Why is it that the people who cut corners always whine the loudest about regulation stifling innovation? You might have heard that a submarine imploded recently while on a luxury tour of the site where the Titanic sank. Ok, maybe not luxury, but a very expensive tour of the Titanic, because anyone with two functioning neurons who looked at the OceanGate Titan might question why a ticket for such a voyage would cost $250,000 when the 'submarine' appeared to be held together with bubble gum and bailing wire. Things got worse on the inside where the 'craft' was controlled by a $40 Logitech gamepad. Despite its 4-star review on Amazon, the most significant problem with this sub wasn't the gamepad, but the materials hiding just outside of view that were used to create the pressure hull of the Titan. Now, pressure hulls of most deep submersion vehicles (DSVs) are spherical and made out of titanium, aluminum or steel. Basically every deep dive record is held by a DSV built around a titanium bathysphere. The Triton was different, it was cylindrical in shape. It was also made out of a combination of titanium, carbon fiber, and acrylic. Despite being warned that a carbon fiber and titanium composite hull was basically a ticking time bomb, Stockton Rush, an aerospace engineer and CEO of OceanGate, continued to take the Titan to depth until it imploded after a handful of dives with 4 paying customers onboard. You see, marine engineers saw problems with Titan's design and the materials that were used in its construction. Notably, carbon fiber isn't a great choice for pressure hulls because it's much less tolerant of compressive forces than tensive ones. So, while carbon fiber might be a great choice for aerospace applications, it's a terrible one for a pressure hull. Carbon fiber subjected to repetitive cycles of compression can fail unexpectedly and although Rush was warned that it was only a matter of time until his sub had a catastrophic failure, he instead sold paying customers trips on a sub that he said was safe. In an interview with David Pogue at CBS, Rush said, "the part that keeps you alive, the part we care about, is that carbon fiber cylinder and the titanium end caps [which were] buttoned down." The problem here is that Rush was the only one that thought any of this was true and duped customers, unknowingly, into playing a very high stakes game of Russian roulette. Rush once said that 'obscenely safe' regulations had been holding back his 'innovations' for years, but refused to submit any of those innovations for testing and certification. Unfortunately, it took the deaths of 5 people to remind us why regulations exist and why it's so important to prove empirically the performance, efficacy, and safety of the thing you developed before releasing it publicly. That's true for subs, but also automobiles, airplanes, medical devices, drugs or any other product whose use can result in serious injury or death.

Deoxyribonucleic acid (DNA) is the genetic material, but early on, most of science thought the genetic material was protein. That changed in 1952. Ok, it didn’t change overnight, because scientists are pretty stubborn. It actually wasn’t accepted until the 60’s, but, in 1951, Alfred Hershey and his technician, Martha Chase, began a series of experiments that conclusively showed that DNA was the genetic material. There was already good evidence that the genetic material wasn’t protein, but early molecular biologists couldn’t wrap their heads around how 4 bases of DNA could code for all of the diversity we see, especially when proteins are made up of long chains of 20 amino acids. Surely, since 20 is greater than 4, you get more diversity with 20! So the hypothesis was that DNA must be the scaffold that holds everything together. Of course, we know now that’s absolutely not true, and it’s basically the opposite - DNA is the genetic material and protein serves a support function. The work that synthesized all of these ideas together was completed by Hershey and Chase in what are now referred to as the Hershey-Chase experiments. They worked with bacterial viruses called bacteriophages. These are very simple viruses that consist of a protein shell surrounding the DNA of the virus. But before the 1950’s, no one knew what phages looked like or how they infected bacteria. In 1951, Thomas F. Anderson, a pioneer of electron microscopy, showed that phages are like little moon landers and attach themselves to the outside of the bacteria but do not enter them. This created a bit of a conundrum, how can protein be the genetic material if none of the phage protein gets inside? Today’s #FigureFriday involves Hershey-Chase, a Waring blender and phages grown in the presence of radioactive food items. Luckily, proteins do not contain Phosphorus (P) and DNA does not contain Sulfur (S), so radioactive P-32 and S-35 could be used to label each component of the bacteriophage individually. Radioactive phages were then combined with bacteria and stuck in a blender. Hershey and Chase discovered that this technique didn’t kill the bacteria, but it was perfect for shaking the empty phage husks from the bacteria. This is documented in Figure 1 where it shows 90% viability of the infected bacteria but that 80% of the protein (S35) remains external while only 30% of the DNA (P32) does after blending. This result supported the electron microscopy observation that the phages are basically just little protein covered DNA injectors! Hershey and Chase followed up by showing that 30% of the DNA that makes it into baby phages after the blender experiment was radiolabeled while <1% of the protein was, essentially proving that DNA, and not protein, is the heritable genetic material. ### Hershey, AD and Chase, M. 1952. Independent Functions of Viral Protein and Nucleic Acid in Growth of Bacteriophage. J Gen Physiol. 36(1): 39–56. DOI: 10.1085/jgp.36.1.39