Histamine H1 receptor breakthrough heralds improved allergy treatments

 

New 3D picture of human membrane protein enables development of targeted anti-histamines without side-effects.

An international team of scientists using Diamond Light Source, the UK’s national synchrotron facility, has successfully solved the complex 3D structure of the human Histamine H1 receptor protein. Published in the journal Nature this week, their discovery opens the way for the development of ‘third generation’ anti-histamines, specific drugs effective against various allergies without causing adverse side-effects.

The team, comprising leading experts from the USA (The Scripps Research Institute in California), Japan (Kyoto University), and the UK (Imperial College London and Diamond), worked across three continents for 16 months on the project.

“It took a considerable team effort but we were finally able to elucidate the molecular structure of the Histamine H1 receptor protein and also see how it interacts with anti-histamines. This detailed structural information is a great starting point for exploring exactly how histamine triggers allergic reactions and how drugs act to prevent this reaction,” said Professor So Iwata, David Blow Chair of Biophysics at Imperial College London.

H1 receptor protein is found in the cell membranes of various human tissues including airways, vascular and intestinal muscles, and the brain. It binds to histamine, an important function of the immune system, but in susceptible individuals this can cause allergic reactions such as hay fever, food and pet allergies. Anti-histamine drugs work because they prevent histamine attaching to H1 receptors.

“First generation anti-histamines such as Doxepin are effective, but not very selective, and because of penetration across the blood-brain barrier, they can cause side effects including sedation, dry mouth and arrhythmia. By showing exactly how histamines bind to the H1 receptor at the molecular level, we can design and develop much more targeted treatments.” said Dr Simone Weyand, post-doctoral scientist at Imperial College London.

The research was technically challenging because membrane proteins are notoriously difficult to crystallise – a step that is vital in solving protein structures using a synchrotron. The proteins were grown in cells at Kyoto University in Japan, then processed cell material was flown to Professor Raymond Stevens at The Scripps Research Institute in La Jolla, California, who leads the GPCR Network of the National Institute of General Medical Sciences' Protein Structure Initiative, and has developed powerful techniques to analyse membrane proteins and crystallise G-protein coupled receptors (GPCRs) funded by the National Institutes of Health Common Fund.

The crystals took around two months to grow and when each batch of around 100 was ready, they were frozen and flown to the UK. Here, Prof Iwata and Dr Weyand (pictured left on I24) worked with Diamond’s scientists to analyse a total of over 700 samples using the Microfocus Macromolecular Crystallography (MX) beamline I24, a unique instrument capable of studying tiny micro-crystals using an X-ray beam a few microns wide.  
Prof Stevens said: “A key aspect of our program is to collaborate with the leading researchers in the world so that we can uncover the mysteries of how GPCRs work. To fully understand this large and important human protein family will take a global community effort and the study of multiple receptors with different techniques and approaches. The collaboration with the Iwata lab is a great example of success made possible by joining forces; in this case, our work on histamine H1 receptor helps to advance the field as quickly and efficiently as possible." 

Prof Iwata added: “The fact that we’ve managed to solve this structure in 16 months starting from pure protein is very exciting as it shows what can be achieved when a team of experts pool skills and experience in sample preparation, experimental techniques and data analysis.  Having the Membrane Protein Laboratory situated inside the Diamond synchrotron itself is a major advantage for projects like this.  We’ve benefited from rapid-access to the beamline and round the clock support for our experiments and data analysis work.”

More information: ‘Structure of the human histamine H1 receptor complex with doxepin’ Tatsuro Shimamura, Mitsunori Shiroishi, SimoneWeyand, Hirokazu Tsujimoto, GraemeWinter, Vsevolod Katritch, Ruben Abagyan, Vadim Cherezov, Wei Liu, GyeWon Han, Takuya Kobayashi, Raymond C. Stevens & So Iwata. Nature, 22 June 2011. http://dx.doi.org/ … /nature10236

Provided by Diamond Light Source

Metal particle generates new hope for H2 energy

Tiny metallic particles produced by University of Adelaide chemistry researchers are bringing new hope for the production of cheap, efficient and clean hydrogen energy.

Led by Associate Professor Greg Metha, Head of Chemistry, the researchers are exploring how the metal nanoparticles act as highly efficient catalysts in using solar radiation to split water into hydrogen and oxygen.

“Efficient and direct production of hydrogen from solar radiation provides a renewable energy source that is the pinnacle of clean energy,” said Associate Professor Greg Metha. “We believe this work will contribute significantly to the global effort to convert solar energy into portable chemical energy.”

The latest research is the outcome of 14 years of fundamental research by Associate Professor Metha’s research group investigating the synthesis and properties of metal nanoparticles and how they work as catalysts at the molecular level.

The group works with metal “clusters” of about one-quarter of a nanometre in size – less than 10 atoms. Associate Professor Metha said these tiny “magic clusters” act as super-efficient catalysts. Catalysts drive chemical reactions, reducing the amount of energy required.

“We’ve discovered ways of producing these tiny metallic clusters, we’ve explored their fundamental chemical activity, and now we are applying their catalytic properties to reactions which have great potential benefit for industrial use and the environment,” said Associate Professor Metha.

PhD student Jason Alvino is exploring splitting water to make hydrogen (and oxygen) using solar energy – a process that is not viable for industry development at the moment.

“We know this catalysis works very efficiently at the molecular level and now need to demonstrate it works on the macroscopic scale,” said Associate Professor Metha.

“Splitting water to make hydrogen and oxygen requires a lot of energy and is an expensive process. We will be using solar radiation as the energy source, so there will be no carbon emissions and because the clusters work so efficiently as a catalyst, it will be a much better process.

“The ultimate aim is to produce hydrogen from water as a cheap portable energy source.”

Associate Professor Metha said there were also other industrial chemical reactions that could be made feasible by these catalysts, using solar radiation as the energy source - with potentially significant environmental benefits. One example was converting carbon dioxide into methane or methanol with water.

This project ‘Solar Hydrogen: photocatalytic generation of hydrogen from water’, has been funded under the three-year clean energy partnership between Adelaide Airport Ltd and the University’s Centre for Energy Technology.

Provided by University of Adelaide (news : web)

Squeezed light from single atoms

MPQ scientists have generated amplitude-squeezed light fields using single atoms trapped inside optical cavities.

In classical optics light is usually described as a wave, but at the most fundamental quantum level this wave consists of discrete particles called photons. Over the time, physicists developed many tools to manipulate both the wave-like and the particle-like quantum properties of the light. For instance, they created single photon sources with single atoms, using their ability to absorb and emit photons one by one. A team around Professor Gerhard Rempe, Director at the Max Planck Institute of Quantum Optics (Garching near Munich) and head of the Quantum Dynamics Division, has now observed that the light emitted by a single atom may exhibit much richer dynamics. Strongly interacting with light inside a cavity, the atom modifies the wave-like properties of the light field, reducing its amplitude or phase fluctuations below the level allowed for classical electromagnetic radiation. This is the very first observation of "squeezed" light produced by a single atom.

The "graininess" of the photons in a light wave causes small fluctuations of the wave's amplitude and phase. For classical beams, the minimal amount of amplitude and phase fluctuations is equal. However, by creating interactions between the photons, one can "squeeze" the fluctuations of the amplitude below this so-called "shot noise" level at the expense of increasing the fluctuations of the phase, and vice-versa. Unfortunately, the photonic interactions inside standard optical media are very weak, and require bright light beams to be observed. Single atoms are promising candidates to enable such interactions at a few-photon level. Their ability to generate squeezed light has been predicted 30 years ago, but the amount of light they emit is very tiny and so far all attempts to set this idea into realization have failed. In the Quantum Dynamics Division at MPQ sophisticated methods for cooling, isolating and manipulating single atoms have been developed over many years, and made this observation possible.

A single rubidium atom is trapped inside a cavity made of two very reflective mirrors in a distance of about a tenth of a millimetre from each other. When weak laser light is injected into this cavity, the atom can interact with one photon many times, and forms a kind of artificial molecule with the photons of the light field. As a consequence, two photons can enter the system at the same time and become correlated. "According to the model of Bohr, a single atom emits exactly one single energy quantum, i.e., one photon. That means that the number of photons is exactly known, but the phase of the light is not defined," Professor Gerhard Rempe explains. "But the two photons that are emitted by this strongly coupled atom are indistinguishable and oscillate together. Therefore this time the wave-like properties of the propagating light field are modified."

When the physicists use a laser beam which is resonant with the excitation frequency of the atom, the measurements show a suppression of the phase fluctuations. If the laser light is resonant with the cavity, they observe a squeezing of the amplitude instead.

The latter situation is illustrated in the image: The atom in the cavity turns a laser beam into light which has less amplitude and more phase fluctuations than the shot-noise limit. "Our experiment shows that the light emitted by single atoms is much more complex than in the simple view of Albert Einstein concerning photo-emission," Dr. Karim Murr emphasizes. "The squeezing that we observe is due to the coherent interaction between the two photons emitted from the system. Our measurement is in excellent agreement with the predictions of quantum electrodynamics in the strong-coupling regime." And Dr. Alexei Ourjoumtsev, who has been working on the experiment as a post doc, adds: "Usually single quantum objects are used to manipulate the particle-like properties of light. It is interesting to see that they can also modify its wave-like properties, and create observable squeezing with excitations beams containing only two photons on average."

So far squeezed light has only been generated with systems containing many atoms, such as crystals, using very high intensity beams, i.e. many photons. For the first time now physicists have succeeded in generating this kind of non-classical radiation with single atoms and extremely weak light fields. The ability of a single atom to induce strong coherent interactions between propagating photons opens up new perspectives for photonic quantum logic with single emitters.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Max Planck Institute of Quantum Optics.

Journal Reference:

A. Ourjoumtsev, A. Kubanek, M. Koch, C. Sames, P. W. H. Pinkse, G. Rempe, K. Murr. Observation of squeezed light from one atom excited with two photons. Nature, 2011; 474 (7353): 623 DOI: 10.1038/nature10170

Scientists a step closer to understanding 'natural antifreeze' molecules

Scientists have made an important step forward in their understanding of cryoprotectants – compounds that act as natural 'antifreeze' to protect drugs, food and tissues stored at sub-zero temperatures.

Researchers from the Universities of Leeds and Illinois, and Columbia University in New York, studied a particular type of cryoprotectants known as osmolytes. They found that small osmolyte molecules are better at protecting proteins than larger ones.

The findings, published in Proceedings of the National Academy of Sciences, could help scientists develop better storage techniques for a range of materials, including human reproductive tissue used in IVF.

Biological systems can usually only operate within a small range of temperatures. If they get too hot or too cold, the molecules within the system can become damaged (denatured), which affects their structure and stops them from functioning.

But certain species of fish, reptiles and amphibians can survive for months below freezing by entering into a kind of suspended animation. They are able to survive these extreme conditions thanks to osmolytes – small molecules within their blood that act like antifreeze –preventing damage to their vital organs.

These properties have made osmolytes attractive to scientists. They are used widely in the storage and testing of drugs and other pharmaceuticals; in food production; and to store human tissue like egg and sperm cells at very low temperatures for a long period of time.

"If you put something like human tissue straight in the freezer, ice crystals start to grow in the freezing water and solutes – solid particles dissolved in the water – get forced out into the remaining liquid. This can result in unwanted high concentrations of solutes, such as salt, which can be very damaging to the tissue," said Dr Lorna Dougan from the University of Leeds, who led the study. "The addition of cryoprotectants, such as glycerol, lowers the freezing temperature of water and prevents crystallisation by producing a 'syrupy' semi-solid state. The challenge is to know which cryoprotectant molecule to use and how much of it is necessary.

"We want to get this right so that we recover as much of the biological material as possible after re-thawing. This has massive cost implications, particularly for the pharmaceutical industry because at present they lose a large proportion of their viable drug every time they freeze it."

Dr Dougan and her team tested a range of different osmolytes to find out which ones are most effective at protecting the 3D structure of a protein. They used an atomic force microscope to unravel a test protein in a range of different osmolyte environments to find out which ones were most protective. They discovered that smaller molecules, such as glycerol, are more effective than larger ones like sorbitol and sucrose.

Dr Dougan said: "We've been able to show that if you want to really stabilise a protein, it makes sense to use small protecting osmolytes. We hope to use this discovery and future research to develop a simple set of rules that will allow scientists and industry to use the best process parameters for their system and in doing so dramatically increase the amount of material they recover from the freeze-thaw cycle."

More information: The paper, 'Probing osmolyte participation in the unfolding transition state of a protein', by Lorna Dougan, Georgi Z Genchev, Hui Lu and Juilo M Fernandez is published in PNAS. http://www.pnas.or … 108.abstract

Provided by University of Leeds (news : web)

Nearer to using methane as a raw material

Researchers from the Universities of Valencia, Huelva and Toulousse have developed a methodology for transforming the simplest hydrocarbon, methane, into more complex organic molecules. The importance of the finding lies in the need to employ in the near future methane as a raw material in the chemical industry.

The use of methane, the simplest hydrocarbon and main component of natural gas, as a source for the production of more complex organic compounds is of great interest from both economic and environmental points of view. However, methane has the strongest C-H links in the whole series of alkanes and it rarely submits to the wishes of chemists.

The second challenge for chemically transforming methane derives from of its gaseous nature and its low solubility in common solvents. These features make it difficult for methane to come in contact with the catalysts and reagents that perform the chemical reaction and, therefore, this does not occur or it does but with great difficulty. For these reasons, very few processes are known to be effective for the functionalization of this hydrocarbon.

Researchers from the Universities of Valencia, Huelva and Toulouse, led by Professors Gregorio Asensio, Pedro J. Pérez and Michel Etienne, have solved the problem. The scientists have developed a methodology for transforming methane into more complex organic molecules. The reaction involves a silver catalyst specifically designed to activate the C-H methane bonds, a process that had already proved effective with heavier hydrocarbons. The challenge of attaining effective contact between the catalyst and the reagents needed for the transformation and methane was achieved by using carbon dioxide in supercritical state as the reaction medium.

Carbon dioxide is a gas under normal conditions, but at temperatures and pressures above their critical values ??(32 oC and 74 atmospheres) it is a fluid similar to a liquid and capable of solubilizing the molecules involved in the reaction. These properties of supercritical carbon dioxide have found wide industrial applications such as, for instance, the decaffeination of coffee. In addition, the chemical inertness of carbon dioxide prevents it from reacting with the catalyst or the reactants involved in the conversion of methane, and therefore is an ideal solvent for these reactions.

The transformation involves a carbene insertion into a C-H methane bond catalyzed by silver complexes with halogenated scorpionate ligands in supercritical carbon dioxide. The described process establishes the feasibility of the insertion of carbenes into C-H methane bonds catalyzed by transition metals. The reaction leads to the creation of a C-C bond over the methane to give ethyl propanoate with a yield of 19% and opens new perspectives to the process of functionalization of methane and of hydrocarbons in general.

The results of this project were recently published in Science. The research was funded by the Spanish Ministry of Science and Innovation, the Regional Governments of Valencia and Andalusia, and the European Union through its ERA Chemistry programme.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Asociación RUVID, via AlphaGalileo.

Journal Reference:

A. Caballero, E. Despagnet-Ayoub, M. Mar Diaz-Requejo, A. Diaz-Rodriguez, M. E. Gonzalez-Nunez, R. Mello, B. K. Munoz, W.-S. Ojo, G. Asensio, M. Etienne, P. J. Perez. Silver-Catalyzed C-C Bond Formation Between Methane and Ethyl Diazoacetate in Supercritical CO2. Science, 2011; 332 (6031): 835 DOI: 10.1126/science.1204131