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Penn St Water M id40923 A synthetic membrane that self assembles and is easily produced may lead to better gas separation, water purification, drug delivery and DNA recognition, according to an international team of researchers. This biomimetic membrane is composed of lipids — fat molecules — and protein-appended molecules that form water channels that transfer water at the rate of natural membranes, and self-assembles into 2-dimensional structures with parallel channels.

“Nature does things very efficiently and transport proteins are amazing machines present in biological membranes,” said Manish Kumar, assistant professor of chemical engineering, Penn State. “They have functions that are hard to replicate in synthetic systems.”
The researchers developed a second-generation synthetic water channel that improves on earlier attempts to mimic aquaporins – natural water channel proteins — by being more stable and easier to manufacture. The peptide-appended pillar[5]arenes (PAP) are also more easily produced and aligned than carbon nanotubes, another material under investigation for membrane separation. Kumar and co-authors report their development in a recent issue of the Proceedings of the National Academy of Science (“Highly permeable artificial water channels that can self-assemble into two-dimensional arrays”).


Penn St Water M id40923

An artificial analogue of the water channel protein, aquaporin, was shown to have permeabilities approaching that of aquaporins and carbon nanotubes. They also arrange in tight two dimensional arrays. (Image: Karl Decker / University of Illinois at Urbana-Champaign, and Yuexiao Shen / Penn State)

“We were surprised to see transport rates approaching the ‘holy grail’ number of a billion water molecules per channel per second,” said Kumar. “We also found that these artificial channels like to associate with each other in a membrane to make 2-dimentional arrays with a very high pore density.”
The researchers consider that the PAP membranes are an order of magnitude better than the first-generation artificial water channels reported to date. The propensity for these channels to automatically form densely packed arrays leads to a variety of engineering applications.
“The most obvious use of these channels is perhaps to make highly efficient water purification membranes,” said Kumar.
Source: Penn State

GNT Thumbnail Alt 3 2015-page-001 Penn State Univ. engineers have developed a new “portable power supply” that will make it easier to manufacture plastics, therapeutics, fuels and other chemicals from sustainable feedstocks using diverse microbial organisms.


“Previously, when engineered DNA was found to work well in one organism, researchers would need to start from scratch to engineer a different organism,” said Howard Salis, principal investigator and assistant professor of chemical engineering and assistant professor of agricultural and biological engineering. “With our ‘portable power supply,’ the same genetic parts can be used to engineer many different bacterial organisms. This will have a huge impact on how organisms are engineered to make many different products.”

Their engineered system is analogous to the power supply inside all computers that plugs into power sockets and converts fluctuating AC power into a smooth DC current.

Manish Kushwaha, a post-doctoral fellow in agricultural and biological engineering, worked with Salis to build the system. He engineered a genetic circuit that could supply the organism with a portable RNA polymerase, a key enzyme responsible for reading DNA and making RNA, which is central to expressing the organism’s genes. But that wasn’t the difficult part.

Kushwaha explained, “The trick was to find a way to make the same amount of RNA polymerase in different organisms without using organism-specific genetic parts. We wanted to find a way to make RNA polymerase inside a cell without relying on the cell’s genetic machinery.”

The solution was to introduce a genetic control system—a positive feedback loop and a negative feedback loop—so that RNA polymerase could be made in any bacterial cell regardless of differences in the cell’s genetic machinery.

As reported in Nature Communications, Salis and Kushwaha demonstrated how their portable power supply works inside three very different bacterial organisms, showing how the same genetic parts could be used to make a recombinant protein and a 3-enzyme pathway.

The researchers hope their work will accelerate synthetic biology efforts in less well-studied bacterial organisms to better take advantage of their natural manufacturing abilities.

Source: Penn State Univ.

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