Navigate Flying Molecular Elephants Safely to the Ground: Mass-Selective Soft Landing up to the Mega-Dalton Range by Electrospray Controlled Ion-Beam Deposition

Abstract

The prototype of a highly versatile and efficient preparative mass spectrometry system used for the deposition of molecules in ultrahigh vacuum (UHV) is presented, along with encouraging performance data obtained using four model species that are thermolabile or not sublimable. The test panel comprises two small organic compounds, a small and very large protein, and a large DNA species covering a 4-log mass range up to 1.7 MDa as part of a broad spectrum of analyte species evaluated to date. Three designs of innovative ion guides, a novel digital mass-selective quadrupole (dQMF), and a standard electrospray ionization (ESI) source are combined to an integrated device, abbreviated electrospray controlled ion-beam deposition (ES-CIBD). Full control is achieved by (i) the square-wave-driven radiofrequency (RF) ion guides with steadily tunable frequencies, including a dQMF allowing for investigation, purification, and deposition of a virtually unlimited m / z range, (ii) the adjustable landing energy of ions down to ∼2 eV/z enabling integrity-preserving soft landing, (iii) the deposition in UHV with high ion beam intensity (up to 3 nA) limiting contaminations and deposition time, and (iv) direct coverage control via the deposited charge. The maximum resolution of R = 650 and overall efficiency up to T total = 4.4% calculated from the solution to UHV deposition are advantageous, whereby the latter can be further enhanced by optimizing ionization performance. In the setup presented, a scanning tunneling microscope (STM) is attached for in situ UHV investigations of deposited species, demonstrating a selective, structure-preserving process and atomically clean layers.

A Preparative Mass Spectrometer to Deposit Intact Large Native Protein Complexes

“…Here, using low gradients, the E tot distribution (FWHM per charge) is sharper than previously reported literature values (FWHM per charge), ,,, pointing to gentle conditions in which gas-phase activation is minimal. Given that the lower gradient conditions also achieved high transmission and good beam focus, we retained them for all other experiments presented here.…”

“…Electrospray ion beam deposition (ES-IBD) is a preparative mass spectrometry , technique, capable of producing highly purified molecular samples for single molecule imaging. It is routinely used for SPM with smaller (bio)­molecules ,− and has been demonstrated also for TEM, − LEEH, , and recently cryo-EM. , In contrast to organic molecular beam epitaxy (OMBE), , ES-IBD is not limited to small and volatile molecules. In ES-IBD, molecules are ionized in an electrospray ion source, transferred into the gas phase, and mass-analyzed in a vacuum.…”

Optimization of a Digital Mass Filter for the Isolation of Intact Protein Complexes in Stability Zone 1,1

“…Using digital waveforms, the stability diagram can be manipulated by changing the duty cycle to move stability zones to a = 0. , This removes the requirement for scanning the DC voltage to perform ion isolation in a mass filter. By removing the necessity for generating very high voltages, high mass-to-charge ions can be readily detected. − …”

Influence of surface and intermolecular interactions on the properties of supported polyoxometalates

“…Ion soft landing (ISL) is a versatile technique that facilitates the preparation and modification of homogeneous films of mass-selected polyatomic ions in predetermined charge states through controlled deposition of gas-phase ions onto surfaces. [13][14][15][16][17][18][19][20][21] This distinguishing capability allows supported ions to be investigated in the absence of interference from counterions, solvent molecules, and other impurities that are present at interfaces prepared using solution based deposition. 22,23 In addition, soft landed ions are deposited without aggregation and crystallite formation.…”