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)
Really? Einstein, the mathematician, was not a scientist?
You are an idiot...
Really? Einstein, the mathematician, was not a scientist?
IIRC, Einstein admitted that math was not one his strengths.
I'm pretty sure that any good high-school Physics teacher would mention this.
Albert Einstein was not a scientist???
Get over it...
The chip sets in your computer don't add to your knowledge of the universe?
In your case, maybe not....
I'm pretty sure that any good high-school Physics teacher would mention this.
But, but, but how important are facts and details, like really, when you are trying to do God's work and change the world for the better for everyone?
See if you can get in with "founder's shares" before the IPO :-P
Cheers!
We have a new nominee for tha all-time most unintentionally funny post in the history of FR:
"It [a2 + b2 = c2] was a theory Pythagoras proved..."
[see post #913]
This is the first serious contender for dislodging the reigning champion of intended irony:
"Wildly elliptical planetary orbits"
If you had attempted to converse about what I wrote I might respond in kind. But you didn't.
make that: "UNintended" irony....
Oh, you are a collectivist... that explains everything...
drinking problem, most likely.
It's a winner, no doubt about it. But the other guy was good for frequent laughs. The current situation just isn't interesting at all.
Useless for what? A good "99.9% of the time" rule of thumb is pretty useful for lots of stuff. :-)
Why don't you spell out your underlying assumptions a little more clearly for those of your disputants who were not trained in science? A little pinch of "mutually exclusive, collectively exhaustive" here, a smidgeon of "uniformity of causes within a closed system" there, and, ...presto!
Full Disclosure: Mutually exclusive, collectively exhausting is a pretty good description of many of the flame wars on these threads, too ;-)
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