Table 1. Unit Cell Parameters Determined from 3D ED Data and Powder XRD Data for samples of β guanine from Hirsch et al.15 and this studya.
| Space
group P21/c |
Space
group P21/b |
|||||||
|---|---|---|---|---|---|---|---|---|
| 3D ED |
Powder
XRD |
Hirsch
et al.15 |
||||||
| Sample | Spider | Fish | Scallop | Spider | Fish | Synthetic | Synthetic Powder XRD | Calculated |
| a/Å | 3.615(22) | 3.630(8) | 3.616(12) | 3.6310(1) | 3.6381(1) | 3.6317(1) | 3.629 | 3.5938 |
| b/Å | 18.39(11) | 18.34(4) | 18.43(5) | 18.4396(2) | 18.4227(2) | 18.4214(11) | 9.813 | 9.7195 |
| c/Å | 9.791(50) | 9.803(19) | 9.790(28) | 9.8145(4) | 9.8172(4) | 9.8138(10) | 18.427 | 18.3401 |
| β/° | 118.02(16) | 117.94(6) | 117.82(9) | 118.048(1) | 117.930(1) | 117.945(4) | 118.04 (γ) | 119.493 (γ) |
| V/Å3 | 574.6(60) | 576.6(23) | 576.9(33) | 579.95(1) | 581.33(1) | 580.00(3) | 557.6 | 557.6 |
a
Unit cells in the columns headed “3D ED” were obtained by indexing the 3D ED data. Unit cells in the columns headed “powder XRD” were determined by Pawley fitting (spider and fish samples) and Rietveld refinement (synthetic sample) of the powder XRD data. The final structure refinement calculations for the fish, spider, and scallop samples used the unit cells determined from powder XRD data together with the diffraction intensities from 3D ED data, as discussed in the text.