Cornell NEMS device Weighs a Single DNA Molecule

karvind writes "Cornell researchers have refined their NEMS device to detect a single DNA molecule and can even count the number of DNA molecules attached to a single receptor by noting the difference in mass. The researchers used the Cornell Nanoscale Facility to create arrays of tiny cantilever oscillators 3 to 5 microns long and 90 nanometers thick on silicon chips. The principle underlying the mass-detection devices is that the frequency at which a solid object vibrates varies with its mass. In the reported experiments, the change in mass of 1 attogram was enough to shift the frequency of vibration by 50 Hz or more, depending on the size of the oscillator. This allowed the researchers not only to detect the binding of DNA molecules, but also to count the number of molecules attached to a single receptor by the total frequency shift. Results are reported in the latest issue of Nano Letters. " (Here's an earlier Slashdot story about weighing molecules by Caltech Researchers.)

Comments

Question

[RaffiRai]

I'm not trolling, because I really want to know. How can we benefit from being able to weigh things that small? I always assumed that stoichiometry was there to get around having to weigh very very small things.

Re:Question

[karvind]

Like any scientific endeavor, the journey is as important as the final goal. Many new techniques and ideas come along to put the whole picture together. So even if a practical realization of this technique may not be feasible, the learning (from the experiments and theory) will be useful.

PhysOrg (Article on Caltech's work on weighing molecules) has comment about the possible applications:

The new method might ultimately permit the creation of microchips, each possessing arrays of miniature mass spectrometers, which are devices for identifying molecules based on their weight. Today, high-throughput proteomics searches are often done at facilities possessing arrays of conventional mass spectrometers that fill an entire laboratory and can cost upwards of a million dollars each, Roukes adds. By contrast, future nanodevice-based systems should cost a small fraction of today's technology, and an entire massively-parallel nanodevice system will probably ultimately fit on a desktop.

Hmmm. Interesting.

[jd]

Since they know the structure and the number of base pairs in an average molecule, they aught to be able to calculate what the weight should be, as they know the ratios of the isotopes and the mass of the individual atoms.

It would be interesting, therefore, to know if you can get a feel for the variance in the DNA makeup by measuring the varince in mass from the expected value. It would certainly be quicker than mapping each strand out in turn.

Or would that be doing something useful with this technology, rather than just showing off?

Little Names

[Doc Ruby]

The device is 3-5 microns wide, which is "micro". But it's 90 nanometers thick, which is "nano". So is a device's scale magnitude named for its "smallest" feature, when it's smaller than "mesoscale" (1 meter), and for its largest, when larger? And since we've been saying "micrometer" too long, so we say "micron" instead, can we start saying "nanon" already? What will we call an orbital solar collector (especially if it's also a "positive fuelcell") that's 10 nanons thick, but 10Km across - nanotech, or megamachine?

A nice little virus/cancer detector

[UnapprovedThought]

From the article:

...they built one that could sense the presence of a single virus -- about 1.5 femtograms. Now, with a refined technique, they have detected a single DNA molecule...

In the reported experiments, the change in mass of 1 attogram was enough to shift the frequency of vibration by 50 Hz or more, depending on the size of the oscillator.

Background: Molecules vibrate at distinctive frequencies as limited by their bonds and as decided by their atomic weights. The higher the temperature, however, the faster the frequency of vibration. Once the temperature goes high enough, the atoms are vibrating so energetically that they may separate from the molecule they are currently attached to, beginning a chemical reaction.

Their measurement technique appears to use the frequency shift of a laser of a known frequency passing (through?) the material being measured to an array of detectors that each detect a different frequency. The shift in frequency from the original as caused by the molecule then determines the weight.

So, is the measurement dependent on an exact lab controlled temperature, or can a measuring device work in environments where the temperature may vary?

Specifically, could the device already be implanted in the bloodstream to accurately detect specific viruses or cancer DNA by weight, or would it need more work to adjust for temperature variations?

Also, I might as well ask, is bombarding DNA with lasers harmful?

oh, come on.

[jwriney]

This is easy. Haven't you ever weighed a dog?

Step 1: Step on scale. Record your weight.
Step 2: Step on scale *carrying one DNA molecule*. Record collective weight.
Step 3: Subtract.

--riney