AA Related Biological Terms

(=atomic absorption)

A method for quantifying elements, usually metals, in biological samples. The method depends upon the absorption of energy by atoms as they are excited in their electronic ground state. The choice of wavelength depends therefore, on the element to be evaluated and the most convenient energy level at which it can be excited. The sample is vapourized in a flame or electric furnace, and monochromatic light of the desired wavelength is shone through the flame or cloud; absorption of the light is proportional to the number of atoms in the observed volume. In a related technique, flame emission photometry, the small numbers of excited atoms in the flame or cloud are detected as they fall to the ground state and emit light at a wavelength which is characteristic of the element and at an intensity which is proportional to the number of atoms in the observed volume. This proportionality is lost when the concentration of atoms is sufficiently high to allow self-absorption, a phenomenon akin to the inner filter effect of fluorescence spectroscopy, in which emission from the centre of the flame or cloud is absorbed by atoms on its periphery. A standard curve, constructed with known concentrations of the element, allows quantification of experimental samples.

A regulatory sequence upstream from some eukaryotic structural genes.

(see prenyl)

Selected and amplified (protein) binding site oligonucleotide. (see cyclic amplification and selection of targets (CASTing))

The weak attraction of neighbouring neutral atoms that includes dipole-dipole and dipole-induced dipole interactions and London dispersion forces.

The dimensions of an atom deduced from its packing in crystals.

An invariant DNA sequence at about minus 70 base pairs from the origin of transcription in many eukaryotic promoters.  

See EDTA.

A consensus sequence surrounding the lariat branch point of eukaryotic pre-mRNA Introns and used during splicing.

The weakest of the imtermolecular forces. Present on all particles and increasing strength with increasing size. Results from the fact that a preponderance of electrons can end up on one side of an atom. The dispersion force which in fact is an induced dipole - induced dipole interaction depends on the polarisability of the interacting molecules and is inversely proportional to the sixth power of separation. In the case of e.g. two CH4 molecules at a separation of 3Å, the dispersion interaction energy is of the order of -1.1 Kcal/mole.