Proteins Under Pressure

In this activity, students will model the impact of pressure on gas molecules to understand the importance of Trimethylamine N-oxide (TMAO) as a protein stabilizer in deep-sea organisms. 

Nearly half of Earth’s ocean exists in a realm humans will never naturally visit. Approximately 49% of the global ocean lies within the Abyssal Plain, between 4,000 and 6,000 meters below the surface. Just above it sits the Midnight Zone (Bathypelagic Zone), spanning 1,000–4,000 meters and encompassing another 36.3% of the ocean. Together, these two zones make up the vast majority of the ocean’s habitable space. And yet — these environments are defined by extreme pressure. For every 10 meters (33 feet) of depth, ocean pressure increases by 14.5 pounds per square inch (psi) — roughly one additional atmosphere of pressure. By the time you reach the depths where ROV Hercules routinely dives during expeditions aboard E/V Nautilus, organisms are experiencing pressures 100 to 600 times greater than the atmospheric pressure at sea level.

At the deepest end of that range, the force pressing down on an organism is equivalent to the weight of up to 15 jumbo jet aircraft. Under those conditions, materials we are familiar with — plastic foam, air-filled objects, and even rigid containers — compress dramatically. Proteins, the molecular machines that allow cells to function, are especially vulnerable. High pressure can force proteins to unfold, a process known as denaturation, causing them to lose their shape and function.

Yet life thrives there. Fish swim. Crustaceans crawl. Microbes metabolize. Entire ecosystems persist in darkness under crushing force. So what makes it possible for organisms to survive — and function — at these depths?