X-ray study throws light on key process for production
A Swedish-German team of researchers has cleared up a key process for the artificial production of silk. With the help of the intense X-rays from DESY's research light source PETRA III, the scientists could watch just how small protein pieces, called nanofibrils, lock together to form a fibre.
Surprisingly, the best fibres are not formed by the longest protein pieces. Instead, the strongest "silk" is won from protein nanofibrils with seemingly less quality, as the team around Dr. Christofer Lendel and Dr. Fredrik Lundell from the Royal Institute of Technology (KTH) in Stockholm reports in the Proceedings of the U.S. National Academy of Sciences.
Due to its many remarkable characteristics, silk is a material high in demand in many areas. It is lightweight, yet stronger than some metals, and can be extremely elastic. Currently, silk is harvested from farmed silkworms, which is quite costly. "Across the globe, many research teams are working on methods to artificially produce silk," says co-author Prof. Stephan Roth from DESY who is an adjunct professor at KTH Stockholm. "Such artificial materials can also be modified to have new, tailor-made characteristics and can serve for applications like novel biosensors or self-dissolving wound dressings, for example."
However, imitating nature proved especially hard in the case of silk. The Swedish team focuses on self-assembling materials. "That's a quite simple process," explains Lundell. "Some proteins assemble themselves into nanofibrils under the right conditions. A carrier fluid with these protein nanofibrils is then pumped through a small canal. Additional water enters perpendicular from the sides and squeezes the fibrils together until they stick together and form a fibre."
The latter process is called hydrodynamic focussing, and Lundell's team has used it before for producing artificial wood fibres from cellulose fibrils. "In fact, the process has several similarities with the way spiders produce their silk threads," says Lendel.
In the new study, the nanofibrils were formed by a protein from cow's whey under the influence of heat and acid. The fibrils shape and characteristics strongly depend on the protein concentration in the solution. At less than four per cent, long, straight and thick fibrils form. They can be up to 2000 nanometres long and 4 to 7 nanometres thick. But at an only slightly higher protein concentration of six per cent or more in the initial solution, the fibrils remain much shorter and thinner with an average length of just 40 nanometres and a thickness of 2 to 3 nanometres. Also, they are curved looking like tiny worms and 15 to 25 times softer than the long, straight fibrils.
In the lab, however, the short and curved fibrils formed much better fibres than the long and straight fibrils. With DESY's bright X-ray light, the researchers could find out why: "The curved nanofibrils lock together much better than the straight ones. The X-ray diffraction patterns show that they largely keep their rather random orientation in the final fibre," says Roth, head of the beamline P03 at PETRA III where the experiments took place.
"The strongest fibres form when a sufficient balance between ordered nanostructure and fibril entanglement is kept," adds Lendel. "Natural silk is an even more complex structure with evolutionary optimized proteins that assemble in a way with both, highly ordered regions - so-called beta-sheet - that give strength and regions with low order that give flexibility. However, the structures of the artificial and natural fibers are essentially different. In particular, the protein chains in natural silk have a larger number of intermolecular interactions that cross-link the proteins and result in a stronger fiber."
In their experiments, the researchers obtained artificial silk fibres that were roughly five millimetres long and of medium quality. "We used the whey protein to understand the underlying principle in detail. The whole process can now be optimised to obtain fibres with better or new, tailor-made properties," says Lendel. This way, the results of the study could help to develop materials with novel features, for example artificial tissue for medical applications.
Deutsches Elektronen-Synchrotron DESY is the leading German accelerator centre and one of the leading in the world. DESY is a member of the Helmholtz Association and receives its funding from the German Federal Ministry of Education and Research (BMBF) (90 per cent) and the German federal states of Hamburg and Brandenburg (10 per cent). At its locations in Hamburg and Zeuthen near Berlin, DESY develops, builds and operates large particle accelerators, and uses them to investigate the structure of matter. DESY's combination of photon science and particle physics is unique in Europe.
Flow-assisted assembly of nanostructured protein microfibers; Ayaka Kamada, Nitesh Mittal, L. Daniel Söderberg, Tobias Ingverud, Wiebke Ohm, Stephan Roth, Fredrik Lundell, Christofer Lendel; Proceedings of the National Academy of Sciences (PNAS), 2017; DOI: 10.1073/pnas.1617260114
Dr. Thomas Zoufal | EurekAlert!
Nonstop Tranport of Cargo in Nanomachines
20.11.2018 | Max-Planck-Institut für molekulare Zellbiologie und Genetik
Researchers find social cultures in chimpanzees
20.11.2018 | Universität Leipzig
Max Planck researchers revel the nano-structure of molecular trains and the reason for smooth transport in cellular antennas.
Moving around, sensing the extracellular environment, and signaling to other cells are important for a cell to function properly. Responsible for those tasks...
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
19.11.2018 | Event News
09.11.2018 | Event News
06.11.2018 | Event News
21.11.2018 | Power and Electrical Engineering
20.11.2018 | Life Sciences
20.11.2018 | Life Sciences