▁which ▁he ▁named ▁pen ic ill in ▁in ▁ 1 9 2 8 . ▁F lem ing ▁believed ▁that ▁its ▁ant ib acter ial ▁properties ▁could ▁be ▁explo ited ▁for ▁chem other apy . ▁He ▁initially ▁character ized ▁some ▁of ▁its ▁bi ological ▁properties , ▁and ▁attempted ▁to ▁use ▁a ▁cru de ▁prepar ation ▁to ▁treat ▁some ▁in fe ctions , ▁but ▁he ▁was ▁unable ▁to ▁purs ue ▁its ▁further ▁development ▁without ▁the ▁aid ▁of ▁trained ▁chem ists . ▁ ▁Ernst ▁Ch ain , ▁Howard ▁Fl ore y ▁and ▁Edward ▁Abraham ▁succeeded ▁in ▁pur ifying ▁the ▁first ▁pen ic ill in , ▁pen ic ill in ▁G , ▁in ▁ 1 9 4 2 , ▁but ▁it ▁did ▁not ▁become ▁widely ▁available ▁outside ▁the ▁Al lied ▁military ▁before ▁ 1 9 4 5 . ▁Later , ▁Norman ▁He at ley ▁developed ▁the ▁back ▁extra ction ▁technique ▁for ▁efficiently ▁pur ifying ▁pen ic ill in ▁in ▁bulk . ▁The ▁chemical ▁structure ▁of ▁pen ic ill in ▁was ▁first ▁proposed ▁by ▁Abraham ▁in ▁ 1 9 4 2 ▁and ▁then ▁later ▁confirmed ▁by ▁Dor othy ▁Crow foot ▁H od g kin ▁in ▁ 1 9 4 5 . ▁Pur ified ▁pen ic ill in ▁displayed ▁pot ent ▁ant ib acter ial ▁activity ▁against ▁a ▁wide ▁range ▁of ▁b acter ia ▁and ▁had ▁low ▁to x icity ▁in ▁humans . ▁Furthermore , ▁its ▁activity ▁was ▁not ▁in hib ited ▁by ▁bi ological ▁constitu ents ▁such ▁as ▁p us , ▁unlike ▁the ▁synth etic ▁sul fon am