Many DNA nanostructures have been constructed by scientists for many different kinds of applications, such as drug delivery, medical diagnosis, and DNA-based computers. But in order to be successful in designing these nanostructures, we must first find out what exactly the 3D structure of DNA looks like!
But how can we look at the structure DNA helix? It's so small! Well, scientists have built powerful microscopes to try and visualize DNA. Atomic force microscopy (AFM) is a powerful technique but does not visualize in 3D very well. Another powerful tool that has been built is called the electron cryomicroscopy (cryoEM).
CryoEM can be used to look at the structure of a 7 nm self-assembled DNA tetrahedron, which is an incredible achievenment for scientists. Never before has such a small biological molecule been looked at with such high resolution!
Source: Nano Letters
Lookin' at DNA Nanostructures
My head is in the clouds...
... and what do I see? Bacteria! Pollen! Fungi! What's going on? A team of atmospheric chemists at University of California at San Diego have performed the first-ever direct detections of biological particles inside ice clouds. Taking samples of water droplets and ice crystal residues using a mass spectrometer while flying at high speeds through clouds in the skies of Wyoming, these researchers have revealed that the growth ice crystals were initiated almost entirely of dust or biological material, such as bacteria, fungal spores, and plant material.
Though it has long been known that microorganisms become airborne and travel great distances, this is the first study that analyzes their influence on cloud formation. Researchers have found that the ice crystal residues were half made up of mineral dust and a third were made up of inorganic ions mixed with nitrogen, phosphorus, and carbon - the signature elements of biological matter.
If we can understand how these particles cause cloud formation, we can then determine the impact they have on the climate. For example, some scientists believe that the dust transported from Asia could be impacting the rainfall in North America!
Source: NSF Press Release 09-100
Harnessing the Power of Viruses
Researchers at MIT have genetically engineered viruses to build the positively and negatively charged ends of a lithium ion battery. With the same energy capacity and power performance as state-of-the-art rechargeable batteries, they could be used to power plug-in hybrid cars and a range of personal electronics.
For the cathode, these genetically engineered viruses are built to coat themselves with iron phosphate, then self-assemble onto carbon nanotbues to create a network of highly conductive material. These viruses are a common bacteriophage, which infect bacteria but art harmless to humans.
Part of a recent wave of clean-energy technologies, these battery prototypes are lightweight, flexible, and pending commercial production.
Source: Eurekaalert
Armor of the Future -- Fish Scales?
Imagine living in a world with fearsome predators - large fearsome predators with sharp teeth, claws, and spiked tails! To survive, the Polypterus senagelus fish evolved special armor scales to protect itself during territorial fighting and feeding. Today, these fish can be found at the bottom of freshwater, muddy shallows and estuaries in Africa. The scales protect the quarrelsome fish from the bites of its fellow fish, as well as predators, and are the new hot topic in designing the armor of the future. U. S. researchers at the Massachusetts Institute of Technology have been studying the light, multilayered design of the Polypterus senegalus and have finally figured out how it works!
The scales are layered on top of each other so that the pressure of a crunching enemy bite is deflected. And when cracks do occur, they don't travel far! The clever design of the scales forces cracks to run in a circle instead of spreading throughout. This allows the puncture wound to be localized and kept to a minimum. Scientists and researchers hope to incorporate this clever design into lightweight and effective human armor systems.
Source: Fish scales may point to armor of the future
Into the Jaws of a Sandworm
Nereis virens, commonly known as sandworms, have a set of fang-like jaws with remarkable mechanical properties. These worms may be small, but they have a strong jaw for grasping, piercing, and tearing prey. The jaw material is high in protein with little mineralization, but despite this, the hardness and stiffness properties in the jaw tip are comparable to human dentin -- which is pretty strong!
The material in the jaw tips of sandworms is even better than synthetic polymers. Though scientists have long studied the mechanical and structural properties of these jaws, the organic composition has previously been overlooked. Scientists are now interested in finding the organic composition and protein structures of the cutting edge of the Nereis jaw. They have found that zinc plays an important role in the mechanical properties of Nereis jaws, by binding to bundles of protein fibers rich in histidine (an important amino acid), and that removing the zinc decreases the hardness by over 65%.
By learning about these sandworm jaws, scientists hope to use this knowledge to design stronger and better materials.
Sources: Journal of Experimental Biology American Chemical Society
Beetle Fog-Catchers
How does a desert beetle living in the Namib Desert in southwest Africa survive in one of the hottest environments in the world? The only water there is available in the form of a morning fog, which travels rapidly across the desert only a few times each month. Zoologists at Oxford University have discovered regions of hydrophilic (water-loving) ridges and hydrophobic (water-avoiding) furrows on the back of the Stenocara beeetle. This pattern of hydrophilic and hydrophobic regions allows the fog to condense into droplets that run down into the beetle's mouth!
But how is this useful? In Chile's Atacama desert, fog nets are being used to harvest moisture. Today, scientists are mimicking the stenocara beetle to create man-made surfaces that can be used to make artificial fog nets and more effective de-humidifiers and distillation equipment.
Source: New Scientist American Chemical Society
Image Source: Squarecirclez
Building Gold Crystals... with DNA?
Researchers at Northwestern University have recently been able to create 3D structures from particles of gold by using DNA. How exactly? The technique involves getting incredibly small particles to self-assemble to a predetermined design. DNA is made up of four basic building blocks - adenine, guanine, cytosine, and thymine (A, G, C, and T), and one strand of DNA can bind with a complementary strand. By using different DNA strands and modifying these strands with gold particles, new nano nuggets of gold of different shapes and sizes can be created.
This process could be used with other materials, with wide applications in therapeutics, diagnostics, optics, and electronics. Scientists are a step closer to the dream of breaking everything down into simple particles and reassembling them into "designer" structures.
Source: DNA does the work: Building new gold crystals
Pitter Patter of Little Feet . . .
Going where? Up the wall! The uncanny ability of geckos to climb shear walls has fascinated scientists for years. Researchers at the University of California - Berkeley, have developed an adhesive that mimics the easy attach and easy release of the reptile's padded feet. This new material is made up of millions of tiny plastic fibers that establish grip, and a mere square two centimeters on a side can support close to a pound! When the tape presses into a surface and slides downwards, it sticks. When the tape is lifted, it releases!
The trick behind a gecko's speedy vertical escape has been exposed! The new material could prove useful for a range of products, from climbing equipment to medical devices.
Source: The Pitter Patter of Little Feet . . . Climbing Straight Up a Wall
Oh My Aching Knees!
Understanding of the human body at the cellular and molecular level can help develop new and improved treatments for diseases such as rheumatoid arthritis. At the University of Leeds, scientists have discovered a new mechenism involving a naturally-occurring protein, thioredoxin, that controls ion channels. Ion channels are proteins on the surface of the cell that act as doorways in and out of the cell. These doorways can let electrically charged atoms (ions) across the cell membrane to carry out different functions, such as blood glucose regulating, heart beat timing, and pain transmission.
Thioredoxin has been found to activate these doorways by donating electrons to it, in a process that Professor Beech compares to "an electronic on-switch". People with inflammatory diseases have high production levels of this thioredoxin protein to protect the body from the stressful and damaging chemical reactions that occur with inflammation. By studying and mimicking this protein, scientists may be able to develop safer and more effective therapeutics.
Source: ‘Electronic switch’ opens doors in rheumatoid joints
Image Source: Wikipedia
Gecko Tape
Scientists at Rensselaer Polytechnic Institute in New York have developed some synthetic gecko tape by creating arrays of carbon nanotubes on flexible polymer tape. Based on the tiny structures found on the foot of a gecko lizard, these pieces of tape can support shear stress four times higher than the gecko foot and even sticks to Teflon! Another nifty property is that this tape can be easily pulled off perpendicular to the surface, but not parallel to it. The bond is about 10 pounds per square centimeters, which is quite a lot for something so small!
Source: Carbon nanotube-based synthetic gecko tapes
Preventing Earthquakes With... Bacteria?
If you live near the sea, your home is probably built over sandy soil. When earthquakes strike, deep and sandy soils can turn into liquid, causing lots of problems for the buildings sitting on top of them. The picture shows a building after the 1989 Loma Prieta earthquake in San Francisco.
It is possible to inject chemicals into the ground to harden the sandy soil, but this often has toxic effects on the soil and water. Researchers have discovered a new way to turn these sandy soils into rocks... using bacteria! As an added advantage, this common bacteria has no harmful effects on the environment. THought this method is currently still limited to laboratories, researchers are working hard to expand this technique.
Source:Bacteria to protect against quakes
Colorful Fossils
Professor Andrew Parker, a scientist at the Natural History Museum, has discovered a way to discover the iridescent colors in animals from fossils of extinct animals. Tiny structures on the surface of the animal fossil cause sunlight to be split (like a prism) into the colors of a rainbow. Colors that result from these tiny structures are known as iridescent colors, like the colors that you see on a CD. These colors are very different from the chemically generated colors found in paints, skin, hair, or animal fur.
The tiny structures act as a diffraction grating (which is a reflecting surface covered in small parallel grooves), and exists in a lot of things naturally. You can find them in the antennae of seed srhimp, in the wing of a butterfly, and also in 515 million-year-old Burgess Shale fossils (shown right).
In the past, any color given to the skin, feathers, or fur of extinct animals have mostly guesswork, but now with this new discovery, we can pinpoint more accurately the color of extinct animals. But the next question that Parker wants to answer is: "Why were the animals at that time so colorful? When did the first eye exist on Earth and what happened when it did?"
Source:Colouring in the Fossil Past
On The Cutting Edge
Researchers at the National Institute of Standards and Technology (NIST) and the University of Colorado at Boulder have designed a carbon nanotube knife that could theoretically work like a tight-wire cheese slicer. The conventional diamond or glass knives that biologists use to cut frozen cell samples often force samples to bend and crack. Because carbon nanotubes are extremely strong and slender in diameter, they make ideal materials for thinly cutting precise slivers of cells.
Why do we need to slice cells? Electron tomography can create 3D images of cells and tissues for scientists to stuy, but the sample needs to be less than 300 nanometers thick. The nanoknife is a carbon nanotude welded to two electrochemically sharpened tungsten needles. The research team has found that the welds were the weakest points in the nanoknife, and are now looking for new and improved welding techniques.
Source:On The Cutting Edge: Carbon Nanotube Cutlery
