Posted in | Nanomaterials

Scientists Discover That Super-Thin Membranes Play Vital Role in Living Beings

Plant photosynthesis depends on membranes, and human beings would be unable to hear without the membrane we call the eardrum. Could yet another membrane help rescue us from a climatic catastrophe?

Life requires two things: a membrane that can distinguish between nothing and something, and that the “something” be an organism that is capable of reproducing.

The eardrum lies in the auditory canal. The membrane system deflects tiny hairs in the cells of the cochlea in the inner ear, which is what enables us to hear sounds.

Some time ago, American scientists created a protein that behaved just like primitive enzymes did when life evolved on Earth. This chunk of protein consisted of two chains, each of which contained 31 amino acids. The scientists also managed to produce membranes shaped like part of the bacterium.

The question is whether life could have emerged in this way, with genetic material accidentally captured inside a membranous envelope, which then led to further evolution.

The basis of all life

One thing that is certain is that super-thin membranes – which may be only a few nanometres (millionths of a millimetre) thick – are found everywhere within us and around us, acting as a sort of barrier that allows certain types of molecule to pass through, while keeping others out. And they are more important and powerful than most of us realize.

The best-known is the eardrum, a thin membrane that protects the inner ear and is also set in motion by sound-induced vibrations, converting sound-waves into minute movements of the bones of the inner ear. These movements are what we perceive as sound.

Organic membranes are also essential in the world of plants. Photosynthesis, the process whereby plants use light from the Sun to convert CO2 into organic compounds such as sugars and oxygen, is one of the most important natural processes on Earth.

“The trick is to capture energy from sunlight and convert it into chemical energy," says Trygve Brautaset, from SINTEF's Department of Biotechnology.
“The machinery for creating energy is located inside of a folded membrane in a plant cell. Here is where we find the light-sensitive parts containing chlorophyll. When sunlight activates the electrons in the molecules here, they shift into a more energetic condition, and solar energy becomes chemical energy. This is a sophisticated system with highly regulated shuttling of ions and molecules that pass through several membranes. Quite amazing. It has been said that all higher life-forms would actually die out within 25 years if this process stopped!”

Do cell membranes control our lives?

Membranes surround every single cell in our own bodies. These membranes are so fine that they were not discovered and confirmed until modern electron microscopy arrived in the late 1950s. For this reason, scientists have only recently discovered the roles played by membranes in our bodies.

Not only do membranes separate the interior of the cell from the external environment, but something in the membrane itself makes important, and correct, decisions about which substances can pass into and out of the cell. The membrane simply treats different molecules in different ways: toxic or unnecessary substances are not permitted to enter.

Cell biologist Bruce Lipton, who has taught in the schools of medicine at both the University of Wisconsin and Stanford University, has dedicated all of his career in research to cell membranes.

He claims, controversially enough, that membranes, rather than genes, are what shape our lives. It is in the membrane that the active intelligence of the cell is found. The membrane receives signals from the cell's environment, depending on which molecules attach themselves to the membrane wall. The membrane interprets the signals and tells the cell what to do. We ourselves largely create these signals through stress, nutrition and feelings, Lipton says.

Manmade membranes

We have learned to simulate the fantastic membranes of the plant and animal world for our own purposes. Today, there are inorganic membranes virtually everywhere, whether as a permeable layer that allows most substances to pass, or as a semi-permeable layer that only allow the passage of select compounds.

There are inorganic membranes under the tiles on our bathroom floor, there are membranes that filter out bacteria from our drinking water and membranes that provide electricity in industrial fuel cells. Membranes are used in structures that need to withstand water pressure. They are used in gardens, under roads and in all sorts of ponds and reservoirs.

Energy and climate

SINTEF scientist Rune Bredesen and Thorleif Holt have been working on membranes for several years. One researcher studies the use of membranes to improve the efficiency of CO2 scrubbing, while the other studies membranes as the basis of saline electricity generation.

The world's first prototype saline power plant was built at Hurum, outside of Oslo, last year. It mixes freshwater and seawater through membranes, and is able to extract energy via osmosis. All over Europe and in the USA, teams of scientists are using membranes in saline power plants. One of SINTEF's tasks is to help develop an optimal membrane for the Hurum plant. Thorleif Holt and his colleagues have tested hundreds of candidates, but have not reached their goal yet.

Now Holt is in a white coat in the laboratory and shows me a so-called sheet membrane. It looks like a glossy piece of paper. With a pair of scissors in his hands, he struggles to get the sheet to split into different layers. Finally, success, and I see the glossy thin membrane and the remaining two layers that still look like the same sheet.
“This,” he says, pointing to the membrane, “this is the layer where the osmotic process occurs. The other two layers are really just to support it.”


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