Sublimation Electrification of Organic Compounds

B. Banstola, K.K. Murray, Sublimation Electrification of Organic Compounds, J. Am. Soc. Mass. Spectrom., 31 (2020) 888-893; doi: 10.1021/jasms.9b00124.

Abstract

Sublimation Electrification of Organic Compounds
Sublimation Electrification of Organic Compounds

The electrification of crystalline deposits of organic compounds under high vacuum was measured and quantified. A group of compounds that produce multiply charged ions by matrix-assisted ionization were deposited on a metal plate, and the current was amplified and recorded; the total charge was obtained by integration of the current. Signals of several hundred picoamperes were obtained within 10 s of the application of high vacuum and persisted for several minutes as the compounds sublimed. The magnitude and sign of the charge were matrix dependent and were affected by the presence of organic or mineral acid in the crystalline deposit, as well as by the application of an electric field. The observations are interpreted as surface electrification caused by the emission of small charged matrix particles during sublimation, with ionic charge carriers comprising protons and hydroxide ions.

MALDI imaging directed laser ablation tissue microsampling for data independent acquisition proteomics

K. Wang, F. Donnarumma, M.E. Pettit, C.W. Szot, T. Solouki, K.K. Murray, MALDI imaging directed laser ablation tissue microsampling for data independent acquisition proteomics, J. Mass Spectrom., 55 (2020) e4475; doi: 10.1002/jms.4475

Abstract

Contour maps obtained from MALDI MSI
Contour maps obtained from MALDI MSI from peaks at (A) 8569, (B) 14 041, (C) 14 122, (D) 14 132, (E) 14 192, (F) 14 211, (G) 15 193, (H) 15 845, (I) 17 139, (J) 17 737, (K) 18 401, (L) 21 912, (M) 22 902, and (N) 28 217 m/z; the color shade indicates signal intensity with the light shade indicating the upper quintile (>80%), midcolor intensity indicates mean (50%-80%), and dark indicates the lower quintile (20%-50%)

A multimodal workflow for mass spectrometry imaging was developed that combines MALDI imaging with protein identification and quantification by liquid chromatography tandem mass spectrometry (LC-MS/MS). Thin tissue sections were analyzed by MALDI imaging, and the regions of interest (ROI) were identified using a smoothing and edge detection procedure. A midinfrared laser at 3-μm wavelength was used to remove the ROI from the brain tissue section after MALDI mass spectrometry imaging (MALDI MSI). The captured material was processed using a single-pot solid-phase-enhanced sample preparation (SP3) method and analyzed by LC-MS/MS using ion mobility (IM) enhanced data independent acquisition (DIA) to identify and quantify proteins; more than 600 proteins were identified. Using a modified database that included isoform and the post-translational modifications chain, loss of the initial methionine, and acetylation, 14 MALDI MSI peaks were identified. Comparison of the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of the identified proteins was achieved through an evolutionary relationships classification system.

Electrospray Photochemical Oxidation of Proteins

R.O. Lawal, F. Donnarumma, K.K. Murray, Electrospray Photochemical Oxidation of Proteins, J. Am Soc. Mass Spectrom. doi:10.1007/s13361-019-02313-4

Springer Nature Sharing Link

Abstract

Electrospray Photochemical Oxidation of Proteins
Electrospray Photochemical Oxidation of Proteins

Photooxidation of peptides and proteins by pulsed ultraviolet laser irradiation of an electrospray in the ion source of a mass spectrometer was demonstrated. A 193-nm excimer laser at 1.5-mJ pulse energy was focused with a cylindrical lens at the exit of a nanoelectrospray capillary and ions were sampled into a quadrupole time-of-flight mass spectrometer. A solution containing a peptide or protein and hydrogen peroxide was infused into the spray at a flow rate of 1 μL/min using a syringe pump. The laser creates OH radicals directly in the spray which modify biomolecules within the spray droplet. These results indicate that photochemical oxidation of proteins can be initiated directly within electrospray droplets and detected by mass spectrometry.

A Nanoparticle Co-matrix for Multiple Charging in MALDI Imaging of Tissue

B. Banstola, K.K. Murray, “A Nanoparticle Co-matrix for Multiple Charging in MALDI Imaging of Tissue,” Rapid Commun. Mass Spectrom. 16 (2019) 12. doi:10.1002/rcm.8424.

Abstract
Rationale: A two‐component matrix of 2‐nitrophloroglucinol (2‐NPG) and silica nanoparticles was used for matrix‐assisted laser desorption ionization (MALDI) mass spectrometry imaging of high‐charge‐state biomolecules in tissue. Potential advantages include increased effective mass range and efficiency of fragmentation.
Methods: A mixture of 2‐NPG matrix and silica nanoparticles was applied to cyrosectioned 10 μm thick mouse brain tissue. The mixture was pipetted onto the tissue for profiling and sprayed for tissue imaging. MALDI images were obtained under high vacuum in a commercial time‐of‐flight mass spectrometer.
Results: The combined 2‐NPG and nanoparticle matrix produced highly charged ions from tissue with high‐vacuum MALDI. Nanoparticles of 20, 70, 400, and 1000 nm in diameter were tested, the 20 nm particles producing the highest charge states. Images of mouse brain tissue obtained from highly charged ions show similar spatial localization.
Conclusions: The combined 2‐NPG and nanoparticle matrix produces highly charged ions from tissue through a mechanism that may rely on the high surface area of the particles which can dry the tissue, and their ability to bind analyte molecules thereby assisting in crystal formation and production of multiply charged ions on laser irradiation.

Nanoparticle Co-matrix Figure 4
Images of consecutive mouse brain tissue sections obtained from 8565 m/z and its multiply charged ions with a) 2-NPG, and b) 2-NPG/nanoparticle matrix.

Matrix-Assisted Laser Desorption Ionization Imaging and Laser Ablation Sampling for Analysis of Fungicide Distribution in Apples

I. Pereira, B. Banstola, K. Wang, F. Donnarumma, B.G. Vaz, K.K. Murray, Matrix-Assisted Laser Desorption Ionization Imaging and Laser Ablation Sampling for Analysis of Fungicide Distribution in Apples, Anal. Chem. 91 (2019) 6051–6056. doi:10.1021/acs.analchem.9b00566.

ABSTRACT: A combination of matrix-assisted laser desorption ionization (MALDI) imaging and infrared (IR) laser ablation sampling with offline electrospray ionization mass spectrometry (ESI-MS) was used to determine the distribution of the fungicide imazalil in apples. MALDI images were used to determine the penetration depth of imazalil up to 7 days after its application. IR laser ablation sampling and ESI-MS were used to quantify the rate of penetration of the fungicide, which was determined to be approximately 1 mm per day. Imazalil concentration decreased in the apple skin over the course of the experiment, and after 7 days the fungicide was detected at 0.015 ppm 6 mm inside the apple. Approximately 60% of the pesticide remained in the skin after 7 days. This work demonstrates the utility of MALDI imaging for spatial localization of fungicide in fruit in combination with IR laser ablation and ESI-MS for quantitative analysis.

Matrix-Assisted Laser Desorption Ionization Imaging and Laser Ablation Sampling for Analysis of Fungicide Distribution in Apples
Pereira, Banstola, Wang, Donnarumma, Vaz, Murray, Matrix-Assisted Laser Desorption Ionization Imaging and Laser Ablation Sampling for Analysis of Fungicide Distribution in Apples, Anal. Chem. 91 (2019) 6051

Piezoelectric matrix-assisted ionization

B. Banstola, C.W. Szot, A.P. Deenamulla Kankanamalage, K.K. Murray, Piezoelectric matrix-assisted ionization, Eur J Mass Spectrom 25 (2019) 202–207. doi:10.1177/1469066718816696

ABSTRACT: We have developed a new actuation method for matrix-assisted ionization with good temporal and spatial resolution using piezoelectric cantilever. A strike from the piezoelectric bimorph cantilever on a thin metal foil was used to remove materials deposited on the opposite side facing the mass spectrometer inlet. Highly charged ions of peptides and proteins were generated from dried droplet deposits and sampled into the inlet of the mass spectrometer. A lateral resolution of 1 mm was obtained with the piezoelectric sampling configuration. Singly charged lipids and gangliosides were detected from tissue with piezoelectric matrix-assisted ionization using a silica nanoparticle co-matrix.

Piezoelectric MAI at inlet to the Bruker Amazon ion trap

ASMS 2019: Deep-ultraviolet Laser Ablation Sampling for Mass Spectrometry

MOG 03:10pm
Deep-ultraviolet Laser Ablation Sampling for Mass Spectrometry
Remilekun O. Lawal; Fabrizio Donnarumma; Kermit K. Murray

193 nm excimer laser ablation setup
193 nm excimer laser ablation setup

High resolution sampling of biological systems is crucial to revealing the differences in proteins and metabolites amongst heterogeneous cells. Laser ablation sampling for mass spectrometry is a powerful method for analyzing biomolecules in tissue under ambient conditions with high spatial control while eliminating the need for external matrices. It allows off-line analysis by liquid chromatography tandem mass spectrometry and can be combined with mass spectrometry imaging for region of interest selection. The most efficient lasers currently used for ablation sampling use mid-infrared wavelengths that are diffraction limited to spot sizes tens of micrometers in diameter. Short wavelength lasers can be focused to order of magnitude smaller spot sizes for efficient ablation with minimal thermal damage to adjacent sample areas.