{"id":2672,"date":"2015-10-20T03:37:21","date_gmt":"2015-10-20T03:37:21","guid":{"rendered":"http:\/\/www.kurzweilai.net\/?p=265016"},"modified":"2015-10-20T03:37:21","modified_gmt":"2015-10-20T03:37:21","slug":"engineered-viruses-provide-quantum-based-enhancement-of-energy-transport","status":"publish","type":"post","link":"https:\/\/hoo.central12.com\/fugic\/2015\/10\/20\/engineered-viruses-provide-quantum-based-enhancement-of-energy-transport\/","title":{"rendered":"Engineered viruses provide quantum-based enhancement of energy transport"},"content":{"rendered":"
\"\"

Rendering of a virus used in the MIT experiments. The light-collecting centers, called chromophores, are in red, and chromophores that just absorbed a photon of light are glowing white. After the virus is modified to adjust the spacing between the chromophores, energy can jump from one set of chromophores to the next faster and more efficiently. (credit: the researchers and Lauren Alexa Kaye)<\/p><\/div>\n

MIT<\/a> engineers have achieved a significant efficiency boost in a light-harvesting system, using genetically engineered viruses to achieve higher efficiency in transporting energy from receptors to reaction centers where it can be harnessed, making use of the exotic effects of quantum mechanics. Emulating photosynthesis in nature, it could lead to inexpensive and efficient solar cells or light-driven catalysis,<\/p>\n

This achievement in coupling quantum research and genetic manipulation, described this week in the journal\u00a0Nature Materials<\/em>, was the work of MIT professors Angela Belcher<\/a>, an expert on engineering viruses to carry out energy-related tasks, and Seth Lloyd<\/a>, an expert on quantum theory and its potential applications, and 15 collaborators at MIT and in Italy.<\/p>\n

The \u201cQuantum Goldilocks Effect\u201d<\/strong><\/p>\n

In photosynthesis, a photon hits a receptor called a chromophore<\/a>, which in turn produces an exciton<\/a> — a quantum particle of energy. This exciton jumps from one chromophore to another until it reaches a reaction center, where that energy is harnessed to build the molecules that support life, or photosynthesis.<\/p>\n

But the hopping pathway of excitons is random and inefficient unless it takes advantage of quantum effects that allow it, in effect, to take multiple pathways at once and select the best ones, behaving more like a wave than a particle.<\/p>\n

To do that, the chromophores have to be arranged just right, with exactly the right amount of space between them. This, Lloyd explains, is known as the \u201cQuantum Goldilocks Effect.\u201d<\/p>\n

\"\"

Molecular models of the genetically engineered viruses. Left virus has long inter-binding site distances of 16\u00c5 and 33\u00c5 within two proteins. Right virus has closer inter-binding site distances of approximately 10\u00c5 and 13\u00c5, achieving faster excitation-energy transport speed. (credit: Heechul Park et al.\/Nature Materials)<\/p><\/div>\n

That\u2019s where the virus comes in. By engineering a virus that Belcher has worked with for years, the team was able to get it to bond with multiple synthetic chromophores — or, in this case, organic dyes. The researchers were then able to produce many varieties of the virus, with slightly different spacings between those synthetic chromophores, and select the ones that performed best.<\/p>\n

In the end, they were able to more than double excitons\u2019 speed, increasing the distance they traveled before dissipating \u2014 a significant improvement in the efficiency of the process.<\/p>\n

The project started from a chance meeting at a conference in Italy. Lloyd and Belcher, a professor of biological engineering, were reporting on different projects they had worked on, and began discussing the possibility of a project encompassing their very different expertise. Lloyd, whose work is mostly theoretical, pointed out that the viruses Belcher works with have the right length scales to potentially support quantum effects.<\/p>\n

In 2008, Lloyd had published a paper demonstrating that photosynthetic organisms transmit light energy efficiently because of these quantum effects. When he saw Belcher\u2019s report on her work with engineered viruses, he wondered if that might provide a way to artificially induce a similar effect, in an effort to approach nature\u2019s efficiency.<\/p>\n

\u201cI had been talking about potential systems you could use to demonstrate this effect, and Angela said, \u2018We\u2019re already making those,\u2019\u201d Lloyd recalls. Eventually, after much analysis, \u201cWe came up with design principles to redesign how the virus is capturing light, and get it to this quantum regime.\u201d<\/p>\n

Within two weeks, Belcher\u2019s team had created their first test version of the engineered virus. Many months of work then went into perfecting the receptors and the spacings.<\/p>\n

Once the team engineered the viruses, they were able to use laser spectroscopy and dynamical modeling to watch the light-harvesting process in action, and to demonstrate that the new viruses were indeed making use of quantum coherence to enhance the transport of excitons.<\/p>\n

\u201cIt was really fun,\u201d Belcher says. \u201cA group of us who spoke different [scientific] languages worked closely together, to both make this class of organisms, and analyze the data. That\u2019s why I\u2019m so excited by this.\u201d<\/p>\n

Inexpensive and efficient solar cells or light-driven catalysis<\/strong><\/p>\n

While this initial result is essentially a proof of concept rather than a practical system, it points the way toward an approach that could lead to inexpensive and efficient solar cells or light-driven catalysis, the team says. So far, the engineered viruses collect and transport energy from incoming light, but do not yet harness it to produce power (as in solar cells) or molecules (as in photosynthesis). But this could be done by adding a reaction center, where such processing takes place, to the end of the virus where the excitons end up.<\/p>\n

\u201cThis is exciting and high-quality research,\u201d says Al\u00e1n Aspuru-Guzik<\/a>, a professor of chemistry and chemical biology at Harvard University<\/a> who was not involved in this work. The research, he says, \u201ccombines the work of a leader in theory (Lloyd) and a leader in experiment (Belcher) in a truly multidisciplinary and exciting combination that spans biology to physics to potentially, future technology.\u201d<\/p>\n

\u201cAccess to controllable excitonic systems is a goal shared by many researchers in the field,\u201d Aspuru-Guzik adds. \u201cThis work provides fundamental understanding that can allow for the development of devices with an increased control of exciton flow.\u201d<\/p>\n

The research was supported by the Italian energy company Eni through the MIT Energy Initiative. The team included researchers at the University of Florence, the University of Perugia, and Eni.<\/p>\n