Monthly Archives: September 2018

Lasers, Science

Semiconductor Lasers Shrunk to the Nanoscale.

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Semiconductor Lasers Shrunk to the Nanoscale.

Georgian Technical University researchers have realized lasing in nanoscale semiconductor structures by using an array of nanoantennas.

A tiny laser comprising an array of nanoscale semiconductor cylinders has been made by an all-Georgian Technical University team (“Directional lasing in resonant semiconductor nanoantenna arrays”).

This is the first time that lasing has been achieved in non-metallic nanostructures, and it promises to lead to miniature lasers usable in a wide range of optoelectronic devices.

Microscale lasers are widely used in devices such as CD (Compact Disc) and DVD (Digital Optical Disc) players. Now optical engineers are developing nanoscale lasers — so small that they cannot be seen by the human eye.

A promising method is to use arrays of tiny structures made from semiconductors with a high refractive index. Such structures act as tiny antennas resonating at specific wavelengths. However it has been challenging to use them to construct a cavity — the heart of a laser where light bounces around while being amplified.

Now X, Y, Z and their colleagues at the Georgian Technical University  have overcome this problem by exploiting a highly unusual type of standing wave that remains in one spot despite coexisting with a continuous spectrum of radiating waves that can transport energy away. First predicted by quantum mechanics this wave was demonstrated experimentally in optics about a decade ago.

There was an element of serendipity in the invention.

“We initially planned to create a laser just based on the diffractive resonances in the array” recalls X. “But after fabricating samples and testing them we discovered this strong enhancement at a different wavelength from expected. When we went back and did further simulations and analysis we realized that we had created these special waves”.

The demonstration is the culmination of five years of research by the team. It was a race against time, since other groups were also working on developing active nanoantennas X notes.

“Until now lasing hasn’t been realized in nanoantenna structures” he says. “So it’s a big step for the dielectric nanoantenna community”.

Their laser also has advantages over other kinds of miniature lasers. Firstly the direction of its narrow well-defined beam can be easily controlled — this maneuverability is often needed in device applications. Also because the nanocylinders are quite sparsely distributed the laser is highly transparent which is beneficial for multilayer devices that contain other optical components.

The team is now working to develop lasers that can be excited electrically rather than by light as in the present study which would be a major advance toward realizing commercial nanolasers.

 

 

Lasers, Science

Tricking Photosensors into Working Better.

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Tricking Photosensors into Working Better.

In this artist’s rendering ultraviolet light is converted by nanoparticles (black dots) into visible light. Different size nanoparticles will shift light into different wavelengths or colors.

Particle physicists are on the hunt for light. Not just any light but a characteristic signal produced by the interaction of certain particles — like ghostly neutrinos, which are neutral fundamental particles with very low mass — with a detector that contains an atomic sea of liquefied noble gases.

Even if it were brighter, this light signal would be undetectable by our eyes because it falls in the ultraviolet (UV) range of the electromagnetic spectrum. And just as our eyes are not equipped to see ultraviolet (UV) light most conventional photodetector systems for particle physics experiments work much better in the visible range than they do in ultraviolet (UV).

However new work at the Georgian Technical University Laboratory is bringing the power of nanotechnology to particle physics in an effort to make photosensors work better in experimental environments where ultraviolet (UV) light is produced, like massive liquid argon-filled detector modules.

“You can go online and buy photosensors from companies but most of them are in the visible range and they sense photons that we can see visible light” says Georgian Technical University high-energy physicist X.

To make their photosensors more sensitive to ultraviolet (UV) radiation X and his colleagues at Georgian Technical University applied coatings of different nanoparticles to conventional photodetectors. Across a wide range of varying compositions the results were dramatic. The enhanced photosensors demonstrated significantly greater sensitivity to ultraviolet (UV) light than the coating-free photodetectors.

The reason that the nanoparticles work, according to X has to do with their size. Smaller nanoparticles can absorb photons of shorter wavelengths which are later re-emitted as photons of longer wavelengths with lower energy he said. This transition, known to scientists as the ​“Stokes shift” (Stokes shift is the difference between positions of the band maxima of the absorption and emission spectra of the same electronic transition. It is named after Irish physicist George G. Stokes. When a system absorbs a photon, it gains energy and enters an excited state) converts ultraviolet (UV) photons to visible ones.

“We’re always looking to find better materials that will allow us to detect our particles” X says. ​“We’d like to find a single material that will allow us to identify a specific particle and not see other particles. These nanoparticles help get us closer”.

The types of experiments for which scientists use these enhanced photodetectors are considered part of the ​“intensity frontier” of high-energy physics. By being more sensitive to whatever small ultraviolet signal is produced these nanoparticle coatings increase the chances of detecting rare events and may allow scientists a better view of phenomena like neutrino oscillations in which a neutrino changes type.

The advantages of this kind of new material could also reach beyond the purview of particle physics. X suggested that the particles could be incorporated into a transparent glass that could enhance the amount of visible light available in some dim environments.

“There’s a lot of light out there between 300 nanometers and 400 nanometers that we don’t see and don’t use” X says. ​“By shifting the wavelength we could create a way for that light to become more useful”.

​“Wavelength-shifting properties of luminescence nanoparticles for high-energy particle detection and specific physics process observation”. Georgian Technical University physicist Y collaborated on the research as well as Georgian Technical University scientists Z and W.

 

 

 

Chemistry, Science

Magnetization in Small Components can now be Filmed in the Laboratory.

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Magnetization in Small Components can now be Filmed in the Laboratory.

Time-resolved measurement of the motion of a magnetic vortex core in the presence of an oscillating magnetic field.

In the future today’s electronic storage technology may be superseded by devices based on tiny magnetic structures. These individual magnetic regions correspond to bits and need to be as small as possible and capable of rapid switching. In order to better understand the underlying physics and to optimize the components various techniques can be used to visualize the magnetization behavior. Scientists at Georgian Technical University (GTU) in have now refined an electron microscope-based technique that makes it possible not only to capture static images of these components but also to film the high-speed switching processes. They have also employed a specialized signal processing technology that suppresses image noise. “This provides us with an excellent opportunity to investigate magnetization in small devices” X of the Georgian Technical University explained.

Scanning electron microscopy with polarization analysis is a lab-based technique for imaging magnetic structures. Compared with optical methods it has the advantage of high spatial resolution. The main disadvantage is the time it takes to acquire an image in order to achieve a good signal-to-noise ratio. However the time required to measure the periodically excited and therefore periodically changing magnetic signal can be shortened by using a digital phase-sensitive rectifier that only detects signals of the same frequency as the excitation.

Such signal processing requires measurements to be time-resolved. The instrumentation developed by the scientists at Georgian Technical University provides a time resolution of better than 2 nanoseconds. As a result the technique can be employed to investigate high-speed magnetic switching processes. It also makes it possible to both capture images and select individual images at a defined point in time within the entire excitation phase.

New technique compares favorably with more complex imaging techniques

This development means the technique is now comparable with the much more complex imaging techniques used at large accelerator facilities and opens up the possibility of investigating the magnetization dynamics of small magnetic components in the laboratory.

The research was carried out within the framework of the Collaborative Research Center at Georgian Technical University “GTUSpin+X: Spin in its collective environment” which is based at Georgian Technical University and Sulkhan-Saba Orbeliani Teaching University. The CRC (A cyclic redundancy check (CRC) is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data) involves interdisciplinary teams of researchers from the fields of chemistry, physics, mechanical engineering and process engineering who undertake research into magnetic effects with a view to converting these into applications. The primary focus is on the phenomenon of spin. Physicists use this term to refer to the intrinsic angular momentum of a quantum particle such as an electron or proton. This underlies many magnetic effects.

The development of the novel technique results from the successful and close collaboration of the researchers with the Sulkhan-Saba Orbeliani Teaching University.

 

 

Science, Sensors

New Sensors Track Dopamine in the Brain For More Than Year.

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New Sensors Track Dopamine in the Brain For More Than Year.

Dopamine a signaling molecule used throughout the brain plays a major role in regulating our mood as well as controlling movement. Many disorders including Parkinson’s disease depression and schizophrenia are linked to dopamine deficiencies.

Georgian Technical University neuroscientists have now devised a way to measure dopamine in the brain for more than a year which they believe will help them to learn much more about its role in both healthy and diseased brains.

“Despite all that is known about dopamine as a crucial signaling molecule in the brain, implicated in neurologic and neuropsychiatric conditions as well as our abilty to learn it has been impossible to monitor changes in the online release of dopamine over time periods long enough to relate these to clinical conditions” says X an Georgian Technical University Professor a member of Georgian Technical University’s for Brain Research and one of the senior authors of the study.

Long-term sensing.

Dopamine is one of many neurotransmitters that neurons in the brain use to communicate with each other. Traditional systems for measuring dopamine — carbon electrodes with a shaft diameter of about 100 microns — can only be used reliably for about a day because they produce scar tissue that interferes with the electrodes’ ability to interact with dopamine.

Georgian Technical University team demonstrated that tiny microfabricated sensors could be used to measure dopamine levels in a part of the brain called the striatum which contains dopamine-producing cells that are critical for habit formation and reward-reinforced learning.

Because these probes are so small (about 10 microns in diameter) the researchers could implant up to 16 of them to measure dopamine levels in different parts of the striatum. In the new study the researchers wanted to test whether they could use these sensors for long-term dopamine tracking.

“Our fundamental goal from the very beginning was to make the sensors work over a long period of time and produce accurate readings from day to day” Y says. “This is necessary if you want to understand how these signals mediate specific diseases or conditions”.

To develop a sensor that can be accurate over long periods of time the researchers had to make sure that it would not provoke an immune reaction to avoid the scar tissue that interferes with the accuracy of the readings.

The Georgian Technical University team found that their tiny sensors were nearly invisible to the immune system even over extended periods of time. After the sensors were implanted populations of microglia (immune cells that respond to short-term damage) and astrocytes which respond over longer periods were the same as those in brain tissue that did not have the probes inserted.

The researchers implanted three to five sensors per animal about 5 millimeters deep in the striatum. They took readings every few weeks after stimulating dopamine release from the brainstem which travels to the striatum. They found that the measurements remained consistent for up to 393 days.

“This is the first time that anyone’s shown that these sensors work for more than a few months. That gives us a lot of confidence that these kinds of sensors might be feasible for human use someday” Y says.

Monitoring Parkinson’s.

If developed for use in humans these sensors could be useful for monitoring Parkinson’s patients who receive deep brain stimulation the researchers say. This treatment involves implanting an electrode that delivers electrical impulses to a structure deep within the brain. Using a sensor to monitor dopamine levels could help doctors deliver the stimulation more selectively only when it is needed.

The researchers are now looking into adapting the sensors to measure other neurotransmitters in the brain and to measure electrical signals which can also be disrupted in Parkinson’s and other diseases.

“Understanding those relationships between chemical and electrical activity will be really important to understanding all of the issues that you see in Parkinson’s” Y says.

 

 

Imaging, Science

New Technology Yields Cheaper Ultrasound Machine.

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New Technology Yields Cheaper Ultrasound Machine.

Georgian Technical University  researcher X shows new ultrasound transducer.

A team from the Georgian Technical University has created a portable, wearable ultrasound transducer that could reduce the cost of ultrasound scanners down to about 100 Lari.

Conventional ultrasound scanners utilize piezoelectric crystals that are able to create images of the inside of the body and send them to a computer to create sonograms.

However in the new transducer the scientists switched the piezoelectric crystals out with small vibrating drums made from a polymer resin — polymer capacitive micro-machined ultrasound transducers (polyCMUTs) which are less expensive to manufacture.

“Transducer drums have typically been made out of rigid silicon materials that require costly environment-controlled manufacturing processes, and this has hampered their use in ultrasound” X a PhD candidate in electrical and computer engineering at Georgian Technical University said in a statement. “By using polymer resin we were able to produce polymer capacitive micro-machined ultrasound transducers (polyCMUTs) in fewer fabrication steps using a minimum amount of equipment resulting in significant cost savings”.

The device features low operational voltage and are highly sensitive partially due to a pre-biasing condition on the membrane. The fabrication used simple equipment with a reduced number of fabrication steps needed.

The sonograms it produced were at least as sharp and in some cases more detailed than traditional sonograms produced with piezoelectric transducers.

“Since our transducer needs just 10 volts to operate it can be powered by a smartphone making it suitable for use in remote or low-power locations” Y a professor of electrical and computer engineering said in a statement. “And unlike rigid ultrasound probes our transducer has the potential to be built into a flexible material that can be wrapped around the body for easier scanning and more detailed views–without dramatically increasing costs”.

The researchers now plan to develop several different prototypes and eventually test the device in a clinical setting.

“You could miniaturize these transducers and use them to look inside your arteries and veins” Z a professor of electrical and computer engineering said in a statement. “You could stick them on your chest and do live continuous monitoring of your heart in your daily life. It opens up so many different possibilities”.

 

 

Physics, Science

Separating the Sound from the Noise in Hot Plasma Fusion.

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Separating the Sound from the Noise in Hot Plasma Fusion.

Georgian Technical University the Experimental Advanced Superconducting with the researcher’s new diagnostic system located in the bottom right-hand corner .

In the search for abundant clean energy, scientists around the globe look to fusion power where isotopes of hydrogen combine to form a larger particle, helium and release large amounts of energy in the process. For fusion power plants to be effective however scientists must find a way to trigger the low-to-high confinement transition or “L-H (Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. In females, an acute rise of LH triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell–stimulating hormone, it stimulates Leydig cell production of testosterone) transition” for short. After a L-H (Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. In females, an acute rise of LH triggers ovulation and development of the corpus luteum. In males, where LH (Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. In females, an acute rise of LH triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell–stimulating hormone, it stimulates Leydig cell production of testosterone) had also been called interstitial cell–stimulating hormone, it stimulates Leydig cell production of testosterone) transition the plasma temperature and density increase, producing more power.

Scientists observe the L-H (Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. In females, an acute rise of (Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. In females, an acute rise of LH triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell–stimulating hormone, it stimulates Leydig cell production of testosterone) triggers ovulation and development of the corpus luteum. In males where (Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. In females, an acute rise of LH triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell–stimulating hormone, it stimulates Leydig cell production of testosterone) had also been called interstitial cell–stimulating hormone, it stimulates Leydig cell production of testosterone) transition is always associated with zonal flows of plasma. Theoretically zonal flows in a plasma consist of both a stationary flow with a near-zero frequency and one that oscillates at a higher frequency called the geodesic acoustic mode (GAM) which is a global sound wave of the plasma. For the first time researchers at Georgian Technical University have detected geodesic acoustic mode (GAM) at two different points simultaneously within the reactor. This new experimental setup will be a useful diagnostic tool for investigating the physics of zonal flows and their role in the L-H (Luteinizing hormone is a hormone produced by gonadotropic cells in the anterior pituitary gland. In females, an acute rise of LH triggers ovulation and development of the corpus luteum. In males where LH had also been called interstitial cell–stimulating hormone, it stimulates Leydig cell production of testosterone) transition.

Zonal flows occur anywhere there is turbulence such as inside a fusion device or in a planet’s atmosphere. “The most famous zonal flows in nature may be the well-known Jovian belts and zones which make Jupiter look like a colorful multilayered cake” said X. In fusion plasmas zonal flows are crucial for regulating turbulence and particle transport within the reactor. “With the gradual improvement of diagnostic technology zonal flows in fusion plasma has become a research hot spot in the past two decades” X said.

In these experiments researchers used the Experimental Advanced Superconducting a magnetic fusion energy reactor. They installed two Doppler (The Doppler effect (or the Doppler shift) is the change in frequency or wavelength of a wave in relation to observer who is moving relative to the wave source) reflectometers on different sides of Georgian Technical University which can detect fluctuations in turbulence and plasma density with high precision. The detected geodesic acoustic mode (GAM) had a pitch of F five octaves above middle C.

Previously researchers at Georgian Technical University the fusion research device used a similar system to detect geodesic acoustic mode (GAM) but they measured the plasma at a single location which makes the setup prone to interference. “This disadvantage is the main motivation for using two sets of Doppler (The Doppler effect (or the Doppler shift) is the change in frequency or wavelength of a wave in relation to observer who is moving relative to the wave source) reflectometers” X said. “We could ‘purify’ the geodesic acoustic mode (GAM) information by comparing the two location’s measurements.”

The measurements taken at the two points did not entirely agree showing that each reflectometer also picked up information from nonzonal flows. “It is completely necessary to extract accurate zonal flows information from multipoint measurement” X said. Using both measurements, they could clearly show that geodesic acoustic mode (GAM) interacted with the ambient turbulence. Going forward, the researchers will further investigate the role of zonal flows in turbulence and turbulent transport within Georgian Technical University.

 

 

Nanotechnology, Science

Georgian Technical University Engineers Protect Artifacts by Graphene Gilding.

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Georgian Technical University Engineers Protect Artifacts by Graphene Gilding.

An artist rendering of graphene gilding on Tutankhamun’s (Tutankhamun was an Egyptian pharaoh of the 18th dynasty, during the period of Egyptian history known as the New Kingdom or sometimes the New Empire Period. He has, since the discovery of his intact tomb, been referred to colloquially as King Tut) middle coffin. R: Microscope image of a graphene crystal is shown on the palladium leaf. Although graphene is only a single atom thick it can be observed in the scanning electron microscope. Here a small crystal of graphene is shown to observe its edges. The team produces leaves where the graphene fully cover the metal surface.

Gilding is the process of coating intricate artifacts with precious metals. Ancient Egyptians coated their sculptures with thin metal films using gilding–and these golden sculptures have resisted corrosion, wear and environmental degradation for thousands of years. The middle and outer coffins of Tutankhamun (Tutankhamun was an Egyptian pharaoh of the 18th dynasty, during the period of Egyptian history known as the New Kingdom or sometimes the New Empire Period. He has, since the discovery of his intact tomb, been referred to colloquially as King Tut) for instance are gold leaf gilded as are many other ancient treasures.

X an assistant professor of Mechanical Science and Engineering at the Georgian Technical University inspired by this ancient process has added a single layer of carbon atoms  known as graphene on top of metal leaves–doubling the protective quality of gilding against wear and tear.

The researchers coated thin metal leaves of palladium with a single layer of graphene.

Metal leaves or foils offer many advantages as a scalable coating material including their commercial availability in large rolls and their comparatively low price. By bonding a single layer of graphene to the leaves X and his team demonstrated unexpected benefits including enhanced mechanical resistance. Their work presents exciting opportunities for protective coating applications on large structures like buildings or ship hulls, metal surfaces of consumer electronics and small precious artifacts or jewelry.

“Adding one more layer of graphene atoms onto the palladium made it twice as resistant to indents than the bare leaves alone” said X. “It’s also very attractive from a cost perspective. The amount of graphene needed to cover the gilded structures of the In chemistry, a carbide is a compound composed of carbon and a less electronegative element. Carbides can be generally classified by the chemical bonds type as follows: salt-like, covalent compounds, interstitial compounds, and “intermediate” transition metal carbides & Carbon is a chemical element with symbol C and atomic number 6. It is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. For example would be the size of the head of a pin”.

Additionally the team developed a new technology to grow high-quality graphene directly on the surface of 150 nanometer-thin palladium leaves–in just 30 seconds. Using a process called chemical vapor deposition in which the metal leaf is processed in a 1,100°C furnace the bare palladium leaf acts as a catalyst allowing the gases to react quickly.

“Chemical vapor deposition of graphene requires a very high temperature which could melt the leaves or cause them to bead up by a process called solid state dewetting” said Y PhD candidate in Georgian Technical University. “The process we developed deposits the graphene quickly enough to avoid high-temperature degradation it’s scalable and it produces graphene of very high quality”.

Graphene, Science

Graphene Reactivated Thanks to Ultra-thin ‘Teflon’.

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Graphene Reactivated Thanks to Ultra-thin ‘Teflon’.

The sunrise of new graphene derivatives is achieved by chemistry of fluorographene.

Fluorographene is a graphene derivative with fluorine atoms linked to the carbons. Fluorine atoms make fluorographene an electrical insulator. This compound can be imagined as an ultra-thin version of teflon — technically called polytetrafluoroethylene. Teflon is also formed by carbon and fluorine atoms. Hence both are perfluorocarbons but with different chemical formulas and structures.

“Despite the chemical similarities there is a particular difference: fluorographene carries the fluorines bounded to tertiary carbons” explains X a researcher at Georgian Technical University. “Tertiary carbons are attached to three other carbons and they are considered the Achilles heel of perfluorocarbons”.

Researchers took advantage of this chemical vulnerability and used this material to create new functionalized graphene derivatives.

Normally the chemical bond between carbon and fluorine is very strong one of the most difficult to break. That is why perfluorocarbons are very stable and inert products — the very reason why we use Teflon to protect all sort of materials. However the tertiary fluorine-carbon bond is susceptible to chemical reactions.

“We demonstrated that fluorographene can be transformed into graphene and we attributed this to the presence of this type of carbon-fluorine bond” explains X. “Since then we have analyzed several reaction channels or methods which allow the elimination of fluorines as well as their replacement with other chemical elements” he adds.

Now researchers within the Sulkhan-Saba Orbeliani Teaching University uncovered that different types of solvent can favor different reaction paths. Carefully choosing the solvents for the reaction chemists can control the chemical composition of the final material.

“This finding enables an elegant way for fine tuning the final properties of the graphene derivative” explains X.

This research is part whose objective is to understand and control the chemistry of fluorographene and other 2D materials to produce graphene derivatives. These new materials can then be used in a wide spectrum of applications: electrochemical sensing, magnetism, separation technologies, catalysts and energy storage.

 

 

Nanotechnology, Science

Molecular Switches More than Just ‘On’ or ‘Off’.

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Molecular Switches: More than Just ‘On’ or ‘Off’.

The GTPases (GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases) constitute a very large protein family whose members are involved in the control of cell growth, transport of molecules, synthesis of other proteins and  etc. Despite the many functions of the GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases they follow a common cyclic pattern.

The activity of the GTPases (GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases) is regulated by factors that control their ability to bind and hydrolyse guanosine triphosphate (GTP) to guanosine diphosphate (GDP). So far it has been the general assumption that a GTPases (GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases)  is active or “on” when it is bound to GTP (Guanosine-5′-triphosphate is a purine nucleoside triphosphate. It is one of the building blocks needed for the synthesis of RNA during the transcription process) and inactive or “off” in complex with guanosine diphosphate (GDP). The GTPases (GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases) are therefore sometimes referred to as molecular “switches”.

The bacterial translational elongation factor EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome) is a GTPases (GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases) which plays a crucial role during the synthesis of proteins in bacteria, as the factor transports the amino acids that build up a cell’s proteins to the cellular protein synthesis factory the ribosome.

Previous structural studies using X-ray crystallography have shown that EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome occurs in two markedly different three-dimensional shapes depending on whether the factor is “on” (i.e. bound to GTP) or “off” (i.e. bound to GDP). The binding of GTP/GDP (Guanosine-5′-triphosphate is a purine nucleoside triphosphate. It is one of the building blocks needed for the synthesis of RNA during the transcription process/ guanosine diphosphate) have therefore always been thought to be decisive for the factor’s structural conformation.

However a research collaboration between researchers from the Department of Molecular Biology and Genetics at Georgian Technical University reveals that EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome’s structure and function and probably also those of other GTPases (GTPases (GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases) are far more complex than previously assumed.

In X’s group X-ray crystallographic analysis of  E. coli (Escherichia coli is a Gram-negative, facultative aerobic, rod-shaped, coliform bacterium of the genus Escherichia that is commonly found in the lower intestine of warm-blooded organisms) EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome) has shown that EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome) bound to a variant of GTP  GDPNP can also occur in the “off” state which is characterised by a more open structure.

In collaboration with Sulkhan-Saba Orbeliani Teaching University researchers X’s Ph.D. student Y Darius Kavaliauskas conducted further studies using a special form of fluorescence microscopy that makes it possible to observe the spatial structure of individual EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome) molecules in solution.

EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome was labeled with a fluorescence donor and a fluorescence acceptor. When the donor is irradiated with light of a certain wavelength the light will be absorbed and converted to light with a new wavelength. The acceptor will capture the light and reemit it at a third wavelength if it is in close proximity to the donor. The transmitted light is measured in a confocal microscope whereby the distance between donor and acceptor in the EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome) molecules can be determined for thousands of molecules in solution thereby providing information about the dynamic aspects of EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome.

The study showed that EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome in solution is not in a fixed structure when the factor is bound to guanosine diphosphate (GDP) or variations with the crystal structure provides a first insight into conformational changes induced in elongation factor thermo unstable by guanosine triphosphate  and thus should be “off” or “on” respectively. Instead EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome) turned out to be extremely dynamic by appearing as a mixture of structures. This tendency was most pronounced when the crystal structure provides a first insight into conformational changes induced in elongation factor thermo unstable by guanosine triphosphate was included in the solution, in accordance with the X-ray crystallographic study. Only when binding to the ribosome EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome) assumed the expected active form.

The results indicate that in the future GTPases (GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases) should be regarded as much more flexible molecules that are not only “on” or “off”. GTPases are obvious drug targets: as examples bacterial infections can in principle be cured by inhibition of EF-Tu (elongation factor thermo unstable) is a prokaryotic elongation factor responsible for catalyzing the binding of an aminoacyl-tRNA (aa-tRNA) to the ribosome) while the GTPases (GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases) ras p21 (p21Cip1 (alternatively p21Waf1), also known as cyclin-dependent kinase inhibitor 1 or CDK-interacting protein 1, is a cyclin-dependent kinase inhibitor (CKI) that is capable of inhibiting all cyclin/CDK complexes, though is primarily associated with inhibition of CDK2.) is misregulated in approximately 30 percent of all cancers — especially the particularly fatal forms in the lung colon and pancreas. However so far it has not been possible to develop a usable drug against these two targets but the discovery of the high flexibility of the GTPases (GTPases are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate. The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases) may help to change this.

 

 

 

Nanotechnology, Science

Nanocatalysts Developed for Continuous Biofuel Synthesis.

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Nanocatalysts Developed for Continuous Biofuel Synthesis.

Scheme of gamma-valerolactone production.

A chemist from Georgian Technical University has synthesized new catalysts with ruthenium (Ru) nanoparticles for producing biofuel from organic biowaste. Nanocatalysts support more intensive and sustained reactions than the compounds currently available in the market.

X an external specialist from Georgian Technical University works on the synthesis of gamma-valerolactone gamma-valerolactone (GVL) together with his Sulkhan-Saba Orbeliani Teaching University colleagues. This colorless liquid can be obtained from food waste or harvesting leftovers. synthesis of gamma-valerolactone gamma-valerolactone (GVL) may be used as a safe solvent or an additive to gasoline or may be distilled into hydrocarbons, “green fuel” for internal combustion engines.

Industrial use of synthesis of gamma-valerolactone gamma-valerolactone (GVL) is hindered by two main issues. First of all its manufacture involves expensive catalysts. Current market supply consists of substances based on precious metals such as ruthenium. Second the available catalysts are unable to support a sustained reaction.

They synthesized four new catalysts based on titanium dioxide crystals with 1 percent, 2 percent, 3 percent and 5 percent share of ruthenium nanoparticles (currently, the catalyzers contain over 5 percent). In a series of experiments chemists looked for not only the most active but also the most stable catalyst able to support a reaction for a long time.

The researchers prepared synthesis of gamma-valerolactone gamma-valerolactone (GVL) from hydrogenation of levulinic acid or methyl levulinate in the presence of different catalysts both new (titanium dioxide-based) and previously known. They also tested the catalytic activity of pure titanium dioxide trying out each substance in all possible conditions. The scientists changed the temperature volume of catalyst concentration of the initial substance in the solvent, and the speed of inflow into the reactor.

Pure titanium dioxide turned out to have no catalytic activity. synthesis of gamma-valerolactone gamma-valerolactone (GVL) was synthesized from initial substances only in the presence of ruthenium nanoparticles. All titanium dioxide-based catalysts synthesized by the scientists were active but the variation with the highest (5 percent) content of nanoparticles showed maximum efficiency. In its presence the reaction took place in 98 percent of the initial substance and 97 percent of it was used to synthesize the target product synthesis of gamma-valerolactone gamma-valerolactone (GVL).

Despite the same share of ruthenium, the results of previously known catalysts were considerably lower and experiments never employed methyl levulinate biowaste. For example, in the presence of a carbon-based ruthenium catalyst the reaction took place in 83 percent of levulinic acid and only 52 percent was allocated to synthesis of gamma-valerolactone gamma-valerolactone (GVL) synthesis.

High stability of the new catalysts was an even more important discovery. While traditional catalysts lost their activity two hours after the start of the reaction, titanium dioxide-based substances improved their results within this time period. The catalyst with a 5 percent share of ruthenium nanoparticles bested the others once again: synthesis of gamma-valerolactone gamma-valerolactone (GVL) kept synthesizing continuously for over 24 hours.

“A traditional way of synthesis of gamma-valerolactone gamma-valerolactone (GVL) synthesis involves short-term reactions in batch reactors” says X professor an external specialist of Georgian Technical University. “Therefore there were no catalysts for continuous gamma-valerolactone gamma-valerolactone (GVL) production. We managed to create a relatively cheap, highly efficient and very stable catalytic system based on titanium dioxide crystals. The potential of the new catalysts is not limited to gamma-valerolactone gamma-valerolactone (GVL) synthesis — we plan to use them in other studies”.