## BP-ffsy

Helical Index practice #3

Power spectrum dimension: 640 x 640 pixel,
1.12 Å/px. Method (cryoSPARC)

peptide tube rmax and rmin: 30Å and 0Å ## Checkpoint

### which two layer-lines (LL) were used?

Note, there may be multiple acceptable answers to this question.  Format: LL (R, Z)
LL (36, 30)
LL (23, 156)

Hint: LL (27, 186) = LL (36, 30) + LL (23, 156).
The distance of LL(27, 186) to meridian is between LL(36,30) and LL(23,156). This suggests LL (36, 30) is probably has a different hand to LL (23, 156)

### What are the possible Bessel order ranges for those two vectors?

LL (36, 30) :
2*π*R*rmax = 2 * 3.14 * (36/640/1.12) * 30 = 9.4                          Bessel order n ≤ 8

LL (23, 156):
2*π*R*rmax = 2 * 3.14 * (23/640/1.12) * 30 = 6.0                           Bessel order n ≤ 5

### What's the correct symmetry (quickly check whether it is in your list)

point group: C3
helical rise: 2.10 Å
helical twist: -54.7 degrees

#### What we do

Use cryo-EM to understand and design large assemblies