Model of Ferredoxin from Rhodopseudomonas palustris based on the Protein Data Bank entry 4ID8:
http://www.rcsb.org/pdb/explore/explore.do?structureId=4id8

"Ferredoxins are iron-sulfur proteins that mediate electron transfer in a range of metabolic reactions."
--http://en.wikipedia.org/wiki/Ferredoxin

STL file created using VMD:
http://www.ks.uiuc.edu/Research/vmd/

The protein backbone is represented in "cartoon" form. The cysteine residues and Fe3S4 cluster are represented as spheres.

Successfully printed by a Replicator 2 in PLA using MakerWare(TM) 2.2.2.89, standard resolution (3 shells, 25% infill), with raft and supports.