Posted in | Microscopy

Three-Dimensional Measurements of Single Biological Molecules

Researchers have developed new microscope technology that enables accurate and precise study of single biological molecules. Called as the standing wave axial nanometry (SWAN) technology, it combines atomic force and optical microscope technologies.

Iowa State University and Ames Laboratory researchers, left to right, Sanjeevi Sivasankar, Chi-Fu Yen and Hui Li have invented microscope technology to study single biological molecules. Photo by Bob Elbert/Iowa State University

The novel technology enables complete three-dimensional measurements. Iowa State assistant professor of physics and astronomy and U.S. Department of Energy’s Ames Laboratory associate, Sanjeevi Sivasankar stated that the novel type of measurement can be employed to find out the position of molecules. Conventional technology enables measurement of single molecules only on a two-dimensional plane’s x and y axes.

Sivasankar has embarked on a research program to develop new tools to study biological cells and also study how biological cells stick to one another. As part of this study, the researchers attached a single molecule fluorescence microscope and a commercial atomic force microscope. The atomic force microscope’s tip was set above a focused laser beam, which leads to a standing wave pattern. Within this standing wave, a molecule that can emit light due to the treatment provided to it is placed. When the atomic force microscope’s tip moves up and down, the molecule’s fluorescence fluctuates and this is in relation to the distance from the surface. This distance can be measured by comparing with a marker.

The technology enabled the researchers to measure the molecule’s height with precision and accuracy in terms of nanometers. The measurements can be taken with a precision of 3.7 nm and accuracy less than an nm. For calibrating and testing the instrument, single strands of DNA and fluorescent nanospheres were used.

The novel technology will be useful for researchers requiring high-resolution data from microscopes.

Iowa State doctoral student in electrical and computer engineering, Chi-Fu Yen, who is also an Ames Laboratory student associate, is a co-author in the study.

The novel technology has been published in the journal Nano Letters.


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