Chemistry World - 3D TV, Biofuel Debt and Reading RNA

10 February 2008

Interview with 

Mark Peplow, Chemistry World


Chris - Time to catch up with the editor of Chemistry world. That's Mark Peplow. Hello Mark.

Mark - Hello Chris.

Chris - 3D television, sounds fantastic, even on the radio!

Hologram installation at MIT MuseumMark - It does sound fantastic.  It's not quite around the corner but the first major step has been taken towards it.  We're all used to this idea of being able to have a hologram where you can effectively get this image which gives you the illusion of three dimensions.  You can look around this object.  A group of scientists from the University of Arizona have now managed to make that hologram and then found away to erase and rewrite it with a new image.  In theory if you can do that frequently enough you can actually get a moving three dimensional film.  The way that they do this relies on a special type of polymer.  What happens when you're taking a holographic image, laser beams bounce off this object from different angles. Where they bounce back and recombine they hit this light sensitive polymer and it stores the 3D signal in a complex pattern of interference.  They've tweaked the polymer that they use with a special dye molecule and found that as long as they put an electric field across it, it means that the dye molecules are shifted, rotated if you like when the laser light hits them.  That means that it takes them about three minutes to draw a full image and then another blast of full laser light resets the molecules ready for the next image to be written.

Chris - Three minutes, that's not a very fast frame rate if I'm honest.

Mark - I know. I guess the crucial thing about this is that it's a proof of principal that it can be done at all.  We talked to a hologram chemistry expert called Kevin Davidson who's at the University of Cambridge here.  He pointed out that there's a lot of work gone on in this area but no one's really demonstrated this ability to do this so reliably and at least repeat time after time.

Chris - So it's gonna be a little while before we can play a game of chess like they do on Star Wars with those kind of figures that act it out on the board for us.

Mark - Yes, absolutely, although that would be cool, wouldn't it.

Chris - I can't wait for those days actually.  What's this about biofuels and carbon debts?

Mark - Yeah, biofuels have been getting a rough ride lately.  The Royal Society which is Britain's major academy of sciences has put out some major warnings recently.  About policy makers rushing too quickly to adopt new biofuel policies.  The idea is that rather than burning petrol which we get from oil out of the ground it would be better to get fuel for the car from plants.  Plants grow by sucking carbon dioxide out of the atmosphere and we're trying to reduce the amount of carbon dioxide we're putting out to reduce the rate of global warming.

Chris - That's good isn't it?  You want the plants to take the CO2 out of the atmosphere and turn them into fuel so there's no net carbon gain.  Why should there be a problem with that?

Mark - Absolutely.  The devil is in the detail as with all of these things.  As people have started to grow more and more biofuels, a good example is sugar cane in Brazil where they turn that into fuel for cars (ethanol), people are doing what's called lifecycle analysis.  They're basically looking at all of the energy that you need to put in to make these fuels and also look at all of the carbon that comes out when you're making these fuels.  The latest pair of studies which was just published in Science magazine on Friday really paints a very damning picture.  Effectively when you cultivate land to grow any biofuel you rack up this carbon debt.  You're releasing so much carbon that was trapped in the soil that it can take sometimes centuries to regain and repay that carbon debt through the advantages of using biofuels.

Chris - So the moral of this story is there's no quick fix, is there?

Mark - Absolutely.  It's interesting because people usually talk about the Brazilian example of using sugar cane as probably the best biofuel to use.  They've found it still took 17 years to repay the carbon taken from when, for example, a random tract of savannah was ploughed up to plant that stuff.

Chris - So there's lots and lots of things to consider rather than just the here and now.  What's this about reading the genetic code directly because this sounds amazing!

Mark - Yeah.  This sounds like really Star Trek stuff and it's really exciting actually.  We're all used to this idea of DNA fingerprinting.  This relies on a chemical reaction called the polymerase chain reaction.  What that means is you have this smear of blood that you find in CSI, there will be millions and millions of molecules of DNA in there but still not enough to get an exact chemical read on the data that's recorded in that DNA.  You have to do this reaction that amplifies the DNA sample by multiplying the molecules over and over again in the sample until you've got enough to do a proper analysis.

Now, that takes a laboratory, it takes time and it can introduce errors.  A group in Dortmund in Germany have found a way.  They've proved a principal that they can read a single molecule of not DNA but its chemical cousin RNA using a device which is a special combination, basically, of two different techniques.  What it looks like, really is a tiny, tiny record player needle where the tip of it is just 20nm across.  It's hooked up to a laser.  What happens is that the tip reads along the length of a single molecule of RNA and guides the laser as it goes.  The laser will illuminate the section of the molecule and the light that comes back carries the characteristic signature of the chemical bases as they're called which holds the data in RNA.  They've proved that although the laser blast will illuminate maybe half a dozen bases at once because the tip moves along it one base at a time.  They can literally read along and show that as they move this tip along they can read each base as it comes along.  At the moment this requires some big bits of kit and it's pretty time consuming but it shows that you can read this single molecule of genetic code.  Because of the advances that have come along in these techniques it means that over the coming years it should get faster, cheaper and easier.

Chris - It's amazing to think how far we've come because you say it's big and bulky but then so was the polymerase chain reaction when we first started.  Thank you for coming in, Mark.


Add a comment