Posted on 11/16/2005 3:40:35 AM PST by snarks_when_bored
* 14:02 15 November 2005
* NewScientist.com news service
* Gaia Vince
A new microscope sensitive enough to track the real-time motion of a single protein, right down to the scale of its individual atoms, has revealed how genes are copied from DNA – a process essential to life.
The novel device allows users to achieve the highest-resolution measurements ever, equivalent to the diameter of a single hydrogen atom, says Steven Block, who designed it with colleagues at Stanford University in California.
Block was able to use the microscope to track a molecule of DNA from an E.coli bacterium, settling a long-standing scientific debate about the precise method in which genetic material is copied for use.
The molecular double-helix of DNA resembles a twisted ladder consisting of two strands connected by “rungs” called bases. The bases, which are known by the abbreviations A, T, G and C, encode genetic information, and the sequence in which they appear “spell out” different genes.
Every time a new protein is made, the genetic information for that protein must first be transcribed from its DNA blueprint. The transcriber, an enzyme called RNA polymerase (RNAP), latches on to the DNA ladder and pulls a small section apart lengthwise. As it works its way down the section of DNA, RNAP copies the sequence of bases and builds a complementary strand of RNA – the first step in a new protein.
“For years, people have known that RNA is made up one base at a time,” Block says. “But that has left open the question of whether the RNAP enzyme actually climbs up the DNA ladder one rung at a time, or does it move instead in chunks – for example, does it add three bases, then jump along and add another three bases.
Light and helium
In order to settle the question, the researchers designed equipment that was able to very accurately monitor the movements of a single DNA molecule.
Block chemically bonded one end of the DNA length to a glass bead. The bead was just 1 micrometre across, a thousand times the length of the DNA molecule and, crucially, a billion times its volume. He then bonded the RNAP enzyme to another bead. Both beads were placed in a watery substrate on a microscope slide.
Using mirrors, he then focused two infrared laser beams down onto each bead. Because the glass bead was in water, there was a refractive (optical density) difference between the glass and water, which caused the laser to bend and focus the light so that Block knew exactly where each bead was.
But in dealing with such small objects, he could not afford any of the normal wobbles in the light that occur when the photons have to pass through different densities of air at differing temperatures. So, he encased the whole microscope in a box containing helium. Helium has a very low refractive index so, even if temperature fluctuations occurred, the effect would be too small to matter.
One by one
The group then manipulated one of the glass beads until the RNAP latched on to a rung on the DNA molecule. As the enzyme moved along the bases, it tugged the glass bead it was bonded too, moving the two beads toward each together. The RNAP jerked along the DNA, pausing between jerks to churn out RNA transcribed bases. It was by precisely measuring the lengths of the jerks that Block determined how many bases it transcribed each time.
“The RNAP climbs the DNA ladder one base pair at a time – that is probably the right answer,” he says.
“It’s a very neat system – amazing to be able see molecular details and work out how DNA is transcribed for the first time,” said Justin Molloy, who has pioneered similar work at the National Institute for Medical Research, London. “It’s pretty incredible. You would never have believed it could be possible 10 years ago.”
Journal reference: Nature (DOI: 10.1038/nature04268)
You have assumed that everything we can treat as 'information' simply for analysis sake is the same as one person communicating to another. This is exactly why the leaders of ID insist on reifying everything.
That's breath too :)
No problem.
Some days my brain just doesn't work as it should. I may have over reacted.
a2 + b2 = c2
If you don't know where that one came from...
The science folks are usually perfectly happy just discussing the science, without getting off into any philosophical implications.
The "ID" folks are seldom content to do so, and seem to generally have a large chip on their shoulders in that regard.
In my short experience on these threads, I'd say you are being charitable in saying 'seldom'.
It is not my prerogative to assert what are the capabilities, or incapabilities, of science.
Well, that about sums it up.
Last time I checked, the automobile and its design had little to do with my feelings.
Of topic, but the aesthetic 'design' of automobiles is very much about human 'feelings'.
Creationism is beyond such trivial distinctions.
It was a theory Pythagoras proved...
Was told about God from an adult.
"It was a theory Pythagoras proved..."
It's not a scientific theory, it's a mathematical theorem. It can only be proved because the premises are axiomatic.
It was not axiomatic before Pythagoras...
So, mathematics is not science in your enlightened world view?
Indeed, Math and science are distinct fields of study, the former based on deductive logic, the latter on empirical observation.
Geometry is not science?
Once again, he stumbles upon the truth. Amazing, just amazing.
You probably never programmed photo-lithographic equipment, plasma etchers or have never even used a scanning electron microscope...
Programming computers (machines), is not a science. It may be creative but it doesn't explore the unknown or add to our knowledge of the universe. But if you'd like to argue that in some cases it is a creative art, I might be with you.
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