Abstract:Vacuum ultraviolet single photon ionization (VUV SPI) is a soft ionization technique that has the potential to address many of the limitations of MALDI for imaging MS. Laser desorption postionization (LDPI) employs VUV SPI for postionization and is experimentally analogous to a MALDI instrument with the addition of a pulsed VUV light source. This review discusses progress in LDPI-MS over the last decade, with an emphasis on imaging MS of bacterial biofilms, analytes whose high salt environment make them partic… Show more
“…Prior 7.87 eV single photon ionization analyses of high ionization energy species derivatized with low ionization energy chromophores typically display intense ions composed in part or entirely of the chromophore. 7,11 …”
Section: Resultsmentioning
confidence: 99%
“…However, the high laser fluence employed here for Au film desorption likely imparted more internal energy into the desorbed neutrals, enhancing fragmentation upon single photon ionization and reducing the parent ion signal. 6,7 …”
Section: Resultsmentioning
confidence: 99%
“…Thus, LDPI-MS imaging should be a robust tool for small molecule quantification with potential applications in the direct analysis of bacterial biofilms on medical devices. 7,12 …”
The potential of laser desorption postionization mass spectrometry (LDPI-MS) imaging for small molecule quantification is demonstrated here. The N-methylpiperazine acetamide of (MPA) ampicillin was adsorbed into polyelectrolyte multilayer surface coatings composed of chitosan and alginate, both high molecular weight biopolymers. These MPA-ampicillin spiked multilayers were then shown to inhibit the growth of E. faecalis biofilms that play a role in early stage infection of implanted medical devices. Finally, LDPI-MS imaging using 7.87 eV single photon ionization was found to detect MPA-ampicillin with the multilayers before and after biofilm growth with limits of quantification and detection of 0.6 and 0.3 nmoles, respectively. The capabilities of LDPI-MS imaging for small molecule quantification are compared to those of MALDI-MS. Furthermore, these results indicate that 7.87 eV LDPI-MS imaging should be applicable to quantification of a range of small molecular species on a variety of complex organic and biological surfaces. Finally, while MS imaging for quantification was demonstrated here using LDPI, it is a generally useful strategy that can be applied to other methods.
“…Prior 7.87 eV single photon ionization analyses of high ionization energy species derivatized with low ionization energy chromophores typically display intense ions composed in part or entirely of the chromophore. 7,11 …”
Section: Resultsmentioning
confidence: 99%
“…However, the high laser fluence employed here for Au film desorption likely imparted more internal energy into the desorbed neutrals, enhancing fragmentation upon single photon ionization and reducing the parent ion signal. 6,7 …”
Section: Resultsmentioning
confidence: 99%
“…Thus, LDPI-MS imaging should be a robust tool for small molecule quantification with potential applications in the direct analysis of bacterial biofilms on medical devices. 7,12 …”
The potential of laser desorption postionization mass spectrometry (LDPI-MS) imaging for small molecule quantification is demonstrated here. The N-methylpiperazine acetamide of (MPA) ampicillin was adsorbed into polyelectrolyte multilayer surface coatings composed of chitosan and alginate, both high molecular weight biopolymers. These MPA-ampicillin spiked multilayers were then shown to inhibit the growth of E. faecalis biofilms that play a role in early stage infection of implanted medical devices. Finally, LDPI-MS imaging using 7.87 eV single photon ionization was found to detect MPA-ampicillin with the multilayers before and after biofilm growth with limits of quantification and detection of 0.6 and 0.3 nmoles, respectively. The capabilities of LDPI-MS imaging for small molecule quantification are compared to those of MALDI-MS. Furthermore, these results indicate that 7.87 eV LDPI-MS imaging should be applicable to quantification of a range of small molecular species on a variety of complex organic and biological surfaces. Finally, while MS imaging for quantification was demonstrated here using LDPI, it is a generally useful strategy that can be applied to other methods.
“…3a). This method is appealing for particles where photo-ionization has been notoriously difficult and photodissociation channels are not available, as is the case for many massive biomolecules [36–38]. Fig.…”
We present matter-wave interferometry as a tool to advance spectroscopy for a wide class of nanoparticles, clusters and molecules. The high sensitivity of de Broglie interference fringes to external perturbations enables measurements in the limit of an individual particle absorbing only a single photon on average, or even no photon at all. The method allows one to extract structural and electronic information from the loss of the interference contrast. It is minimally invasive and works even for dilute ensembles.
“…21, 22 LDPI-MS, also referred to as two laser mass spectrometry (L2MS), 23 does not require the addition of a matrix compound to enhance desorption. LDPI-MS is not sensitive to ion suppression since it detects desorbed neutrals and shows some advantages for quantification.…”
7.87 to 10.5 eV vacuum ultraviolet (VUV) photon energies were used in laser desorption postionization mass spectrometry (LDPI-MS) to analyze biofilms comprised of binary cultures of interacting microorganisms. The effect of photon energy was examined using both tunable synchrotron and laser sources of VUV radiation. Principal components analysis (PCA) was applied to the MS data to differentiate species in Escherichia coli-Saccharomyces cerevisiae coculture biofilms. PCA of LDPI-MS also differentiated individual E. coli strains in a biofilm comprised of two interacting gene deletion strains, even though these strains differed from the wild type K-12 strain by no more than four gene deletions each out of approximately 2000 genes. PCA treatment of 7.87 eV LDPI-MS data separated the E. coli strains into three distinct groups, two “pure” groups, and a mixed region. Furthermore, the “pure” regions of the E. coli cocultures showed greater variance by PCA at 7.87 eV photon energies compared to 10.5 eV radiation. This is consistent with the expectation that the 7.87 eV photoionization selects a subset of low ionization energy analytes while 10.5 eV is more inclusive, detecting a wider range of analytes. These two VUV photon energies therefore give different spreads via PCA and their respective use in LDPI-MS constitute an additional experimental parameter to differentiate strains and species.
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