Invited lectures-Anion–nucleic acid interactions. Just anecdotal?

摘要

Interactions with nucleic acids involving cationic species (mainly Na~+, K~+ and Mg~(2+)) are relatively well characterized. Conversely, less is known about anionic species interacting with nucleic acids [1, 2]. Although the cytosolic concentration of Cl~- ions is much smaller (≈4–20 mmol/L) than the extracellular concentration (≈100 mmol/ L), Cl~- ions have been recurrently found in nucleic acid crystallographic structures in close contact to electropositive nucleobase groups. In this respect, Cl~- anions present very specific binding patterns and display strict coordination distances (≈3.2 ?). We will describe associated binding patterns along with binding properties of other halide ions and put these patterns in relation with those of further inorganic (SO_4~(2-); PO_4~(3-), …) and organic (CH_3CO_2~-, …) anions. Considerations related to the characterization of these anions in crystallographic structures will also be presented. This is of importance since some anion (Cl~- or SO_4~(2-)) electron densities were misattributed to Mg~(2+) cations, therefore blurring our perception of the role they play in nucleic acid structure and function.