Because of our ability to transform inorganically produced, naked α-SeNPs into ZnSe and CdSe fluorescent particles under mild conditions, we can apply the same method to a biological system. Previously, we isolated and engineered a recombinant enzyme capable of synthesizing 33 +/-6.3 nm α-SeNPs over a wide range of precursor concentrations. In this instance, we expect that the modified enzyme acts to both synthesize the particles and passivate the surface of the resulting particles. We observe that enzymatically produced α-SeNPs appear to be stable for at least a year when stored at 4C, while chemically synthesized particles convert to t-Se over a period of a few weeks when stored at 4C. On the basis of this observation, we investigated whether enzymatically synthesized α-SeNPs are also subject to disproportionate to metal selenides. Biological approaches to nanoparticle synthesis have the advantage that enzymes are relatively easy to functionalize and template against an existing structure. Table : Disproportionation of α-SeNPs with various metal cations.