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Prions, Pruisner argued, were proteins that were found normally in the brain - but with a twist. These proteins had somehow folded themselves into a new shape, and could induce normal proteins that they bumped into to link up and refold themselves as well. In this way, the prion could itself spread through the brain, converting normal proteins into aberrant ones, and eventually causing damage to brain tissue. Other researchers didn't necessarily buy the theory, however. Some claimed that there was no evidence that prions existed at all. Others admitted their existance, but did not understand how something that contained no genetic material could possibly reproduce or cause disease. And others still felt that while the prion might be able to cause disease, they were only able to do so as a "co-factor" - the changed prion somehow activated some other hidden virus or other infectious agent. Now, 15 years later, Prusiner's theory has held its ground. Some people still shun it - but in an impressive show of support, this week the Nobel Prize committee awarded Prusiner this year's prize in medicine. Even more dramatically, it awarded the prize soley to Prusiner, with no co-recipient, an honor that has not been given for over 10 years (and only six times in the past 40 years). On this segment of Science Friday, guest host Joanne Silberner will look at the work of Dr. Prusiner, and talk about controversy and consternation it has caused. Then... building normal proteins. A group of biologists at California Institute of Technology have developed a method for building proteins from scratch - a technique that's significant because nature depends on proteins to build many, many things. The long, complexly folded chains of amino acids are essential to the building of cells. Human skin and nails are composed of proteins, as are enzymes. Animal muscle tissue and eggs are largely made up of proteins. The shape of the protein is as important (if not more important) than the exa ct sequence of atoms making up the molecule. Each short amino acid sequence twists and folds differently depending on what other acids are near it and what kind of solution the molecule is in. When amino acids are strun g together to form a protein, which often can contain over a hundred amino acids, the combined folding and kinking makes the end shape of the protein very difficult to predict. Even a short protein fragment, like the 28-amino acid chain that the Caltech researchers produced, has over 1.9 x1027 possible configurations. To give them an instruction booklet for their molecular tinkertoys, the team created a computer alg orithm based on over 20 years worth of data about the way that proteins fold in different environments. That algorithm, when allowed enough time to crunch numbers, can predict the best sequence of amino acids needed to build a protein with a desired shape. Using that information, the researchers were able to use existing techniques to actually build a protein piece that matched the computer's predictions very closely. The researchers hope that their techniques can be extended to larger and larger proteins, needing only more computing time and power to handle the larger number of permutations. How did they do it? And what might scientists be able to do with the power to build protein molecules to their own specifications? Join guest host Joanne Silberner as she takes a look at the art and science of molecular protein design.
Guests: Fred Cohen David Perlman Steve Mayo Bassil I. Dahiyat Books/Articles Discussed:
Related links: A press release dealing with the prize, from UCSF, Prusiner's home. Dr. Prusiner's article in the current issue of Science A Prusiner article on prions from January, 1995's Scientific American "What is a prion?" from Scientific American's Ask an Expert page All you ever wanted to know about Mad Cow Disease, prions, and their link to human disease. Caltech press release on the discovery with pictures and additional links |
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