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)
"Why should an "argument from incredulity" be considered a bad argument?"
On that hilarious note, I'm going to bed. :)
If you have any physical evidence that doesn't call for the viewer to make an inference . . .
In other words, "If you can put God on display for direct observation, I'd like to see Him."
You ass.
Once again, you're demonstrating that your responses are emotional and not based on reason.
Is that one of the ad hominem attacks you're admittedly prone to?
And if you can't produce even a shred of physical evidence, if merely asking for physical evidence reduces you to profanity, how can you with a straight face call your personal cosmological preferences "science?"
At least with black holes, there's some physical evidence. We can talk about mass, and gravitation and radiation. The only evidence for a Designer is "I want there to be a designer."
Simple. If intelligence is considered natural, then there is nothing above nature and even the so-called supernatural becomes natural, particularly insofar as it interacts with the standard concept of nature, but even in total if you can but access it. Even "God" is natural and operates according to the laws in His domain.
Fine, we agree. ID isn't scientific. Thank you.
One down, so many to go.
mark
The vengeance, i.e. revenge for wrongs against the Creator, was placed upon Jesus, who is God, instead of the rest of us. That is mercy. It works when God is the actor. It fails when man is the actor.
Orwell is spot-on in discerning the human capacity to swop moral terms. God does not play games, or roll dice. I have no inkling as to Orwell's theological moorings. Maybe he is a modern-day Caiaphas.
?
What color is the sky in your world, Cliff?
Words don't seem to have much meaning in your arguments. I quote you, you accuse me of making things up. Interesting.
For all the evos out there, THIS is science. Something you can actually observe and repeat. There is no theorizing involved. And no made-up pictures of humans coming from apes.
Sleep tight. You can answer the question later.
Come on. I don't know anyone alive, save for a few nut cases, who think "everything that could possibly be known is known." The argument has to to with probabilities and statistics.
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