Biochemists identify how tissue cells detect and perfect

Scientists have discovered how cells detect tissue damage and modify their repair properties accordingly. The findings, published today [6 October] in the journal Developmental Cell, could open up new opportunities for improving tissue repair in patients following illness or surgery.

The Wellcome Trust-funded study, led by biochemists at the University of Bristol, examined the signalling process in damaged tissue cells and identified the cellular mechanisms responsible for activating effective repair.

In healthy adults the majority of tissue cells lie dormant unless challenged by wounding, at which point they sense a change in the molecular environment. Plasma leaking from damaged blood vessels and causes fibroblast cells to migrate into the damaged tissue, contract the wound, and plug the gap by depositing a substance such as collagen, which provides the structural support.

Dr Mark Bass, lead author and Research Fellow in the University's School of Biochemistry, said: "Each of these processes requires the turnover of cellular adhesions, and the challenge has been to determine how cells detect tissue damage and modify their adhesive properties accordingly."

Using atomic force microscopy, the team were able to determine how a molecule sensor, syndecan-4, triggers the uptake and redeployment of adhesive molecules. This novel signalling pathway causes fibroblasts and keratinocytes to migrate in response to the changing tissue architecture and follow the matrix fibres that make up the skin. Such linear migration towards a damage signal allows the cells to arrive at the wound far more efficiently than if activated cells searched randomly about the tissue, and results in a very efficient healing response.

Dr Bass added: "We find that this signalling cascade is essential for efficient healing, this opens up considerable opportunities for improving tissue repair in patients."

More information: The Wellcome Trust-funded study, entitled 'A syndecan-4 hair trigger initiates wound healing through caveolin- and RhoG-regulated integrin endocytosis' by Dr Mark Bass is published in the journal Developmental Cell.

Provided by University of Bristol (news : web)

A coating that prevents barnacles forming colonies

It is not necessary for an effective anti-fouling coating to release toxins into the environment. Scientists at the University of Gothenburg have shown that it is instead possible to mix into the coating molecules on which the adult barnacles cannot grow. The result has been published in the scientific journal Biofouling.

Fouling of hulls is a problem for all boat owners, and one of the most difficult organisms to deal with is barnacles. A research group at the Department of Cell and Molecular Biology has therefore studied the biology of barnacles in detail, and focussed on one particularly sensitive stage in the barnacle life cycle.

"When newly matured adult barnacles attempt to penetrate through the coating in order to establish a fixed location to grow, they are extremely sensitive to certain molecules known as 'macrocyclic lactones', which are normally produced by certain bacteria", says Professor Hans-Björne Elwing of the Department of Cell and Molecular Biology at the University of Gothenburg.

A better effect with no toxin released to the environment

When such molecules are mixed into the anti-fouling coating, the treated surface is first colonised by barnacles in the normal way. But as soon as the young barnacles have matured into adults and attempt to establish stronger contact with the surface, they lose contact and probably die. It is also the case that certain brown algae counteract the colonisation by barnacles on the surfaces of leaves in a similar manner.

"Using this discovery, we have managed to create coatings with new binding agents that shut down the release of the macrocyclic lactones into the marine environment. Further, only trace amounts of the macrocyclic lactones are required in the coating to give full effect against barnacles."

The research group has shown through field trials on leisure craft that the addition of macrocyclic lactones can fully replace copper in coatings used on such craft, on both the eastern and the western coasts of Sweden, and for several seasons.

"While it is true that it is only barnacles that are affected by the additive, the growth of algae and similar organisms can be counteracted relatively simply by other methods."

Provided by University of Gothenburg (news : web)

Combating mood disorders: New approach simplifies the search for more specific drugs

Many psychiatric conditions are caused by aberrant metabolism of the neurotransmitter serotonin. Researchers in the Department of Pharmacy at LMU have now developed a new screening method, which will facilitate the search for new drugs that modulate the biological activity of serotonin.

Psychiatric ailments such as depression, obsessive-compulsive disorder or anxiety states are often associated with disturbances in the metabolism of the neurotransmitter serotonin. Neurotransmitters are compounds that are released from the synapses at nerve cell endings and activate the firing of neighboring neurons. Thus, as their name suggests, they mediate the transmission of nerve impulses. The serotonin transporter (SERT) is responsible for reuptake of the transmitter into neurons, terminating its action. SERT is a major target for drugs that are used to treat many mood disorders, and the search for new SERT inhibitors is of continuing therapeutic relevance. A research team led by Professor Klaus Wanner of the Department of Pharmacy in the Center for Pharmaceutical Research at Ludwig-Maximilians Univeristät München (LMU) has now developed a novel binding assay, based on the use of mass spectrometry (MS), which promises to simplify the search for potential SERT inhibitors very significantly. The major advantage of the technique is that, unlike conventional binding assays, it avoids the need to use radiolabeled substances. A paper that describes the new assay will appear in the journal ChemMedChem on 4. October. The article has been rated as a "very important paper" and is featured on the cover of the upcoming issue of the journal.

To be effective, most drugs must bind selectively to defined molecular targets in the body. The target may be an enzyme found in certain cells or a protein on the plasma membrane of a specific cell type. Drug candidates must therefore be assessed for their affinity for the target by means of binding assays. These assays often involve the use of a chemical that is already known to recognize and bind selectively to the target as. The ability of a test substance to find and interact with the target is then measured in terms of how well it competes with this "marker" ligand. The greater its ability to displace the marker from the binding site, the higher is its own affinity for the target, and the more likely it is to be clinically effective. In the MS-based binding assay developed by Wanner's group, quantification of the marker is carried out using mass spectrometry. In contrast to conventional techniques, which employ radiolabeled ligands, MS binding assays do not require the use of markers containing radioactive isotopes. This means that the marker can be assayed in its unaltered, native state. "This label-free technique provides all the advantages offered by classical binding studies, while avoiding the need to work with radioactive compounds," explains Wanner. His team has now validated the MS-based binding assay for use in the search for new inhibitors of SERT function. "Because SERT regulates the concentration of serotonin in the synaptic cleft, the protein serves as the major target for the treatment of depression, obsessive-compulsive disorders and anxiety states," says Wanner. Using the well-known antidepressant (S)-fluoxetine as a native marker, his group has now shown that the results of the MS-based assay are in very good agreement with those obtained using radiolabeled ligands. Indeed, the team now routinely uses the MS method to screen for novel, pharmacologically active SERT inhibitors. In addition, Wanner has plans to adapt the approach for use with other target molecules of clinical interest. (göd)

More information: (S)- and (R)-Fluoxetine as Native Markers in Mass Spectrometry (MS) Binding Assays Addressing the Serotonin Transporter.
M. Hess, G. Höfner, K. Wanner. ChemMedChem 2011, vol 6, no. 10, 4. October; First published online 26. July 2011 doi:10.1002/cmdc.201100251

Provided by Ludwig-Maximilians-Universität M?nchen

Study sheds light on the mysterious structure of water-air interface

Findings by Japanese researchers at the RIKEN Advanced Science Institute and their colleagues at Tohoku University and in the Netherlands have resolved a long-standing debate over the structure of water molecules at the water surface. Published in the Journal of the American Chemical Society, the research combines theoretical and experimental techniques to pinpoint, for the first time, the origin of water's unique surface properties in the interaction of water pairs at the air-water interface.

The most abundant compound on the Earth's surface, water is essential to life and has shaped the course of human civilization. As perhaps the most common liquid interface, the air-water interface offers insights into the surface properties of water in everything from atmospheric and environmental chemistry, to cellular biology, to regenerative medicine. Yet despite its ubiquity, the structure of this interface has remained shrouded in mystery.

At the heart of this mystery are two broad bands in the vibrational spectrum for surface water resembling those of bulk ice and liquid water. Whether these bands are the result of hydrogen bonds themselves, of intra-molecular coupling between hydrogen bonds within a single water molecule, or of inter-molecular coupling between adjacent water molecules, is a source of heated debate. One popular but controversial hypothesis suggests one of the spectral bands corresponds to water forming an actual tetrahedral "ice-like" structure at the surface, but this interpretation raises issues of its own.

Enlarge

This is a snapshot in the MD simulation trajectory of the HOD / D2O mixture that shows the water pair at the surface. White, green and red represent H, D and O atoms, respectively. Credit: RIKEN

The researchers set out to resolve this debate through a comprehensive study combining theory and experiment. For their experiments, they applied a powerful spectroscopy technique developed at RIKEN to selectively pick out surface molecules and rapidly measure their spectra. To eliminate coupling effects, which are difficult to reproduce in simulations, they used water diluted with D2O (heavy water) and HOD (water with one hydrogen atom, H, replaced by deuterium, D). Doing so eliminates coupling of OH bonds within a single molecule (since there is only one OH bond) and reduces the overall concentration of OH bonds in the solution, suppressing intermolecular coupling.

With other influences removed, the researchers at last pinpointed the source of water's unique surface structure not in an "ice-like" structure, but in the strong hydrogen bonding between water pairs at the outermost surface. The extremely good match between experimental and theoretical results confirms this conclusion, at long last bringing clarity to the debate over the structure of the water surface and setting the groundwork for fundamental advances in a range of scientific fields.

Provided by RIKEN (news : web)

Scientists develop the most advanced computer model to-date of the scattering of polarized light from chiral molecules

An international research team has described the first calculations of Raman optical activity (ROA) spectra using coupled-cluster theory – one of the most reliable quantum chemical methods available. ROA is a valuable tool for the structural characterization of a wide range of molecules, including large biomolecules such as viruses and proteins for which the technique holds a particular prominence.

“We have developed the most advanced computer model to-date of the scattering of polarized light from chiral molecules”, says T. Daniel Crawford, researcher at Virginia Tech (USA), who carried out the simulations together with Kenneth Ruud of the University of Tromso (Norway). Chirality – or handedness – is a very important property in chemistry. The new results are presented in the journal ChemPhysChem.

A long-term goal of this area of research is to enable laboratory chemists to carry out their own simulations to study compounds ranging from small molecules to pharmaceuticals and viruses. “This will allow them to identify which ‘hand’ of the compound reacts in a desired way –from providing a certain scent to fighting tumors”, Crawford says. He points out that the model developed by him and his Norwegian colleague is capable of providing predictions of many molecular properties that equal –and sometimes exceed– the accuracy of even the best available experiments. Besides describing the fundamental theoretical aspects of the coupled-cluster functions used in the calculation of ROA spectra, Crawford and Ruud have demonstrated the effectiveness of their method through benchmark computations on (S)-methyloxirane –a compound for which experimental gas-phase data are available. Such rare experimental data, which are free of perturbative solvent effects, provide an excellent testing ground for advanced quantum-chemical methods.

According to the researchers, their future work will focus on more systematic comparisons between coupled-cluster ROA spectra and both density functional theory (DFT) and experiment, including more molecular examples. “Ultimately, we and the world's other quantum chemists seek to carry out ‘computational experiments’ that will provide reliable data more quickly, more safely, and with less expense than laboratory analyses”, Crawford adds.

More information: Daniel Crawford, Coupled-Cluster Calculations of Vibrational Raman Optical Activity Spectra, ChemPhysChem, Permalink to the article: http://dx.doi.org/ … hc.201100547

Provided by Wiley (news : web)