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.

Electrospinning is a highly versatile method to process solutions or melts, mainly of polymers, into continuous fibers with diameters ranging from a few micrometers to a few nanometers. This technique is applicable to virtually every soluble or fusible polymer. The polymers can be chemically modified and can also be tailored with additives ranging from simple carbon-black particles to complex species such as enzymes, viruses, and bacteria. Electrospinning appears to be straightforward, but is a rather intricate process that depends on a multitude of molecular, process, and technical parameters. The method provides access to entirely new materials, which may have complex chemical structures. Electrospinning is not only a focus of intense academic investigation; the technique is already being applied in many technological areas.

Electrospinning: A Fascinating Method for the Preparation of Ultrathin Fibers

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

Solutions passed through a small capillary at 2-10 kV relative to ground are electrosprayed into a bath gas to form a gaseous dispersion of ions that is expanded into vacuum in a small supersonic free jet A portion of the jet is passed through a skimmer to form a molecular beam that contains a variety of ionic species Mass spectrometric analysis reveals that these species include solute cations in aggregation with solvent molecules and/or nonionized solute species The nature of the product ions depends upon the composition and feed rate of the original solution, the temperature and composition of the bath gas, and the voltage applied to the capillary The exploratory experiments reported here suggest that this novel ion source may be useful for producing in vacuo a wide variety of cluster ions for examination by various spectroscopic techniques Also inviting is the prospect of extending the applicability of mass spectrometric analysis to large organic molecules that are too complex, too fragile, or too nonvolatile for ionization by more conventional methods Another intriguing possibility is to use the technique on probing the microscopic structure and properties of solutions

Electrospray ion source: another variation on the free-jet theme

Chemistry has its origins as a quantitative science in the careful weighing of products and reactants by Lavoisier and his followers beginning some 200 years ago. Ever since then, the constantly evolving gravimetric balance has been a faithful servant of the laboratory chemist and has played a major role in developing the analytical methods that are the foundation of contemporary chemical science. Perhaps the ultimate stage in the evolution of that balance is represented by the modern mass spectrometer. It is able to determine with high precision the masses of individual atoms and molecules by transforming them into ions and measuring the response of their trajectories in vacuo to various combinations of electric and magnetic fields. Clearly, the sine qua non of such mass determination is the transformation of analyte atoms and molecules from their initial state in a sample to ions in vacuo ready for ”weighing.” Over the years, ingenious investigators have produced a variety of methods for achieving this transformation. One of them, electrospray ( E S ) ionization, has recently shown itself capable of producing intact ions, with multiple charges, from remarkably large, complex, and fragile parent species. Our assignment here is to review what has thus far been learned about this still uncommon technique and what it seems able to offer practitioners of mass spectrometric analysis. Our approach will be to set forth the present state of the ES ionization art in terms of a sort of menu of its procedures, processes, performance, and promise. Until very recently we have been almost the only group that has worked with ES ionization since the pioneering efforts of Malcolm Dole (1) some 20 years ago. Consequently, this review is more tutorial than most. Moreover, it may seem like a cook book that is overly preoccupied with the authors’ own culinary adventures. The reasoil is that many of the dishes to be described were first tried out in our own kitchen. Therefore, we earnestly urge the reader to remember what every gourmet knows: the piquancy of any dish on a bill of fare is due much less to its ingredients than to the skill of the chef whc. prepares it.

Electrospray ionization–principles and practice

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

John B. Fenn

Papers

Electrospray ionization for mass spectrometry of large biomolecules

Electrospray ion source: another variation on the free-jet theme

Electrospray ionization–principles and practice

Electrospray interface for liquid chromatographs and mass spectrometers.

Electrospray Ionization for Mass Spectrometry of Large Biomolecules