A chemical spider that spins a polymer thread using a simple catalyst could drive a nanomotor, according to researchers at Pennsylvania State University, US. Ayusman Sen and colleagues say that these nanomotors have potential applications in the deposition of polymers within the channels of microdevices for instance.
- Alternative Agriculture – The debate over genetically engineered crops rages on, but other technologies offer new hope for sustainable farming.
- The Genes of Parkinsons Disease – Parkinson’s cases with genetic origins are shedding light on the cellular mechanisms of the disease, bringing researchers closer to a cause — and perhaps a cure
- New nanomaterials unlock new electronic and energy technologies – A new way of splitting layered materials to give atom thin "nanosheets" has been discovered. This has led to a range of novel two-dimensional nanomaterials with chemical and electronic properties that have the potential to enable new electronic and energy storage technologies.
- Scripps Research scientists develop powerful new methodology for stabilizing proteins – A team of scientists at The Scripps Research Institute has discovered a new way to stabilize proteins — the workhorse biological macromolecules found in all organisms. Proteins serve as the functional basis of many types of biologic drugs used to treat everything from arthritis, anemia, and diabetes to cancer.
- ‘Tall order’ sunlight-to-hydrogen system works, neutron analysis confirms – Researchers at the Department of Energy's Oak Ridge National Laboratory have developed a biohybrid photoconversion system — based on the interaction of photosynthetic plant proteins with synthetic polymers — that can convert visible light into hydrogen fuel.
Robert Slinn refluxes the chemistry news and extracts a goodly yield for Reactive Reports in his regular column: Slinn Pickings.
What’s happening in the world of chemistry, Robert Slinn filters the latest news for Reactive Reports.
- Voiding defects: New technique makes LED lighting more efficient – Light-emitting diodes (LEDs) are an increasingly popular technology for use in energy-efficient lighting. Researchers from North Carolina State University have now developed a new technique that reduces defects in the gallium nitride (GaN) films used to create LEDs, making them more efficient.
- Scrambling to Close the Isotope Gap – Two reactors, one in the Netherlands and the other in Canada, produce 60% of the world's radioactive molybdenum-99, which decays into technetium-99, a radioisotope used in more than 30 million procedures a year worldwide for imaging everything from blood flow through the heart to bone cancer—and both reactors are decades beyond their intended life expectancy.
- Common weed petty spurge as a skin cancer treatment – Sap from the common garden weed petty spurge appears to treat non-melanoma skin cancers, experts are reporting in the British Journal of Dermatology.
- Shining new light on air pollutants using entangled porous frameworks – Certain types of pollution monitoring may soon become considerably easier. A group of researchers centered at Kyoto University has shown in a recent Nature Communications paper that a newly-formulated entangled framework of porous crystals (porous coordination polymers, or PCPs) can not only capture a variety of common air pollutants, but that the mixtures then glow in specific, easily-detected colours.
- Breakthrough in low temperature growth of carbon nanotubes – Researchers at the University of Surrey have discovered a way to grow high-quality carbon nanotubes over large areas at substrate temperatures below 350ºC which would make this technology compatible with CMOS (a technology for constructing integrated circuits) and suitable for large area substrates.
- Columbia University researchers use nanoscale transistors to study single-molecule interactions – An interdisciplinary team from Columbia University has figured out a way to study single-molecule interactions on very short time scales using nanoscale transistors. They show how, for the first time, transistors can be used to detect the binding of the two halves of the DNA double helix with the DNA tethered to the transistor sensor.
- Anti-estrogen medication reduces risk of dying from lung cancer – A new study has found that tamoxifen, an anti-estrogen breast cancer medication, may reduce an individual's risk of death from lung cancer.
- No longer pining for organic molecules to make particles in the air – The fresh scent of pine has helped atmospheric scientists find missing sources of organic molecules in the air — which, it could well turn out, aren't missing after all.
- Weizmann Institute Scientists used Accelerated Evolution to Develop Enzymes that Provide Protection Against Nerve Gas – A multidisciplinary team of scientists at the Weizmann Institute of Science have succeeded in developing an enzyme that breaks down organophosphorus nerve agents efficiently before damage to nerves and muscles is caused. Recent experiments performed in a U.S. military laboratory (USAMRICD) have shown that injecting a relatively small amount of this enzyme into animals provides protection against certain types of nerve agents, for which current treatments show limited efficacy.
One of the important components of the extracellular matrix is collagen, which comprises the major structural protein component of higher organisms. However, it remains a major challenge to emulate the unique structural and biological properties of native collagenous biomaterials in synthetic analogues. Consequently, numerous opportunities exist for synthetic collagens in biomedical applications as extracellular matrix analogues, if the appropriate materials could be constructed that retain and expand upon the desirable properties of native collagen fibrils.
The exploration of chemical and molecular genetic techniques to design and synthesize collagen-mimetic polypeptides and fibers that are competent for self-assembly into structurally defined protein fibrils is an intriguing avenue for exploration. In this context, Shyam Rele and colleagues have been leading the efforts in the de novo design of nanostructured biological materials through self-assembly of peptides and proteins.
Rele, together with Elliot Chaikof and Vince Conticello in the Laboratory of Bio/Molecular Engineering and Advanced Vascular Technologies at Emory University School of Medicine have been successful in designing and synthesizing the first ever Synthetic Collagen Peptide system which is a 36 amino acid long unit which self-assembles into a fibrous structure with well-defined periodicity reminiscent of native collagen observed in the human body.
Specifically, the synthesized peptide protomer which is made up of three heterotrimeric peptide repeat units contains a hydrophobic proline-hydroxyproline-glycine core flanked on both the sides by distinct sets of peptide repeats containing either negatively (Glutamic acid) or positively (Arginine) charged amino acid residues. When positioned appropriately, these charged amino acids bias and adopt the triple helical self-assembly which undergoes fibrillogenesis at physiological temperatures producing D-periodic microfibers driven through electrostatic interactions.
Transmission electron microscopy on annealed samples revealed that fiber growth proceeded within several hours by initial formation of smooth fibrils that were hundreds of nanometers in length and tens of nanometers in diameter. These fibrils displayed tapered tips similar to the tactoidal ends of native collagen fibers from which continued fiber growth is thought to occur. The D-periodicity of the synthetic collagen-mimetic microfibers was approximately 18 nm. Significantly, the collagen mimic shows a high propensity for self-association following a nucleation-growth mechanism even at lower concentrations (<1.0 mg/mL) and neutral pH.
This following discovery for making human collagen in the laboratory is pathbreaking in the field of nanotechnology and bio-inspired biomaterials. Several scientists for the past three decades have been trying to synthesize and emulate collagen's remarkable properties and have failed in their attempts to mimic the long, fibrous molecules found in nature.
The ability of Rele, Chaikof and Conticello to generate a synthetic collagen in a laboratory (in vitro) on a nanomolecular level for the first time, therefore represents an important milestone in nanotechnology and biomaterial development. Such self-assembling peptides may have broad applications in medicine, neurodegenerative diseases, protein folding catalyst design, bio-nanotechnology, tissue engineering and origins of life research. Furthermore, generation of such nanostructured molecules which mimic native structural proteins will lay the future ground work for unraveling complex phenomena including collagen fiber formation in protein conformational diseases and for the design of new materials with biological, chemical, and mechanical properties that exceed those of currently available synthetic polymers.
The propensity to generate such self-assembling, biologically compatible peptide scaffolds to arrange themselves into fibers, tubules, and a variety of geometrical layers, establishes an important substrates for cell growth, differentiation, and biological function, and will have an important impact in the treatment of cardiovascular, orthopedic, and neurological disease.
Adapted from a write-up supplied by Rele. Further details can be found in JACS, vol 129, 14780-14787.
A way to toughen up the latex particles used to make emulsion paints has been developed by UK chemists. The approach involves adding tiny slivers of clay armor to make the particles more hard wearing and fire resistant.
Until now, latex emulsion paints have been made by adding a soap-like surfactant molecule to allow the hydrophobic, or water-hating, polymer ingredients to mix with water. The surfactant stabilizes the paint mixture and allows decorators everywhere the chance to slap on a multitude of colors with a matt or satin finish to walls, ceilings, and other surfaces.
Now, chemist Stefan Bon and Patrick Colver of the University of Warwick have taken a different approach. They have found a simple way to individually coat the prospective paint’s polymer particles with disks of Laponite clay just a few billionths of a meter in diameter. These nanodisks, just 1 nanometer thick and 25 nanometers in diameter, create an armored layer on the individual polymer latex particles in the paint. Because the Laponite clay has an ambivalent chemical nature, it can bond both to the hydrophobic particles but also sit comfortably in the “hydro”, the water. So, not only does it provide particulate protection, it makes the surfactant additive redundant in emulsion paint.
The Lapointe clay disks can be applied using current industrial paint manufacturing equipment and treatment with ultrasound—sonication—say the researchers. Starting materials for the polymers are styrene, lauryl (meth)acrylate, butyl (meth)acrylate, octyl acrylate, and 2-ethyl hexyl acrylate.
The new clay armor is not only about improving home improvements. The team says the same technology can also be used to create highly sensitive materials for sensors. The researchers can take a closely packed sample of the armored polymers and heat it to burn away the polymer cores of the armored particles leaving just a network of nanoscopic interconnected hollow spheres. This gives a very large useful surface area in a very small space which is an ideal material to use in creating compact but highly sensitive sensors.
Bon, S., & Colver, P. (2007). Pickering Miniemulsion Polymerization Using Laponite Clay as a Stabilizer Langmuir, 23 (16), 8316-8322 DOI: 10.1021/la701150q
Temperature-controlled “triple-shaped plastics” that can change shape from one form to another, then another, have been developed by researchers in Germany and the US. Such materials might find use as switches and actuators in microelectromechanical systems (MEMS) and in medicine as intelligent stents for treating blocked blood vessels.
Scientists at the GKSS Research Centre of Biomaterial Development in Teltow, near Berlin, and the Massachusetts Institutes of Technology in Cambridge, USA, created these new materials by blending two distinct polymers composed of long chain-like molecules and adding bonds at varying points between them. These cross-links control the permanent shape of the new material at the molecular level. Like a rubber band, the polymer network can be deformed but then snaps back into its original permanent shape once you let go, often with painful effect. A rubber band is composed of a single-shape polymer.
In a dual-shape polymer, the hypothetical dual-shape rubber band can be deformed, and the polymer chains are stretched and twisted. But, if it is cooled below a critical temperature in this new shape, different cross-links form that lock it into this particular shape. When it returns to its original temperature, it does not snap back. Reactive Reports first reported on dual-shape polymers produced by the MIT lab headed by Robert Langer in Issue 25
In the novel triple-shape polymers, there is a second critical temperature below which a third shape can be “locked in”, because there are two different polymers cross-linked to each other that respond to two different temperatures by forming different types of cross-links at each temperature. This means each polymer chain in the mix can alter the overall shape of the material. The first change comes at one temperature and the second at another.
Shape-memory polymers have been around for a while and represent what researchers describe as “a promising class of materials”. All previous efforts have led to dual-shape materials, however, this is the first triple-shape polymer that can change from shape A, to shape B, and then to shape C. The new materials are made from MACL, which contains poly(epsilon-caprolactone) (PCL) segments and poly(cyclohexyl methacrylate) (PCHMA) segments.
This triple-shape behavior opens up the possibility of countless technological applications. The first of many might lie in medicine. “An intelligent stent could be introduced into a blood vessel in a small compact geometry,” explains the head of biomaterials at GKSS, Andreas Lendlein, who is working with Robert Langer’s team at MIT on the project. “It could then be inflated at the implantation site to a full expanded size medical device,” he says. “On demand a removal could be facilitated by shrinking the stent to an easy to handle size, using temperature control.”
Another application might lie in the realm of assembly technology. Here, anchor units for fixing a device could be deployed in the first shape-shift step and then locked into a precise position with a second production step. The shape-shifting process is only reversible with a change in temperature, which means it remains intact. “This is a new principle in materials,” explains Langer, “and it will be producing new opportunities. I imagine that if you had things you want to install, and then remove, the ability to change their shapes at will could be useful.”
Proc Natl Acad Sci, 2006, 103, 18043-18047; http://dx.doi.org/10.1073/pnas.0608586103