denaturation A condition in which a protein unfolds or its polypeptide chains are disordered, rendering the molecule less soluble and usually nonfunctional.

denature To unfold a protein or break it up, changing its usual three-dimensional structure. Proteins can be denatured by chemical action, heat, or even agitation of a protein solution.

denatured protein A protein having unfolded or disordered polypeptide chains, which render the molecule less soluble and usually nonfunctional. Sometimes a denatured protein can be refolded (renatured).

derivatization A sampling technique; chemical conversion into a derivative form for identification purposes.

design space The multidimensional combination and interaction of input variables (e.g., material attributes) and process parameters that have been demonstrated to provide assurance of quality. Working within the design space is not considered a change. Movement out of the design space is considered to be a change and would normally initiate a regulatory post-approval change process. Design space is proposed by the applicant and is subject to regulatory assessment and approval. [From ICH Q8]

desorption The opposite of adsorption; the release of adsorbed molecules, particles, or cells into the surrounding medium.

detergents Cleaning agents: chemicals with both hydrophobic (averse to water) and hydrophilic (water-attracted) properties that can dissolve fats and oils.

dialysis/diafiltration Membrane ultrafiltration in which a large solute (such as a protein) is washed or dialyzed with another solution; for example, changing buffer conditions without affecting protein concentration.

diastereomer A stereoisomer (one of two or more molecules with the same atoms in the same order but different three-dimensional shapes) having two or more chiral centers that is not a mirror image of another stereoisomer of the same compound; glucose, galactose, and mannose are all diastereomers.