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)
I prefer Benjamin Franklin as attributed:
"Beer is proof that God loves us and wants us to be happy." :-)
and my corollary:
"Hangovers prove we are a fallen race." :-(
Fortran forever!
...oh, and vi too. :-)
Roughly as interesting as watching a drunk trying to cross a busy intersection, and for the same reason.
How about this ?
"Perhaps in matters of formal logic, yes, arguments from incredulity hold no water. But science is not pure, formal logic, nor does it need to use formal logic in order to be "scientific."
And then,
"Much good science is born of hunches, as well as logical fallacies."
Uncle Fester is a well that never runs dry. :)
The chip sets in your computer don't add to your knowledge of the universe?
When my lab partner dropped our photographically etched silicon wafer attempt to create a diode ( required to get credit in this semiconductor EE class ), and it disintegrated in the ultrasound bath and we had to start all over again, I didn't think it added significantly to my knowledge of the universe, but it did add to my knowledge.
But if you actually dig a bit deeper, you'll run into other stuff...
The quote "One is either a German or a Christian, you cannot be both" (which the Brits turned into a propaganda poster juxtaposed with a photo of bombed-out city buildings...)
The contents of some Nazi-era school textbooks, with nice lines like "Jesus and Hitler were both persecuted; but while Jesus was crucified, Hitler went on to become chancellor"
The persecution of the Jews (read up on the Old Testament promises to Abraham about how God expected the Jews to be treated; or the New Testament writings of Paul about the Jews being subjected to a temporary hardening of their hearts, in order that God show mercy on goyim as well :-)
etc.
The cheap shots are unbecoming of you...
Cheers!
It's truly an art form to cram so much that is so wrong into so few words.
700 x 1000 = 7.0 x 105
How much time do you spend on these threads?
OK, fair enough as far as it goes.
But he was so intelligent anyway, that he could probably wipe the floor with most of the people on this thread in mathematics.
By analogy Randy Johnson's off-speed pitches are still faster than what most people on this thread could manage to throw; even though they're not fast "for him".
More details? I was quoting a contemporary British propaganda poster; and was unaware of the quote as being connected to any research on Hitler, controversial or otherwise.
Cheers!
Takes many "years" of education to accomplish such feats. :-)
But he was so intelligent anyway, that he could probably wipe the floor with most of the people on this thread in mathematics.
By analogy Randy Johnson's off-speed pitches are still faster than what most people on this thread could manage to throw; even though they're not fast "for him".
OK. But Einstein admitted he needed help with the math for his theories and sought it from his contemporaries.
If Randy is smart, he's done the same. He may have natural talent, but I'd guess he'd be the first to say his coaches have helped him immensely.
Will have to see--if I ever find the time--if there are other sources for the quote about "either a German or a Christian."
Cheers!
Anyone who thinks mathematics is not science is a dope...
That is the whole point of while you are here to begin with, isn't it? You are here to bash the religionists.
It only frustrates you that it doesn't work with an atheist. Of course, since I am an equal opportunity secularist: I take shots at atheists too, because some of you are no better, and most often times worse, than the godists.
Ad hominem - - latin - - to the man....
_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-
By insulting anyone who disagrees with you...
argumentum misericordian - - latin - - appeal to sympathy
Go get a tissue...
Were some QM events not random, we wouldn't be having this discussion. (At least not using a semi-conductor based device.)
Anyone who thinks mathematics is not science is a dope.
Then you are a dope. Math is abstract. Science attempts to describe reality. Ignoring left-wing postmodern decontrunctionist hypothesis' of reality (I'm guessing you don't subscribe to these), Science is not abstract. Math is a tool used by science to describe reality.
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