March 13, 2018 at 11:45PM

Today I learned: 1) The number line can be thought of as a limit of a circle with increasingly large radius. This is useful for proofs involving the number line, and can get you a factor of pi in sums that otherwise isn't obvious. For more, see https://www.youtube.com/watch?v=d-o3eB9sfls. 2) Synthetic biological circuits break. A lot. Almost all synthetic circuits are bad for the cell they're in, so most mutations that break the circuit will be selected for pretty quickly. One of the most common types of circuit-breaking mutations is accidental insertion by Insertional Sequence (IS) elements, which are small DNA fragments that make transposons, which flip the IS out of whatever DNA it's in and move it somewhere else. Bacterial genomes have lots of IS elements (E. coli has a few dozen, depending on the strain), so any engineering in bacteria will run afoul of them eventually. So. IS elements are common in bacterial genomes, and they mess up biocircuits. Why not remove them from the genome? Well, somebody has -- Scarab Genomics LLC sells a variety of IS-free cell strains for a variety of cloning needs, for the low low price of... actually, I don't know how much they cost. You have to make an account with them and sign in to see prices. More importantly, though, Scarab Genomics has some pretty nasty licencing restrictions on their strains -- they get a cut on any IP you develop using their lines, for example. Not nice. 3) Strong ribosomal binding sites (RBSs) can protect mRNAs against degradation. Probably. This is a pretty new finding, but it looks like if an RNA is covered in ribosomes, the ribosomes can physically block RNAses from binding and degrading the RNA. Strong RBS -> lots of attached ribosomes -> less degradation. The effect is modest, but measurable.