Quality control of [125I]-(un)labeled pro/actMMP-2/-9 and dose-dependency of pro/actMMP-2-binding to nitrocellulose-immobilized collagenous molecules. (A) Unlabeled or [125I]-labeled pro/actMMP-2/-9 (~1 ng) were quality-checked in substrate gel zymography (left) before the dried gel was subjected to autoradiography (right). Note that after [125I]-labeling, MMP structure and activity remained unchanged. (B) Serial dilutions of collagens or collagen type I (CI) derivatives dotted to a nitrocellulose membrane were incubated with 5 ng of [125I]-labeled pro/actMMP-2 before thorough washing. Bound MMP was monitored by autoradiography. Images shown represent three independent experiments.