Saturday, July 2, 2011

Versatile membrane makes large-scale energy-efficient separation possible

Hessel Castricum from the University of Amsterdam has developed a versatile membrane that is capable of separating gas and liquid mixtures in an energy-efficient manner. He conducted his research with colleagues from the University of Twente and the Energy research Centre of the Netherlands. The new membrane can probably be employed under industrial conditions on a large scale in the future. This has not been possible until now, because virtually all membranes developed so far are insufficiently stable. What is also striking about this discovery is that the functionality of the membrane can be adjusted by varying the structure. This new membrane can lead to significant energy and cost savings.

The results were singled out as a research highlight in the journal Advanced Functional Materials.

Membranes are an inexpensive means of separation compared, for example, to distillation: easy and energy-efficient (and therefore relatively cheap). The separation of molecular mixtures with a membrane is, however, a method that is currently rarely used, especially for large processes. This is mainly due to the fact that little or no systems have been sufficiently tested to be applied reliably. The limited stability of most materials is the main cause.

Variable by organic bridge

The newly developed type of membrane can be used for many years at high (relevant) temperatures in mixtures in which a lot of water is present. It is therefore extremely stable. The material also allows much faster transport of molecules than, for example, polymers.

The membrane is made from a hybrid material that has both ceramic and polymeric properties. The scientists discovered that it is possible to alter the characteristic building block of this membrane: an organic bridge between two silicon atoms. Because of this variation, the membrane can be optimised for separation of different mixtures.

By using short bridges, it is possible to make the membrane selective for the smallest molecules, such as hydrogen and water. In contrast, slightly larger molecules such as CO2 or alcohols can pass more easily through the membrane by using larger bridges. Moreover, the material can actually be made water-repellent, by using, for example, long organic bridges. As a result, industry can decide to adopt membrane technology sooner and for more processes. Examples of potential applications include the dewatering of bio-fuels, CO2 sequestration and hydrogen production.

For these techniques to be used in practice, the reliability of the new membrane technology needs to be examined on a larger scale than in a lab. In this respect, it is perhaps interesting that a pilot plant has recently been opened at Plant One in the Botlek area of Rotterdam. The first material developed will be tested there on a larger scale.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by Universiteit van Amsterdam (UVA).

Journal Reference:

Hessel L. Castricum, Goulven G. Paradis, Marjo C. Mittelmeijer-Hazeleger, Robert Kreiter, Jaap F. Vente, Johan E. ten Elshof. Tailoring the Separation Behavior of Hybrid Organosilica Membranes by Adjusting the Structure of the Organic Bridging Group. Advanced Functional Materials, 2011; 21 (12): 2319 DOI: 10.1002/adfm.201002361

'Smart materials' that make proteins form crystals to boost research into new drugs

Scientists have developed a new method to make proteins form crystals using 'smart materials' that remember the shape and characteristics of the molecule. The technique, reported in Proceedings of the National Academy of Sciences, should assist research into new medicines by helping scientists work out the structure of drug targets.

The process of developing a new drug normally works by identifying a protein that is involved in the disease, then designing a molecule that will interact with the protein to stimulate or block its function. In order to do this, scientists need to know the structure of the protein that they are targeting.

A technique called X-ray crystallography can be used to analyse the arrangement of atoms within a crystal of protein, but getting a protein to come out of solution and form a crystal is a major obstacle. The number of proteins identified as potential drug targets is increasing exponentially as scientists make progress in the fields of genomics and proteomics, but with current methods, scientists have successfully obtained useful crystals for less than 20 per cent of proteins that have been tried.

Now researchers at Imperial College London and the University of Surrey have developed a more effective method for making proteins crystallise using materials called 'molecularly imprinted polymers' (MIPs). MIPs are compounds made up of small units that bind together around the outside of a molecule. When the molecule is extracted, it leaves a cavity that retains its shape and has a strong affinity for the target molecule.

This property makes MIPs ideal nucleants -- substances that bind protein molecules and make it easier for them to come together to form crystals. Many substances have been used as nucleants before, but none are designed specifically to attract a particular protein.

"Proteins are very comfortable in solution," said Professor Naomi Chayen, from the Department of Surgery and Cancer at Imperial College London, who led the research. "They need some convincing to come out and form a crystal.

"MIPs help this process by using the protein as a template for forming its own crystal. Once the first molecule or group of molecules is held in place, other molecules can arrange themselves around it and start to build a crystal."

In the study, Professor Chayen and her colleagues found that six different MIPs induced crystallisation of nine proteins, yielding crystals in conditions that do not give crystals otherwise. They also tested whether MIPs would be effective at producing crystals from a series of preliminary trials for three target proteins for which scientists have not previously been able to obtain crystals of sufficient quality. The presence of MIPs gave rise to crystals in eight to 10 per cent of such trials, yielding valuable crystals that would have been missed using other known nucleants.

"Rational drug design depends on knowing the structure of the protein you're trying to target, and getting good crystals is essential for studying the structure," Professor Chayen said. "With MIPs we can get better crystals than we can with other methods, and also improve the probability of getting crystals from new proteins. This is a really significant innovation that could have a major impact on research leading to the development of new drugs."

The research was funded by the Engineering and Physical Sciences Research Council and the European Commission.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Imperial College London, via EurekAlert!, a service of AAAS.

Journal Reference:

Emmanuel Saridakis, Sahir Khurshid, Lata Govada, Quan Phan, Daniel Hawkins, Gregg V. Crichlow, Elias Lolis, Subrayal M. Reddy, Naomi E. Chayen. Protein crystallization facilitated by molecularly imprinted polymers. Proceedings of the National Academy of Sciences, 2011; DOI: 10.1073/pnas.1016539108

Toxic compounds in groundwater: Degrading vinyl chloride under anaerobic conditions

Vinyl chloride is a cancer-causing compound formed from solvents in groundwater systems under anaerobic conditions. These solvents are used in many industrial applications around the world and often belong to the most encountered groundwater pollutants in industrialized countries. Groundwater is a major drinking water resource, and it is vital to determine if vinyl chloride can be further degraded into harmless compounds.

A group of scientists at Ecole Polytechnique Fédérale de Lausannne (EPFL) and the University of Neuchâtel, Switzerland, has studied the degradation of the toxic compound in a laboratory setting mimicking a natural groundwater system. This work has been funded by the Swiss Federal Office for Education and Science within the framework of the EC Environment/Water Program.

In this experiment, solutions containing vinyl chloride, as well as some mineral salts, were pumped through laboratory columns. The toxic compound was regularly analyzed in inlet and outlet samples. After several weeks of cycling, vinyl chloride concentrations began to decrease, reaching zero after about four months. Ethene, an organic compound often used as a plant hormone, is one of the possible degradation products.

Christof Holliger, Director of the EPFL laboratory, explained that ethene's outlet concentration was always lower than the inlet vinyl chloride concentration.

The complete results from this study were published in the May-June 2011 issue of Journal of Environmental Quality.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by American Society of Agronomy.

Journal Reference:

Theo H. M. Smits, Antoine Assal, Daniel Hunkeler, Christof Holliger. Anaerobic Degradation of Vinyl Chloride in Aquifer Microcosms. Journal of Environment Quality, 2011; 40 (3): 915 DOI: 10.2134/jeq2010.0403

Gold nanoparticles help earlier diagnosis of liver cancer

 Hepatocellular carcinoma is the most common cancer to strike the liver. More than 500,000 people worldwide, concentrated in sub-Saharan Africa and Southeast Asia, are diagnosed with it yearly. Most of those afflicted die within six months.

A big obstacle to treatment of liver cancer is the lack of early diagnosis. Current techniques, including ultrasound, CT and MRI scans, spot tumors only when they have grown to about 5 centimeters in diameter. By that time, the cancer is especially aggressive, resisting chemotherapy and difficult to remove surgically.

Now a research team led by Brown University reports some promising results for earlier diagnosis. In lab tests, the team used gold nanoparticles ringed by a charged polymer coating and an X-ray scatter imaging technique to spot tumor-like masses as small as 5 millimeters. The approach, detailed in the American Chemical Society journal Nano Letters, marks the first time that metal nanoparticles have been used as agents to enhance X-ray scattering signals to image tumor-like masses.

"What we're doing is not a screening method," said Christoph Rose-Petruck, professor of chemistry at Brown University and corresponding author on the paper. "But in a routine exam, with people who have risk factors, such as certain types of hepatitis, we can use this technique to see a tumor that is just a few millimeters in diameter, which, in terms of size, is a factor of 10 smaller."

The team took gold nanoparticles of 10 and 50 nanometers in diameter and ringed them with a pair of 1-nanometer polyelectrolyte coatings. The coating gave the nanoparticles a charge, which increased the chances that they would be engulfed by the cancerous cells. Once engulfed, the team used X-ray scatter imaging to detect the gold nanoparticles within the malignant cells. In lab tests, the nontoxic gold nanoparticles made up just 0.0006 percent of the cell's volume, yet the nanoparticles had enough critical mass to be detected by the X-ray scatter imaging device.

"We have shown that even with these small numbers, we can distinguish these [tumor] cells," Rose-Petruck said.

The next step for the researchers is on the clinical side. Beginning this summer, the group will attach a cancer-targeting antibody to the nanoparticle vehicle to search for liver tumors in mice. The antibody that will be used was developed by Jack Wands, director of the Liver Research Center at Rhode Island Hospital and professor of medical science at the Warren Alpert Medical School of Brown University.

"We have developed a monoclonal antibody that targets a cell surface protein highly expressed on liver cancer cells," Wands said. "We plan to couple the antibody to the gold nanoparticles in an attempt to detect the growth of early tumors in the liver by X-ray imaging."

The researchers say the X-ray scatter imaging method could be used to detect nanoparticle assemblies in other organs. "The idea should be that if you can figure out to get that [nanoparticle] to specific sites in the body, you can figure out how to image it," said Danielle Rand, a second-year graduate student in chemistry and the first author on the paper.

Contributing authors include Yanan Liu from Brown, Wands, Zoltan Derdak and Vivian Ortiz from the Liver Research Center, and Milan Taticek at the Czech Technical University in Prague.

The National Institutes of Health and the U.S. Department of Energy funded the research.

Story Source:

The above story is reprinted (with editorial adaptations) from materials provided by Brown University.

Journal Reference:

Danielle Rand, Vivian Ortiz, Yanan Liu, Zoltan Derdak, Jack R. Wands, Milan Tati´cˇek, Christoph Rose-Petruck. Nanomaterials for X-ray Imaging: Gold Nanoparticle Enhancement of X-ray Scatter Imaging of Hepatocellular Carcinoma. Nano Letters, 2011; : 110606111628071 DOI: 10.1021/nl200858y