From metal binding to nanoparticle formation: monitoring biomimetic iron oxide synthesis within protein cages using mass spectrometry.

Mass measurements of metal-mineralized protein cages allowed quantitative examination of the effects of metal-ion concentration on the final nanoparticle size. Modeling using a kinetic master equation suggests that particle growth involves both a binding phase and a growth phase (see picture; I: relative abundance; LiDps: a DNA binding protein; (n)Fe: number of Fe atoms).