at Related Biological Terms

An agent that damages cellular DNA, a necessary condition for tumorigenesis. (see also anti-oncogene (tumour suppressor gene); tumour promoter)

The number of substrate molecules that a single catalytic site of an enzyme molecule can convert into product in a given time. (see also catalytic rate constant (kcat))

A conformation of a five-membered ring in which no four centres lie in the same plane. (see also chair form; envelope conformation)

A pattern of molecular organization by which responses to external stimuli are processed by cells to effect modulation of output, such as chemotaxis in bacteria, or osmolarity regulation in plant cells. An example is a kinase that, following its interaction with an activated receptor, phosphorylates a function-specific response regulator. Koshland, D.E., Jr. (1993) Science 262, 532

A form of displacement chromatography in which, after an initial separation in the first dimension of a labelled oligomer (e.g. an oligoribonucleotide), separation in the second dimension proceeds in the presence of a high concentration of a heterogeneous mixture of oligomers (e.g. an unfractionated endonuclease digest of yeast RNA).

In protein chemistry, the postulate that the folding of a protein occurs without any stable intermediate between the denatured and native states. (see also framework model; molten globule intermediate)Baldwin, R.L. (1990) Nature (London) 346, 409-410

A route to cellular proteolysis that depends upon conjugation of the targeted protein to a small protein, ubiquitin, followed by hydrolysis. Ciechanover, A. and Schwartz, A.L. (1994) FASEB J. 8, 182-191

(see analytical ultracentrifugation; preparative ultracentrifugation)

A separation procedure in which a solution is forced through a membrane with a pore size that is selected to retain macromolecules of a certain size and to pass smaller ones.

A method for replacement of an amino acid residue of a protein with a non-naturally occurring amino acid. The mRNA that encodes the protein is modified to encode a nonsense suppressor codon. For example, mRNA is modified to use the UAG codon; this mRNA, together with a nonsense suppressor tRNA with the anticodon CUA, and with an unnatural amino acid at its 3'-end, is introduced into an expression system, possibly a Xenopus oocyte. Nowak, M.W., Kearney, P.C., Sampson, J.R., et al. (1995) Science 268, 439-442 Learn more about amino acid chart.