Towards Single-Molecule Nanomechanical Mass Spectrometry

Citation

Hanay, Mehmet Selim (2011) Towards Single-Molecule Nanomechanical Mass Spectrometry. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z9JW8BVH. https://resolver.caltech.edu/CaltechTHESIS:06022011-092614335

Abstract

We present an initial attempt to perform mass spectrometry (MS) of single proteins and gold nanoparticles with nanoelectromechanical systems (NEMS). Mass spectrometry, the identification of molecules based on their masses, is one of the most important techniques in proteomics research currently. NEMS devices, with their exquisite sensitivities, low costs, and abilities to detect neutral molecules, offers a promising paradigm for performing mass spectrometry.

In our first-generation experiments, protein molecules, and gold nanoparticles were ionized by electrospray ionization (ESI) and transported to a NEMS chip, through a differential vacuum system, by hexapolar ion guides. NEMS was transduced by magnetomotive technique and the fundamental mode of the flexural resonance was monitored. Species landing on the NEMS are weighted through the change in the frequency of the resonator. Two protein species (66 kDa and 200 kDa) and 5 nm gold nanoparticles were analyzed with this technique, with mass resolution level of 15 kDa.

A method to remove the position dependency of the frequency shift was developed employing two different modes of a nanomechanical beam. The uncertainties of mass and position values are calculated as a function of the frequency noise of the first and second modes of the beam.

In our second-generation experiments, the first and second flexural modes of a doubly-clamped beam were tracked in real time. Nanoparticles and biospecies are again produced through ESI and transported through ion optics. The adsorption of 10 nm GNPs and IgM protein (950 kDa) were observed. Mass values for these events are obtained with the multimode analysis technique and shown to be consistent with the expected values.

Thesis Files