Model of Yeast transfer RNA based on the Protein Data Bank entry 4TNA:
http://www.rcsb.org/pdb/explore/explore.do?structureId=4tna

"A Transfer RNA (abbreviated tRNA) is an adaptor molecule composed of RNA, typically 73 to 94 nucleotides in length, that serves as the physical link between the nucleotide sequence of nucleic acids (DNA and RNA) and the amino acid sequence of proteins."
-http://en.wikipedia.org/wiki/Transfer_RNA

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

Successfully printed by a Replicator 2 in PLA using MakerWare(TM) 2.4.1.24, standard resolution (3 shells, 25% infill), with raft and supports.