Category: Research

brianwang writes "Michael Hall and Marcel Reginatto of the Physical-Technical Institute in Braunschweig, Germany, have published a paper with an expression that looks like Heisenberg's original relation, but gives the exact uncertainty in the measurements of position and momentum. Hall says it is an equation rather than an inequality, which is "a far stronger relation". So strong, in fact, that in a paper published this month in Journal of Physics A, have managed to derive the basics of quantum mechanics from it, including the Schrödinger equation that describes the behaviour of quantum-mechanical wave functions. http://www.newscientist.com/news/news.jsp?id=ns999 92209 It implies a tight relationship between uncertainty and energy that makes it easier to understand why, in quantum mechanics, systems have a minimum kinetic energy even if there aren't any forces acting. "There's a kind of quantum kinetic energy that comes from the uncertainty," he says. What's more, the new uncertainty equation makes it possible to estimate the minimum energy that a given quantum system should have. This is useful in cases when it's not possible to calculate the lowest energy levels precisely, particularly in complicated systems such as atoms with many orbiting electrons."

from the Natural-Nanomachines dept.
An article in Science News ("Channel Surfing: Atomic-resolution snapshots illuminate cellular pores that control ion flow", by John Travis, 9 March 2002) describes the work of researchers who have been uncovering the details of the structure and function of ion channels — protein complexes that act as natural, highly-specific atom sorting devices.

In addition to revealing the operating principles of natural sorters, the research has provided insights into the design of de novo sorter designs, as shown in another online article on the Nature Science Update website ("New channel built: Chemists copy from cells to make a tunnel for salt", by Philip Ball, 13 March 2002), which describes work by George Gokel and colleagues at Washington University in St Louis, Missouri, who created a synthetic peptide-based channel can be opened and closed by applying a voltage.

Additional details of research into ion channels and other types of natural atom sorters can be found in Nanodot posts from 17 January 2002 and 2 November 2001.

from the Natural-Nanomachines dept.
The translation of DNA/RNA instructions and the synthesis of proteins is arguably the most complex single-site operation carried out by biological systems at the molecular level, and it's done by relatively huge molecular machines called ribosomes. Insight into the operation of these naturally evolved molecular assembly devices could be invaluable to the design of artificial molecular machines.

According to a press release [new URL for archived press release], two UCLA molecular biologists propose a solution in the 21 March 2002 issue of the journal Nature. In their paper, James A. Lake, UCLA professor of molecular, cell and developmental biology, and UCLA graduate student Anne B. Simonson attempt to explain the molecular details of the protein synthesis process, including the location and movement of more than 10,000 atoms. In addition, they have located a novel binding site for transfer RNA (tRNA) when it enters the ribosome.

The research, which involved sophisticated computer simulation, was federally funded by grants from the National Science Foundation, the National Institutes of Health, the Department of Energy and the Astrobiology Institute

Previous research aimed at working out the structure and function of the ribosome was noted here on Nanodot on 4 April 2001 (with links to earlier posts).

from the Natural-Nanomachines dept.
According to a press release (7 March 2002), a molecular pump that helps cells produce chemical energy has been visualised by scientists at Imperial College, London. The structure of the pump, a key enzyme in bacterial respiration, reveals the molecular mechanisms that underpins cellular respiration, and confirms a Nobel Prize-winning theory proposed over 40 years ago by Peter Mitchell. Professor So Iwata and colleagues from the Laboratory of Membrane Protein Crystallography, Imperial College Centre for Structural Biology described their study of the structure of the enzyme formate dehydrogenase-N looks at a resolution of 1.6 angstroms in the 7 March 2002 issue of Science.

Their work with the bacteria E. coli provides the first real evidence for the 'chemiosmotic' theory proposed by Dr Peter Mitchell in 1961. Initially dismissed by mainstream science, Mitchell's theory on energy conversion is now accepted as a fundamental principle in the field of bioenergetics, the process by which living cells release energy in a controlled and useable form by converting metabolic energy derived from respiration into a compound called adenosine triphosphate (ATP). "In all cells, metabolites are converted via a series of respiratory enzymes into an electric potential or 'proton motive force' across the cell membrane. This proton motive force drives the generation of ATP," said Professor Iwata.

Professor Iwata and his team are the first to solve the structure of a respiratory enzyme that produces the proton motive force by the "redox-loop mechanism" originally proposed by Peter Mitchell. "Forty years on, this is the first enzyme structure to be determined that shows Peter Mitchell's original hypothesis of how cells convert energy into a usable form is correct," said Professor Iwata.