They would then need to make the proteins in the lab, though there was no understanding of how these proteins might behave. Glass approached Lieberman, whose lab studies the structure of proteins. Dustin Huard, a scientist in Liebermans lab and very first author of the paper, then ready prospect proteins that could possibly bind to the methane clathrates. To test the proteins, Johnson formed methane clathrates herself by recreating the high pressure and low temperature level of the seafloor in the laboratory. The scientists initially believed the part of the protein that was similar to fish antifreeze proteins would play a function in clathrate binding.
Methane clathrate (white, ice-like product) under a rock from the seafloor of the northern Gulf of Mexico. Deposits such as these show that methane and other gases cross the seafloor and get in the ocean. Credit: NOAA
Gigatons of greenhouse gas are caught under the seafloor, and thats an advantage. Along continental coasts, where slopes descend into the ocean, small ice cages hold methane gas in location, preventing it from launching and rising into the atmosphere.
Though seldom highlighted in media, these developments, referred to as methane clathrates, are under examination due to their possible impact on environment change. Throughout offshore drilling operations, methane ice can block pipelines, leading to freezing and rupture. The 2010 Deepwater Horizon oil catastrophe is believed to have resulted from a build-up of methane clathrates.
However previously, the biological procedure behind how methane gas stays stable under the sea has actually been nearly entirely unknown. In a development study, a cross-disciplinary team of Georgia Tech researchers found a formerly unidentified class of bacterial proteins that play an essential function in the formation and stability of methane clathrates.
A group led by Jennifer Glass, associate professor in the School of Earth and Atmospheric Sciences, and Raquel Lieberman, professor and Sepcic-Pfeil Chair in the School of Chemistry and Biochemistry, showed that these unique bacterial proteins reduce the growth of methane clathrates as successfully as industrial chemicals presently utilized in drilling, however are non-toxic, environment-friendly, and scalable. Their research study, moneyed by NASA, informs the look for life in the planetary system, and might also increase the safety of transferring natural gas.
The research study, published in the journal PNAS Nexus, underscores the importance of basic science in studying Earths natural biological systems and highlights the advantages of cooperation across disciplines.
” We wanted to comprehend how these developments were staying stable under the seafloor, and specifically what systems were adding to their stability,” Glass stated. “This is something nobody has actually done previously.”
Sifting Through Sediment
The effort started with the group analyzing a sample of clay-like sediment that Glass obtained from the seafloor off the coast of Oregon.
Glass assumed that the sediment would include proteins that affect the growth of methane clathrate and that those proteins would look like well-known antifreeze proteins in fish, which assist them make it through in cold environments.
Morphological effect of inhibitors on methane clathrate shell. Left: an animation showing methane clathrate development at the beginning of clathrate development and at 3 h, with and without inhibitors. : representative photos of speculative methane clathrate of each growth phase, identified by treatment. Credit: Georgia Institute of Technology
To confirm her hypothesis, Glass and her research group would first have to recognize protein prospects out of millions of potential targets included in the sediment. They would then need to make the proteins in the lab, though there was no understanding of how these proteins may behave. No one had worked with these proteins before.
Glass approached Lieberman, whose laboratory research studies the structure of proteins. The first step was to utilize DNA sequencing coupled with bioinformatics to determine the genes of the proteins consisted of in the sediment. Dustin Huard, a researcher in Liebermans lab and very first author of the paper, then ready prospect proteins that could possibly bind to the methane clathrates. Huard utilized X-ray crystallography to identify the structure of the proteins.
Producing Seafloor Conditions in the Lab
Huard passed off the protein candidates to Abigail Johnson, a former Ph.D. student in Glass laboratory and co-first author on the paper, who is now a postdoctoral researcher at the University of Georgia. To evaluate the proteins, Johnson formed methane clathrates herself by recreating the high pressure and low temperature of the seafloor in the laboratory. Johnson dealt with Sheng Dai, an associate teacher in the School of Civil and Environmental Engineering, to construct an unique pressure chamber from scratch.
Johnson placed the proteins in the pressure vessel and adjusted the system to mimic the pressure and temperature conditions needed for clathrate formation. By pressurizing the vessel with methane, Johnson forced methane into the bead, which caused a methane clathrate structure to form.
She then measured the quantity of gas that was taken in by the clathrate– a sign of how quickly and how much clathrate formed– and did so in the presence of the proteins versus no proteins. Johnson discovered that with the clathrate-binding proteins, less gas was taken in, and the clathrates melted at greater temperature levels.
Once the group confirmed that the proteins impact the development and stability of methane clathrates, they utilized Huards protein crystal structure to perform molecular characteristics simulations with the aid of James (JC) Gumbart, teacher in the School of Physics. The simulations allowed the group to identify the specific site where the protein binds to the methane clathrate.
A Surprisingly Novel System
The research study unveiled unanticipated insights into the structure and function of the proteins. The scientists at first thought the part of the protein that resembled fish antifreeze proteins would play a role in clathrate binding. Remarkably, that part of the protein did not contribute, and a completely various mechanism directed the interactions.
They discovered that the proteins do not bind to ice, but rather communicate with the clathrate structure itself, directing its development. Specifically, the part of the protein that had similar characteristics to antifreeze proteins was buried in the protein structure, and instead contributed in supporting the protein.
The scientists found that the proteins carried out better at customizing methane clathrate than any of the antifreeze proteins that had been tested in the past. They likewise carried out simply as well as, if not better than, the hazardous business clathrate inhibitors presently used in drilling that present major ecological hazards.
Preventing clathrate development in gas pipelines is a billion-dollar industry. It would significantly decrease the threat of ecological damage if these naturally degradable proteins could be utilized to prevent disastrous natural gas leakages.
” We were so fortunate that this in fact worked, because although we selected these proteins based upon their similarity to antifreeze proteins, they are totally various,” Johnson stated. “They have a comparable function in nature, but do so through a totally different biological system, and I believe that really excites individuals.”
Methane clathrates likely exist throughout the planetary system– on the subsurface of Mars, for instance, and on icy moons in the external solar system, such as Europa. The groups findings indicate that if microbes exist on other planetary bodies, they might produce similar biomolecules to maintain liquid water in channels in the clathrate that could sustain life.
” Were still discovering a lot about the standard systems on our planet,” Huard said. “Thats one of the fantastic things about Georgia Tech– various neighborhoods can come together to do truly cool, unforeseen science. I never ever thought I would be working on an astrobiology project, but here we are, and weve been really effective.”
Reference: “Molecular basis for inhibition of methane clathrate growth by a deep subsurface bacterial protein” by Dustin J E Huard, Abigail M Johnson, Zixing Fan, Lydia G Kenney, Manlin Xu, Ran Drori, James C Gumbart, Sheng Dai, Raquel L Lieberman and Jennifer B Glass, 14 August 2023, PNAS Nexus.DOI: 10.1093/ pnasnexus/pgad268.
The study was moneyed by NASA and the National Science Foundation.