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![[Figure 5]](jm5003fig5mag.jpg)
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Figure 5
Extended hydrogen-bonded water networks. (a) presents a well defined hydrogen-bond network found in PDB entry 2j9n (Viola et al., 2007  ). The blue mesh represents the contours of σA-derived maximum-likelihood 2mFo − DFc maps at the 1σ level, and the green arrows in the chemical scheme shown in (b) point towards the hydrogen-accepting electron lone pairs. Note that each bond has a proper donor–acceptor pair (which clearly defines the proper orientation of the Gln30 residue) and the different types of interactions: direct backbone–side chain, side chain–side chain and water-mediated interactions between residues. Typical X—O—H angles are 120° for the sp2-hybridized orbitals of the –OH groups and 104.5° for H—O—H in the nearly tetrahedrally coordinated water O atom. The covalent O—H distance is 0.96 Å. (c) depicts a well defined water network in the intermolecular space of a high-resolution (1.2 Å) structure revealing typical, ice-like five-membered and six-membered water-ring networks, while the central water atom possesses an almost perfect tetrahedral arrangement of hydrogen-bond partners (PDB entry 1bpi; Parkin et al., 1996; figure adapted from Rupp, 2009). |
![[Figure 5]](jm5003fig5.jpg)
 | STRUCTURAL BIOLOGY |
ISSN: 2059-7983
