Add final pH from Harold

protein_ligand/README.md

@@ -51,7 +51,7 @@ This will be validated by both positive hit data for PHIPA, and negative data wh
 Fragment binding predictions here are important because accurate predictions could improve library design, including the ability to design bespoke libraries for specific targets.
 
 PHIP2 was crystallized in space group C2 at 4C at approximately neutral pH by vapour diffusion in ~100 nL sitting drops, by mixing 50 nL protein (in 50 mM HEPES pH 7.5 and 0.5 M NaCl) with 50 nL reservoir buffer (20% PEG8000 and 0.1 M potassium phosphate).  
-The exact pH was not determined.
+The pH was 5.6.
 The resulting crystals were soaked with 20 mM final concentration of each fragment from ethylene glycol stock solutions, plunged into liquid nitrogen and shot at the i04-1 beamline located at the Diamond Light Source (Harwell, UK).
 The diffraction data were analyzed with [PanDDA](https://pandda.bitbucket.io/) ([Pearce et al., 2017](https://www.nature.com/articles/ncomms15123)) which revealed a number of fragments located across four distinct sites.