Before revision: One of these is predicting the pKa of an ionizable group .
After revision: |first1=K.P.|last1=Tan|first2=T.B.|last2=Nguyen|first3=S.|last3=Patel|first4=R.|last4=Varadarajan|first5=M.S.|last5=Madhusudhan|journal=NAR|year=2013|volume=41|issue=W1|pages=W314-321|pmid=23766289|doi=10.1093/nar/gkt503.</ref>One of these is predicting the pKa of an ionizable group .