أرشيف الوسم : quaternary

Alkaloid A cyclic organic compound that contains nitrogen in a negative oxidation state and is of limited distribution among living organisms. Over 10,000 alkaloids of many different structural types are known; and no other class of natural products possesses such an enormous variety of structures. Therefore, alkaloids are difficult to differentiate from other types of organic nitrogen-containing compounds. Simple low-molecular-weight …

acridinium esters: esters of acridine-9-carboxylic acid. They have a quaternary nitrogen centre and are derivatized at the 9 position to give a labile phenyl ester moiety. Acridinium esters such as 2′,6′-dimethyl-4′-[N-succinimidyloxy carbonyl]phenyl-10-methylacridinium- 9-carboxylate can be used as chemiluminescent labels for antibodies. Light emission is activated by adding hydrogen peroxide under alkaline conditions. In hybridization protection assays, single-stranded DNA probes labelled …

An enzyme that has two structurally distinct forms, one of which is active and the other inactive. In the active form, the quaternary structure of the enzyme is such that a substrate can interact with the enzyme at the active site. The conformation of the substrate-binding site becomes al­tered in the inactive form and inter­action with the substrate is not …