▁produce ▁unus ually ▁pot ent ▁and ▁specific ▁protein ▁kin ase ▁in hib itors . ▁ ▁Additionally , ▁many ▁of ▁these ▁bal an ol ▁con gen ers ▁show ▁substantial ▁specific ity ▁toward ▁PK A ▁over ▁PK C . ▁El im ination ▁of ▁the ▁hydro x yl ▁group ▁from ▁the ▁ben z oph en one ▁ring ▁( produ cing ▁ 1 0 " - de ox y bal an ol ), ▁for ▁instance , ▁el ic its ▁select ivity ▁two ▁orders ▁of ▁magnitude ▁greater ▁for ▁PK A ▁over ▁PK C . ▁Pot ent ▁in hib itory ▁activity ▁was ▁also ▁shown ▁to ▁be ▁dependent ▁on ▁the ▁car box y lic ▁acid ▁of ▁the ▁ben z oph en one ▁ring ▁and ▁the ▁presence ▁of ▁a ▁five - ▁or ▁seven - member ed ▁a ze p ane ▁ring . ▁ ▁Bal an ol ' s ▁flexible ▁structure ▁also ▁plays ▁an ▁important ▁role ▁in ▁its ▁select ivity . ▁Specifically , ▁bal an ol ' s ▁dist al ▁ben z oph en one ▁ring ▁is ▁able ▁to ▁rotate . ▁In ▁fact , ▁in ▁complex ▁with ▁PK A , ▁bal an ol ' s ▁dist al ▁ben z oph en one ▁ring ▁was ▁observed ▁to ▁be ▁nearly ▁orthogonal ▁with ▁the ▁neighbor ing ▁ring . ▁This ▁flex ibility ▁could ▁allow ▁bal an ol ▁to ▁adapt ▁to ▁numerous ▁protein ▁micro environ ments ▁in ▁order ▁to ▁ex ert ▁its ▁in hib itory ▁properties ▁on ▁various ▁protein ▁kin ases . ▁Bal an ol ' s ▁select ivity ▁for ▁some ▁kin ases ▁and ▁not ▁others ,