Table 1. Ion flux for protein samples at 10 mbar source pressure.
For each protein complex the molecular weight (M), main charge state (z) in native MS and the ion current after subtraction of the buffer signal are provided. The ion current is converted into number of ions and the amount of ions that can be trapped in the dark time (99.4 ms) is calculated. Using the beam properties at SPB/SFX, the minimal speed to refresh ions between individual pulses in a bunch train can be calculated to determine for how long ions can be refreshed. Ideally, this time should be at least 600 µs to allow use of the entire pulse train. Four different conditions are compared: (A) ion density of 1000 mm−3, particle speed 2 µm/220 ns for larger focus; (B) ion density of 10 000 mm−3, particle speed 2 µm/220 ns for larger focus; (C) ion density of 1000 mm−3, particle speed 0.2 µm/220 ns for smaller focus; and (D) ion density of 10 000 mm−3, particle speed 0.2 µm/220 ns for smaller focus [retrieves the same values as condition (A)].
| Sample | M (MDa) | z | Ions (pA) | Ions (s−1) | Ions (dark) | A&D t (µs) | B t (µs) | C t (µs) |
|---|---|---|---|---|---|---|---|---|
| GroEL | 0.8 | 69 | 10.3 | 931944 | 92635 | 10190 | 1019 | 101899 |
| T3 | 3 | 135 | 0.7 | 33317 | 3311 | 364 | 36 | 3643 |
| T4 | 4 | 158 | 0.5 | 18856 | 1874 | 206 | 21 | 2062 |