Spinning a tale of spider silk
By studying the behavior of minute quantities of liquid silk harvested from the spinning glands of the golden silk orb-weaving spider, MIT researchers are unraveling the secrets of this strong and durable material. Their goal is to create synthetic silk, a long-sought prized polymer that could find use in artificial tendons and ligaments, parachutes, and bulletproof vests.

The golden silk spider spins one of the strongest webs in the spider world—in some cases, strong enough to catch small birds. Researchers Nikola Kojic and Gareth McKinley and colleagues at MIT set out to study the flow properties of the protein-rich liquid silk in order to see if they could understand how it irreversibly transforms into tough fibers as it exits the spider.

But native liquid silk is not easy to come by—a good harvest from the spider consists of one to five microliters, not enough to perform the necessary viscosity and flow tests. So the researchers built microsized analytical instruments to study tiny volumes of the liquid.

They found that freshly harvested silk solution is highly viscous, three million times thicker than water. But when they applied force to the liquid, mimicking its propulsion through the spider’s narrow spinneret channel, its viscosity dropped dramatically. The researchers attribute this to the alignment of the long protein molecules in the solution as the spider squeezes the solution through its spinneret.

The researchers used another small instrument to pull on the viscous solution and found that the liquid silk dried quickly in fine fibers with the protein molecules aligned, making the fiber very strong.

The study appeared this week in the Journal of Experimental Biology.

Breast cancer gene keeps chromosomes in line
Women who carry mutations in the breast cancer genes BRCA1 or BRCA2 are three to five times more likely to develop breast or ovarian cancer in their lives than women without those mutations. Researchers have some clues as to how normal BRCA proteins might fend off tumors—the proteins help repair DNA damage, for one—but other protective functions have not been apparent.

A new paper in this week’s Cell shows that the BRCA1 protein plays a larger role, ensuring that newly divided cells get the right complement of genetic material. Without BRCA1, cells can end up with extra or too few chromosomes, or ones that are broken. This type of disarray contributes to tumor development.

The work, from the labs of David Livingston at the Dana-Farber Cancer Institute and Johannes Walter at Harvard Medical School, reveals a surprising role for BRCA1 in the formation of the mitotic spindle. This structure, present only in dividing cells, ensures that chromosomes line up properly and are allocated correctly to the two newly forming nuclei.

The researchers discovered the link between the BRCA1 protein and spindle formation by studying cell extracts that normally display orderly spindle formation and precise separation of chromosomes. When they removed the BRCA1 protein or its partner protein BARD1 from the extracts, the spindle structure became less organized and chromosomes moved in a less coordinated fashion.

The lack of BRCA1 didn’t stop the whole process of division, but produced two unevenly sized nuclei carrying either too few or too many chromosomes.

The results could explain why cancer cells with BRCA1 mutations show widespread chromosomal abnormalities. The importance of BRCA1 as a watchdog of cell division is apparent from this sobering statistic: half of all women with a defect in the BRCA1 gene will develop breast cancer by the age of 50.

College students take illicit drugs seriously
A study of illicit use of prescription stimulants among college students has found that the primary reason students gave for using the drugs was to improve concentration and enhance academic performance. Less than a third of users reported taking the drugs to get high.

The study, from Christian Teter at Northeastern University, used a self-administered Web survey to sample 4,580 undergraduate college students at a large Midwestern university last year. Overall, 6 percent of students reported using stimulants—normally prescribed for attention-deficit-hyperactivity disorder (ADHD)—without medical authorization.

More than 75 percent of college students who reported using the stimulants illicitly chose amphetamine-dextroamphetamine products, like Adderall, over methylphenidate products, like Ritalin.

The researchers suggest one reason for this difference may be that Adderall is an extended-release drug with effects lasting 10 to 12 hours, whereas Ritalin and similar stimulants may produce a “roller coaster” response with effects lasting six hours or less. The high rate of use may also reflect the fact that Adderall is the most commonly prescribed brand-name stimulant in the United States.

Understanding how and why students use psychostimulants is necessary to effectively combat their improper use, the authors say.

The study appeared in the October issue of the journal Pharmacotherapy.