A new carbon nanotool springs to life Multiwall nanotubes contain several

concentric cylinders of carbon atoms, one packed inside another, like nesting wood- en dolls. Now, physicists have managed to peel back the outermost layers on one end of such a structure just 100 atoms or so wide and pull out the inner cylinders.

The finding suggests that these nan- otubes could, one day, be the tiny bear- ings and springs of nanosize machines.

John Cumings, a physics graduate stu- dent at the University of California, Berke- ley, performed the experiments by incor- porating a scanning tunneling microscope (STM) into a transmission electron micro- scope. While the electron microscope took high-resolution pictures, he used a tough nanotube attached to the STM’s probe to manipulate a multiwall nanotube fixed to the microscope stage.

After removing the outer few layers of atoms from the fixed tube’s end, Cumings found he could slide its inner cylinders- perhaps four or so-in and out of the outer shell.

During one test, the connection be- tween Cumings’ probe and the telescop ing nanotube broke. To his surprise, the extended layers snapped back into their sheath, as a nearly frictionless spring would. Cumings and Alex Zettl, also at

A computer graphic illustrates a telescoping nanotube, which could act as a tiny bearing or spring.

Berkeley, described the research in the July 28 SCIENCE.

“It’s interesting because they’re direct- ly imaging the structure of the nanotube during a dynamic process,” comments Richard Superfine of the University of North Carolina at Chapel Hill.

Cumings and Zettl suggest that van der Waals forces, which lubricate graphite sheets, also operate between the layers of multiwall carbon nanotubes. The forces, which would snap wayward tubes back inside, also would permit nearly perfect bearinglike movement, they say. Although Cumings wasn’t able to test ro- tation of one tube within another, he be- lieves an extended section should easily turn about its long axis, and he hopes to prove it soon.

Cumings extended and retracted lay-

JULY 29,2000

ers on several nanotubes 10 to 20 times each. The nanotubes that Cumings ma- nipulated show no signs of wear and tear under nanoscale magnification, he and Zettl report.

“This is really like molecular perfec- tion,” Cumings says. When developers in- corporate parts onto a microchip-or potentially a nanochip-they want them to last. “It’s like having an automobile that you know you can’t take into the shop,” he says.

Building up a “nanotechnology tool- box” is an active area of research, says Superfine. “We’re trying to develop and understand the fundamental elements that go into any kind of nanomachine,

whether it’s bearings or springs or gears,” he adds.

The next challenge will be to integrate components, such as the one that Cum- ings found, into functional devices, Su- perfine says.

“That’s going to be the next fun part,” he says. “I think over the next couple years, what you’ll start seeing is people assembling devices by hand. The next step [after that] . . . is going to be under- standing how you can set up a process where you can make 10,000 of these or so on a chip.”

“I think that the report of Cumings and Zettl will send shock waves in the nanoscience community, and even larger,” adds Laszlo Forr6, of the kale Polytech- nique FaCrale de Lausanne in Switzerland. “It will open new avenues.” -J Corman

Molecule may protect against kidney damage Kidney failure immediately after heart-

bypass surgery hikes a patient’s risk of other complications and death. Scien- tists now report that people whose genes encode a protein called apolipoprotein E N (apoE-N) are less likely to suffer such kidney failure than are patients who make another version of the protein.

Scientists are just beginning to under- stand the workings of apoE-IV and its counterparts, apoE-I1 and apoE-111. Every person makes one or two of the three sub- types. Most people produce apoE-111, and up to one-fourth, apoE-IV. The proteins play a role in immune reactions, activate certain enzymes, and usher fat particles to and from the liver during processing.

Scientists know that people with apoE 11, the least common form, have a height- ened risk of chronic kidney failure. This condition takes years to develop into a full-blown kidney problem that requires dialysis. That link spurred Mark Stafford- Smith, an anesthesiologist at Duke Uni- versity Medical Center in Durham, N.C., to investigate whether differences in apoE status might also influence the risk of abrupt kidney failure. The problem strikes about 8 percent of heart-bypass patients soon after surgery.

Stafford-Smith and his colleagues ana- lyzed the concentrations of creatinine in blood taken from 414 nondiabetic and 150 diabetic heart-bypass patients before and after surgery. Creatinine, a com- pound formed by muscle breakdown, is filtered out of the blood by the kidneys. Too much creatinine in blood signals that the kidneys are failing.

Nondiabetic patients with at least some apoEIl protein experienced a 34 percent jump in creatinine concentrations after by- pass surgery, and those with only apoE-111 saw a 27 percent rise. However, creatinine rose only 18 percent, on average, in people with apoE-IV or with a combination of apoEIII and apoEN, the researchers re- port in the August ANESTHESIOLOGY. Among

SCIENCE NEWS, VOL. 158

the patients with diabetes, creatinine con- centrations rose 30 percent in people with some apoElI, 40 percent in those with only apoEIU, but only 23 percent in people with apoEN, with or without apoEXI1.

This study is the first to match apoE status with signs of sudden kidney trou- ble, Stafford-Smith says. While the ob- served bloodcreatinine increases lie within the normal range, they represent a worrisome trend, he says.

Nearly all heart-bypass patients suffer minor kidney damage. Of bypass patients who develop abrupt kidney problems that require hospitalization but not dialysis, 20 percent die while still in the hospital. The other 80 percent-when compared with bypass patients without kidney prob lems-have more complications and are three times more likely to require a stay in an extendedcare facility, StaffordSmith says. Among the 1 to 2 percent of patients who need dialysis immediately after by- pass surgery, most die in the hospital.

Thus, knowing people’s apoE status might help surgeons decide which pa- tients are at greatest risk of kidney failure from heart surgery, he says.

How bypass surgery leads to kidney damage remains unclear. Some patients also suffer strokes or brain damage after the operation. In such cases, small parti- cles, possibly dislodged in surgery, a p pear to clog brain capillaries.

Ironically, because apoE-IV has a poor record of clearing fat particles from the blood, some evidence suggests it could contribute to certain neurological prob- lems. Moreover, apoE-1V appears to be a bad actor in Alzheimer’s disease, al- though the mechanism for that is unclear (SN: 5/18/96, p. 312).

The new study shows how a molecule “can pop up time and again playing what are perhaps opposite roles” in different diseases, says Lanny J. Haverkamp, a neu- roscientist at Baylor College of Medicine in Houston. -A! seppa

71