Site of the day: http://www.nytimes.com/
)
IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) is a solar sail which gathers sunlight as propulsion by means of a large sail. This spacecraft was launched May 20, 2010 together with the Akatsuki Venus Climate Orbiter aboard an H-IIA launch vehicle. This solar powered sail craft will employ both photon propulsion and thin film solar power generation during its interplanetary cruise.
The Planetary Society has assembled a page of resources for the press on JAXA's deep-space missions, including IKAROS. For the latest news on IKAROS, visit The Planetary Society Blog.
About IKAROS
Is IKAROS energy-saving?
IKAROS is a satellite to navigate space, deploying a large solar sail. Traditional satellites always needed fuels wherever their destinations were. The asteroid probe Hayabusa was driven by ion engines, which were energy-saving but still needed fuel called xenon gas.
Flyable without fuel, IKAROS is more than energy saving – it requires no energy. IKAROS can both approach to and recede from the Sun with elaborate use of its solar cells and the pressure of sunlight.
How does IKAROS fly?
Earth makes one revolution a year around the sun. The Earth's orbit around the sun is constant because the centrifugal force produced by the earth's orbital motion and the force of the sun's gravity are balanced. What would happen if Earth slowed down in its orbit? Earth would get closer to the Sun as the centrifugal force weakened. The same dynamics apply to IKAROS.
Imagine that IKAROS is orbiting the Sun at the same speed and in the same orbit as Earth. If IKAROS speeds up, with its large sail inclined toward the Sun, it will start moving away from the sun, heading outward toward the orbit of Mars. But, if it slows down, it will start falling downward to the Sun and approach to the orbit of Venus.
What is IKAROS' destination?
IKAROS is planned to approach Venus' orbit after a six-month flight. Then, it will travel, relying only on the solar force, until it reaches the far side of the Sun three years after launch.
What does IKAROS look like?
At launch, it has a fat, short cylindrical shape. A polyamide sail is wound tightly around it. The sail is designed to be deployed in space by centrifugal force produced by rotation of the satellite itself.
(http://www.planetary.org/explore/topics/ikaros/)
Read also:
IKAROS Begins Attitude Control by Louis Friedman
http://www.planetary.org/blog/article/00002567/
Lou Friedman in Japan: IKAROS sail deployment proceeding
http://www.planetary.org/blog/article/00002523/
Saturday, July 3, 2010
Sunday, June 20, 2010
Nano Design, Just Like in Nature
Site of the day: http://www.bloomberg.com/
ScienceDaily (June 15, 2010) — Researchers at Vienna University of Technology (TU Vienna) are using biological principles as the inspiration to develop a new bionic fuel cell.
Every living cell in our body can do it: covered with a thin membrane known as a cell membrane or nanomembrane, the cells can deliberately let specific substances in and out. Although it is thousands of times thinner than a human hair, this nanomembrane has an extremely complex structure and function. Three Nobel prizes have already been awarded for improving our understanding of these nanomembranes.
Microscopic ducts convey water, electrical charges and nutrients around and in doing so, create an equilibrium within the cell. However, we still do not know about many of the functions and structural details, as it is only the water and proton exchange that has been researched in depth. "These extremely fine cell membrane ducts, with the ability to selectively convey protons, function in exactly the same way as fuel cells created by humans," explains Dr Werner Brenner, "only this naturally occurring process is considerably more efficient."
Fuel cells: an alternative to oil
Today, fuel cells are seen as a serious alternative to oil, which until now has been the basis for electrical energy and mobility. However, the earth's oil reserves are rapidly running out, under economic pressure to drill ever deeper into the seabed. Oil combustion also generates CO2, soot and other residues. The only waste product from a fuel cell is water.
The EU project focuses on the design of the main component of every fuel cell -- i.e. the membrane -- with the intention of conveying protons more efficiently than in previous solutions. "The first results have been encouraging. It will not be easy, but it is possible. Nature has been producing these structures for billions of years and their effectiveness can be seen in every living organism. Our task is to transfer the structure of these natural nanoducts to an artificial nanomembrane, which is itself only a few hundred nanometres thick," explains Dr Jovan Matovic.
A wide range of scientific approaches are required for this project, ranging from solid state physics and nanotechnology through to chemistry. Therefore, international cooperation with six universities, research institutes and businesses is also of great importance. The EU project is being coordinated by the TU Vienna research team of Assist Prof Dr Werner Brenner, Dr Jovan Matovic and Dr Nadja Adamovic at the Institute of Sensor and Actuator Systems.
The University research team is confident: "The results of this project should have far-reaching significance for our society. If we succeed in creating the nanoducts exactly as planned, then completely different fields of application will open up, such as the accurately controlled delivery of medicine, water desalination or even new types of sensors," explains Dr Nadja Adamovic, "In this project, the boundaries between "artificial and "natural" are becoming even more blurred."
(http://www.sciencedaily.com/releases/2010/06/100615151705.htm)
ScienceDaily (June 15, 2010) — Researchers at Vienna University of Technology (TU Vienna) are using biological principles as the inspiration to develop a new bionic fuel cell.
Every living cell in our body can do it: covered with a thin membrane known as a cell membrane or nanomembrane, the cells can deliberately let specific substances in and out. Although it is thousands of times thinner than a human hair, this nanomembrane has an extremely complex structure and function. Three Nobel prizes have already been awarded for improving our understanding of these nanomembranes.
Microscopic ducts convey water, electrical charges and nutrients around and in doing so, create an equilibrium within the cell. However, we still do not know about many of the functions and structural details, as it is only the water and proton exchange that has been researched in depth. "These extremely fine cell membrane ducts, with the ability to selectively convey protons, function in exactly the same way as fuel cells created by humans," explains Dr Werner Brenner, "only this naturally occurring process is considerably more efficient."
Fuel cells: an alternative to oil
Today, fuel cells are seen as a serious alternative to oil, which until now has been the basis for electrical energy and mobility. However, the earth's oil reserves are rapidly running out, under economic pressure to drill ever deeper into the seabed. Oil combustion also generates CO2, soot and other residues. The only waste product from a fuel cell is water.
The EU project focuses on the design of the main component of every fuel cell -- i.e. the membrane -- with the intention of conveying protons more efficiently than in previous solutions. "The first results have been encouraging. It will not be easy, but it is possible. Nature has been producing these structures for billions of years and their effectiveness can be seen in every living organism. Our task is to transfer the structure of these natural nanoducts to an artificial nanomembrane, which is itself only a few hundred nanometres thick," explains Dr Jovan Matovic.
A wide range of scientific approaches are required for this project, ranging from solid state physics and nanotechnology through to chemistry. Therefore, international cooperation with six universities, research institutes and businesses is also of great importance. The EU project is being coordinated by the TU Vienna research team of Assist Prof Dr Werner Brenner, Dr Jovan Matovic and Dr Nadja Adamovic at the Institute of Sensor and Actuator Systems.
The University research team is confident: "The results of this project should have far-reaching significance for our society. If we succeed in creating the nanoducts exactly as planned, then completely different fields of application will open up, such as the accurately controlled delivery of medicine, water desalination or even new types of sensors," explains Dr Nadja Adamovic, "In this project, the boundaries between "artificial and "natural" are becoming even more blurred."
(http://www.sciencedaily.com/releases/2010/06/100615151705.htm)
Saturday, May 8, 2010
Faster, Cheaper DNA Sequencing Method Devised
Site of the day: http://fooledbyrandomness.com/
ScienceDaily (Dec. 22, 2009) — Boston University biomedical engineers have devised a method for making future genome sequencing faster and cheaper by dramatically reducing the amount of DNA required, thus eliminating the expensive, time-consuming and error-prone step of DNA amplification.
In a study published in the Dec. 20 online edition of Nature Nanotechnology, a team led by Boston University Biomedical Engineering Associate Professor Amit Meller details pioneering work in detecting DNA molecules as they pass through silicon nanopores. The technique uses electrical fields to feed long strands of DNA through four-nanometer-wide pores, much like threading a needle. The method uses sensitive electrical current measurements to detect single DNA molecules as they pass through the nanopores.
"The current study shows that we can detect a much smaller amount of DNA sample than previously reported," said Meller. "When people start to implement genome sequencing or genome profiling using nanopores, they could use our nanopore capture approach to greatly reduce the number of copies used in those measurements."
Currently, genome sequencing utilizes DNA amplification to make billions of molecular copies in order to produce a sample large enough to be analyzed. In addition to the time and cost DNA amplification entails, some of the molecules -- like photocopies of photocopies -- come out less than perfect. Meller and his colleagues at BU, New York University and Bar-Ilan University in Israel have harnessed electrical fields surrounding the mouths of the nanopores to attract long, negatively charged strands of DNA and slide them through the nanopore where the DNA sequence can be detected. Since the DNA is drawn to the nanopores from a distance, far fewer copies of the molecule are needed.
Before creating this new method, the team had to develop an understanding of electro-physics at the nanoscale, where the rules that govern the larger world don't necessarily apply. They made a counterintuitive discovery: the longer the DNA strand, the more quickly it found the pore opening.
"That's really surprising," Meller said. "You'd expect that if you have a longer 'spaghetti,' then finding the end would be much harder. At the same time this discovery means that the nanopore system is optimized for the detection of long DNA strands -- tens of thousands basepairs, or even more. This could dramatically speed future genomic sequencing by allowing analysis of a long DNA strand in one swipe, rather than having to assemble results from many short snippets.
"DNA amplification technologies limit DNA molecule length to under a thousand basepairs," Meller added. "Because our method avoids amplification, it not only reduces the cost, time and error rate of DNA replication techniques, but also enables the analysis of very long strands of DNA, much longer than current limitations."
With this knowledge in hand, Meller and his team set out to optimize the effect. They used salt gradients to alter the electrical field around the pores, which increased the rate at which DNA molecules were captured and shortened the lag time between molecules, thus reducing the quantity of DNA needed for accurate measurements. Rather than floating around until they happened upon a nanopore, DNA strands were funneled into the openings.
By boosting capture rates by a few orders of magnitude, and reducing the volume of the sample chamber the researchers reduced the number of DNA molecules required by a factor of 10,000 -- from about 1 billion sample molecules to 100,000.
The research was funded by the National Human Genome Research Institute of the Institutes of Health and by the National Science Foundation.
Journal Reference:
Electrostatic Focusing of Unlabelled DNA into Nanoscale Pores Using a Salt Gradient. Nature Nanotechnology, Online December 21, 2009 DOI: 10.1038/natureNNANO.2009.379
(http://www.sciencedaily.com/releases/2009/12/091220143923.htm)
ScienceDaily (Dec. 22, 2009) — Boston University biomedical engineers have devised a method for making future genome sequencing faster and cheaper by dramatically reducing the amount of DNA required, thus eliminating the expensive, time-consuming and error-prone step of DNA amplification.
In a study published in the Dec. 20 online edition of Nature Nanotechnology, a team led by Boston University Biomedical Engineering Associate Professor Amit Meller details pioneering work in detecting DNA molecules as they pass through silicon nanopores. The technique uses electrical fields to feed long strands of DNA through four-nanometer-wide pores, much like threading a needle. The method uses sensitive electrical current measurements to detect single DNA molecules as they pass through the nanopores.
"The current study shows that we can detect a much smaller amount of DNA sample than previously reported," said Meller. "When people start to implement genome sequencing or genome profiling using nanopores, they could use our nanopore capture approach to greatly reduce the number of copies used in those measurements."
Currently, genome sequencing utilizes DNA amplification to make billions of molecular copies in order to produce a sample large enough to be analyzed. In addition to the time and cost DNA amplification entails, some of the molecules -- like photocopies of photocopies -- come out less than perfect. Meller and his colleagues at BU, New York University and Bar-Ilan University in Israel have harnessed electrical fields surrounding the mouths of the nanopores to attract long, negatively charged strands of DNA and slide them through the nanopore where the DNA sequence can be detected. Since the DNA is drawn to the nanopores from a distance, far fewer copies of the molecule are needed.
Before creating this new method, the team had to develop an understanding of electro-physics at the nanoscale, where the rules that govern the larger world don't necessarily apply. They made a counterintuitive discovery: the longer the DNA strand, the more quickly it found the pore opening.
"That's really surprising," Meller said. "You'd expect that if you have a longer 'spaghetti,' then finding the end would be much harder. At the same time this discovery means that the nanopore system is optimized for the detection of long DNA strands -- tens of thousands basepairs, or even more. This could dramatically speed future genomic sequencing by allowing analysis of a long DNA strand in one swipe, rather than having to assemble results from many short snippets.
"DNA amplification technologies limit DNA molecule length to under a thousand basepairs," Meller added. "Because our method avoids amplification, it not only reduces the cost, time and error rate of DNA replication techniques, but also enables the analysis of very long strands of DNA, much longer than current limitations."
With this knowledge in hand, Meller and his team set out to optimize the effect. They used salt gradients to alter the electrical field around the pores, which increased the rate at which DNA molecules were captured and shortened the lag time between molecules, thus reducing the quantity of DNA needed for accurate measurements. Rather than floating around until they happened upon a nanopore, DNA strands were funneled into the openings.
By boosting capture rates by a few orders of magnitude, and reducing the volume of the sample chamber the researchers reduced the number of DNA molecules required by a factor of 10,000 -- from about 1 billion sample molecules to 100,000.
The research was funded by the National Human Genome Research Institute of the Institutes of Health and by the National Science Foundation.
Journal Reference:
Electrostatic Focusing of Unlabelled DNA into Nanoscale Pores Using a Salt Gradient. Nature Nanotechnology, Online December 21, 2009 DOI: 10.1038/natureNNANO.2009.379
(http://www.sciencedaily.com/releases/2009/12/091220143923.htm)
Friday, May 7, 2010
Remote Controlled Robot Performs Heart Surgery on British Man
Site of the day: http://www.wired.com/
May 5th, 2010 by Aaron Saenz
On April 28th, for the first time ever, a British doctor at Leicester’s Glenfield Hospital used a catheter robot to perform heart surgery on a patient while not in the operating room. The Remote Catheter Manipulation System (RCMS), developed by Catheter Robotics in the US, feeds a long thin wire (catheter) from a vein in the patient’s groin up to the heart where it uses electrodes to stimulate and then heal the heart by selectively burning tissue. This operation is used to correct an irregular heartbeat. Typically, the catheter is fed into the body by hand, but the robot allowed surgeon Andre Ng to perform the operation from outside the OR. That’s a great advantage to the doctor as this enabled him to avoid the 250+ X-rays exposures that are used during the operation to monitor inside the patient’s body. The RCMS also helped speed up the process considerably. This success is another sign of the rise in robotic surgery all across the world. We’ve got a great video about the operation for you after the break.
The use of robots in hospitals has been increasing for decades. The DaVinci robot is already used in the vast majority of prostate surgeries in the US. Catherine Mohr, one of the pioneers in the field, has long predicted that they will come to dominate surgeries in the future. All of the systems currently in use are almost completely remote controlled. Some controls are very complex, the DaVinci has a stereoscopic work station and two control arms, while others are fairly simple, Dr. Ng used two buttons to change the direction of the catheter, and thread it into and out the patient. Eventually, however, there will just be one button: “go”. Robots won’t simply turn surgery into a video game, they’ll actually perform the entire operation with a minimum of human guidance.
Many of the headlines surrounding Dr. Ng’s success has referred to this as the “first robotic heart surgery” or some variation thereof. That’s a negligent way of phrasing things. Heart surgeries have been performed using remote controlled robot arms for several years (often via the DaVinci system). In fact, it’s not even the first surgery using a robot catheter. As far as I can tell, what is unique about the Leicester operation was that it was the first using a robotic catheter with such simplified controls and that a surgeon performed this type of correction for arrhythmia while outside the OR.
Despite my frustration at these headlines, this operation still is an important first. Getting surgeons out of the OR not only saves them from risky radiation exposure, it heralds a time when any surgery can be performed by a surgeon located anywhere in the world. After all, Dr. Ng performed the operation via computer monitors and a remote control, he could have easily been in another country as another room (given the appropriate secured internet connection).
While the day of universal robotic surgery is still rather far off, I’m amazed by how relatively cheap and easy it is to use one of these catheter robots. While the price tag may seem steep ($540,000 or £350,000) it’s not outrageously expensive for hospital equipment. Furthermore, doctors already familiar with the catheter operation should be able to convert to the robotic system with a minimum of training because of its simple controls.
The advantages of robot surgery are increasing. These machines allow for surgeries to be performed with small incisions (sometimes only one) rather than opening the entire chest. They can prevent surgeons from receiving repeated exposure to radiation. Robots may also allow for long distance remote control, giving patients a wider range of surgeons to select from. In the end, these advantages are likely to bring more and more robotics into the OR, and robots may become the tool of choice for most surgeries. Eventually the sophistication of these systems will allows them to meet and then exceed the talents of human surgeons in all but the most creative of operations. Dr. Ng’s work saw a remarkable achievement with a procedure performed through a robot. Soon, however, we will see procedures performed by a robot. That, my friends, will be the start of amazing things.
(http://singularityhub.com/2010/05/05/remote-controlled-robot-performs-heart-surgery-on -british-man-video/)
Read also:
http://www.gizmag.com/heart-surgery-rc-robot/14947/
http://spectrum.ieee.org/biomedical/devices/heart-surgeons-adapting-to-robots
May 5th, 2010 by Aaron Saenz
On April 28th, for the first time ever, a British doctor at Leicester’s Glenfield Hospital used a catheter robot to perform heart surgery on a patient while not in the operating room. The Remote Catheter Manipulation System (RCMS), developed by Catheter Robotics in the US, feeds a long thin wire (catheter) from a vein in the patient’s groin up to the heart where it uses electrodes to stimulate and then heal the heart by selectively burning tissue. This operation is used to correct an irregular heartbeat. Typically, the catheter is fed into the body by hand, but the robot allowed surgeon Andre Ng to perform the operation from outside the OR. That’s a great advantage to the doctor as this enabled him to avoid the 250+ X-rays exposures that are used during the operation to monitor inside the patient’s body. The RCMS also helped speed up the process considerably. This success is another sign of the rise in robotic surgery all across the world. We’ve got a great video about the operation for you after the break.
The use of robots in hospitals has been increasing for decades. The DaVinci robot is already used in the vast majority of prostate surgeries in the US. Catherine Mohr, one of the pioneers in the field, has long predicted that they will come to dominate surgeries in the future. All of the systems currently in use are almost completely remote controlled. Some controls are very complex, the DaVinci has a stereoscopic work station and two control arms, while others are fairly simple, Dr. Ng used two buttons to change the direction of the catheter, and thread it into and out the patient. Eventually, however, there will just be one button: “go”. Robots won’t simply turn surgery into a video game, they’ll actually perform the entire operation with a minimum of human guidance.
Many of the headlines surrounding Dr. Ng’s success has referred to this as the “first robotic heart surgery” or some variation thereof. That’s a negligent way of phrasing things. Heart surgeries have been performed using remote controlled robot arms for several years (often via the DaVinci system). In fact, it’s not even the first surgery using a robot catheter. As far as I can tell, what is unique about the Leicester operation was that it was the first using a robotic catheter with such simplified controls and that a surgeon performed this type of correction for arrhythmia while outside the OR.
Despite my frustration at these headlines, this operation still is an important first. Getting surgeons out of the OR not only saves them from risky radiation exposure, it heralds a time when any surgery can be performed by a surgeon located anywhere in the world. After all, Dr. Ng performed the operation via computer monitors and a remote control, he could have easily been in another country as another room (given the appropriate secured internet connection).
While the day of universal robotic surgery is still rather far off, I’m amazed by how relatively cheap and easy it is to use one of these catheter robots. While the price tag may seem steep ($540,000 or £350,000) it’s not outrageously expensive for hospital equipment. Furthermore, doctors already familiar with the catheter operation should be able to convert to the robotic system with a minimum of training because of its simple controls.
The advantages of robot surgery are increasing. These machines allow for surgeries to be performed with small incisions (sometimes only one) rather than opening the entire chest. They can prevent surgeons from receiving repeated exposure to radiation. Robots may also allow for long distance remote control, giving patients a wider range of surgeons to select from. In the end, these advantages are likely to bring more and more robotics into the OR, and robots may become the tool of choice for most surgeries. Eventually the sophistication of these systems will allows them to meet and then exceed the talents of human surgeons in all but the most creative of operations. Dr. Ng’s work saw a remarkable achievement with a procedure performed through a robot. Soon, however, we will see procedures performed by a robot. That, my friends, will be the start of amazing things.
(http://singularityhub.com/2010/05/05/remote-controlled-robot-performs-heart-surgery-on -british-man-video/)
Read also:
http://www.gizmag.com/heart-surgery-rc-robot/14947/
http://spectrum.ieee.org/biomedical/devices/heart-surgeons-adapting-to-robots
Wednesday, April 14, 2010
Memristors
Site of the day: http://molecularstation.com/
H.P. Sees a Revolution in Memory Chip
PALO ALTO, Calif. — Hewlett-Packard scientists on Thursday are to report advances in the design of a new class of diminutive switches capable of replacing transistors as computer chips shrink closer to the atomic scale.
by John Markoff
H.P. Sees a Revolution in Memory Chip
PALO ALTO, Calif. — Hewlett-Packard scientists on Thursday are to report advances in the design of a new class of diminutive switches capable of replacing transistors as computer chips shrink closer to the atomic scale.
The devices, known as memristors, or memory resistors, were conceived in 1971 by Leon O. Chua, an electrical engineer at the University of California, Berkeley, but they were not put into effect until 2008 at the H.P. lab here.
They are simpler than today’s semiconducting transistors, can store information even in the absence of an electrical current and, according to a report in Nature, can be used for both data processing and storage applications.
The researchers previously reported in The Proceedings of the National Academy of Sciences that they had devised a new method for storing and retrieving information from a vast three-dimensional array of memristors. The scheme could potentially free designers to stack thousands of switches in a high-rise fashion, permitting a new class of ultradense computing devices even after two-dimensional scaling reaches fundamental limits.
Memristor-based systems also hold out the prospect of fashioning analog computing systems that function more like biological brains, Dr. Chua said.
“Our brains are made of memristors,” he said, referring to the function of biological synapses. “We have the right stuff now to build real brains.”
In an interview at the H.P. research lab, Stan Williams, a company physicist, said that in the two years since announcing working devices, his team had increased their switching speed to match today’s conventional silicon transistors. The researchers had tested them in the laboratory, he added, proving they could reliably make hundreds of thousands of reads and writes.
That is a significant hurdle to overcome, indicating that it is now possible to consider memristor-based chips as an alternative to today’s transistor-based flash computer memories, which are widely used in consumer devices like MP3 players, portable computers and digital cameras.
“Not only do we think that in three years we can be better than the competitors,” Dr. Williams said. “The memristor technology really has the capacity to continue scaling for a very long time, and that’s really a big deal.”
As the semiconductor industry has approached fundamental physical limits in shrinking the size of the devices that represent digital 1’s and 0’s as on and off states, it has touched off an international race to find alternatives.
New generations of semiconductor technology typically advance at three-year intervals, and today the industry can see no further than three and possibly four generations into the future.
The most advanced transistor technology today is based on minimum feature sizes of 30 to 40 nanometers — by contrast a biological virus is typically about 100 nanometers — and Dr. Williams said that H.P. now has working 3-nanometer memristors that can switch on and off in about a nanosecond, or a billionth of a second.
He said the company could have a competitor to flash memory in three years that would have a capacity of 20 gigabytes a square centimeter.
“We believe that that is at least a factor of two better storage than flash memory will be able to have in that time frame,” he said.
The H.P. technology is based on the ability to use an electrical current to move atoms within an ultrathin film of titanium dioxide. After the location of an atom has been shifted, even by as little as a nanometer, the result can be read as a change in the resistance of the material. That change persists even after the current is switched off, making it possible to build an extremely low-power device.
The new material offers an approach that is radically different from a promising type of storage called “phase-change memory” being pursued by I.B.M., Intel and other companies.
In a phase-change memory, heat is used to shift a glassy material from an amorphous to a crystalline state and back. The switching speed of these systems is slower and requires more power, the H.P. scientists say.
by John Markoff
(http://www.nytimes.com/2010/04/08/science/08chips.html)
http://spectrum.ieee.org/tag/memristor
Wednesday, April 7, 2010
Nanoscale 'Stealth' Probe Slides Into Cell Walls Seamlessly, Say Engineers
A 'stealth' probe sits firmly fused into a cell membrane. The membrane is represented by the small blue spheres, with the hydrophobic portion inside shown by squiggly fine blue lines. The silicon part of the probe is black and the chromium bands that bound the thin gold band are silver-gray. The gold band is obscured by the carbon atoms that are attached to it and that integrate with the hydrophobic part of the membrane. (Credit: Benjamin Almquist)
Site of the day: http://www.wired.com/
ScienceDaily (Apr. 2, 2010) — A nanometer-scale probe designed to slip into a cell wall and fuse with it could offer researchers a portal for extended eavesdropping on the inner electrical activity of individual cells.
Everything from signals generated as cells communicate with each other to "digestive rumblings" as cells react to medication could be monitored for up to a week, say Stanford engineers.
Current methods of probing a cell are so destructive they usually only allow a few hours of observation before the cell dies. The researchers are the first to implant an inorganic device into a cell wall without damaging it.
The key design feature of the probe is that it mimics natural gateways in the cell membrane, said Nick Melosh, an assistant professor of materials science and engineering in whose lab the research was done. With modification, the probe might serve as a conduit for inserting medication into a cell's heavily defended interior, he said. It might also provide an improved method of attaching neural prosthetics, such as artificial arms that are controlled by pectoral muscles, or deep brain implants used for treating depression.
The 600-nanometer-long, metal-coated silicon probe has integrated so smoothly into membranes in the laboratory, the researchers have christened it the "stealth" probe.
"The probes fuse into the membranes spontaneously and form good, strong junctions there," Melosh said. The attachment is so strong, he said, "We cannot pull them out. The membrane will just keep deforming rather than let go of the probes."
Melosh and Benjamin Almquist, a graduate student in materials science and engineering, are coauthors of a paper describing the research published March 30 in Proceedings of the National Academy of Sciences.
Up to now, poking a hole in a cell membrane has largely relied on brute force, Melosh said.
"We can basically rip holes in the cells using suction, we can use high voltage to puncture holes in their membranes, both of which are fairly destructive," he said. "Many of the cells don't survive." That limits the duration of any observations, particularly electrical measurements of cell function.
The key to the probe's easy insertion -- and the membrane's desire to retain it -- is that Melosh and Almquist based its design on a type of protein naturally found in cell walls that acts as a gatekeeper, controlling which molecules are allowed in or out.
A cell membrane is essentially a walled fortress. Within the wall itself is a water-repellant, or hydrophobic, zone. Since almost all molecules in a living being are water soluble, the hydrophobic region acts as a barrier to keep the molecules from slipping through the cell wall. The only way in or out is via the specialized proteins that form bridges across the membrane.
Those "transmembrane" protein gateways match the architecture of the membrane, with a hydrophobic center section bounded by two water soluble, or hydrophilic, layers.
"What we have done is make an inorganic version of one of those membrane proteins, which sits in the membrane without disrupting it," Melosh said. "Now we can envision using it for doing our own gate keeping."
To build their probe, Melosh and Almquist appropriated nanofabrication methods from the semiconductor industry to make tiny silicon posts, the tips of which they coated with three thin layers of metal -- a layer of gold between two of chromium -- to match the sandwich structure of the membrane. They then coated the gold band with carbon molecules to render it hydrophobic; the chromium bands are naturally hydrophilic.
"Getting that hydrophobic band just a few nanometers in thickness was an incredible technical challenge," Melosh said. Applying such a thin layer to the tip of a probe only 200 nanometers in diameter was impossible using existing methods, so he and Almquist devised a new technique using metal deposition to create the thin band that was needed.
That carefully applied metal coating on the stealth probe could give researchers electrical access to the inside of a cell, where they might monitor the electrical impulses generated by various cellular activities, Melosh said. That, combined with the probe's stability in the membrane, could be a huge asset to studies of certain electrically excitable cells such as neurons, which send signals throughout the brain, spinal cord and other nerves.
A device called a "patch clamp" can be used to monitor those sorts of electrical signals among cells now, Melosh said, but in its current form, it is comparatively crude.
"You come in with it, touch it to the cell surface, apply suction and tear a hole in the cell to give you access," he said. "However, it is a fairly slow procedure that has to be done one cell at a time, and it kills the cell within an hour or so."
"If the stealth probe will give us a long-term patch clamp, we'll really be able to get the ability to watch these networks over long periods of time, perhaps up to a week," he said.
"Ideally, what you'd like to be able to do is have an access port through the cell membrane that you can put things in or take things out, measure electrical currents … basically full control," said Melosh. "That's really what we've shown -- this is a platform upon which you can start building those kinds of devices."
The next step is to demonstrate the functionality of the probe in living cells. Almquist and Melosh are now working with human red blood cells and cervical cancer cells, as well as ovary cells from a species of hamster.
Journal Reference:
Almquist et al. Fusion of biomimetic stealth probes into lipid bilayer cores. Proceedings of the National Academy of Sciences, 2010; 107 (13): 5815
DOI: 10.1073/pnas.0909250107
(http://www.sciencedaily.com/releases/2010/04/100401143123.htm)
Sunday, April 4, 2010
Microbes Reprogrammed to Ooze Oil for Renewable Biofuel
Site of the day: http://futurepundit.com/
ScienceDaily (Mar. 29, 2010) — Using genetic sleight of hand, researcher Xinyao Liu and professor Roy Curtiss at Arizona State University's Biodesign Institute have coaxed photosynthetic microbes to secrete oil -- bypassing energy and cost barriers that have hampered green biofuel production. Their results appear in this week's advanced online issue of the Proceedings of the National Academy of Sciences or PNAS.
The challenges of developing a renewable biofuel source that is competitive with the current scalability and low-cost of petroleum have been daunting. "The real costs involved in any biofuel production are harvesting the fuel precursors and turning them into fuel," said Roy Curtiss, director of the Biodesign Institute's Center for Infectious Diseases and Vaccinology and professor in the School of Life Sciences. "By releasing their precious cargo outside the cell, we have optimized bacterial metabolic engineering to develop a truly green route to biofuel production."
Photosynthetic microbes called cyanobacteria offer attractive advantages over the use of plants like corn or switchgrass, producing many times the energy yield with energy input from the sun and without the necessity of taking arable cropland out of production.
Lead author Xinyao Liu and Curtiss, applied their expertise in the development of bacterial-based vaccines to genetically optimize cyanobacteria for biofuel production. Last year, they were able to modify these microbes, priming them to self-destruct and release their lipid contents. In the group's lastest effort however, the energy-rich fatty acids were extracted without killing the cells in the process.
"In China, we have a saying," Liu says. "We don't kill the hen to get the eggs." Rather than destroying the cyanobacteria, the group has ingeniously reengineered their genetics, producing mutant strains that continuously secrete fatty acids through their cell walls. The cyanobacteria essentially act like tiny biofuel production facilities.
Liu realized that if cyanobacteria could be cajoled into overproducing fatty acids, their accumulation within the cells would eventually cause these fatty acids to leak out through the cell membrane, through the process of diffusion. To accomplish this, Liu introduced a specific enzyme, known as thioesterase, into cyanobacteria.
The enzyme is able to uncouple fatty acids from complex carrier proteins, freeing them within the cell where they accumulate, until the cell secretes them. "I use genes that can steal fatty acids from the lipid synthesis pathway," Liu explains noting that thioesterase acts to efficiently clip the bonds associating the fatty acids with more complex molecules. This use of modified thioesterases to cause secretion of fatty acids was first described for Escherichia coli by John Cronan of the University of Illinois more than a decade ago.
A second series of modifications enhances the secretion process, by genetically deleting or modifying two key layers of the cellular envelope -- known as the S and peptidoglycan layers -- allowing fatty acids to more easily escape outside the cell, where their low water solubility causes them to precipitate out of solution, forming a whitish residue on the surface. Study results show a 3-fold increase in fatty acid yield, after genetic modification of the two membrane layers.
To improve the fatty acid production even further, the group added genes to cause overproduction of fatty acid precursors and removed some cellular pathways that were non-essential to the survival of cyanobacteria. Such modifications ensure that the microbe's resources are devoted to basic survival and lipid production.
Liu emphasizes that the current research has moved along at a lightening clip, with only about 6 months passing from the initial work, through production of the first strains -- a fact he attributes to the formidable expertise in the area of microbial genetic manipulation, assembled at the Biodesign Institute. "I don't think any group would have the capacity to do this as fast," he said.
Professor Roy Curtiss agrees, noting that "the seminal advance has been to combine a number of genetic modifications and enzyme activities previously described in other bacteria and in plants in the engineered cyanobacteria strains along with the introduction of newly discovered modifications to increase production and secretion of fatty acids. The results to date are encouraging and we are confident of making further improvements to achieve enhanced productivity in strains currently under construction and development. In addition, optimizing growth conditions associated with scale-up will also improve productivity."
The team, which includes researchers Daniel Brune and Wim Vermaas, is also optimistic that significantly higher fatty acid yields will be obtainable, as research continues.
The research opens the door to practical use of this promising source of clean energy.
(http://www.sciencedaily.com/releases/2010/03/100329152525.htm)
ScienceDaily (Mar. 29, 2010) — Using genetic sleight of hand, researcher Xinyao Liu and professor Roy Curtiss at Arizona State University's Biodesign Institute have coaxed photosynthetic microbes to secrete oil -- bypassing energy and cost barriers that have hampered green biofuel production. Their results appear in this week's advanced online issue of the Proceedings of the National Academy of Sciences or PNAS.
The challenges of developing a renewable biofuel source that is competitive with the current scalability and low-cost of petroleum have been daunting. "The real costs involved in any biofuel production are harvesting the fuel precursors and turning them into fuel," said Roy Curtiss, director of the Biodesign Institute's Center for Infectious Diseases and Vaccinology and professor in the School of Life Sciences. "By releasing their precious cargo outside the cell, we have optimized bacterial metabolic engineering to develop a truly green route to biofuel production."
Photosynthetic microbes called cyanobacteria offer attractive advantages over the use of plants like corn or switchgrass, producing many times the energy yield with energy input from the sun and without the necessity of taking arable cropland out of production.
Lead author Xinyao Liu and Curtiss, applied their expertise in the development of bacterial-based vaccines to genetically optimize cyanobacteria for biofuel production. Last year, they were able to modify these microbes, priming them to self-destruct and release their lipid contents. In the group's lastest effort however, the energy-rich fatty acids were extracted without killing the cells in the process.
"In China, we have a saying," Liu says. "We don't kill the hen to get the eggs." Rather than destroying the cyanobacteria, the group has ingeniously reengineered their genetics, producing mutant strains that continuously secrete fatty acids through their cell walls. The cyanobacteria essentially act like tiny biofuel production facilities.
Liu realized that if cyanobacteria could be cajoled into overproducing fatty acids, their accumulation within the cells would eventually cause these fatty acids to leak out through the cell membrane, through the process of diffusion. To accomplish this, Liu introduced a specific enzyme, known as thioesterase, into cyanobacteria.
The enzyme is able to uncouple fatty acids from complex carrier proteins, freeing them within the cell where they accumulate, until the cell secretes them. "I use genes that can steal fatty acids from the lipid synthesis pathway," Liu explains noting that thioesterase acts to efficiently clip the bonds associating the fatty acids with more complex molecules. This use of modified thioesterases to cause secretion of fatty acids was first described for Escherichia coli by John Cronan of the University of Illinois more than a decade ago.
A second series of modifications enhances the secretion process, by genetically deleting or modifying two key layers of the cellular envelope -- known as the S and peptidoglycan layers -- allowing fatty acids to more easily escape outside the cell, where their low water solubility causes them to precipitate out of solution, forming a whitish residue on the surface. Study results show a 3-fold increase in fatty acid yield, after genetic modification of the two membrane layers.
To improve the fatty acid production even further, the group added genes to cause overproduction of fatty acid precursors and removed some cellular pathways that were non-essential to the survival of cyanobacteria. Such modifications ensure that the microbe's resources are devoted to basic survival and lipid production.
Liu emphasizes that the current research has moved along at a lightening clip, with only about 6 months passing from the initial work, through production of the first strains -- a fact he attributes to the formidable expertise in the area of microbial genetic manipulation, assembled at the Biodesign Institute. "I don't think any group would have the capacity to do this as fast," he said.
Professor Roy Curtiss agrees, noting that "the seminal advance has been to combine a number of genetic modifications and enzyme activities previously described in other bacteria and in plants in the engineered cyanobacteria strains along with the introduction of newly discovered modifications to increase production and secretion of fatty acids. The results to date are encouraging and we are confident of making further improvements to achieve enhanced productivity in strains currently under construction and development. In addition, optimizing growth conditions associated with scale-up will also improve productivity."
The team, which includes researchers Daniel Brune and Wim Vermaas, is also optimistic that significantly higher fatty acid yields will be obtainable, as research continues.
The research opens the door to practical use of this promising source of clean energy.
(http://www.sciencedaily.com/releases/2010/03/100329152525.htm)
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