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Justin M Wiseman

Publications and source records attributed to Justin M Wiseman.

12 recordsLinked to original sources
PubMed2006

Detection Technologies. Ambient mass spectrometry.

A recent innovation in mass spectrometry is the ability to record mass spectra on ordinary samples, in their native environment, without sample preparation or preseparation by creating ions outside the instrument. In desorption electrospray ionization (DESI), the principal method described here, electrically charged droplets are directed at the ambient object of interest; they release ions from the surface, which are then vacuumed through the air into a conventional mass spectrometer. Extremely rapid analysis is coupled with high sensitivity and high chemical specificity. These characteristics are advantageously applied to high-throughput metabolomics, explosives detection, natural products discovery, and biological tissue imaging, among other applications. Future possible uses of DESI for in vivo clinical analysis and its adaptation to portable mass spectrometers are described.

Animals↗
PubMed2006

Coupling desorption electrospray ionization with ion mobility/mass spectrometry for analysis of protein structure: evidence for desorption of folded and denatured States.

A desorption electrospray ionization (DESI) source has been coupled to an ion mobility time-of-flight mass spectrometer for the analysis of proteins. Analysis of solid-phase horse heart cytochrome c and chicken egg white lysozyme proteins with different DESI solvents and conditions shows similar mass spectra and charge state distributions to those formed when using electrospray to analyze these proteins in solution. The ion mobility data show evidence for compact ion structures [when the surface is exposed to a spray that favors retention of "nativelike" structures (50:50 water:methanol)] or elongated structures [when the surface is exposed to a spray that favors "denatured" structures (49:49:2 water:methanol:acetic acid)]. The results suggest that the DESI experiment is somewhat gentler than ESI and under appropriate conditions, it is possible to preserve structural information throughout the DESI process. Mechanisms that are consistent with these results are discussed.

Absorption↗
PubMed2006

Desorption electrospray ionization mass spectrometry for the analysis of pharmaceuticals and metabolites.

The performance of desorption electrospray ionization (DESI) in the analysis of a group of pharmaceuticals and their glucuronic acid conjugates is reported. The suitability of different sprayer solvents and different surfaces was examined. In the positive ion mode, water/methanol/trifluoroacetic acid performed best, whereas, in the negative ion mode, water/methanol/ammonium hydroxide was found to be the most suitable spray solvent. Of the surfaces investigated, polymethylmethacrylate (PMMA) was found to give the best performance in terms of sensitivity. Spray solution flow rate and the distance of the sprayer tip from the surface were also found to have significant effects on the signal intensity. Analytes with basic groups efficiently formed the corresponding protonated molecules in the positive ion mode, whereas acidic analytes, such as the glucuronic acid conjugates, formed intense signals due to the deprotonated molecules in the negative ion mode. Ionization of neutral compounds was less efficient and in many cases it was achieved through adduct formation with simple anions or cations.

Molecular Structure↗
PubMed2005

Ambient mass spectrometry using desorption electrospray ionization (DESI): instrumentation, mechanisms and applications in forensics, chemistry, and biology.

Analytical characteristics of DESI are summarized. Examples of applications to small and large molecules, to in situ analysis, and to high-throughput analyses are presented. Evidence is provided for both a heterogeneous charge-transfer mechanism and a droplet pick-up mechanism of ionization. The speed, lack of the need for sample preparation, selectivity, and sensitivity of DESI are all demonstrated and discussed. Instrumentation is also discussed. Forensic applications as well as emerging areas of application including tissue imaging are given emphasis.

Animals↗
PubMed2004

Preparative linear ion trap mass spectrometer for separation and collection of purified proteins and peptides in arrays using ion soft landing.

A preparative mass spectrometer for microarray fabrication is reported. The instrument includes an atmospheric pressure ionization source, a linear ion trap mass analyzer, an ion collection surface positioning system, and a surface loading chamber with independent vacuum pumping. It was designed for the production of protein arrays using the ion soft-landing technique to collect ions on a surface after separation by mass/charge ratio. Small microarrays have been prepared by isolating and soft landing individual protein or peptide ions after electrospray ionization of mixtures. The composition and purity of the separated materials has been confirmed using independent external mass spectrometric analysis of rinse solutions of the collected spots, either by the new method of electrosonic spray ionization MS or by nanospray ionization MS. The ability to retain bioactivity in the mass-selected and collected biomolecules has been demonstrated in particular cases. The reported instrument has also been characterized as an analytical mass spectrometer.

Amino Acid Sequence↗
PubMed2004

Mass spectrometry sampling under ambient conditions with desorption electrospray ionization.

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.

Journal Article↗
PubMed2004

Electrosonic spray ionization. A gentle technique for generating folded proteins and protein complexes in the gas phase and for studying ion-molecule reactions at atmospheric pressure.

Electrosonic spray ionization (ESSI), a variant on electrospray ionization (ESI), employs a traditional micro ESI source with supersonic nebulizing gas. The high linear velocity of the nebulizing gas provides efficient pneumatic spraying of the charged liquid sample. The variable electrostatic potential can be tuned to allow efficient and gentle ionization. This ionization method is successfully applied to aqueous solutions of various proteins at neutral pH, and its performance is compared to that of the nanospray and micro ESI techniques. Evidence for efficient desolvation during ESSI is provided by the fact that the peak widths for various multiply charged protein ions are an order of magnitude narrower than those for nanospray. Narrow charge-state distributions compared to other ESI techniques are observed also; for most of the proteins studied, more than 90% of the protein ions can be accumulated in one charge state using ESSI when optimizing conditions. The fact that the abundant charge state is normally as low or lower than that recorded by ESI or nanospray indicates that folded protein ions are generated. The sensitivity of the ionization technique to high salt concentrations is comparable to that of nanospray, but ESSI is considerably less sensitive to high concentrations of organic additives such as glycerol or 2-amino-2-(hydroxymethyl)-1,3-propanediol (Tris base). Noncovalent complexes are observed in the case of myoglobin, protein kinase A/ATP complex, and other proteins. The extent of dissociation of protein ions in ESSI is comparable to or even smaller than that in the case of nanospray, emphasizing the gentle nature of the method. The unique features of ESSI are ascribed to very efficient spraying and the low internal energy supplied to the ions. Evidence is provided that the method is capable of generating fully desolvated protein ions at atmospheric pressure. This allows the technique to be used for the study of ion-molecule reactions at atmospheric pressure and examples of this are shown.

Atmospheric Pressure↗
PubMed2004

Ion soft-landing into liquids: Protein identification, separation, and purification with retention of biological activity.

Protein ions, after mass spectrometric separation, can be soft-landed into liquid surfaces with preservation of their native structures. Retention of biological activity is strongly favored in glycerol-based surfaces but not in self-assembled monolayer solid surfaces. Soft-landing efficiency for multiply-charged hexokinase ions was found to be some four times higher for a glycerol/fructose liquid surface than for a fluorinated self-assembled monolayer surface. Soft-landing into liquid surfaces is also shown to allow (1) protein purification, (2) on-surface identification of the soft-landed material using MALDI, and (3) protein identification by in-surface tryptic digestion. Pure lysozyme was successfully isolated from different mixtures including an oxidized, partially decomposed batch of the protein and a partial tryptic digest. Liquid glycerol/carbohydrate mixtures could be used directly to record MALDI spectra on the soft-landed compounds provided they were fortified in advance with traditional MALDI matrices such as p-nitroaniline and alpha-cyano-4-hydroxycinnamic acid. Various proteins were soft-landed and detected on-target using these types of liquid surface. Soft-landing of multiply-charged lysozyme ions onto fluorinated self-assembled monolayer surfaces was found to occur with a limited amount of neutralization, and trapped multiply-charged ions could be desorbed from the surface by laser desorption. Initial data is shown for a new approach to protein identification that combines top-down and bottom-up approaches by utilizing protein ion soft-landing from a protein mixture, followed by tryptic digestion of the landed material and detection of characteristic tryptic fragments by MALDI.

Amino Acid Sequence↗
PubMed2003

Preparing protein microarrays by soft-landing of mass-selected ions.

Intact, multiply protonated proteins of particular mass and charge were selected from ionized protein mixtures and gently landed at different positions on a surface to form a microarray. An array of cytochrome c, lysozyme, insulin, and apomyoglobin was generated, and the deposited proteins showed electrospray ionization mass spectra that matched those of the authentic compounds. Deposited lysozyme and trypsin retained their biological activity. Multiply charged ions of protein kinase A catalytic subunit and hexokinase were also soft-landed into glycerol-based liquid surfaces. These soft-landed kinases phosphorylated LRRASLG oligopeptide and D-fructose, respectively.

Apoproteins↗