Researchers figure out how to outperform nature's photosynthesis

Says io9: “They frankensteined together proteins from Synechococcus sp. with those from Clostridium acetobutylicum using molecular wire to create a 'hybrid biological/organic nanoconstruct' that was more efficient than either on their own.”

These researchers have created a tiny solar-powered device that works twice as fast as nature to produce hydrogen biofuel. In describing their research they say that although solar biohydrogen systems using photosystem I (PSI) have been developed, few attain the electron transfer throughput of oxygenic photosynthesis.

They say they optimized a nanoconstruct that tethers FB, the terminal [4Fe-4S] cluster of PSI from Synechococcus sp. PCC 7002, to the distal [4Fe-4S] cluster of the [FeFe]-hydrogenase (H2ase) from Clostridium acetobutylicum.

“On illumination, the PSI-[FeFe]-H2ase nanoconstruct evolves H2 at a rate of 2,200 ± 460 µmol mg chlorophyll-1 h-1, which is equivalent to 105 ± 22 e-PSI-1 s-1. Cyanobacteria evolve O2 at a rate of approximately 400 µmol mg chlorophyll-1 h-1, which is equivalent to 47 e-PSI-1 s-1, given a PSI to photosystem II ratio of 1.8.

“The greater than twofold electron throughput by this hybrid biological/organic nanoconstruct over in vivo oxygenic photosynthesis validates the concept of tethering proteins through their redox cofactors to overcome diffusion-based rate limitations on electron transfer.”

The researchers are among scientists in general who are looking at photosynthesis to invent materials and design new processes that can help save our planet. Associate Professor John Stride, of the University of New South Wales, commented to the ABC that “nature has had millennia to solve problems, and photosynthesis is very efficient.”

In turning to biomimicry, scientists are designing devices based on photosynthesis. As for the study authors, in making their biofuel device they replaced the FNR enzyme with hydrogenase.

One of the co-authors, Penn State Professor Donald Bryant, said there are good prospects for using some of these biological photosynthesis systems to produce biofuels for the future.

More information: Solar hydrogen-producing bionanodevice outperforms natural photosynthesis, PNAS, Published online before print December 12, 2011, doi: 10.1073/pnas.1114660108

Abstract
Although a number of solar biohydrogen systems employing photosystem I (PSI) have been developed, few attain the electron transfer throughput of oxygenic photosynthesis. We have optimized a biological/organic nanoconstruct that directly tethers FB, the terminal [4Fe-4S] cluster of PSI from Synechococcus sp. PCC 7002, to the distal [4Fe-4S] cluster of the [FeFe]-hydrogenase (H2ase) from Clostridium acetobutylicum. On illumination, the PSI–[FeFe]-H2ase nanoconstruct evolves H2 at a rate of 2,200 ± 460 µmol mg chlorophyll-1 h-1, which is equivalent to 105 ± 22 e-PSI-1 s-1. Cyanobacteria evolve O2 at a rate of approximately 400 µmol mg chlorophyll-1 h-1, which is equivalent to 47 e-PSI-1 s-1, given a PSI to photosystem II ratio of 1.8. The greater than twofold electron throughput by this hybrid biological/organic nanoconstruct over in vivo oxygenic photosynthesis validates the concept of tethering proteins through their redox cofactors to overcome diffusion-based rate limitations on electron transfer.

? 2011 PhysOrg.com

New protein structure expands nature's repertoire of biomolecules

The artificial protein made by the Bristol team – which they have named CC-Hex – has 6 polypeptide chains that the team designed from first principles; that is, whilst the chains take inspiration from biology they are not based on or related to any one particular natural protein.  Each chain folds into a helix, and these assemble to form a bundle (see top image).

This is interesting because nature appears not to have used this structure, or at least natural analogues of CC-Hex have not yet been observed.  Moreover, the structure is intriguing as the helices come together to form a ring that defines a central channel (see middle and bottom images).

 The protein has a central channel with defined chemistry that can be altered and controlled

This central channel provides the basis for engineering new proteins such as ion channels, which may be used as components of sensor and purification devices, and catalysts, which could pave the way to new industrial enzymes

The team, led by Professor Dek Woolfson and Professor Leo Brady, has also shown that the chemistry inside the channel can be altered using further design, chemical synthesis and X-ray crystallography.

Despite quite radical changes to the internal chemistry, the protein structure is robust to these alterations.  This is exciting because it is precisely how many natural proteins function: they alter chemistry within defined and highly controlled cavities within protein structures.  With this in mind, the team believes that CC-Hex represents an exciting opportunity to design new proteins, including enzymes and ion channels, from scratch.

Professor Dek Woolfson said of the discovery: “This is an exciting time for our labs.  Not only have we found a part of protein space that nature seems to have neglected, but we believe that the new structure will allow us to engineer protein functions much more rationally and confidently than has been possible before.”

More information: ‘A de novo peptide hexamer with a mutable channel’ by NR Zaccai, B Chi, AR Thomson, AL Boyle, GJ Bartlett, M Bruning, N Linden, RB Sessions, PJ Booth, RL Brady, and DN Woolfson in Nat. Chem. Biol. DOI: 10.1038/NChemBio.692

Provided by University of Bristol (news : web)

Solving the riddle of nature’s perfect spring

 Scientists have unravelled the shape of the protein that gives human tissues their elastic properties in what could lead to the development of new synthetic elastic polymers.

University of Manchester researchers, working with colleagues in Australia and the United States, used state-of-the-art techniques to reveal the structure of tropoelastin, the main component of elastin.

Elastin allows tissues in humans and other mammals to stretch, for example when the lungs expand and contract for respiration or when arteries widen and narrow over the course of a billion heart beats.

The study, published in the Proceedings of the National Academy of Sciences, revealed how evolution has triumphed where engineering has so far failed by generating a molecule with near-perfect elasticity that will last a lifetime.

"All mammals rely on elastin to provide their tissues with the ability to stretch and then return to their original shape," said researcher Dr Clair Baldock, from the University of Manchester's Wellcome Trust Centre for Cell Matrix Research. "This high level of physical performance demanded of elastin vastly exceeds and indeed outlasts all human-made elastics.

"It is the co-ordinated assembly of many tropoelastins into elastin that gives tissues their stretchy properties and this exquisite assembly helps to generate elastic tissues as diverse as artery, lung and skin.

"We discovered that tropoelastin is a curved, spring-like molecule with a 'foot' region to facilitate attachment to cells. Stretching and relaxing experiments showed that the molecule had the extraordinary capacity to extend to eight-times its initial length and can then return to its original shape with no loss of energy, making it a near-perfect spring."

She added: "Elastics are used in applications as diverse as clothing, vehicles, tissue engineering and even space travel, so understanding how the structure of tropoelastin creates its exceptional elastic properties will hopefully enable the development of synthetic 'elastin-like' polymers with potentially wide-ranging applications and benefits."

Initiator and research project leader Tony Weiss, Professor in the School of Molecular Bioscience, The University of Sydney, added: "Tropoelastin is a tiny protein 'nanospring' in the human body. Our bodies assemble these nanosprings to put elasticity into tissues like skin, blood vessels and lung.

"Our finding is the result of more than a decade of international collaboration. Our scientific teamwork spans Australia, the UK, USA and Europe. Tropoelastin's extraordinary capacity to extend to eight-times its initial length and then return to its original shape, with no loss of energy, is nature showing us how to make an ideal nanospring."

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by University of Manchester.

Journal Reference:

Clair Baldock, Andres F. Oberhauser, Liang Ma, Donna Lammie, Veronique Siegler, Suzanne M. Mithieux, Yidong Tu, John Yuen Ho Chow, Farhana Suleman, Marc Malfois, Sarah Rogers, Liang Guo, Thomas C. Irving, Tim J. Wess and Anthony S. Weiss. Shape of tropoelastin, the highly extensible protein that controls human tissue elasticity. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1014280108