We had an interesting talk today by Antti Niemi from Uppsala University modestly titled "Can Theory of Everything Explain Life?" It was about string theory of a somewhat different kind. The string in this case is a protein and what the theory should explain is its folding. The talk was basically a summary of this paper: "A phenomenological model of protein folding." In a nutshell the idea is to put a U(1) gauge theory on a discretized string (the protein), define a gauge-invariant free energy and minimize it. The claim is that this provides a good match to available data.
I know next to nothing about protein folding, so it's hard for me to tell how good the model is. From the data he showed, I wasn't too impressed that one can fit a scatter plot with two maxima by a function that has 5 free parameters, but then that fit is not in the paper and I didn't quite catch the details. One thing I learned from this talk though is that PDB sometimes doesn't stand for Particle Data Book, but for Protein Data Bank. If you know more about protein folding than I, let me know what you think. I found it quite interesting.
Something else that I learned in the talk is that the DNA of the bacterium Escherichia Coli is a closed string rather than an open string (see picture). I think I had heard that before. There's enzymes that act on the DNA, so-called topoisomerases that don't change the DNA sequence but the topology of the string. In other words, these enzymes can produce knots. Simple knots, but still. I think I had also heard that before. However, I thought the topology-change of the DNA is a process that is useful for the winding/unwinding and reading/reproducing of the DNA. It seems however that the topology of the DNA affects the synthesis of proteins, in particular the folding and function of the proteins. This probably isn't really news for anybody who works in the field but I actually didn't know that the topology of the DNA, not only it's sequence, has functional consequences. Alas, that flashed by only briefly and wasn't really content of the talk. But I find it intriguing.