Talking Point

A new way to remove carbon dioxide from air

A new way of removing carbon dioxide from a stream of air could provide a significant tool in the battle against climate change. The new system can work on the gas at virtually any concentration level, even down to the roughly 400 parts per million currently found in the atmosphere. Most methods of removing carbon dioxide from a stream of gas require higher concentrations, such as those found in the flue emissions from fossil fuel-based power plants. A few variations have been developed that can work with the low concentrations found in air, but the new method is significantly less energy-intensive and expensive, the researchers say.

The technique, based on passing air through a stack of charged electrochemical plates, is described in a new paper in the journal Energy and Environmental Science, by MIT postdoc Sahag Voskian, who developed the work during his PhD, and T. Alan Hatton, the Ralph Landau Professor of Chemical Engineering. The device is essentially a large, specialized battery that absorbs carbon dioxide from the air (or other gas stream) passing over its electrodes as it is being charged up, and then releases the gas as it is being discharged. In operation, the device would simply alternate between charging and discharging, with fresh air or feed gas being blown through the system during the charging cycle, and then the pure, concentrated carbon dioxide being blown out during the discharging. As the battery charges, an electrochemical reaction takes place at the surface of each of a stack of electrodes. These are coated with a compound called polyanthraquinone, which is composited with carbon nanotubes. The electrodes have a natural affinity for carbon dioxide and readily react with its molecules in the airstream or feed gas, even when it is present at very low concentrations. The reverse reaction takes place when the battery is discharged -- during which the device can provide part of the power needed for the whole system -- and in the process ejects a stream of pure carbon dioxide. The whole system operates at room temperature and normal air pressure.

“The greatest advantage of this technology over most other carbon capture or carbon absorbing technologies is the binary nature of the adsorbent's affinity to carbon dioxide,” explains Voskian. In other words, the electrode material, by its nature, “has either a high affinity or no affinity whatsoever,” depending on the battery’s state of charging or discharging. Other reactions used for carbon capture require intermediate chemical processing steps or the input of significant energy such as heat, or pressure differences. “This binary affinity allows capture of carbon dioxide from any concentration, including 400 parts per million, and allows its release into any carrier stream, including 100 percent CO2,” Voskian says. That is, as any gas flows through the stack of these flat electrochemical cells, during the release step the captured carbon dioxide will be carried along with it. For example, if the desired end-product is pure carbon dioxide to be used in the carbonation of beverages, then a stream of the pure gas can be blown through the plates. The captured gas is then released from the plates and joins the stream.

In some soft-drink bottling plants, fossil fuel is burned to generate the carbon dioxide needed to give the drinks their fizz. Similarly, some farmers burn natural gas to produce carbon dioxide to feed their plants in greenhouses. The new system could eliminate that need for fossil fuels in these applications and in the process actually be taking the greenhouse gas right out of the air, Voskian says. Alternatively, the pure carbon dioxide stream could be compressed and injected underground for long-term disposal, or even made into fuel through a series of chemical and electrochemical processes. Compared to other existing carbon capture technologies, this system is quite energy efficient, using about one gigajoule of energy per ton of carbon dioxide captured, consistently.

An antibody that protects against wide-ranging strains

A nationwide team of researchers has found an antibody that protects mice against a wide range of potentially lethal influenza viruses, advancing efforts to design of a universal vaccine that could either treat or protect people against all strains of the virus. The study, which Scripps Research conducted jointly with Washington University School of Medicine in St. Louis and Icahn School of Medicine at Mount Sinai in New York, points to a new approach to tackle severe cases of the flu, including pandemics.  Scripps Research's Ian Wilson, DPhil, one of three senior co-authors, says the antibody at the center of the study binds to a protein called neuraminidase, which is essential for the flu virus to replicate in the body. The protein, located on the surface of the virus, enables infected host cells to release the virus so it can spread to other cells. Tamiflu, the most widely used drug for severe flu infection, works by inactivating neuraminidase. However, many forms of neuraminidase exist, depending on the flu strain, and such drugs aren't always effective – particularly as resistance to the drugs is developing.

“There are many strains of influenza virus that circulate so every year we have to design and produce a new vaccine to match the most common strains of that year,” says co-senior author Ali Ellebedy, PhD, an assistant professor of pathology and immunology at Washington University. “Now imagine if we could have one vaccine that protected against all influenza strains, including human, swine and other highly lethal avian influenza viruses. This antibody could be the key to design of a truly universal vaccine.” Ellebedy discovered the antibody –  an immune molecule that recognizes and attaches to a foreign molecule — in blood taken from a patient hospitalized with flu at Barnes-Jewish Hospital in St. Louis in the winter of 2017. He noticed that a particular blood sample was unusual: In addition to containing antibodies against hemagglutinin, the major protein on the surface of the virus, it contained other antibodies that were clearly targeting something else. He sent three of the antibodies to co-senior author Florian Krammer, PhD, a microbiology professor at the Icahn School of Medicine at Mount Sinai. An expert on neuraminidase, Krammer tested the antibodies against his extensive library of neuraminidase proteins. At least one of the three antibodies blocked neuraminidase activity in all known types of neuraminidase in flu viruses, representing a variety of human and nonhuman strains. “The breadth of the antibodies really came as a surprise to us,” says Krammer. “Typically, anti-neuraminidase antibodies can be broad within a subtype, like H1N1, but an antibody with potent activity across subtypes was unheard of. At first, we did not believe our results. Especially the ability of the antibodies to cross between influenza A and influenza B viruses is just mind-boggling. It is amazing what the human immune system is capable of if presented with the right antigens.”

To find out whether the antibodies could be used to treat severe cases of flu, Krammer and colleagues tested them in mice that were given a lethal dose of influenza virus. All three antibodies were effective against many strains, and one antibody, called ‘1G01’, protected against all 12 strains tested, which included all three groups of human flu virus as well as avian and other nonhuman strains. “All the mice survived, even if they were given the antibody 72 hours after infection,” Ellebedy says. “They definitely got sick and lost weight, but we still saved them. It was remarkable. It made us think that you might be able to use this antibody in an intensive care scenario when you have someone sick with flu and it’s too late to use Tamiflu.” Tamiflu must be administered within 24 hours of symptoms. A drug that could be used later would help many people diagnosed after the Tamiflu window has closed. But before the researchers could even think of designing such a drug based on the antibody, they needed to understand how it was interfering with neuraminidase. They turned to Scripps Research's Wilson, known globally for his work as a structural biologist. Wilson and Xueyong Zhu, PhD, a staff scientist in Wilson’s lab, mapped the structures of the antibodies while they were bound to neuraminidase. The structures showed that the antibodies provide such broad protection because they target the conserved residues in the active site of the neuraminidase protein. That site stays much the same across distantly related flu strains because even minor changes could abolish the protein's ability to do its job, thereby preventing the virus from replicating. The researchers are working on developing new and improved treatments and vaccines for influenza based on antibody 1G01.

New data on the evolution of plants and origin of species

The history and evolution of plants can be traced back by about one billion years. Algae were the first organisms to harness solar energy with the help of chloroplasts. In other words, they were the first plant organisms to perform photosynthesis. Today, there are over 500,000 plant species, including both aquatic and terrestrial plants. They all evolved from a common ancestor. How this leap in biodiversity happened is still unclear. An international team of researchers, including scientists from Martin Luther University Halle-Wittenberg, presents the results of a unique project on the evolution of plants, using genetic data from 1,147 species the team created the most comprehensive evolutionary tree for green plants to date. The aim of the new study was to unravel the genetic foundations for this development. “Some species began to emerge and evolve several hundreds of millions of years ago. However, today we have the tools to look back and see what happened at that time,” explains plant physiologist Professor Marcel Quint from the Institute of Agricultural and Nutritional Sciences at MLU.

Quint is leading a sub-project with bioinformatician Professor Ivo Grosse, also from MLU, as part of the “One Thousand Plant Transcriptomes Initiative”, a global network of about 200 researchers. The team collected samples of 1,147 land plant and algae species to analyse each organism's genome-wide gene expression patterns (transcriptome). Using these data, the researchers reconstructed the evolutionary development of plants and the emergence of individual species. Their focus was on plant species that, as of yet, have not been studied on this level, including numerous algae, moss and also flowering plants. “This was a very special project because we did not just analyse individual components, but complete transcriptomes, of over one thousand plants, providing a much broader foundation for our findings,” explains Ivo Grosse.  The new data reveals that the genetic foundations for this expansion in biodiversity had been laid much earlier. “The transition from aquatic to terrestrial plants was the starting point for all further genetic developments. This development was the greatest challenge for plants, and so they needed more genetic innovations than ever before,” says Porsch. “We found an enormous increase in genetic diversity at the time of this transition, after that it reached a plateau. From this time on, almost all of the genetic material was available to drive evolutionary progress and generate the biodiversity we see today,” concludes Ivo Grosse. According to the researchers, the major expansion of flowering plants only started many millions of years later because, among other things, there was a lack of suitable environmental conditions for a long time. Furthermore, as evolution is not a planned process, certain genetic potentials only manifested themselves much later – or not at all. – TTN