Fig 1.
Chemical structures of the Lilial 1a–1d and Bourgeonal 2a–2d derivatives investigated.
Fig 2.
Docking poses of 1a–1d and 2a–2d at hOR17-4.
(A) (S)-1a–(S)-1d. (B) (R)-1a–(R)-1d, (C) 2a–2d, (D) 1a–1d and 2a–2d. Carbon compounds (1a and 2a) are shown in yellow, silicon compounds (1b and 2b) in cyan, germanium compounds (1c and 2c) in green, and tin compounds (1d and 2d) in grey. Helices are numbered in Roman numerals. All docking poses share a high similarity throughout the entire set of compounds. The carbonyl oxygen atom of Ile208 forms a favorable contact with the hydrophobic bulk group of the investigated ligands.
Table 1.
Docking free binding energies.
Fig 3.
Exponential regression of odor threshold concentration [O] and average X–C distance r (X = C, Si, Ge, Sn).
In vivo data points [71] are given as blue diamonds, regression curves as black lines. Error bars depict the standard deviation. The data points of rac-1a–rac-1d deviate from an exponential form, while the data for 2a–2d follow an exponential form.
Table 2.
Assessment of exponential connection of odor threshold concentration [O] and X–C distance r according to Eq (2)1.
Fig 4.
Determination of ΔFbind(r) and ΔFvib(r).
ΔFbind(r) was calculated by linear regression of ΔGbind from docking runs (A) or QM calculations (B) in reference to the average X–C distance r (X = C, Si, Ge, Sn). In a similar way, ΔFvib(r) (C) was calculated by linear regression of ΔEvib from QM calculations in reference to r. For (B) and (C), data points are shown as the energy difference to compound 2a. (D) and (E) display ΔFbind(r) and ΔFvib(r) after and additional ab initio QM minimization of the ligands within the rigid protein binding site.
Table 3.
C-X vibrations in compounds 2a–2d.