15 mo Flashcards
Why are you using ccc2?
CCC2 transports copper in post-golgi compartments to allow the biogenesis of the multicopper ferric oxidase Fet3, which is required for iron uptake.
In cultured animal cells, which have been exposed to elevated copper concentrations, these proteins are able to migrate to the plasma membrane or to a cytoplasmic vesicular compartment to increase the resistance of the cell to copper
Plant version - RAN1
Why are you using ace1?
Induces SOD1, CUP1 and CUP2 which are involved in protecting against copper toxicity.
How does tryptophan reduce to nanoparticle form?
Lot of work performed on silver nanoparticles, for this L-tryptophan and L-tyrosine are often used because they are redox active.
Tryptophan residue present in the peptide is converted to a transient tryptophyl radical, which donates an electron to the metal ion to form a metal nanoparticle.
How does pH affect nanoparticle formation?
Studies on silver nanoparticle formation with peptides show that it is a combination of the pH and the peptide chemistry that result in particular nanoparticle formation.
Aggregation of peptide modified silver nanoparticles can be controlled by pH. At pH 3, the lysine side chains and the C-terminal carboxylic acid groups are protonated, which leads to a positively charged shell. As a result of the high positive charge, particles exist as individual species and no aggregation occurs.
At high pH, pH 11, the C-terminal carboxylate is deprotonated and carries a negative charge, and the lysine residues are no longer charged. At this pH the particles aggregate into large aggregates.
How do the peptides form the nanoparticles?
Theres little information about how peptides control the assembly of nanoparticles.
Peptides form nanoparticles though a mild reduction process, and they don’t just sit on top of the nanoparticles like thiols do, adopt a certain periodic order within the nanoparticles as they form.
X-ray powder diffraction shown that the peptide acts as a simple and mild capping agent.
How do peptides bind to ionic gold?
There are lots of features that are important in the binding and reducing process of peptides forming nanoparticles.
They have particular absorbing groups like, amine groups and sulphur atoms in disulphide bonds; protonated lysine residues, negatively charged carboxylate groups etc.
But its also impotrant to note that it’s not having LOADS of these groups that makes a really good ordered particle growth. If you have too many there are lots of competing interactions, preventing this.
Ideally, for silver nanoparticle formation at least, you want, four amine groups and one disulphide per peptide, 1200-1300 peptides per particle.
How do the peptides bind to metallic gold?
So the mechanism of pepide formation of gold nanoparticles isn’t very well understood. But there is evidence that tryptophan for example, when it reduces ionic gold to metallic gold it donates an electron, so that level of binding.
Then depending on pH of the solution this can lead to the formation of aggregates of nanoparticles, for example at like, pH 11, the c terminal carboxylic acid group is deprotonated and carries a negative charge- and presumable the repulsive forces exerted by the single terminate carboxylate groups are not suffiecient to prevent aggregation. Also hydrophillic/hydrophobic interactions are involved. At higher pH, you get deprotonated lysine, and this is less hydrophillic - so from that you get hydrophobic interactions and hydrogen bonding, leading to large aggregates.
Where are these going to be grown?
For remediation of sites, the in situ inactivation like growing plants may offer a solution for dealing with large bare areas contaminated with metals. Cost effective, less disruptive to soil and to the natural landscape.
There are waste pilings or tailings surrounding old gold mines. Conventional mining can’t remove 100% of the gold from surrounding minerals so some gets wasted. Chris Anderson in NZ used mustard plants to retrieve gold from chemically treated soil containing gold particles.
How is gold taken up by the transporter?
Taken up as a single ion, Au 1+, as a cation like Cu 1+. The charge plays a part in the activity of the transporter, and it would have to be gold on its own as a cation as transporters have particular binding sites.
Are the ionic radius the same for copper as it is for gold?
Cu1+ : 77pm Cu2+: 73pm Cu3+ 54 Au1+: 137 Au3+: 85 Pd+: 59pm (2 coordinates) Pd2+: 86pm Pd3+: 76pm Pt2+: 80
How to extract nanoparticles?
Efficient extraction, isolation and purification of nnaoparticles is difficult and problematic.
Can smelt the biomass and extract the metals that way.
Or because these nanoparticles are bound to particlar peptide sequences you can extract the peptides along with the nanoparticles. Extraction using antibodies, immunoaffinity chromatograohy
What is the role of gold within the plant?
Plants take up into their tissues all the micro and macro elements which are essential to growth and reproduction; nitrogen, phosphorous, postassium, iron, copper etc. They also take up elements for which there is no defined role, like chromium, nickel, arsenic, tin. Gold has been detected in plant tissues as early as the 1900, when the method of fire ashing was used to produce gold beads from hardwood trees.
Is copper similar to gold?
Copper shares periodicity with gold, and silver and palladium.
Where are the nanoparticles deposited in the plants?
Andrew Taylor showed that arabidopsis can accumulate ionic gold from solution through roots and translocate it to the aerial biomass. However in this case he only found nanoparticles in the roots and not the shoots. But studies of silver nanoparticle formation found that ions are taken up through the root and reduced to NP within the plant. Once they’re formed, they can move via the transpiration stream to the aerial tissues. Wang et al also reported xylem and phloem based transport of copper oxide nanoparticles.
What is the pH of regions in the plant?
The plant tissues are typically 6.4pH, the vacuole is around 5.5, cytoplasm 7.3, the golgi 6.2
The rhizosphere pH changes with regulation of internal charge balance
