Magnetic actuation enables nanoscale thermal analysis

 Polymer nano-films and nano-composites are used in a wide variety of applications from food packaging to sports equipment to automotive and aerospace applications. Thermal analysis is routinely used to analyze materials for these applications, but the growing trend to use nanostructured materials has made bulk techniques insufficient.

In recent years an atomic force microscope-based technique called nanoscale thermal analysis (nanoTA) has been employed to reveal the temperature-dependent properties of materials at the sub-100 nm scale. Typically, nanothermal analysis works best for soft polymers. Researchers at the University of Illinois at Urbana-Champaign and Anasys Instruments, Inc. have now shown that they can perform nanoscale thermal analysis on stiff materials like epoxies and filled composites.

"This new technique lets us measure temperature and frequency-dependent properties of materials rapidly over a wide bandwidth," noted William King, the College of Engineering Bliss Professor in the Department of Mechanical Science and Engineering at Illinois, who led the research. The technique works by flowing a current around the U-shaped arms of a self-heating atomic force microscope (AFM) cantilever and interacting that current with a magnetic field. The magnetic field allows the tip-sample force to be modulated right near the tip of the AFM.

"We are able to achieve nanometer-scale force control that is independent from the heating temperature," according to Byeonghee Lee, first author of the paper.

"Conventional nanothermal analysis has struggled with highly filled, highly crosslinked materials and sub-100 nm thin films. This new technique has allowed us to reliably measure and map glass transitions and melting transions on classes of materials that were previously very challenging," said Craig Prater, chief technology officer at Anasys Instruments and co-author on the paper.

The research was performed in King's Nanoengineering Laboratory and at Anasys Instruments. King is also affiliated with the Department of Materials Science and Engineering, the Department of Electrical and Computer Engineering, the Beckman Institute for Advanced Science and Technology, the Micro and Nanotechnology Laboratory, and the Materials Research Laboratory, all at the University of Illinois. The research was sponsored by the Air Force Office of Scientific Research and the National Science Foundation.

Story Source:

The above story is reprinted from materials provided by University of Illinois College of Engineering.

Note: Materials may be edited for content and length. For further information, please contact the source cited above.

Journal Reference:

Byeonghee Lee, Craig B Prater, William P King. Lorentz force actuation of a heated atomic force microscope cantilever. Nanotechnology, 2012; 23 (5): 055709 DOI: 10.1088/0957-4484/23/5/055709

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

New technique enables study of 'challenging' proteins

The technique, an enhanced form of nuclear magnetic resonance (NMR) spectroscopy, could enable the structure of a protein to be identified within hours, rather than weeks or months, radically speeding up the process of drug discovery. The findings are published online in the Journal of the American Chemical Society.

Dr Mark Lorch from the University of Hull, who led the research, explains: "Membrane proteins are important targets for the pharmaceutical industry, but they're very difficult to create in large quantities. For some, NMR isn't feasible at all, but even when it is, only small amounts of data can be gained from each small sample, which makes the whole process of identifying the structure very time consuming and expensive.

"Using this technique, we were able to get significant structural data from a small sample of a protein in just 20 hours of NMR time. This is the first time the technique has been shown to work on the size of sample that can be realistically created from any biological protein."

The researchers, from the Universities of Hull, Bristol and Goethe University, used a method known as dynamic nuclear polarisation (DNP), which boosts the number of nuclei that can be measured through NMR and so increases the signal picked up from the protein.

Although DNP has been used before on large sample sizes of well-studied proteins, the researchers are the first to show its effectiveness in studying a more challenging protein, opening the door to the study of biological samples that are currently inaccessible to conventional NMR.

The study focused on the Sec translocon protein, which transports other proteins either across or into biological membranes. This process is triggered when a signal peptide called LamB binds with Sec translocon and the researchers wanted to identify structural information on how the two interact. This would have been impossible through traditional NMR, as the signal peptide makes up such a small part of the sample to be studied. However, using DNP to enhance the signal from the peptide, the researchers were able to get significant information in a very short period of time.

Provided by University of Hull

New technology enables molecular-level insight into carbon sequestration

 

Flaviu Turcu co-invented a novel NMR system for carbon sequestration research applications with EMSL staff, David Hoyt (Principal Investigator) and Jesse Sears, and PNNL colleagues, Jian Zhi Hu and Kevin Rosso. Turcu, pictured above, holds the high-pressure MAS rotor and stands behind the high-pressure rotor loading reaction chamber pieces of the system.

Carbon sequestration is a potential solution for reducing greenhouse gases that contribute to climate change, but its scientific challenges are complex. Analytical tools are needed that provide information about the mineral-fluid interactions of carbon dioxide (CO2) at the molecular level.

As part of Pacific Northwest National Laboratory (PNNL)'s Carbon Sequestration Initiative, a team of EMSL and PNNL researchers developed and patented such a tool—a unique high-pressure magic angle spinning (MAS) nuclear magnetic resonance (NMR) capability that operates in conditions characteristic of geologic carbon sequestration.

Described in the September 2011 issue of the Journal of Magnetic Resonance, this new technology consists of a reusable high-pressure MAS rotor, a high-pressure rotor loading/reaction chamber for in situ sealing and reopening of the high-pressure MAS rotor, and a MAS probe with a localized radiofrequency coil for background signal suppression.

This new capability can help determine reaction intermediates and final products that occur during mineral dissolution reactions relevant to the geologic disposal of CO2, as these researchers reported in the July 2011 issue of the International Journal of Greenhouse Gas Control.

Identifying reaction intermediates is not possible using only ex situ measurements and is critical to determining the mechanisms of mineral dissolution at high pressures. This new capability has the potential to further the exploration of solid-state chemistry at new levels of high pressure and temperature in many science areas.

More information: References: Hoyt DW, RVF Turcu, JA Sears, KM Rosso, SD Burton, AR Felmy, and JZ Hu. 2011. “High-pressure Magic Angle Spinning Nuclear Magnetic Resonance,” Journal of Magnetic Resonance, DOI:10.1016/j.jmr.2011.07.019

Hoyt DW, JA Sears, RVF Turcu, KM Rosso, and JZ Hu. 2011. U.S. Patent submission E-16894, “Devices and Process for High-Pressure Magic Angle Spinning Nuclear Magnetic Resonance,” filed July 28, 2011 (provisional patent submitted December 13, 2010).

Kwak JH, JZ Hu, RVF Turcu, KM Rosso, ES Ilton, C Wang, JA Sears, MH Engelhard, AR Felmy, and DW Hoyt. 2011. "The Role of H2O in the Carbonation of Forsterite in Supercritical CO2." International Journal of Greenhouse Gas Control 5:1081-1092.

Provided by Environmental Molecular Sciences Laboratory (news : web)

Unique gel capsule structure enables co-delivery of different types of drugs

Researchers at the Georgia Institute of Technology have designed a multiple-compartment gel capsule that could be used to simultaneously deliver drugs of different types. The researchers used a simple "one-pot" method to prepare the hydrogel capsules, which measure less than one micron.

The capsule's structure -- hollow except for polymer chains tethered to the interior of the shell -- provides spatially-segregated compartments that make it a good candidate for multi-drug encapsulation and release strategies. The microcapsule could be used to simultaneously deliver distinct drugs by filling the core of the capsule with hydrophilic drugs and trapping hydrophobic drugs within nanoparticles assembled from the polymer chains.

"We have demonstrated that we can make a fairly complex multi-component delivery vehicle using a relatively straightforward and scalable synthesis," said L. Andrew Lyon, a professor in the School of Chemistry and Biochemistry at Georgia Tech. "Additional research will need to be conducted to determine how they would best be loaded, delivered and triggered to release the drugs."

 

Lyon and Xiaobo Hu, a former visiting scholar at Georgia Tech, created the microcapsules. As a graduate student at the Research Institute of Materials Science at the South China University of Technology, Hu is co-advised by Lyon and Zhen Tong of the South China University of Technology. Funding for this research was provided to Hu by the China Scholarship Council.

The researchers began the two-step, one-pot synthesis procedure by forming core particles from a temperature-sensitive polymer called poly(N-isopropylacrylamide). To create a dissolvable core, they formed polymer chains from the particles without a cross-linking agent. This resulted in an aggregated collection of polymer chains with temperature-dependent stability.

"The polymer comprising the core particles is known for undergoing chain transfer reactions that add cross-linking points without the presence of a cross-linking agent, so we initiated the polymerization using a redox method with ammonium persulfate and N,N,N',N'-tetramethylethylenediamine. This ensured those side chain transfer reactions did not occur, which allowed us to create a truly dissolvable core," explained Lyon.

For the second step in the procedure, Lyon and Hu added a cross-linking agent to a polymer called poly(N-isopropylmethacrylamide) to create a shell around the aggregated polymer chains. The researchers conducted this step under conditions that would allow any core-associated polymer chains that interacted with the shell during synthesis to undergo chain transfer and become grafted to the interior of the shell.

Cooling the microcapsule exploited the temperature-sensitivities of the polymers. The shell swelled with water and expanded to its stable size, while the free-floating polymer chains in the center of the capsule diffused out of the core, leaving behind an empty space. Any chains that stuck to the shell during its synthesis remained. Because the chains control the interaction between the particles they store and their surroundings, the tethered chains can act as hydrophobic drug carriers.

Compared to delivering a single drug, co-delivery of multiple drugs has several potential advantages, including synergistic effects, suppressed drug resistance and the ability to tune the relative dosage of various drugs. The future optimization of these microcapsules may allow simultaneous delivery of distinct classes of drugs for the treatment of diseases like cancer, which is often treated using combination chemotherapy.

Provided by Georgia Institute of Technology (news : web)

Unique gel capsule structure enables co-delivery of different types of drugs

Researchers at the Georgia Institute of Technology have designed a multiple-compartment gel capsule that could be used to simultaneously deliver drugs of different types. The researchers used a simple "one-pot" method to prepare the hydrogel capsules, which measure less than one micron.

The capsule's structure -- hollow except for polymer chains tethered to the interior of the shell -- provides spatially-segregated compartments that make it a good candidate for multi-drug encapsulation and release strategies. The microcapsule could be used to simultaneously deliver distinct drugs by filling the core of the capsule with hydrophilic drugs and trapping hydrophobic drugs within nanoparticles assembled from the polymer chains.

"We have demonstrated that we can make a fairly complex multi-component delivery vehicle using a relatively straightforward and scalable synthesis," said L. Andrew Lyon, a professor in the School of Chemistry and Biochemistry at Georgia Tech. "Additional research will need to be conducted to determine how they would best be loaded, delivered and triggered to release the drugs."

Details of the microcapsule synthesis procedure were published online on July 5, 2011 in the journal Macromolecular Rapid Communications.

Lyon and Xiaobo Hu, a former visiting scholar at Georgia Tech, created the microcapsules. As a graduate student at the Research Institute of Materials Science at the South China University of Technology, Hu is co-advised by Lyon and Zhen Tong of the South China University of Technology. Funding for this research was provided to Hu by the China Scholarship Council.

The researchers began the two-step, one-pot synthesis procedure by forming core particles from a temperature-sensitive polymer called poly(N-isopropylacrylamide). To create a dissolvable core, they formed polymer chains from the particles without a cross-linking agent. This resulted in an aggregated collection of polymer chains with temperature-dependent stability.

"The polymer comprising the core particles is known for undergoing chain transfer reactions that add cross-linking points without the presence of a cross-linking agent, so we initiated the polymerization using a redox method with ammonium persulfate and N,N,N',N'-tetramethylethylenediamine. This ensured those side chain transfer reactions did not occur, which allowed us to create a truly dissolvable core," explained Lyon.

For the second step in the procedure, Lyon and Hu added a cross-linking agent to a polymer called poly(N-isopropylmethacrylamide) to create a shell around the aggregated polymer chains. The researchers conducted this step under conditions that would allow any core-associated polymer chains that interacted with the shell during synthesis to undergo chain transfer and become grafted to the interior of the shell.

Cooling the microcapsule exploited the temperature-sensitivities of the polymers. The shell swelled with water and expanded to its stable size, while the free-floating polymer chains in the center of the capsule diffused out of the core, leaving behind an empty space. Any chains that stuck to the shell during its synthesis remained. Because the chains control the interaction between the particles they store and their surroundings, the tethered chains can act as hydrophobic drug carriers.

Compared to delivering a single drug, co-delivery of multiple drugs has several potential advantages, including synergistic effects, suppressed drug resistance and the ability to tune the relative dosage of various drugs. The future optimization of these microcapsules may allow simultaneous delivery of distinct classes of drugs for the treatment of diseases like cancer, which is often treated using combination chemotherapy.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Georgia Institute of Technology Research News. The original article was written by Abby Robinson.

Journal Reference:

Xiaobo Hu, Zhen Tong, L. Andrew Lyon. One-Pot Synthesis of Microcapsules with Nanoscale Inclusions. Macromolecular Rapid Communications, 2011; DOI: 10.1002/marc.201100338

Tuned enzymes: Extra guest molecule in an enzyme's binding pocket enables methane oxidation

 Our fossil fuel reserves are limited. When they run out, we will not only be lacking in fuel, but chemical industry will lose its most important feedstock. In contrast, natural gas has barely been used as a raw material. If it were possible to efficiently convert methane, the main component of natural gas, into chemically useful materials like methanol, we would gain some time to make the transition to alternative sources of raw materials.

In the journal Angewandte Chemie, Manfred T. Reetz and a team at the Max Planck Institute for Carbon Research in Mülheim (Germany) have now introduced a new approach for the enzymatic production of methanol from methane. Their secret is the inclusion of an inert guest in the enzyme’s binding pocket in order to make it smaller so that it can effectively bind methane.

Methanol is a useful starting material for many chemical syntheses, and it can also be added to conventional fuels to drive fuel cells. Conventional processes for producing methanol from methane involve detours (synthesis gas), are markedly complex and energy intensive, and require high temperatures and pressures. Nature, on the other hand, has a much more elegant route: the enzyme methane monooxygenase does the job gently and efficiently. Unfortunately this is a very complex enzyme that cannot easily be produced and used in an artificial environment. The cytochrome P450 (CYP) family of enzymes could represent an alternative starting point. The main job of these enzymes is the oxidation of various substances produced by the body or introduced to it. In the reaction, carbon–hydrogen bonds are oxidized to make alcohol groups (–OH). The active component of these enzymes is a heme, an iron–porphyrin complex similar to that in our hemoglobin.

The problem is that the binding pocket of this enzyme is just too big to snugly bind and oxidize small molecules such as methane. Instead of trying to devise complex methods to create a suitable enzyme, Reetz and his co-workers came up with a clever trick: chemically “tuning” a CYP enzyme. The scientists added an additional guest into the binding pocket in order to make it smaller.

The natural substrates for CYP enzymes are fatty acids. As a guest molecule, the researchers chose a compound that resembles a fatty acid, a carbonic acid in which all of the hydrogen atoms in the hydrocarbon chain have been replaced with fluorine atoms. This type of molecule is as water-repellent as the original, but takes up more room. The fluorine atoms make it chemically inert so that it does not participate in any reactions. Like the molecule it is modeled on, this guest is able to bring the iron–heme complex of the enzyme into its catalytically active state (high-spin state). The significantly smaller binding pocket now allows methane to bind effectively so that it can be oxidized to methanol.

Says Reetz: “The road to success is still far for a technical implementation, yet, the concept opens up new perspectives for the development of further reactions, such as the oxidation of other chemical compounds.”

More information: Manfred T. Reetz, Tuning a P450 Enzyme for Methane Oxidation, Angewandte Chemie International Edition, http://dx.doi.org/ … ie.201006587