Another piece of the ion pump puzzle

V-ATPases consist of a so-called ‘V complex’, which transfers energy derived from ATP hydrolysis into rotational motion, thereby promoting ion transport through to the membrane-bound V0 complex. These two complexes are joined by three ‘stalks’, including a central stalk composed of subunits named D and F, although this segment of the protein is poorly characterized. “The structure of this central axis of V-ATPase has not been obtained,” says Takeshi Murata of the RIKEN Systems and Structural Biology Center in Yokohama, “and we believe such structural studies are very important to understand this protein’s precise mechanism.”

Murata and colleagues recently succeeded in obtaining high-resolution structural information about the DF complex of V-ATPase obtained from the bacteria Enterococcus hirae1. By comparing this structural information against an equivalent segment from F-ATPase, which synthesizes rather than hydrolyzes ATP, the researchers were able to identify functional domains that may be specifically required by V-ATPases.

They determined that the E. hirae D subunit is composed of a pair of long helical structures coiled around each other, with a short hairpin-shaped loop at one end. According to Murata, the discovery of this latter structure was unexpected. “This short beta-hairpin region is a unique structure, although the rest of the D structure is very similar to that of other rotary complexes such as F-ATPase and flagellar motors,” he says. This segment does not appear to be essential for V-ATPase assembly, but ATP processing efficiency was reduced when the researchers deleted this hairpin from the subunits.

In contrast, the E. hirae F subunit assumed a more compact structure, relatively similar to its A- and F-ATPase counterparts; the researchers determined that it specifically associates with the middle portion of the D subunit’s coiled helical segment, an interaction that depends heavily on a particular helix within the F subunit. 

Although untangling this structure represents a major step forward, this complex must also be understood as part of a far larger entity (Fig. 1). Murata and colleagues have already begun tackling this. “We recently succeeded at solving the structure of V1-ATPase with a resolution of 2.1 Angstroms,” says Murata, “and we are now preparing this manuscript for publication.”

More information: Saijo, S.,et al. Crystal structure of the central axis DF complex of the prokaryotic V-ATPase. Proceedings of the National Academy of Sciences USA 108, 19955–19960 (2011).

Provided by RIKEN (news : web)

New technology to aid crystallization prediction

The software, which has been developed at the University of Leeds, in collaboration with the Cambridge Crystallographic Data Centre (CCDC) is called Visual HABIT. It offers a significant improvement on existing predictive resources and will enable companies to adopt a more 'bottom up' approach to the design of products or formulated products in the pharmaceutical, agrochemical and fuel sectors.

The software helps companies predict crystal properties in different chemical environments, something which will reduce extensive early-stage laboratory research, bringing down development costs and helping to bring new products to market more efficiently. It also has the ability to show what happens to crystalline particles under different processing conditions.

"Being able to see how crystal properties change within different processing environments is really important, because often companies have put in years of work before they even get to this stage," says Professor Kevin Roberts who is leading the research. "As chemical engineers, we have to make sure that the quality of a product remains the same in a manufacturing environment as in the laboratory. It's a bit like ensuring a meal cooked for 1000 guests is exactly the same quality as the same meal cooked for just four people. Our aim is to ensure that in scaling up different processes, none of the quality is lost. Our technology will help overcome some of the obstacles that slow down the research and development processes in these sectors."

Visual HABIT will also be a valuable resource for the nuclear sector, where crystallisation during long term storage can create difficulties in the effective processing of waste.

"We're excited about our software because we can see enormous benefits to all the sectors we're working with," says Professor Roberts. "If companies already know – at the beginning of the development process - how different chemical formulations are going to behave under a range of conditions, it'll speed up development times, cut costs and may result in superior products."

The Leeds research group, called Synthonic Engineering, is working with CCDC and five industry partners from across the pharmaceutical, agrochemical, fuel, nuclear and instrumentation sectors to ensure effective translation of the new technology. It aims to commercialise the technology within 12 months.

"We are delighted to be part of this collaborative venture" says Colin Groom, Executive Director of the CCDC. "In the past we have focussed on how knowledge and understanding derived from Cambridge Structural Database can be used in the discovery and development of drugs. This partnership allows us to explore the application of crystallographic and structural information to particle engineering. Our experience in software development will ensure practical and useful software tools are delivered in an exciting area that is new to us."

Provided by University of Leeds (news : web)

Glowing White: Solvent-free luminescent organic liquids for organic electronics

Current approaches to organic electronics mainly involve plastic film supports with conducting paths and components made of organic molecules inexpensively printed or glued on. Organic electronics are interesting as potential “disposable electronics” for applications like electronic price tags. Even more intriguing are devices that cannot be produced with standard electronics, such as flexible films with integrated circuits for use as novel flat-panel displays or “electronic paper”. A third area of interest involves applications such as photovoltaics that are dependent on economical mass production in order to be profitable.

The development of large components like displays requires organic coatings that emit white light and are inexpensive to produce. Previous gel- or solvent-based liquid “dyes” are easy to apply, but are often not colorfast or are barely luminescent after drying. For solids, on the other hand, processing is often too complex.

A team led by Takashi Nakanishi at the National Institute for Materials Science in Tsukaba (Japan) has taken a different approach: they use uncharged organic substances that are luminescent liquids at room temperature and require no solvent. The electronically active parts of the molecules consist of linear chains of carbon atoms linked by ?-conjugated double bonds. This means that electrons can move freely over a large portion of the molecule. The core is shielded by low-viscosity organic side chains that ensure that the core areas do not interact with each other and that the substance remains liquid.

The researchers were able to prepare a liquid that fluoresces blue under UV light. They then dissolved green- and orange-emitting dyes in this solvent-free liquid. This results in a durable, stable white-emitting paste whose glow can be adjusted from a “cool” bluish white to a “warm” yellowish white by changing the ratio of the dyes. It is possible to use this ink directly in a roller-ball pen for writing, or to apply it with a brush on a wide variety of surfaces. Application to a commercially available UV-LED allowed the researchers to produce white light-emitting diodes.

More information: Takashi Nakanishi, Solvent-Free Luminescent Organic Liquids, Angewandte Chemie International Edition, http://dx.doi.org/10.1002/anie.201108853

Provided by Wiley (news : web)

Researchers create more efficient hydrogen fuel cells

A research team from the University of Central Florida may have found a way around both hurdles.

The majority of hydrogen fuel cells use catalysts made of a rare and expensive metal – platinum. There are few alternatives because most elements can't endure the fuel cell's highly acidic solvents present in the reaction that converts hydrogen's chemical energy into electrical power. Only four elements can resist the corrosive process – platinum, iridium, gold and palladium. The first two are rare and expensive, which makes them impractical for large-scale use. The other two don't do well with the chemical reaction.

UCF Professor Sergey Stolbov and postdoctoral research associate Marisol Alcántara Ortigoza focused on making gold and palladium better suited for the reaction.

They created a sandwich-like structure that layers cheaper and more abundant elements with gold and palladium and other elements to make it more effective.

The outer monoatomic layer (the top of the sandwich) is either palladium or gold. Below it is a layer that works to enhance the energy conversion rate but also acts to protect the catalyst from the acidic environment. These two layers reside on the bottom slice of the sandwich -- an inexpensive substrate (tungsten), which also plays a role in the stability of the catalyst.

"We are very encouraged by our first attempts that suggest that we can create two cost-effective and highly active palladium- and gold-based catalysts –for hydrogen fuel cells, a clean and renewable energy source," Stolbov said.

Stolbov's work was recently published in the Journal of Physical Chemistry Letters.

By creating these structures, more energy is converted, and because the more expensive and rare metals are not used, the cost could be significantly less.

Stolbov said experiments are needed to test their predictions, but he says the approach is quite reliable. He's already working with a group within the U.S. Department of Energy to determine whether the results can be duplicated and have potential for large-scale application.

If a way could be found to make hydrogen fuel cells practical and cost effective, vehicles that run on gasoline and contribute to the destruction of the ozone layer could become a thing of the past.

Stolbov joined UCF's physics department in 2006. Before that he was a research assistant professor at Kansas State University. He earned multiple degrees in physics from Rostov State University in Russia and was a Postdoctoral Fellow at the Carnegie Institution of Washington, D.C. He is a frequent international speaker and has written dozens of articles on physics.

Provided by University of Central Florida (news : web)