Category: Research

A brief item on the Physical Review Focus website ("Nanotubes in the fast lane", by J.R. Minkel, 18 January 2002) summarizes a paper in the 28 January 2002 print issue of Physical Review Letters in which researchers calculate that a group of concentric nanotubes nested inside an outer set of tubes can slide back and forth a billion times every second. Such a gigahertz oscillator could be a major advance in nanotechnology that would enable applications such as ultra-fast optical filters and nano-antennae. The researchers contend that the low friction between tubes — a tenth or less of the nano-newton-scale attractive force — allows the ensuing oscillation to match a Pentium 4 computer chip's speed in processing electronic signals, and that this demonstrates the feasibility of fabricating such devices.

Some readers of this article may find interesting echoes of the rod logic mechanical nanocomputer proposed by K. Eric Drexler back in 1988.

According to a press release (18 January 2002), researchers at the University of California at San Francisco have found that stem cells for eggs and sperm also control aging in the roundworm C. elegans. The unsuspected role may find parallels in other organisms including humans, they suggest.

The finding shows for the first time that genes act in the adult animal to control its rate of aging. The stem cells, it seems, can modify lifespan even as aging is proceeding. The key stem cells, the scientists found, are not those that actually become egg or sperm, but their sister cells from the same stem cell pool, known as "proliferating germline stem cells," that divide continuously in the animalís reproductive tissues. Their study is reported in the 18 January 2002 issue of Science.

According to a press release, a team of scientists led by Howard Hughes Medical Institute (HHMI) investigator Roderick MacKinnon at The Rockefeller University has determined the three-dimensional structure of the chloride ion channel. Their work was reported in the 17 January 2002, issue of Nature. Additional information is available in a second press release from Rockefeller University, where the MacKinnon lab is located. The same team worked out the details of the function of another type of ion channel, or molecular sorter, for potassium in November 2001.

The researchers discovered the chloride ion channel has a completely different structure from the potassium ion channel. While the potassium ion channel has one large single pore with a water-filled, pyramid-shaped cavity, the chloride ion channel has two pores, each shaped like an hourglass with a narrow constriction at the center. The scientists also discovered the arrangement of the protein subunits that make up the channel are arranged entirely differently in the two types of channels. In the potassium ion channel, four protein subunits contribute to a single pore. In the chloride ion channel, each protein subunit has its own pore and the two halves of the subunit have opposite orientations in whatís called two-fold rotational symmetry. Future experiments in MacKinnonís laboratory will focus on determining how the chloride ion channel opens and closes to maintain the appropriate concentration of ions inside the cell.

Similar work on a membrane channel specific for water molecules was reported here on Nanodot in December 2001.

from the beyond-the-proteome dept.
An article in the 12 January 2002 issue of Science News ("Biological Dark Matter: Newfound RNA suggests a hidden complexity inside cells", by John Travis) summarizes research done over the past decade or so that indicates terrestrial biology may have a second component to its genetic systems that expresses functional RNA, rather than messenger RNA that guides the synthesis of proteins. Many previously unrecognized gene sequences apparently encode RNA molecules that have important regulatory and developmental functions.