F. Cao, F. Donnarumma, K. K. Murray, Appl. Surf. Sci. DOI:10.1016/j.apsusc.2018.03.239
The role of laser wavelength in atomic force microscopy (AFM) tip-enhanced laser ablation was studied using an apertureless tip and a nanosecond pulsed laser. An optical parametric oscillator (OPO) laser wavelength tunable from 410 to 2400 nm was used to irradiate a gold-coated silicon AFM probe held 15 nm above the surface of an anthracene film. The absorption of laser energy by the tip at 532 nm is sufficient to melt the gold coating and increase the diameter of the tip from about 100 nm to approximately 1 µm. The ablation crater volume was measured and found to have a maximum at 500 nm and an approximately linear drop to 800 nm. Craters could not be produced between 800 and 1200 nm and the crater was slightly smaller at 450 nm compared to 500 nm. A crater rim was observed with a volume comparable to that of the crater but lower density. The mechanism of ablation is postulated to be the result of energy absorption by the tip through plasmon resonance of the gold coating followed by melting of the anthracene by ballistic, contact, or radiative heating of the anthracene film.
A mass spectrometry discussion group for Louisiana: LAMSDG
Infrared Laser Ablation Microsampling for Mass Spectrometry Imaging (CHE-1709526) is a $0.35M award to Louisiana State University and Baylor University from the National Science Foundation Division of Chemistry to support the development of new techniques for biological imaging. Thank you NSF for 20+ years of support.
65th American Society for Mass Spectrometry Conference on Mass Spectrometry and Allied Topics, Indianapolis Indiana, June 4 – 8, 2017
MALDI – Past and Future, Kermit K. Murray
Combined Proteomic and RNA Expression Analysis of Laser Ablation Extracted Tissue, Chao Dong, Kelin Wang, Fabrizio Donnarumma, Scott W. Herke, Michael E. Pettit, Touradj Solouki,3 and Kermit K. Murray, presented at the 65th ASMS Conference on Mass Spectrometry and Allied Topics, Indianapolis, Indiana, June 5, 2017.
Infrared Laser Ablation Sample Transfer with Conserved Biological Function, Kelin Wang, Matthew D. Baldone, Fabrizio Donnarumma, and Kermit K. Murray, presented at the 65th ASMS Conference on Mass Spectrometry and Allied Topics, Indianapolis, Indiana, June 5, 2017.
Pulsed Valve Matrix-assisted Ionization, Bijay Banstola and Kermit K. Murray, presented at the 65th ASMS Conference on Mass Spectrometry and Allied Topics, Indianapolis, Indiana, June 6, 2017.
Combined Solid and Liquid Matrix High Vacuum Sublimation and Evaporation Coating for MALDI Imaging, Fan Cao, Fabrizio Donnarumma, Md Amir Hossen, and Kermit K. Murray, presented at the 65th ASMS Conference on Mass Spectrometry and Allied Topics, Indianapolis, Indiana, June 6, 2017.
Online Atomic Force Microscope Tip-enhanced Laser Ablation Mass Spectrometry, Md Amir Hossen, Bijay Banstola, Fan Cao, and Kermit K. Murray, presented at the 65th ASMS Conference on Mass Spectrometry and Allied Topics, Indianapolis, Indiana, June 6, 2017.
Infrared Laser Ablation Microsampling and Data Independent Acquisition Mass Spectrometry for Tissue Proteomics, Kelin Wang, Fabrizio Donnarumma, Carson W .Szot, Michael E. Pettit, Touradj Solouki, and Kermit K. Murray
Laser Ablation Capture of Formalin Fixed Paraffin Embedded Tissue for LC-MS/MS Proteomics Analysis, Fabrizio Donnarumma, Michael E. Pettit, Touradj Solouki, and Kermit K. Murray
We have developed a new ionization approach for matrix-assisted ionization with high temporal resolution using an electrically actuated pulsed valve. Matrix and analyte samples are deposited on a thin metal foil and placed at the inlet of an ambient ionization mass spectrometer. When the pulsed valve is actuated, a short puff of high pressure gas impinges on the foil and ejects particulate from the sample on the opposite side. Highly charged ions are formed from the particles at the mass spectrometer inlet. Using this source, multiply charged protein ions are produced within a selectable 4 second time window.
Analytica Chimica Acta, Volume 963, 22 April 2017, Pages 76–821. Banstola, B., Grodner, E.T., Cao, F., Donnarumma, F., Murray, K.K.: Systematic assessment of surfactants for matrix-assisted laser desorption/ionization mass spectrometry imaging. Anal. Chim. Acta. 963, 76–82 (2017).
A systematic method for evaluation of MALDI profiling and imaging was developed and applied to the use of three surfactants, sodium dodecyl sulfate (SDS), Triton X-100, and Tween 20, on rat brain tissue. For profiling studies, mass spectra were acquired from regular arrays of spots with manually deposited surfactant and matrix. The studies recorded the total number of peaks in the mass spectra from 2 to 20 kDa and compared the number of peaks and peak intensities with and without surfactant. It was found that SDS decreases the total number of peaks at all concentrations but does lead to an increase in the number of peaks below 5 kDa. Triton X-100 at 0.05% concentration yielded the highest number of peaks and highest number of new peaks, with the best results above 5 kDa. Correlation of the increase in signal with the estimated hydrophobicity suggests that Triton X-100 improves mass spectrometry quality through an increase in the intensity of hydrophobic protein peaks. Tween 20 provided good performance at 0.05% concentration across all mass ranges. For imaging studies, multiple images were obtained and the integrated intensity ratio for images obtained with and without surfactant was compared for 10 selected peaks. It was found that SDS tends to degrade imaging performance whereas Triton X-100 and Tween 20 improved performance compared to no surfactant, especially above 7 kDa.
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