4D microscope captures motion in space and time
4 Mar 2013 by Evoluted New Media
Scientists from the California Institute of Technology have developed techniques for visualising the behaviour of biological nanostructures in space and time. Outlined in PNAS, the technique allows biologists to directly measure the mechanical properties of these biological structures, such as DNA, and map their variation.
“This type of visualisation is taking us into domains of the biological sciences that we have not explored before,” said Nobel Laureate Ahmed Zewail, Professor of Physics at Caltech. “We are providing methodology to find out directly the stiffness of a biological network that has nanoscale properties.”
Zewail and his colleague Ulrich Lorenz were able to visualise, for the first time, the motion of DNA nanostructures in space and time using the four-dimensional electron microscope developed at Caltech’s Physical Biology Centre for Ultrafast Science and Technology.
“In nature, the behaviour of matter is determined by its structure – the arrangement of its atoms in the three dimensions of space – and by how the structure changes with time, the fourth dimension,” Zewail explained. “If you watch a horse gallop in slow motion, you can follow the time of the gallops, and you can see in detail what, for example, each leg is doing over time. When we get to the nanometre scale, that is a different story – we need to improve the spatial resolution to a billion times that of the horse in order to visualise what is happening.”
Zewail was awarded the Nobel Prize in 1999 for his development of femtochemistry, which uses ultrashort laser flashes to observe chemical reactions occurring in a femosecond (one millionth of a billionth of a second.) But although femtochemistry can capture atoms and molecules in motion, giving the time dimension, it can’t show the dimensions of space and thus the material’s structure because it uses laser light with a wavelength that far exceeds the dimension of a nanostructure.
The 4D electron microscope, on the other hand, uses a stream of individual electrons that scatter off objects to produce an image. The electrons are accelerated to wavelengths of picometers (a trillionth of a meter) and allow the visualisation of the structure in space with a resolution a thousand times higher than that of a nanostructure, with a time resolution of femtoseconds or longer.
Zewail believes this technique has the potential for broad applications to not only cell biology, but also in the materials science of nanostructures.
