Soft warm light

Berkeley Lab's Advanced Light Source produces light at all wavelengths, from hard x-rays through visible light to the infrared (IR). ALS beamline 1.4.3, designed and operated by Wayne McKinney and Michael Martin, is dedicated to IR spectroscopic studies on the microscopic scale.

Hoi-Ying Holman works with Wayne McKinney and Michael Martin at the ALS's infrared beamline 1.4.3.

Because the synchrotron beam is much brighter than conventional IR sources, it can be focused to a few micrometers (millionths of a meter), roughly the size of animal cells or colonies of bacteria. Nor does IR kill organisms, as intense ultraviolet or x-rays can, making it ideal for studying chemical changes in living cells.

The IR beamline is also used for many other investigations, like structural studies of unusual materials, forensics (detective work) to identify drugs and fibers, and examining substances under high pressure in diamond anvil cells.

More on infrared beamline 1.4 at the ALS

Hydrocarbon villainy

Dioxins are one of the most potent of the polychlorinated aromatic hydrocarbons, toxins that can cause cancer, birth defects, and other problems in humans. In one notable study using IR spectroscopy at the Advanced Light Source, Hoi-Ying Holman and her colleagues studied changes caused by a form of dioxin on individual human liver cells under the microscope.

They found that dioxin binds to a cell receptor that causes increased production of cytochrome, which breaks down toxins. But among several other changes they observed, some suggested an increased methylation of the cell's DNA. Because methyl groups, simple hydrocarbons, can prevent gene expression, this may be how dioxin does its damage in liver cells.

In a separate study, Holman and her colleagues used IR spectromicroscopy to show that some bacteria promote the breakdown of other kinds of hydrocarbons, polycylic aromatic hydrocarbons (PAHs), by humic acid, a product of decaying organisms. Introducing such microorganisms into sites polluted by PAHs may be a promising path to bioremediation.

More about studies of living cells