Bacterial proteins transform iron and other minerals for energy, growth

Scientists review decades of work into bacterial proteins that transform iron and other minerals for energy and growth. Cleaning up polluted soil and growing crops for biofuels benefit from a deeper understanding of how microbes alter subsurface minerals. Scientists at Pacific Northwest National Laboratory, University of East Anglia, and University College London assess the state of understanding of a key enzymatic pathway employed by bacteria in these transformations: chains of proteins called multi-heme cytochromes. The proteins perform a variety of tasks, primarily acting as electron conduits, and take multiple forms. The review, which focuses on the microbe Shewanella oneidensis, appears in Journal of the Royal Society Interfaces. The article covers more than 150 studies of the protein, spanning more than three decades.

“The proteins participate in electron transfer reactions that contribute to biogeochemical cycling of nitrogen, sulfur, and iron on the global scale. The properties of multi-heme cytochromes have attracted multidisciplinary interest and contribute beyond environmental sciences to advances in bioenergy and bioelectronic devices,” said Dr Kevin Rosso, Geochemist, PNNL.

Called the subsurface environment by scientists, the soil, rocks, and water that stretch far beneath our feet are far from simple or static. Yet, scientists lack detailed knowledge of the complex processes that can cause local and regional fluxes to drive nutrients away from farms, or spread or immobilize uranium from nuclear waste sites. The review provides a one-stop shop of information on a key part of the complex, dynamic processes and highlights opportunities for additional research.

Another twist is that, one day, multi-heme cytochrome reactions could lead to bio-based batteries. When the microbes use iron, much like humans use oxygen, to burn fuel for energy, the associated flow of electrons can be captured and delivered to targets, such as electrodes in fuel cells. Lead researcher Professor Julea Butt at the University of East Anglia said, “these bacteria can generate electricity for us in the right environment.”

In their 27-page review article, the four researchers discuss the structures, properties, and functions of the multi-heme cytochromes, especially how they channel their electrons. “This is an exciting advance in our understanding of how some bacterial species move electrons from the inside to the outside of a cell and helps us understand their behavior as robust electron transfer modules,” said Butt.

While scientists have answered numerous questions about multi-heme cytochromes, just as many unanswered questions remain. “If we can unravel the relationships between encoding the protein and how it functions as an electron conduit, then we can start to think about customizing aspects of design for device purposes,” said Rosso.

Read full story here - Bacterial proteins transform iron and other minerals for energy, growth

New hybrid sodium ion capacitor from peanut shells

Scientists in Canada have created a hybrid sodium ion capacitor (NIC) from peanut shells in a pioneering study bridging the gap between conventional ion batteries and supercapacitors. A hybrid ion capacitor is capable of storing charge both electrostatically and electrochemically, providing an intermediate in terms of energy and power between traditional batteries and supercapacitors.

“In conventional batteries the cathode often limits performance and so what people are starting to do is swap regular cathodes for supercapacitor cathodes. Ions are adsorbed onto the surface of the cathode in an NIC, which avoids the degradation seen in batteries due to ion absorption into the bulk,” explained David Mitlin, University of Alberta, who led the research. These cathodes can drastically improve the cycling life of such devices. A high surface area cathode material is therefore crucial for achieving energy–power performance to rival other state-of-the-art energy storage devices.

According to Mitlin, peanut shells are easy to source, cheap and have limited commercial use, mostly ending up in landfill sites. However, the shells were hardly chosen at random – the team recognised important structural characteristics of both the inner and outer peanut shells to give desirable anode and cathode materials, respectively. The homogenous inner portion of the shell, primarily consisting of highly cross-linked polymer lignin, lent itself to the fabrication of inter-dilated graphene layers perfect for intercalating large sodium ions as an efficient anode. The cathode, a high surface area graphene-like material, was synthesised from the cellulose-rich heterogeneous outer peanut casing.

This careful precursor selection process was underscored by the poor device performance when the whole peanut shell was used to synthesise both electrode materials. The optimised system, however, achieved 88 per cent capacity retention after 100,000 cycles at 51.2A/g, a performance that is competitive with lithium ion capacitors.

This was surely no easy task as sodium has proven to be notoriously difficult to incorporate into such energy storage devices, relative to lithium, due to its larger ionic radius. Sodium, however, is cheaper and easier to get hold of. Mitlin admits there were difficulties along the way: ‘few people have actually done it, but this was also a challenge as there was limited literature to refer back to.’

Materials experts have praised the work. Yuping Wu from the University of Fudan in China was impressed by the excellent cycling stability of the electrodes: ‘These data show that this NIC can be a promising choice for applications.’ Chengdu Liang, of Oak Ridge National Laboratory in the US, admires the project but recognises that more investigation is necessary: ‘This research exemplifies the versatility of using biomaterials as the feedstock for energy storage devices. However, every aspect is still under scrutiny so from laboratory discoveries to real-world applications, there is a long way to go.’

Read full story here - New hybrid sodium ion capacitor from peanut shells

Honeybee hives could hold potential hair loss therapy

Hair loss can be devastating for the millions of men and women who experience it. Now scientists are reporting that a substance from honeybee hives might contain clues for developing a potential new therapy. They found that the material, called propolis, encouraged hair growth in mice. The study appears in ACS’ Journal of Agricultural and Food Chemistry.

Researcher Ken Kobayashi and colleagues noted that propolis is a resin-like material that honeybees use to seal small gaps in their hives. Not only does it work as a physical barrier, but it also contains active compounds that fight fungal and bacterial invasions. People from ancient times had noticed propolis’ special properties and used it to treat tumors, inflammation and wounds. More recently, research has shown that the substance promotes the growth of certain cells involved in hair growth though no one had yet tested whether that in turn would result in new locks. Kobayashi’s team wanted to find out.

When the researchers tested propolis on mice that had been shaved or waxed, the mice that received the treatment regrew their fur faster than those that didn’t. The scientists also noticed that after the topical application, the number of special cells involved in the process of growing hair increased. Although they tried the material on mice that could grow fur rather than balding mice, the researchers noted that hair loss conditions often result from abnormal inflammation. Propolis contains anti-inflammatory compounds, so they expect it could help treat balding conditions. They added that further testing is needed to see if the beehive material affects human hair follicles.

Read full story here - Honeybee hives could hold potential hair loss therapy

New method to detect horse meat

UK chemists have developed a method to distinguish horse meat from beef using a benchtop NMR machine. The new test is quicker, cheaper and simpler than the current gold standard used by food safety bodies.

In early 2013, the discovery that some beef burgers contained horse meat caused a Europe-wide meat authenticity crisis. Researchers have since been looking for meat purity tests that can replace standard DNA tests, which are accurate but expensive, slow and don’t give reliable quantitative results.

Now a group of researchers from Norwich and Oxford, UK, has developed a method to distinguish beef from horse meat in only 10 minutes. The team analysed the levels of triglycerides in both horse and beef extracts using a 60MHz benchtop NMR machine. In two labs, the group tested 117 fresh and frozen meat samples, only misidentifying a single one. They now hope to extend their method to spot horse meat in processed foods that are supposed to only have beef in them.

Read full story here - New method to detect horse meat

Artificial skin developed using traditional electronics

An artificial skin that wraps around a prosthetic hand and senses touch and warmth has been developed using traditional electronics. The flexible sensors array was demonstrated in a rat model, where signals were transmitted and sensed in the brain.

Many robots and prosthetic limbs have been created, but their skins cannot sense their environment. This new stretchable prosthetic skin comes equipped with ultra-thin, single crystalline silicon nanoribbon sensors for strain, pressure and temperature, as well as humidity sensors, heaters and stretchable multi-electrode arrays for nerve stimulation. The skin is tuned to stretch as befits its location on the prosthetic.

The group said that their design can dramatically boost perception capabilities in changing environments. Integration of stretchable humidity sensors and heating elements allows for the sensation of skin moisture and body temperature regulation, respectively.

Electrical stimuli can be sent from the prosthetic skin to the body to stimulate peripheral nerves via an ultra-thin multi-electrode array. “The overarching goal is for arrays of stretchable sensors to capture information about the external environment and ultimately interface these devices with peripheral nerves to transmit signals to the brain,” explained study author Roozbeh Ghaffari.

“We built the systems very thin and that allowed for very low bending stiffness, which then allows you to wrap around any surface and to be able to stretch. You need to do some work on the geometry side to bring interconnects between individual sensors,” noted Ghaffari, who is a co-founder of MC10, a company developing wearable sensors based on the same technology. MC10 collaborated with Korean scientists to develop the artificial skin.

“This is a fantastic demonstration from a technology point of view. It is a combination of well-known systems and approaches, but they have made something that looks really impressive. Other groups have shown similar things, but not with the complexity shown here,” said soft matter physicist Siegfried Bauer at Johannes-Kepler University in Linz, Austria.

He pointed to a recent paper by George Whitesides’ team at Harvard University, US, where they developed an ionic skin that senses stimuli using ions – just like natural skin. “I like both approaches. But we’ll have to see which one wins out. This one relies on traditional materials but is extremely well advanced,” said Bauer.

“The authors reported some significant advances and wide-ranging demonstrations that pull together many different types of materials in sensors and actuators for the skin, with additional examples of interfaces to the peripheral nervous systems. The work powerfully illustrates the scalability and wide-ranging capabilities of ideas in ultra-thin, silicon-based, epidermal electronics,” said Materials Scientist John Rogers, University of Illinois.

Ghaffari noted that efforts are underway by others to selectively stimulate nerves. “Interfacing with peripheral nerves and stimulating individual nerve fibres such that you can pinpoint specific sensations is still very much in its infancy. In terms of doing this at high resolution, we are showing how to on the sensor side,” added Ghaffari.

Read full story here - Artificial skin developed using traditional electronics

New “high-entropy” metal alloy with higher strength-to-weight ratio

Researchers from North Carolina State University and Qatar University have developed a new “high-entropy” metal alloy that has a higher strength-to-weight ratio than any other existing metal material. High-entropy alloys are materials that consist of five or more metals in approximately equal amounts. These alloys are currently the focus of significant attention in materials science and engineering because they can have desirable properties. The NC State research team combined lithium, magnesium, titanium, aluminum and scandium to make a nanocrystalline high-entropy alloy that has low density, but very high strength.

“The density is comparable to aluminum, but it is stronger than titanium alloys. It has a combination of high strength and low density that is, as far as we can tell, unmatched by any other metallic material. The strength-to-weight ratio is comparable to some ceramics, but we think it’s tougher – less brittle – than ceramics,” said Dr Carl Koch, Kobe Steel Distinguished Professor of Materials Science and Engineering, NC State and senior author of a paper on the work.

There are a wide range of uses for strong, lightweight materials, such as in vehicles or prosthetic devices. “We still have a lot of research to do to fully characterize this material and explore the best processing methods for it. One thing we’ll be looking at is whether scandium can be replaced or eliminated from the alloy,” said Koch.

At this point, the primary problem with the alloy is that it is made of 20 per cent scandium, which is extremely expensive.

Read full story here - New “high-entropy” metal alloy with higher strength-to-weight ratio

Measuring methane emissions from natural gas

A team of researchers from the Cockrell School of Engineering at The University of Texas at Austin and environmental testing firm URS reported that a small subset of natural gas wells are responsible for the majority of methane emissions from two major sources - liquid unloadings and pneumatic controller equipment - at natural gas production sites.

With natural gas production in the United States expected to continue to increase during the next few decades, there is a need for a better understanding of methane emissions during natural gas production. The study team believes this research will help to provide a clearer picture of methane emissions from natural gas production sites.

The UT Austin-led field study closely examined two major sources of methane emissions - liquid unloadings and pneumatic controller equipment - at well pad sites across the United States. Researchers found that 19 per cent of the pneumatic devices accounted for 95 per cent of the emissions from pneumatic devices, and 20 per cent of the wells with unloading emissions that vent to the atmosphere accounted for 65 per cent to 83 per cent of those emissions.

“To put this in perspective, over the past several decades, 10 per cent of the cars on the road have been responsible for the majority of automotive exhaust pollution. Similarly, a small group of sources within these two categories are responsible for the vast majority of pneumatic and unloading emissions at natural gas production sites,” said David Allen, Chemical Engineering Professor, Cockrell School.

Additionally, for pneumatic devices, the study confirmed regional differences in methane emissions first reported by the study team in 2013. The researchers found that methane emissions from pneumatic devices were highest in the Gulf Coast and lowest in the Rocky Mountains.

The study is the second phase of the team’s 2013 study, which included some of the first measurements for methane emissions taken directly at hydraulically fractured well sites. Both phases of the study involved a partnership between the Environmental Defense Fund, participating energy companies, an independent Scientific Advisory Panel and the UT Austin study team.

The unprecedented access to natural gas production facilities and equipment allowed researchers to acquire direct measurements of methane emissions.

Pneumatic devices, which use gas pressure to control the opening and closing of valves, emit gas as they operate. These emissions are estimated to be among the larger sources of methane emissions from the natural gas supply chain. The Environmental Protection Agency reports that 477,606 pneumatic (gas actuated) devices are in use at natural gas production sites throughout the US.

“Our team’s previous work established that pneumatics are a major contributor to emissions. Our goal here was to measure a more diverse population of wells to characterize the features of high-emitting pneumatic controllers,” said Allen.

The research team measured emissions from 377 gas actuated (pneumatic) controllers at natural gas production sites and a small number of oil production sites throughout the US.

The researchers sampled all identifiable pneumatic controller devices at each well site, a more comprehensive approach than the random sampling previously conducted. The average methane emissions per pneumatic controller reported in this study are 17 per cent higher than the average emissions per pneumatic controller in the 2012 EPA greenhouse gas national emission inventory (released in 2014), but the average from the study is dominated by a small subpopulation of the controllers. Specifically, 19 per cent of controllers, with measured emission rates in excess of 6 standard cubic feet per hour (scf/h), accounted for 95 per cent of emissions.

The high-emitting pneumatic devices are a combination of devices that are not operating as designed, are used in applications that cause them to release gas frequently or are designed to emit continuously at a high rate.

The researchers also observed regional differences in methane emission levels, with the lowest emissions per device measured in the Rocky Mountains and the highest emissions in the Gulf Coast, similar to the earlier 2013 study. At least some of the regional differences in emission rates can be attributed to the difference in controller type (continuous vent vs. intermittent vent) among regions.

After observing variable emissions for liquid unloadings for a limited group of well types in the 2013 study, the research team made more extensive measurements and confirmed that a majority of emissions come from a small fraction of wells that vent frequently. Although it is not surprising to see some correlation between frequency of unloadings and higher annual emissions, the study’s findings indicate that wells with a high frequency of unloadings have annual emissions that are 10 or more times as great as wells that unload less frequently.

The team’s field study, which measured emissions from unloadings from wells at 107 natural gas production wells throughout the US, represents the most extensive measurement of emissions associated with liquid unloadings in scientific literature thus far.

A liquid unloading is one method used to clear wells of accumulated liquids to increase production. Because older wells typically produce less gas as they near the end of their life cycle, liquid unloadings happen more often in those wells than in newer wells. The team found a statistical correlation between the age of wells and the frequency of liquid unloadings. The researchers found that the key identifier for high-emitting wells is how many times the well unloads in a given year.

Because liquid unloadings can employ a variety of liquid lifting mechanisms, the study results also reflect differences in liquid unloadings emissions between wells that use two different mechanisms (wells with plunger lifts and wells without plunger lifts). Emissions for unloading events for wells without plunger lifts averaged 21,000 scf (standard cubic feet) to 35,000 scf. For wells with plunger lifts that vent to the atmosphere, emissions averaged 1,000 scf to 10,000 scf of methane per event. Although the emissions per event were higher for wells without plunger lifts, these wells had, on average, fewer events than wells with plunger lifts. Wells without plunger lifts averaged fewer than 10 unloading events per year, and wells with plunger lifts averaged more than 200 events per year.   Overall, wells with plunger lifts were estimated to account for 70 percent of emissions from unloadings nationally.

Additionally, researchers found that the Rocky Mountain region, with its large number of wells with a high frequency of unloadings that vent to the atmosphere, accounts for about half of overall emissions from liquid unloadings.

The study team hopes its measurements of liquid unloadings and pneumatic devices will provide a clearer picture of methane emissions from natural gas well sites and about the relationship between well characteristics and emissions.

Read full story here - Measuring methane emissions from natural gas