Figure 2.

UnDowser diagnosis of HOH “waters”: (a) Stereo image of a positive ion modeled as HOH, with six near‐octahedral oxygen ligands. Lenses of green all‐atom contact dots show putative donor–acceptor H‐bond overlaps, but two distances are so short they also have serious clashes (clusters of hotpink spikes). HOH 606 in 6hhm.33 (b) A confusing HOH with one clash to an Asp carboxyl O, but also a good H‐bond to an Arg guanidinium, so not interpretable as an ion of either charge. HOH 603 in 6hhm. (c) A genuine water, with a strong, round density peak and 2 H‐bonds with backbone atoms of opposite partial charge. HOH 414 in http://firstglance.jmol.org/fg.htm?mol=6a4v (Hwang, unpublished). (d) Stereo image of an HOH with one polar and four nonpolar clashes. There is no electron density even at zero, suggesting that it should be deleted. HOH 504 in http://firstglance.jmol.org/fg.htm?mol=5onu 34