SPACI score report for 4g23 in ASTRAL 2.08:

PDB Entry: 4g23
SPACI score: 0.45
AEROSPACI score: 0.45

Experiment type: XRAY
Resolution: 1.98
R-factor: 0.187
PCK1 PROCHECK Ramachandran: 1
PCK2 PROCHECK Chi-1 angle: 2
PCK3 PROCHECK H-bonds: 2
WCK1 WHAT_CHECK Packing: -1.368
WCK2 WHAT_CHECK Ramachandran: -0.878
WCK3 WHAT_CHECK Chi angles: -0.664
WCK4 WHAT_CHECK Backbone: 3.622

Note: Here are links to pages about PROCHECK and WHAT_CHECK.

Here is the full WHAT_CHECK report on this protein (linked from the WHAT_CHECK site).