Table 2. SAXS data collection and statistics.
PerR | PerR-DNA mixture | |||
1∶1 | 2∶1 | 4∶1 | ||
Data-collection parameters | ||||
Instrument | Synchrotron 23A SWAXS endstation of NSRRC | |||
Beam geometry | 0.5 mm dia. beam | |||
Wavelength (Å) | 0.8857 | 0.82825 | 0.82825 | 0.82825 |
q range (Å−1) | 0.0085–0.37 | 0.007–0.39 | 0.007–0.39 | 0.007–0.39 |
Exposure time (s) | 300a | 300a | 300a | 300a |
Concentration range (µM) | 20.0 | Protein 26.5 | Protein 26.5 | Protein 26.5 |
68.1 | DNA 26.5 | DNA 13.3 | DNA 6.63 | |
177.6 | ||||
Temperature (K) | 288 | 288 | 288 | 288 |
Structural parameters | ||||
Rg (Å) [from P(r)] | 24.58±0.04 | 39.11±0.04 | 38.62±0.06 | 36.59±0.08 |
Rg (Å) [from Guinier] | 24.8±0.4 | 38.9±0.3 | 38.1±0.1 | 35.5±0.2 |
I(0) (cm−1) [from Guinier] | 0.033 | 0.12 | 0.08 | 0.05 |
0.113 | ||||
0.352 | ||||
D max (Å) | ∼77 | ∼125 | ∼125 | ∼125 |
Porod volume estimate (Å3) | ∼58100b | ∼354000 | ∼335000 | ∼122000 |
Dry volume calculated from sequence (Å3) | 37682 | N/A | N/A | N/A |
Molecular-mass determination | ||||
Partial specific volume (cm3g−1) | 0.73 | N/A | N/A | N/A |
Contrast (Δρ*10−10cm−2) | 3.148 | N/A | N/A | N/A |
Molecular mass Mr | ∼35 | ∼80 | ∼50 | ∼40 |
[estimated from Porod Volume] kDa | ||||
Calculated monomeric Mr from sequence | 37700 | N/A | N/A | N/A |
Software employed | ||||
Primary data reduction | NSRRC 23A SWAXS package | |||
Data processing | SCATTER 1.7 and ATSAS 2.4 | |||
Ab initio analysis | DAMMIN | N/A | N/A | N/A |
Validation and averaging | DAMAVER | N/A | N/A | N/A |
Rigid-body modelling | N/A | N/A | N/A | N/A |
Computation of model intensities | FoXS | FoXS | FoXS | FoXS |
Envelope representations | Chimera | N/A | N/A | N/A |
Minimal ensemble analysis | N/A | MES | MES | MES |
a. 300s with 60s single exposure time for 5 successive exposures.
b. Only globular proteins with smooth surfaces: “Porod volume” ∼ “Dry volume”; uncertainty is contributed mainly from Q-invariant (upper limit of 20% is used with NSRRC 23A SWAXS)”.