Laser-induced acoustic desorption

We propose and evaluate a new mechanism to account for analyte ion signal enhancement in ultraviolet-laser desorption mass spectrometry of droplets in the presence of corona ions. Our new insights are based on timing control of corona ion production, laser desorption, and peptide ion extraction achieved by a novel pulsed corona apparatus. We demonstrate that droplet charging rather than gas-phase ion-neutral reactions is the major contributor to analyte ion generation from an electrically isolated droplet. Implications of the new mechanism, termed charge assisted laser desorption/ionization (CALDI), are discussed and contrasted to those of the laser desorption atmospheric pressure chemical ionization method (LD-APCI). It is also demonstrated that analyte ion generation in CALDI occurs with external electric fields about one order of magnitude lower than those needed for atmospheric pressure matrix assisted laser desorption/ionization or electrospray ionization of droplets.

Section: Introductionmentioning

confidence: 99%

Charge assisted laser desorption/ionization mass spectrometry of droplets

Jorabchi

Westphall

Smith

2008

“…Existing ionization sources may be installed onto the platform due to the inherent versatility of the breadboard for roll-up accessibility. Analyte desorption may be induced by one of a number of regimes, including laser desorption as in MALDESI, laserinduced acoustic desorption (LIAD) [20], heated nitrogen gas amplification, sequencing, and annotation of plastomes (ASAP) [21], and impact of high velocity charged droplets as in DESI [6], followed by a number of post-desorption ionization methods including atmospheric pressure photo ionization (APPI) [22], atmospheric pressure chemical ionization (APCI) [23], and electrospray ionization (ESI) [24]. In addition to the hybrid ionization sources listed above, this platform is amenable to basic electrospray ionization [24] and atmospheric pressure matrix-assisted laser desorption ionization [25].…”

Section: Desorption and Ionization Source Versatilitymentioning

confidence: 99%

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

Sampson

Hawkridge

Muddiman

2008

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...

“…With an increase in the biological importance of oligo-or polysaccharides associated with cell-cell recognition, protein targeting, and metabolic diseases, polysaccharide and glycol-conjugate research has been attracting more attention [4,5]. Although different ionization methods [6][7][8][9][10][11][12][13] have been developed for the analysis of saccharides, matrix-assisted laser desorption/ionization (MALDI) [8] and ESI [11,[14][15][16][17][18] are the most used ionization methods. MALDI time-of-flight (TOF) MS has been used for the analysis of saccharides, and the sensitivity has been improved to the low femtomole level by reductive amination of the samples [19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Analysis of Saccharides by the Addition of Amino Acids

Özdemir

Lin

Gillig

et al. 2016

Abstract. In this work, we present the detection sensitivity improvement of electrospray ionization (ESI) mass spectrometry of neutral saccharides in a positive ion mode by the addition of various amino acids. Saccharides of a broad molecular weight range were chosen as the model compounds in the present study. Saccharides provide strong noncovalent interactions with amino acids, and the complex formation enhances the signal intensity and simplifies the mass spectra of saccharides. Polysaccharides provide a polymer-like ESI spectrum with a basic subunit difference between multiply charged chains. The protonated spectra of saccharides are not well identified because of different charge state distributions produced by the same molecules. Depending on the solvent used and other ions or molecules present in the solution, noncovalent interactions with saccharides may occur. These interactions are affected by the addition of amino acids. Amino acids with polar side groups show a strong tendency to interact with saccharides. In particular, serine shows a high tendency to interact with saccharides and significantly improves the detection sensitivity of saccharide compounds.