McKelvey School of Engineering

Using light’s properties to indirectly see inside a cell membrane

Using properties of light from fluorescent probes is at the heart of a new imaging technique that allows for an unprecedented look inside cell membranes. (Image: Jin Lu)

For those not involved in chemistry or biology, picturing a cell likely brings to mind several discrete, blob-shaped objects; maybe the nucleus, mitochondria, ribosomes and the like.

There’s one part that’s often overlooked, save perhaps a squiggly line indicating the cell’s border: the membrane. But its role as gatekeeper is an essential one, and a new imaging technique developed at the McKelvey School of Engineering at Washington University in St. Louis is providing a way to see into, as opposed to through, this transparent, fatty, protective casing.

The new technique, developed in the lab of Matthew Lew, assistant professor in the Preston M. Green Department of Electrical and Systems Engineering, allows researchers to distinguish collections of lipid molecules of the same phase — the collections are called nanodomains — and to determine the chemical composition within those domains.


The details of this technique — single-molecule orientation localization microscopy, or SMOLM — were published online Aug. 21 in Angewandte Chemie, the journal of the German Chemical Society.

Editors at the journal — a leading one in general chemistry — selected Lew’s paper as a “Hot Paper” on the topic of nanoscale papers. Hot Papers are distinguished by their importance in a rapidly evolving field of high interest.

Using traditional imaging technologies, it’s difficult to tell what’s “inside” versus “outside” a squishy, transparent object like a cell membrane, Lew said, particularly without destroying it.

“We wanted a way to see into the membrane without traditional methods” — such as inserting a fluorescent tracer and watching it move through the membrane or using mass spectrometry — “which would destroy it,” Lew said.

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