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)
Since I did not fully agreed with the quote, I decided to remove it.
So what didn't you agree with? This is kind of important, you know. It's got something to do with you're credibility and all that... I'm sure you understand.
Spin a few times and unwind. You're a little tight.
See!
You're talking to yourself ;^)
Oh well...
I can't make ya drink.
Feliz Navidad (sp?)
Some have said it appears that English is not mine!
ALL the time?
Methinks thou exaggerates hyperboly
Hey!!!!!!!!!
Something about a happy nw year??
Go with god?
You put it much better than I did. Bravo!
Since I did not fully agreed with the quote, I decided to remove it.
So what didn't you agree with? This is kind of important, you know. It's got something to do with you're credibility and all that... I'm sure you understand.
This is your chance to explain yourself, Stingy Dog. What part of the frankly racist quote did you not "fully agree with"?
Even better, which part of the rant against "race mixing" did you agree with?
Like there are good puns? Next you'll be emitting puns with intricate rhyme.
Then can we say you have gone from bad to verse?
OK, by popular request, then...
A mosquito was heard to complain,
"I fear they have addled my brain!
The cause of my sorrow
is para-dichloro-
diphenyl-trichloro-ethane!"
Full Disclosure: If it weren't for bad puns, there'd be no puns at all.
Cheers!
Asking him to undo his a-helix?
As we used to say in biochem, "Relax. Unwind. Denature your proteins."
Cheers!
Right. One word: Nonlocality.
Second point: whered the mass, energy and time come from?
Third point: Whered the information come from. It's one thing to postulate that this is just how chemicals act when aligned this way.. But, they don't just align this way by themselves.
You took a choo choo and a coal car and proved that the man in the coal car shovels caol into the engine. You haven't explained the engine, the car or the guy, much less how they know to do what they do. You observed something - that is science. Once you start down the trail of fictions you leave what we know and enter the world of Stephen King.
normal and legitimate placemarker
Well, on another thread I thought there were.
I had posted half a score of what I thought were my funniest; hoping to get a laugh.
But, no pun in ten did.
Another Scriptural admonition!
Genesis 9:7
As for you, be fruitful and increase in number; multiply on the earth and increase upon it."
(I do you, however, that the amount of Conservitives would increase, instead...)
And I previewed this!!!
Try.
(I do wish you, however, that the amount of Conservi atives would increase, instead...)
COFFEE!!
Coffee
Where's my coffee????
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