Direct characterization of intact polypeptides by matrix‐assisted laser desorption electrospray ionization quadrupole Fourier transform ion cyclotron resonance mass spectrometry

Adaptation of desorption electrospray ionization to a transmission mode (TM-DESI) entails passing an electrospray plume through a sample that has been deposited onto a mesh substrate. A combination of mass spectrometry and fluorescence microscopy studies is used to illustrate the critical role material composition, mesh open space, and mesh fiber diameter play on the transmission, desorption, and ionization process. Substrates with open spaces less than 150 m and accompanying minimal strand diameters produce less scattering of the plume and therefore favor transmission. Larger strand diameters typically encompass larger open spaces, but the increase in the surface area of the strand increases plume scattering as well as solvent and analyte spreading on the mesh. Polypropylene (PP), ethylene tetrafluoroethylene (ETFE), and polyetheretherketone (PEEK) materials afford much better desorption than similarly sized polyethylene terephthalate (PETE) or nylon-6,6 (PA66) substrates. Ultimately, the manner in which the electrospray plume interacts with the mesh as it is transmitted through the substrate is shown to be critical to performing and optimizing TM-DESI analyses. In addition, evidence is presented for analyte dependent variations in the desorption mechanisms of dry and solvated samples. . In DESI, ions are produced by directing charged solvent droplets from an electrospray source toward a sample that is either a bulk material in its native state (e.g., pharmaceutical tablet) or one that has been deposited from solution onto a sampling surface. Analytes present at the surface are desorbed and ionized by the incoming plume and subsequently transferred to the mass spectrometer inlet by the influence of the applied potential and the pressure differential between atmospheric pressure and the low-pressure region of the mass analyzer. To date, DESI has found many applications including forensic analysis [2][3][4][5] Recent adaptations of DESI, including geometry independent DESI in gas tight enclosures [35] and transmission mode desorption electrospray ionization (TM-DESI), have been developed to reduce the geometry dependence of DESI experiments [36]. In the transmission DESI mode the sample is not deposited onto a continuous solid surface but rather onto a sampling mesh. In this adaptation, the incident spray angle and collection angle are fixed at 0°and the spray is transmitted through the sample (Figure 1). Along with the simplification of the experimental geometry, the transmission mode also allows convenient analysis of both dry (i.e., following evaporation of the deposition solvent) and wet (i.e., solvated) samples with similar performance characteristics to those achieved using traditional DESI [36].Surface variables including the chemical composition, porosity, texture, and electrical conductivity of the substrate have been reported to affect DESI analyses [2,24,[37][38][39]. Dramatic reductions in response have been noted for high conductivity surfaces due to neutralization of the incoming ion plume at the su...

Section: Desorption Of Liquid Samples From Mesh Substratesmentioning

confidence: 92%

The influence of material and mesh characteristics on transmission mode desorption electrospray ionization

Chipuk

Brodbelt

2008

“…MALDESI-FT-ICR mass spectra of peptides and proteins (1-8.6 kDa) including bradykinin, angiotensin I, melittin, glucagon, and ubiquitin each mixed with organic matrix have been shown previously [12,13]. Comparable data were obtained using the new source; representative MALDESI-FT-ICR mass spectra of bradykinin and melittin both mixed with DHB are included in Supplemental Material ( Figure S3).…”

Section: Maldesi-ltq-ft-icr Of Peptides and Proteinsmentioning

confidence: 94%

“…A new version of the MALDESI source was constructed based in part on the previous source design [12,13]. A photo of the new source is shown in Figure 1 with major parts indicated.…”

Section: Maldesi Source Design and Constructionmentioning

confidence: 99%

“…T he introduction and development of hybrid ambient ionization sources such as laser desorption atmospheric pressure ionization (LDAPI) [1,2], fused droplet electrospray ionization/extraction electrospray (FD-ESI, EESI) [3,4], direct analysis in real time (DART) [5], desorption electrospray ionization (DESI) [6], electrospray assisted laser desorption ionization (ELDI) [7][8][9][10][11], matrix-assisted laser desorption electrospray ionization (MALDESI) [12,13], and infrared laser desorption electrospray ionization [14,15] have advanced the capabilities of mass spectrometry. MALDESI, for example, is a pulsed ionization source that holds promise in areas ranging from top-down proteomics, tissue imaging, and ionization mechanism elucidation.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Construction of a versatile high precision ambient ionization source for direct analysis and imaging

Sampson

Hawkridge

Muddiman

2008

Self Cite

The design and construction of a high precision ambient ionization source matrix-assisted laser desorption electrospray ionization (MALDESI) are described in full detail, including a complete parts list. The computer controlled high precision motion control system and high repetition rate Explorer laser are demonstrated during MALDESI-FT-ICR analysis of peptides and proteins ranging from 1 to 17 kDa. The high stability ionization source platform described herein demonstrates both the advantages of the new MALDESI source and versatility for application to numerous desorption and ionization techniques. [6], electrospray assisted laser desorption ionization (ELDI) [7][8][9][10][11], matrix-assisted laser desorption electrospray ionization (MALDESI) [12,13], and infrared laser desorption electrospray ionization [14,15] have advanced the capabilities of mass spectrometry. MALDESI, for example, is a pulsed ionization source that holds promise in areas ranging from top-down proteomics, tissue imaging, and ionization mechanism elucidation. The pulsed nature of MALDESI combined with its ability to generate multiply-charged ions are characteristics that are particularly well suited for Fourier transform ion cyclotron resonance (FT-ICR) and Orbitrap (LTQ-Orbi) mass spectrometry due to the inverse relationship of frequency to m/z and v(m/z), respectively. The consequence of this relationship is high resolving power, <3 ppm mass measurement accuracy, and amenability to a multitude of tandem MS/MS techniques for bottom-up and top-down proteomics (e.g., CID, ETD, ECD, SORI, and IRMPD) [16][17][18]. Many of these MS/MS techniques in FT-ICR and Orbitrap instruments would benefit from a pulsed ionization source where intact proteins and polypeptides with complex post-translational modifications could be carefully interrogated rather than the typical "continuous" ionization encountered during a LC- The advancement and acceptance of MALDESI and related hybrid ionization techniques are critically dependent on the widespread dissemination of detailed source designs such that results can be reproduced and improved in a variety of laboratories. Furthermore, there are certainly unanticipated potential applications that could benefit from novel or improved source designs. Herein, we provide a detailed description and characterization of the third version of the MALDESI source utilized in this laboratory. The further improvement to this design both within our laboratory as well as other laboratories should enable MALDESI and related hybrid ambient ionization sources to mature to a level of analytical robustness now widely enjoyed for ESI and MALDI. Experimental MaterialsBradykinin, angiotensin I, melittin, glucagon, bovine ubiquitin, lysozyme, myoglobin, and 2,5-dihydroxybenzoic acid were purchased from Sigma-Aldrich (St. Louis, MO) and used without further purification. HPLC-grade acetonitrile and high purity water were purchased from Burdick and Jackson (Muskegon, MI). The electrospray solution was prepared by mixing acetonitrile and w...

“…Secondary electrospray ionization (SESI) [8 -11] involves the gas-phase interaction of charged ESI droplets with neutral sample molecules for analysis by ion mobility spectrometry (IMS) or MS. Fused droplet electrospray ionization (FD-ESI) [12,13] aerosolizes the sample solution via a nebulizer for interaction with a highly charged acidic methanol solution and reduces interferences from buffers and complex mixtures. Extractive electrospray ionization (EESI) [14 -18] employs two nebulizing sprayers, one with ESI solvents and a second containing the analyte of interest for a liquidliquid extraction process to reduce interferences from complex mixtures.Closely related to RADIO due to step-wise desorption with subsequent ionization are electrosprayassisted laser desorption ionization (ELDI) [19] and solid-state matrix assisted laser desorption electrospray ionization (ss-MALDESI) [20,21]. ss-MALDESI utilizes a UV or IR laser for analyte desorption and ESI for post-ionization.…”

mentioning

confidence: 99%

Generation of multiply charged peptides and proteins by radio frequency acoustic desorption and ionization for mass spectrometric detection

Dixon

Sampson

Muddiman

2008

Self Cite

The design and implementation of a radio frequency acoustic desorption ionization (RADIO) source has been demonstrated for the analysis of multiply charged peptides and proteins. One L aliquots of melittin, BNP-32, and ubiquitin ( ϳ1 g of analyte) were deposited onto a quartz crystal microbalance (QCM) electrode before radio frequency actuation for desorption. Continuous electrospray parallel to/above the sampling surface enabled the ionization of Laser-induced acoustic desorption (LIAD) [1-4] demonstrates the soft desorption of analyte using a shock wave generated by a laser pulse and the potential to couple post-desorption ionization techniques such as chemical ionization at atmospheric pressure. Array of micro-machined ultrasonic electrosprays [5][6][7] (AMUSE), applies an rf signal to a ceramic piezoelectric transducer with a solution cavity between a micromachined silicone nozzle array for droplet-on-demand generation. The preceding techniques address RADIO's desorption mechanism. Several other techniques are mentioned below as they utilize postdesorption ionization (as in RADIO). Secondary electrospray ionization (SESI) [8 -11] involves the gas-phase interaction of charged ESI droplets with neutral sample molecules for analysis by ion mobility spectrometry (IMS) or MS. Fused droplet electrospray ionization (FD-ESI) [12,13] aerosolizes the sample solution via a nebulizer for interaction with a highly charged acidic methanol solution and reduces interferences from buffers and complex mixtures. Extractive electrospray ionization (EESI) [14 -18] employs two nebulizing sprayers, one with ESI solvents and a second containing the analyte of interest for a liquidliquid extraction process to reduce interferences from complex mixtures.Closely related to RADIO due to step-wise desorption with subsequent ionization are electrosprayassisted laser desorption ionization (ELDI) [19] and solid-state matrix assisted laser desorption electrospray ionization (ss-MALDESI) [20,21]. ss-MALDESI utilizes a UV or IR laser for analyte desorption and ESI for post-ionization.The desorption phenomena can be attributed in part to the shock wave desorption observed in LIAD, however for RADIO, the transfer of energy is accomplished by applying an rf waveform to a piezoelectric material (analogous to AMUSE). Postdesorption electrospray is the proposed ionization pathway as in SESI, FD-ESI, EESI, and ss-MALDESI. Experimental MaterialsMelittin, BNP-32, ubiquitin, and formic acid were obtained from Sigma Aldrich (St. Louis, MO). HPLC grade acetonitrile and water were purchased from Burdick and Jackson (Muskegon, MI). Nitrogen (99.98%) and LTQ helium bath gas (99.999%) were obtained from MWSC High Purity Gases (Raleigh, NC). MethodsElectrospray solutions consisted of acetonitrile:water (50:50% by volume) with 0.1% formic acid. Melittin was diluted to 347 M in water, BNP-32 was diluted to 300 M in water with 0.1% formic acid, and ubiquitin was diluted to 99 M in 50:50:0.1% water:acetonitrile:formic acid. QCM substrates were spotted with 1 L of...