Introduction
It was realized, long ago, that a
folded protein “consists of one polypeptide chain which continues
without interruptions throughout the molecule (or, in certain cases, of
two or more such chains)” and that “this chain is folded into a
uniquely defined configuration, in which it is held by hydrogen bonds”
[1]. Later on, a series of other non-covalent interactions have been
discovered to be responsible for protein folding, stability, plasticity,
and function, like van der Waals, hydrophobic and electrostatic
interactions [2]. One of these non-covalent interactions has
received little attention insofar: it is the chalcogen bond.
It is an attractive interaction
between chalcogen atoms (sulfur, selenium or tellurium) and
nucleophiles. In molecular moieties like R-X-R (X = S, Se or Te), the
nucleophile tends to occupy a position along the extension of one of the
R-X covalent bonds (Figure 1 )[3]. Although recent
publications reviewed extensively both theoretical and experimental
studies of chalcogen bonds [4][5], minor attention has been paid
to this non-covalent interaction in biological systems.