From transporting substances to and from the cell to blocking pathogens, the cell membrane is on the front line of many key functions. Studying this fragile structure is difficult, but a new technique, based on labelling with stable isotopes of hydrogen, has recently enabled detailed investigations of the cell membrane in a living, intact bacterial cell. A cross-section of Bacillus subtilis shows the cell membrane, formed by two layers of lipids (in blue and red), between the cell wall (above) and the cytoplasm, containing proteins (orange), DNA and RNA (green). Altering the ratio of hydrogen atoms and their stable isotope, deuterium, in membrane lipids affects the way that neutrons, neutral subatomic particles, are scattered by the membrane, allowing nanoscale structures inside it to be revealed. This technique could unlock a new depth of understanding of the structure and function of cellular membranes, with a wide range of potential applications.
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