Sunday, November 6, 2011

PolyU scientist develop new textile materials for sportswear

A novel type of fabric that can absorb water and perspiration on one side and transport it to the other has been invented by a team of textile scientists based at The Hong Kong Polytechnic University (PolyU).


A novel type of fabric that can absorb water and perspiration on one side and transport it to the other has been invented by a team of scientists based at The Hong Kong Polytechnic University (PolyU). The finding was published in the latest issue of the (Issue dated 13 October 2011) of the Royal Society of Chemistry.


This ground-breaking research was done by Professor John Xin, Acting Head of PolyU’s Institute of Textile and Clothing; his PhD student Miss Kong Yee-yee; and Dr Liu Yuyang of the Stevens Institute of Technology in the US. The researchers have made the fabric hydrophilic on one side by coating it with nano titania, which gives the material photo-induced hydrophilicity. This means that its hydrophilicity can be controlled by light. The fabric becomes hydrophobic after being stored in the dark.


The fabric could be used to wick sweat away from the human skin. In the light, water can be transported in a controllable manner from the hydrophobic side (next to the skin) to the hydrophilic side and then spread out rapidly along the channels on the hydrophilic side.


This differs from other that do a similar thing. Current materials work by creating a surface energy gradient across the fabric by a pressure difference. Professor John Xin’s work introduces nano and smart elements into the system, taking advantage of titania’s properties.


A pioneering researcher, Professor John Xin and is renowned for his nano-technology breakthrough for to develop a special which can be made into self-cleaning clothes. This breakthrough by Professor Xin and Dr Walid Daoud in 2004 was also reported by Nature.


Provided by Hong Kong Polytechnic University

Self-replication process holds promise for production of new materials

New York University scientists have developed artificial structures that can self-replicate, a process that has the potential to yield new types of materials. The work, conducted by researchers in NYU's Departments of Chemistry and Physics and its Center for Soft Matter Research, appears in the latest issue of the journal Nature.

In the natural world, self-replication is ubiquitous in all living entities, but artificial self-replication has been elusive. The discovery in Nature reports the first steps toward a general process for self-replication of a wide variety of arbitrarily designed seeds. The seeds are made from DNA tile motifs that serve as letters arranged to spell out a particular word. The replication process preserves the letter sequence and the shape of the seed and hence the information required to produce further generations.

This process holds much promise for the creation of . DNA is a robust functional entity that can organize itself and other into complex structures. More recently DNA has been used to organize inorganic matter, such as , as well. The re-creation by the NYU scientists of this type of assembly in a laboratory raises the prospect for the eventual development of self-replicating materials that possess a wide range of patterns and that can perform a variety of functions. The breakthrough the NYU researchers have achieved is the replication of a system that contains complex information. Thus, the replication of this material, like that of DNA in the cell, is not limited to repeating patterns.

To demonstrate this self-replication process, the NYU scientists created artificial DNA tile motifs —short, nanometer-scale arrangements of DNA. Each tile serves as a letter—A or B—that recognizes and binds to complementary letters A' or B'. In the natural world, the DNA replication process involves complementary matches between bases—adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C) -- to form its familiar double helix. By contrast, the NYU researchers developed an artificial tile or motif, called BTX (bent triple helix molecules containing three DNA double helices), with each BTX molecule comprised of 10 DNA strands. Unlike DNA, the BTX code is not limited to four letters—in principle, it can contain quadrillions of different letters and tiles that pair using the complementarity of four DNA single strands, or "sticky ends," on each tile, to form a six-helix bundle.

In order to achieve self-replication of the BTX tile arrays, a seed word is needed to catalyze multiple generations of identical arrays. BTX's seed consists of a sequence of seven tiles—a seven-letter word. To bring about the self-replication process, the seed is placed in a chemical solution, where it assembles complementary tiles to form a "daughter BTX array"—a complementary word. The daughter array is then separated from the seed by heating the solution to ~ 40 oC. The process is then repeated. The daughter array binds with its complementary tiles to form a "granddaughter array," thus achieving self-replication of the material and of the information in the seed—and hence reproducing the sequence within the original seed word. Significantly, this process is distinct from the replication processes that occur within the cell, because no biological components, particularly enzymes, are used in its execution—even the DNA is synthetic.

"This is the first step in the process of creating artificial self-replicating materials of an arbitrary composition," said Paul Chaikin, a professor in NYU's Department of Physics and one of the study's co-authors. "The next challenge is to create a in which self-replication occurs not only for a few generations, but long enough to show exponential growth."

"While our replication method requires multiple chemical and thermal processing cycles, we have demonstrated that it is possible to replicate not just molecules like cellular DNA or RNA, but discrete structures that could in principle assume many different shapes, have many different functional features, and be associated with many different types of chemical species," added Nadrian Seeman, a professor in NYU's Department of Chemistry and a co-author of the study.

Provided by New York University (news : web)

Why carbon nanotubes spell trouble for cells

It's been long known that asbestos spells trouble for human cells. Scientists have seen cells stabbed with spiky, long asbestos fibers, and the image is gory: Part of the fiber is protruding from the cell, like a quivering arrow that's found its mark.


But scientists had been unable to understand why cells would be interested in asbestos fibers and other materials at the nanoscale that are too long to be fully ingested. Now a group of researchers at Brown University explains what happens. Through molecular simulations and experiments, the team reports in Nature Nanotechnology that certain nanomaterials, such as carbon nanotubes, enter cells tip-first and almost always at a 90-degree angle. The orientation ends up fooling the cell; by taking in the rounded tip first, the cell mistakes the particle for a sphere, rather than a long cylinder. By the time the cell realizes the material is too long to be fully ingested, it's too late.


"It's as if we would eat a lollipop that's longer than us," said Huajian Gao, professor of engineering at Brown and the paper's corresponding author. "It would get stuck."


The research is important because nanomaterials like carbon nanotubes have promise in medicine, such as acting as vehicles to transport drugs to specific cells or to specific locations in the human body. If scientists can fully understand how nanomaterials interact with cells, then they can conceivably design products that help cells rather than harm them.


"If we can fully understand (nanomaterial-cell dynamics), we can make other tubes that can control how cells interact with nanomaterials and not be toxic," Gao said. "We ultimately want to stop the attraction between the nanotip and the cell."


Like asbestos fibers, commercially available carbon nanotubes and gold nanowires have rounded tips that often range from 10 to 100 nanometers in diameter. Size is important here; the diameter fits well within the cell's parameters for what it can handle. Brushing up against the nanotube, special proteins called receptors on the cell spring into action, clustering and bending the membrane wall to wrap the cell around the nanotube tip in a sequence that the authors call "tip recognition." As this occurs, the nanotube is tipped to a 90-degree angle, which reduces the amount of energy needed for the cell to engulf the particle.


Once the engulfing — endocytosis — begins, there is no turning back. Within minutes, the cell senses it can't fully engulf the nanostructure and essentially dials 911. "At this stage, it's too late," Gao said. "It's in trouble and calls for help, triggering an immune response that can cause repeated inflammation."


The team hypothesized the interaction using coarse-grained molecular dynamic simulations and capped multiwalled carbon nanotubes. In experiments involving nanotubes and gold nanowires and mouse liver cells and human mesothelial cells, the nanomaterials entered the cells tip-first and at a 90-degree angle about 90 percent of the time, the researchers report.


"We thought the tube was going to lie on the cell membrane to obtain more binding sites. However, our simulations revealed the tube steadily rotating to a high-entry degree, with its tip being fully wrapped," said Xinghua Shi, first author on the paper who earned his doctorate at Brown and is at the Chinese Academy of Sciences in Beijing. "It is counter-intuitive and is mainly due to the bending energy release as the membrane is wrapping the tube."


The team would like to study whether nanotubes without rounded tips — or less rigid nanomaterials such as nanoribbons — pose the same dilemma for cells.


"Interestingly, if the rounded tip of a carbon nanotube is cut off (meaning the tube is open and hollow), the tube lies on the cell membrane, instead of entering the cell at a high-degree-angle," Shi said.

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Uncharted territory: Scientists sequence the first carbohydrate biopolymer

DNA and protein sequencing have forever transformed science, medicine, and society. Understanding the structure of these complex biomolecules has revolutionized drug development, medical diagnostics, forensic science, and our understanding of evolution and development. But, one major molecule in the biological triumvirate has remained largely uncharted: carbohydrate biopolymers.


Today, for the first time ever, a team of researchers led by Robert Linhardt of Rensselaer Polytechnic Institute has announced in the October 9 Advanced Online Publication edition of the journal Nature the sequence of a complete complex carbohydrate biopolymer. The surprising discovery provides the scientific and medical communities with an important and fundamental new view of these vital , which play a role in everything from and development to and blood clotting.


The paper is titled "The proteoglycan bikunin has a defined sequence."


"Carbohydrate biopolymers, known as glycosaminoglycans, appear to be really important in how cells interact in higher organisms and could explain evolutionary differences and how development is driven. We also know that carbohydrate chains respond to disease, injury, and changes in the environment," said Linhardt, who is the Ann and John H. Broadbent Jr. '59 Senior Constellation Professor of and at Rensselaer. "In order to understand how and why this all happens, we first need to know their structure. And today, at least for the simplest glycosaminoglycan structure, we can now do this."


The first glycosaminoglycan sequenced was obtained from bikunin. Bikunin is a proteoglycan, a protein to which a single glycosaminoglycan chain is attached. Unlike less sophisticated carbohydrate biopolymers, such as starch and , the proteoglycans are decorated with structurally complex carbohydrates that enable them to perform more sophisticated and defined roles in the body. Bikunin, for example, is a natural anti-inflammatory that is used as a drug for the treatment of acute pancreatitis in Japan. It has the simplest chemical structure of any proteoglycan. Linhardt views the discovery of the structure of bikuin as the first step on the ladder to the discovery of the structure of more complex proteoglycans.


"The first genome sequences of DNA were on the simplest organisms such as bacteria. Once the technology was developed it ultimately led to the sequencing of the human genome," he said. "In our efforts to sequence carbohydrate biopolymers we don't yet know if the defined structure we observe for this simple protoglycan will hold for much more complex proteoglycans."


But, looking for structure in more complex proteoglycans will be among the next steps in the research for Linhardt and his team. The search for structure could help put to rest a long-running debate in the scientific community as to whether biopolymers require a defined structure to function.


"Despite all that is known about glycan formation, our understanding has not yet been deep enough to infer sequence or even determine if sequence occurs," Linhardt said. "These findings represent a new way of looking at these complex biomolecules as ordered structures."


Linhardt's research into carbohydrate sequencing began 30 years ago. In his previous work, he determined that some order existed in at least a portion of some carbohydrate biopolymers, but it did not represent the entire finished puzzle.


"Previously, we could see a pattern, but we could not see if all the chains were playing the same music. The tools did not yet exist. Now we can recognize it as a symphony."


To uncover the entire structure, Linhardt and his team, which was led by his doctoral student Mellisa Ly, borrowed a technique from the field of protein research called the proteomics top-down approach. As opposed to the bottom-up approach that first breaks apart a complex biopolymer into pieces and then rebuilds it piece by piece like a jigsaw puzzle, the top-down approach used by Linhardt and colleagues allows the researcher to picture the whole intact puzzle. This can only be accomplished with some of the most sophisticated technology available to the scientific community today, including very high-powered mass spectrometers.


Linhardt used a mass spectrometer located in the Rensselaer Center for Biotechnology and Interdisciplinary Studies (CBIS) to make his initial discoveries, and had these results independently confirmed on a separate and higher-level spectrometer at the University of Georgia. Mass spectrometers break down a molecule into separate charged particles or ions. These ions can then be categorized and analyzed based on their mass-to-charge ratio. These ratios then allow for sequencing of the entire molecule.


"This was truly the convergence of really sophisticated spectroscopy and its application to biology," Linhardt said. "We were fortunate to have a lot of time to play with the instrument at CBIS to understand its capabilities."


Beyond the technology it also took faith and determination. According to Linhardt, "It takes a student that is willing to try something even when the odds are pretty low. If it doesn't work, you make incremental progress. If it does work, you can make a great discovery. But, from the beginning you need to be a believer that it is worth taking the chance because it takes a lot of hard work in the lab."


And the odds weren't in Linhardt's favor. Despite being the most simple of proteoglycans, there were still 290 billion different possible sequences for the molecule.


"The first sample we looked at, we got the structure," Linhardt said. "In the end we did 15 chains and they all came back playing the same exact symphony."


Provided by Rensselaer Polytechnic Institute (news : web)

Water channels in the body help cells remain in balance

microscopical water channels are also present in the cells of the body, where they ensure that water can be transported through the protective surface of the cell. Scientists at the University of Gothenburg, Sweden, have discovered that one type of the body's water channels can be modified such that it becomes more stable , which may be significant in the treatment of several diseases.

"It's important to understand how the water channels, which are known as 'aquaporins', in the body work, since they control many of the processes in our cells and tissues. They also determine what is to be transported into and out of the cell, and they are thus highly significant in the development of new treatments for various diseases, such as , cerebral oedema, and cancer", says Kristina Hedfalk of the Department of Chemistry at the University of Gothenburg.

Aquaporins are vital

There are 13 different types of aquaporins in the . One of these, AQP2, is found in the where it is responsible for a large-volume recirculation of water from the primary urine every day. Without this, we would urinate nearly 10 litres every day. Another variant, AQP4, is found in the brain where it contributes to regulation of the in the sensitive . This regulation is particularly important in those who are affected by cerebral oedema, which is a life-threatening condition that can follow a blow to the head or a stroke.

The research group, which consists of Fredrik Öberg, Jennie Sjöhamn, Gerhard Fischer, Andreas Moberg, Anders Pedersen, Richard Neutze and Kristina Hedfalk, describes their studies of one of the most recently discovered aquaporins in an article in the scientific journal The Journal of Biological Chemistry. This aquaporin, AQP10, is preferentially found in the intestine, and is particularly interesting since it transports both water and sugar alcohols.

Carbohydrates stabilise the water channel

"AQP10 differs from other aquaporins by having a large carbohydrate structure of branched sugar molecules, somewhat similar to a tree, attached on its outer surface. This makes it significantly more stable. This may be because aquaporins in the intestine need to be particularly stable. What we have shown is that AQP10 retains its transport ability, even if the carbohydrate structure is removed."

More information: The article 'Glycosylation Increases the Thermostability of Human Aquaporin 10 Protein' has been published in the September edition of The Journal of Biological Chemistry.

Provided by University of Gothenburg (news : web)