March 09, 2018 at 08:28PM

Today I learned: 1) According to Harvard professor Johan Paulsson, if you fuse most fluorescent proteins to a protein that naturally multimerizes (that is, a protein that forms a complex of two or more copies of itself), the fluorescent protein attachment will cause the whole protein to clump dramatically. I'd read this before, but misread it slightly and thought that this applied to *any* fluorescent protein fusion. The thinking is that fluorescent proteins normally bind to each other, but only very weakly; however, when two or three or ten of them are all fused to one complex, it acts as a nucleation site for larger-scale aggregation. Citation: http://ift.tt/2HisT4D 2) You know the weird thing in quantum mechanics where particles kind of appear and disappear at random in a kind of quantom froth? Well, there's a way of viewing that phenomena as a consequence of simple formulations of quantum mechanics married to special relativity -- essentially, quantum systems get random spikes in energy, and special relativity says that you can interconvert between matter an energy, so there must be occasional production of particles from random QM fluctuations. According to Anthony Zee, the "marriage of QM with special relativity" is also one of the primary motivations for developing quantum field theory. I don't yet understand this claim, nor why it should be true. 3) Say you're a cell, and you want to make some specific amount of a protein. There are, roughly, two variables you can (dependently) vary to get the right amount of output protein -- transcription speed and translation speed*. For a fixed amount of output, you could have TONS of transcription and a little bit of translation on each of the many mRNAs you make, or extremely little transcription and TONS of translation on every mRNA you make, or anywhere in between. Today I learned that, across a wide variety of organisms, cells overwhelmingly choose to have low transcription and high translation over high transcription and low translation. Citation: http://ift.tt/2oIM3K9. This flies in the face of experimental data I've seen before that tells us that translation is much, much more energetically expensive for a cell than transcription and, in particular, that high-strength RBSs are *even more* energetically expensive than you'd expect. So... I don't know why cells would do this. The Alon paper has some arguments that don't make sense to me. One possibility, though, is that expressing low transcriptional rates makes gene expression *noisier*, which could be better for some processes. Still, I'd be surprised if the *vast majority* of genes are better expressed noisily than consistently. * Okay, you can also modify degradation speed and a couple other things, but I'm going to neglect those, because they turn out not to be too interesting in this story.