(D) Top panel, the association of GSK716 induced a marked quenching and blue-shift of the α1-antitrypsin intrinsic tryptophan fluorescence spectrum with respect to unbound protein (inset graph). The association of 10µM GSK716 with four α1-antitrypsin variants that vary in their propensity to polymerise, ranging from inert (M), to mild (S), moderate (Baghdad denoted 'B') and severe (Z). Representative progress curves of the change in intrinsic tryptophan fluorescence at 330nm for 0.2mg/ml protein are shown. Bottom panel, the half-time of association calculated from three such independent experiments (error bars are ±SEM) show a correspondence with the polymerisation propensity of the four variants. The change in Z α1-antitrypsin fluorescence was faster than the dead-time of the apparatus (~10s) and scaling was with reference to unbound intensity. 