The usual strategy to prepare gold nanoparticles involves the reduction of a gold salt in
solution by various reducing agents in the presence of a stabilizer. These particles are mostly
spherical with poor monodispersity. An alternative means is to use biological material to
mediate particle synthesis. Microorganisms such as fungi have demonstrated the ability to
produce nanoparticles of different shapes and sizes extending beyond the scope of chemical
means, and the microbial interaction with metals also supply eco-friendly methods for
nanoparticle production.
It has been hypothesized that the proteins involved in nanoparticle synthesis require a
co-factor such as NADH / NADPH, as previous studies have indicated that NADH- and
NADPH-dependent enzymes are important factors in the biosynthesis of metal nanoparticles.
Thermus scotoductus SA-01, a thermophilic bacterium, isolated from an AngloGold
Ashanti mine near Carletonville, Republic of South Africa, was used for purification of a
gold(III) reducing and nanoparticle synthesizing protein. This bacterium has the ability to
produce gold nanoparticles, and more than one pathway can be followed to produce these
particles. A protein was purified to homogeneity by using a combination of several liquid
chromatography resins. The N-terminal sequence was obtained by using automated Edman
degradation. The protein purified is not a classical oxido-reductase and was identified as an
ABC transporter peptide-binding protein (~70kDa). This discovery shows that gold
nanoparticles can be produced by proteins other than oxidoreductases. The interaction of the
protein extracted and purified from Thermus scotoductus SA-01, as well as the recombinant
proteins, with liquid gold under varying physico-chemical conditions have been studied using
TEM, EDS, and by measuring the plasmon resonance band, to illustrate the effect on particle
morphology and to elucidate the protein mechanism.
The size and the shape of particles could, to an extent, be manipulated by controlling
the environmental parameters. The purified protein as well as the recombinant proteins was
only able to produce nanoparticles in the presence of sodium dithionite and it is thus
hypothesized that the donation of electrons via the disulphide bridge in the protein is involved
in the reduction of the gold ions. Even though the recombinant proteins had the ability toproduce nanoparticles they were not as efficient as the native protein, but when the optimum
parameters for the recombinant proteins are established they could be used in the upscale
production of gold nanoparticles or gold nanosheets.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ufs/oai:etd.uovs.ac.za:etd-11222010-141830 |
| Date | 22 November 2010 |
| Creators | van Marwijk, Jacqueline |
| Contributors | Prof E van Heerden |
| Publisher | University of the Free State |
| Source Sets | South African National ETD Portal |
| Language | en-uk |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.uovs.ac.za//theses/available/etd-11222010-141830/restricted/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University Free State or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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