|Single-Molecule Mass Spectrometry enabled by Nanoelectromechanical Systems (NEMS-MS)|
We are working with nano-machines sensitive enough to interface with the world of proteins and biomolecules
Why is this important? Basically...
The first item above deserves a more detailed observation... See the bottom of the page for a fuller explanation on the importance and context of protein detection.
What is the current state of art?
We have just finished performing a proof of principle experiment of the protein mass detection using a single NEMS device. The schematics of the experiment, the simplified circuit for the measurement and the device micrograph are shown in the figures. We use a commercial electrospray ionization system to produce the ionized protein in the gas phase. These proteins, generated at room temperature and atmospheric pressure, are then transported to the NEMS, located about 2 meters away, using a ion guiding system. The NEMS is placed about 5mm from the end of the ion guiding system. The NEMS temperature is maintained at 40K to ensure physioadsorprtion of the proteins. Each protein that lands on the NEMS produces a change in the resonant frequency. The change in frequency of the NEMS is a function of the mass of the protein and its position along the length of the NEMS. These changes in the resonant frequency of the NEMS are tracked using a phase locked loop.
You can read about our latest research in reference (1)
What are we working on right now?
We are working on making these devices even more sensitive, in a systematic, repeatable way. We are rushing to develop techniques to detect both position and mass of the added proteins. We are collaborating with LETI to fabricate an array of these devices on the same chip.
What advantages does our method have over other protein detection methods, namely mass-spectrometry?
Conventional mass spectrometry is a great technological success, cultivated through decades of scientific progress. Mass spectrometers are basically a family of instruments that measure electromagnetic properties of ionized bio-molecules thus determining their mass-to-charge ratios (unlike NEMS based MS). You can read about different kind of mass spectrometers and their working principles here: http://masspec.scripps.edu/
In order to make a useful measurement to obtain biologic information, mass spectrometers have a multitude of performance criteria, which includes for example: mass resolution, mass accuracy, detection limit, sample consumption, data acquisition rate, possession cost, operation cost, calibration requirement...
No mass spectrometer in existence is perfect. All of them have positive sides, as well as negative sides. Within this spectrum of instruments, our nano-mechanics based approach have the following unique capabilities:
References and Related Papers
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