Monolayer protected gold clusters: Application to biology

Water-soluble monolayer protected gold clusters (MPCs) have been an object of investigation by many research groups since their first syntheses reported in 1998. This dissertation reports three fundamental advances in the study and application of water soluble MPCs: (1) An expanded repertoire of ligands for synthesis of MPCs; (2) redox labeling strategy for conjugating MPCs to protein; (3) The creation of MPC-DNA conjugates wherein short DNA oligonucleotides are capable of hybridization.; The basic requirements for a ligand to form a monolayer protecting a gold cluster were established some time ago for alkanethiolate MPCs, but there has been no such information published for water-soluble MPCs. We identify 6 new ligands capable of forming water-soluble MPCs, as well as 17 water-soluble ligands that fail to form MPCs. Our findings contribute not only to definition of the requirements for MPC formation but also to the variety of MPCs available for applications in chemistry and biology.; Conjugates of a glutathione monolayer protected gold cluster (MPCs) with a single chain Fv antibody fragment (scFv) a presenting reduced cysteine residue were created. The interaction between the scFv and MPC is such that a gold-thiolate bond is made between the scFv protein's cysteine residue and the core of an MPC. This allows specific, discrete and rigid affixment of the gold cluster on the scFv. This chemistry for creating these conjugates requires MPC oxidation for activation and MPC reduction for deactivation once conjugates are made. Purification of the conjugate from reactants is done using biochemical techniques. Cryoelectron microscopy provides verification of the complex.; The synthesis and purification of monolayer protected gold clusters derivitized with one, two, or three terminal thiol modified oligonucleotides is reported. These MPC-DNA conjugates are both electrophoretically and chromatographically isolable based upon the number of bound oligonucleotides. The DNA of these DNA-MPC conjugates is also shown as capable of hybridizing with complementary DNA. These properties are remarkable because previous reports showed that gold nanoparticles modified with a discrete number of short oligonucleotides were neither electrophoretically isolable nor capable of DNA hybridization.