fluorescent labelling


New Technique Lets Scientists See Through Whole Organisms

by Michael Keller

Seeing is believing when it comes to understanding how organisms work. For biologists trying to learn about what’s going on inside a body, one of the biggest obstacles is not being able to put their eyeballs on a part or system without other objects getting in the way. The answer is usually going in with one invasive tool or another, which ends up damaging or destroying the thing they’re trying to investigate. 

Now California Institute of Technology scientists say they have improved upon a solution to clearing up the picture. The technique builds on work that garnered widespread attention last year. In that effort, assistant professor of biology Viviana Gradinaru and her team used detergent and a polymer to make a rodent brain transparent for study in unprecedented detail. 

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I wonder which is preferable, to walk around all your life swollen up with your own secrets until you burst from the pressure of them, or to have them sucked out of you, every paragraph, every sentence, every word of them, so at the end you’re depleted of all that was once as precious to you as hoarded gold, as close to you as your skin - everything that was of the deepest importance to you, everything that made you cringe and wish to conceal, everything that belonged to you alone - and must spend the rest of your days like an empty sack flapping in the wind, an empty sack branded with a bright fluorescent label so that everyone will know what sort of secrets used to be inside you?
—  Margaret Atwood
Identifying DNA/RNA

beatrixcendana - There are two methods to identify nucleic acids. One is a simple agarose gel electrophoresis where you use a molecular weight marker to determine the size fragment of a piece of DNA/RNA. This doesn’t tell you the identity of the nucleic acid fragment but it is a cheap way to confirm you’re on the right track. If you know your band is supposed to be 400 base pairs and your fragment is at 900 base pairs, you know something is wrong.

The way to identify a nucleic acid sequence is by using a Southern (for DNA) or northern (for RNA) blot to probe your sample with a fluorescently or radioactively labeled strand of the complementary sequence. This tells you that the particular nucleic acid sequence is present in your sample. There is also a western blot (for proteins) which is similar, but an antibody is used to probe the sample. There is no eastern blot although it is an ongoing joke amongst molecular biologists.

If you don’t know what you’re trying to find, e.g. cloning and sequencing a novel gene, you can use chromatography to identify the sequence.

Breaking The Supposed Limit In Seeing The Microscopic World Earns Three Chemistry Nobel

by Michael Keller

Three researchers were awarded the 2014 Nobel Prize in Chemistry today for breaking through what was thought to be an absolute optical limit in seeing microscopic objects like viruses and molecules.

The Nobel committee responsible for deciding the winners chose to honor the separate work of two Americans, Eric Betzig and William Moerner, and German Stefan Hell. These scientists pioneered what is called super-resolved fluorescence microscopy, which has opened up a whole new frontier for understanding how life works at the nanoscale. (Txchnologist has previously featured more of Betzig’s groundbreaking work here.)

“I was sitting in my office when the call from Stockholm reached me,” said Hell, who is the director of the Max Planck Institute for Biophysical Chemistry. “I am enormously gratified that my work and that of my colleagues has received the highest distinction for scientific research."  

Their innovations, using light to excite molecules that have been tagged with fluorescent markers, are now being used around the world. They are letting researchers use visible light to glimpse separate objects that are closer together than what was thought to be the limit of 0.2 microns.  This minimum is called the Abbe diffraction limit, which is half the length of the wavelength of the light used to see something through a microscope.

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