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.
Its 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. Its pretty incredible. You would never have believed it could be possible 10 years ago.
Journal reference: Nature (DOI: 10.1038/nature04268)
I doubt that our level of knowledge is sufficient to answer your question at this time. Certainly mine isn't. But Science progresses every day so who knows?
I pick up references in several posters and I think it's a breath of fresh air sometimes. I started a little Ogden Nash earlier.
We'll be watching you more closely from now on. b_sharp and Gumlegs and Doctor Stochastic are particularly good at this stuff.
From a purely conceptual standpoint science does not have limits. In practice, however, it is indeed limited. All that is necessary for science to take place is a.) a human observer, and b.) phenomena to observe.
Obviously this is too wide a definition for you. It's got to be guys in lab coats handing down formal declarations of sacred truth. Hahahaha! You're the mystic, not me.
Id you haven't got something of substance to say, say it to someone else, please.
Wow. Who would have thought a new-fangled super microscope would give us a thousand posts? But then most posts had nothing to do with the thread.
"Causative of organized matter" does not mean "origins of matter." If you are this incapable of understanding plain English it is no wonder you blather on with considerable lack of coherence in regard to the argument at hand.
Check the root meaning of the word science, and it might become more apparent to you what I mean, too.
I consider it pure mysticism to attribute the ordered arrangement of matter to something other than intelligent design. Since you do not have an answer, I can only assume you believe in some mysterious force.
May I ask how one can have order without design, or design without order? Looks like you are the one interested in redfining things.
"Check the root meaning of the word science, and it might become more apparent to you what I mean, too."
Science still needs physical evidence and testable, falsifiable theories.
"I consider it pure mysticism to attribute the ordered arrangement of matter to something other than intelligent design. Since you do not have an answer, I can only assume you believe in some mysterious force."
Now you are a blatant liar. I DID give you an answer, I specifically said WE CAN'T KNOW. That is the ONLY logical answer to give. It's pure mysticism to say that intelligent design (which you can't define) HAS to be the answer when you have
1) No evidence.
2) Can't test your feeling.
3) There is no hypothetical fact or discovery that could possibly weaken your feeling.
Stop lying now about what I have said.
"May I ask how one can have order without design, or design without order? Looks like you are the one interested in redfining things."
"Order" does not = "design".
I appreciated your reply. Virology is an interesting field I'm sure, especially these days!
Not according to the root meaning. It only needs those things if one is insistent upon a narrow meaning. That is an approach particularly well-suited to ideologues like yourself.
You have a low standard for the capabilities of science. Don't worry, science does just fine without your self-imposed limitations.
Is the "=" sign the only one you know?
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