Electrospray ionization has recently emerged as a powerful technique for producing intact ions in vacuo from large and complex species in solution. To an extent greater than has previously been possible with the more familiar "soft" ionization methods, this technique makes the power and elegance of mass spectrometric analysis applicable to the large and fragile polar molecules that play such vital roles in biological systems. The distinguishing features of electrospray spectra for large molecules are coherent sequences of peaks whose component ions are multiply charged, the ions of each peak differing by one charge from those of adjacent neighbors in the sequence. Spectra have been obtained for biopolymers including oligonucleotides and proteins, the latter having molecular weights up to 130,000, with as yet no evidence of an upper limit.

https://science.sciencemag.org/content/sci/246/4926/64.full.pdf

Electrospray ionization for mass spectrometry of large biomolecules

Recent successes illustrate the role of mass spectrometry-based proteomics as an indispensable tool for molecular and cellular biology and for the emerging field of systems biology. These include the study of protein-protein interactions via affinity-based isolations on a small and proteome-wide scale, the mapping of numerous organelles, the concurrent description of the malaria parasite genome and proteome, and the generation of quantitative protein profiles from diverse species. The ability of mass spectrometry to identify and, increasingly, to precisely quantify thousands of proteins from complex samples can be expected to impact broadly on biology and medicine.

Mass spectrometry-based proteomics

https://link.springer.com/content/pdf/10.1016/1044-0305(94)80016-2.pdf

An approach to correlate tandem mass spectral data of peptides with amino acid sequences in a protein database.

FLICE, a novel FADD-homologous ICE/CED-3-like protease, is recruited to the CD95 (Fas/APO-1) death--inducing signaling complex.

A new method of desorption ionization is described and applied to the ionization of various compounds, including peptides and proteins present on metal, polymer, and mineral surfaces. Desorption electrospray ionization (DESI) is carried out by directing electrosprayed charged droplets and ions of solvent onto the surface to be analyzed. The impact of the charged particles on the surface produces gaseous ions of material originally present on the surface. The resulting mass spectra are similar to normal ESI mass spectra in that they show mainly singly or multiply charged molecular ions of the analytes. The DESI phenomenon was observed both in the case of conductive and insulator surfaces and for compounds ranging from nonpolar small molecules such as lycopene, the alkaloid coniceine, and small drugs, through polar compounds such as peptides and proteins. Changes in the solution that is sprayed can be used to selectively ionize particular compounds, including those in biological matrices. In vivo analysis is demonstrated.

https://science.sciencemag.org/content/sci/306/5695/471.full.pdf

Mass Spectrometry Sampling Under Ambient Conditions with Desorption Electrospray Ionization

L'effluent de chromatographie en phase liquide projete electrostatiquement dans un bain de gaz froid cree une dispersion de gouttelettes chargees qui s'evapore rapidement. Lorsque les gouttelettes deviennent plus petites, l'augmentation de la densite de charge superficielle et la baisse du rayon de courbure creent un champ suffisamment fort pour desorber les ions du solute. Une partie passe a travers un canal et forme un jet libre supersonique, puis passera dans l'analyseur de masse

Electrospray interface for liquid chromatographs and mass spectrometers.

Electrospray Ionization for Mass Spectrometry of Large Biomolecules

A method of changing the energy of charged particles contained in a gas comprises allowing the gas to flow into a region of reduced pressure through a tube like member so that viscous forces exerted on the charged particles by the flowing gas molecules determine the kinetic energy of the charged particles. A potential gradient is maintained along the length of the tube so that the potential energy of the charged particles is changed as they pass through the tube. At the end of the tube a free jet expansion occurs so that the kinetic energy of the charged particles is no longer determined by the flowing gas, so that they can be accelerated to any desired kinetic energy by means of another potential gradient. The invention can be used to interface any high pressure ion source to a magnetic sector mass spectrometer, or to permit the operation of an electrospray ion source with an earthed inlet capillary with either a quadrupole or a magnetic sector mass spectrometer.

Process and apparatus for changing the energy of charged particles contained in a gaseous medium

The subject invention teaches the use of mechanical vibration to enhance the electrostatic dispersion of sample solutions into the small, highly charged droplets that can produce ions of solute species for mass spectrometric analysis. Such vibration turns out to be surprisingly effective as ultrasonic frequencies for solutions with flow rates, conductivities and surface tensions too high for stable dispersion by electrostatic forces alone as in conventional electrospray ionization. Several embodiments of the invention are described for purposes of illustration. Other possible embodiments will become apparent to those skilled in the art.

Craig M. Whitehouse

Papers

Electrospray ionization for mass spectrometry of large biomolecules

Electrospray interface for liquid chromatographs and mass spectrometers.

Electrospray Ionization for Mass Spectrometry of Large Biomolecules

Process and apparatus for changing the energy of charged particles contained in a gaseous medium

Method and apparatus for improving electrospray ionization of solute species