at Related Biological Terms

A property of diffracted radiation that is useful in X-ray crystallographic analysis for identification of diffracting centres. The otherwise symmetrical diffraction pattern is subtly perturbed when incident energy of an appropriate wavelength interacts with a diffraction centre (in practice, a sulphur or heavy metal atom) that changes the phase of the diffracted radiation in a manner that is characteristic of that atom.

(see origin recognition complex (ORC))

In nucleic acid chemistry, the orientation about the glycosidic bond of a nucleoside or nucleotide that places the base away from the sugar moiety; contrasted with the syn conformation, in which the base and sugar are oriented towards each other. (see also Z-DNA) Recommended reading: lipofectamine 2000 protocol

A polymerase with a higher than usual degree of fidelity in proofreading. Reha-Kranz, L.J. (1995) Trends Biochem. Sci. 20, 136-140

A bacteriophage protein that prevents the normal termination of transcription, e.g. the N protein that binds to nut (N utilization) sites, thus countering the action of the rho protein.

An antimetabolite that blocks the action of tetrahydrofolic acid-dependent reactions, usually by inhibition of folic acid reductase.

The appearance on the surface of a cell of a foreign protein, e.g. one that arises from viral infection, in a complex with a class I major histocompatibility complex protein. It is this complex that is recognized by killer T-cells. Barinaga, M. (1990) Science 250, 1657-1658

The surface of a protein that is internalized in native proteins and that becomes available for interaction with water during denaturation.

(see entropy effect)

A type of peptidase that has at its active site two aspartate residues. (see also cysteine proteinase (thiol proteinase); metalloproteinase; serine proteinase)