SLAC Today is available online at:
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In this issue:
From the Director: The SLAC Management Plan
A Strange Discovery: Bacteria Built with Arsenic
Word of the Week: X-ray Fluorescence

SLAC Today

Friday - December 3, 2010

From the Director:
The SLAC Management Plan

(Photo - Persis Drell)
(Photo by Harvey Lynch.)

Over the last three years, the way in which we manage SLAC has changed in many ways. Starting last spring, the associate lab directors and I felt it would be good to write down and codify our management strategy. Our plan is completed and we are soliciting input from the broader laboratory. I encourage you to to read the plan (SLAC internal) and give me your feedback.

The document is, by design, short. We tried to keep it to less than 25 pages and that set the level of detail we included. The first chapter is "What is SLAC." I have received the most comments on this section of the plan—many of them very helpful—so you might expect this will change as we review and include the input we have gotten so far. Most comments so far address expanding or rephrasing the list of core capabilities that are currently given.  Read more...

A Strange Discovery:
Bacteria Built with Arsenic

Staff Scientist Sam Webb, who led the research undertaken at the Stanford Synchrotron Radiation Lightsource. (Photo by Brad Plummer.)

In a study that could rewrite biology textbooks, scientists have found the first known living organism that incorporates arsenic into the working parts of its cells. What's more, the arsenic replaces phosphorus, an element long thought essential for life. The results, based on experiments at the Stanford Synchrotron Radiation Lightsource, were published online yesterday in Science Express.

"It seems that this particular strain of bacteria has actually evolved in a way that it can use arsenic instead of phosphorus to grow and produce life," said SSRL Staff Scientist Sam Webb, who led the research at SLAC. "Given that arsenic is usually toxic, this finding is particularly surprising."

Phosphorus forms part of the chemical backbone of DNA and RNA, the spiraling structures that carry genetic instructions for life. It is also a central component of ATP, which transports the chemical energy needed for metabolism within cells. Scientists have for decades thought that life could not survive without it.  Read more...

Word of the Week: X-ray Fluorescence

The X-ray fluorescence setup at SSRL Beamline 2-3. (Image courtesy Sam Webb.)

Bombarding a material with high-energy light such as X-rays or gamma rays can blast electrons from their atomic orbits, leaving their fellow electrons and the nucleus they surround in an unbalanced state. If the incoming light is energetic enough, it can knock away even tightly held electrons close to the nucleus. As outer electrons pop in to fill those vacant inner spots, they release energy, often in the form of X-rays. As a result, the material glows, or fluoresces, with X-ray light.

Since different types of atoms fluoresce at characteristic wavelengths, researchers can use this phenomenon to identify chemical elements within a sample. This is one of two X-ray techniques used recently at the Stanford Synchrotron Radiation Lightsource's Beamline 2-3 to help locate the element arsenic in a surprising strain of bacteria. (See "Strange Discovery: Bacteria Built with Arsenic," above.)

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