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. 2009 Jan 2;106(2):440–444. doi: 10.1073/pnas.0811882106

Fig. 2.

Fig. 2.

Hydrogen bonds in PYP. (A) Correlation of donor-H(D) and H(D)-acceptor bond lengths with the donor–acceptor distances and a histogram of hydrogen bond lengths. The open and closed triangles show the donor-H(D) and the H(D)-acceptor distances, respectively. The SHBs are shown as a red circle (pCA-E46) and a blue circle (pCA-Y42). The solid lines represent the calculated donor-H(D) distances, assuming bent angles of 120° and 180°, respectively. (B and C) The nuclear and electron density maps with the structure models of the two SHBs, pCA-E46 (B) and pCA-Y42 (C). The blue mesh represents the positive nuclear density of the deuterium atoms, contoured at 80% of the maximum peak height of the FO − FC difference maps omitting each deuterium atom involved in the hydrogen bond; contour levels of 80% of the maximum peak height correspond to 8.26 σ for pCA-E46 and 6.86 σ or pCA-Y42. The yellow mesh (contoured at 4.1 σ) and the red mesh (contoured at −5.3 σ) show the 2FO − FC electron density maps of the heavy atoms and the FO − FC difference nuclear density map omitting the hydrogen atoms, respectively.