This belief led me away from lab ideas such as chemical synthesis of gold nanoparticles (as depicted in the materials for my The Need for Self-Assembly lecture note set) because you cannot really see what is happening in chemical synthesis and must accept the suggested self-assembly mechanisms on faith. And as one who spent a career trying to optimize various forms of nanoscale self-assembly, I felt that it was essential that any student lab on self-assembly not only include this balance but that it do so in a way that was clearly visible to the students. This delicate balance of assembly and disassembly is at the heart of all self-assembly processes, ranging from crystal growth to protein folding. Then, over time, it is likely that more and more of our reactants will find their way into the configuration we intended. Nevertheless, under just the right conditions of temperature and reactant concentrations, our desired lowest energy configuration will be slightly more robust, and will stay together slightly longer. Or, even worse, it will assemble part of one structure here, and part of another structure over there. Instead, via a statistical process, nature will sample all of the structures, assembling them and disassembling them.
But that does not mean that nature will home right in on this structure. If we did our design work properly, the structure we intended has the lowest energy of these alternatives.
Real-world self-assembly will almost always produce many, many alternative structures. Nature is seldom, if ever, so accommodating. This is loosely correct, but it trivializes self-assembly by implying that once the parts are correctly designed and built, all we have to do is get out of the way.
On the class homepage, I described self-assembly as being " when we design the parts so that they know how we want them to finally come together."
0 kommentar(er)
