Forschungsarbeit, 2018
83 Seiten, Note: Mass spectrometry
Introduction
1. Experimental
1.1. Synthesis
1.2. Analytical instrumentation and methods
1.2.1. Mass spectrometric measurements
1.2.2. Sample preparation for the MALDI-MS measurements
1.3. Theory/Computations
1.3.1. Stochastic dynamics
1.3.2. Chemometrics
1.3.3. Computational quantum chemistry
2. Results and discussion
2.1. Experimental MALDI mass spectrometric data – qualitative analysis
2.2. Experimental MALDI mass spectrometric data – quantitative analysis
2.3. MALDI mass spectrometric method performances
2.4. Experimental electrospray ionization mass spectrometric data – quantitative analysis
2.5. Correspondence between diffusion parameters obtained on the base on stochastic dynamics and current monitoring method
3. Theoretical data
Conclusion
The primary objective of this work is to establish a robust quantitative framework for Matrix-Assisted Laser Desorption/Ionization (MALDI) mass spectrometry by applying stochastic dynamics. The research addresses the challenge of accurately determining 3D molecular and electronic structures of analytes by modeling the temporal behavior of mass spectrometric signal intensities, thereby overcoming issues related to sample heterogeneity and non-uniform distribution.
1.2.1. Mass spectrometric measurements
Mass spectrometric measurements were carried out by TSQ 7000 instrument (Thermo Fisher Inc., Rockville, MD, USA). A triple quadruple mass spectrometer (TSQ 7000 Thermo Electron, Dreieich, Germany) equipped with an ESI 2 source were used for ESI–MS and APCI–MS measurements. The quantification using the lastly mentioned instrument was carried out via a combination of mass detectors (trap, linear ion trap and orbitrap), accumulating spectra for t = 7–30 mins (420–1800 s). The selected reaction monitoring approach was used, where the data were saved as individual files. The relative intensities of the species studied were obtained using QualBrowser software 2.7. The program package ProteoWizard 3.0.11565.0 (2017) was used as well. The mass resolving power R = 98 101. The ESI, atmospheric pressure chemical ionization (APCI) and collision induced dissociation (CID) resolving powers are R = 55 121, 19 341, 15 700, respectively. A standard LTQ Orbitrap XL (Thermo Fisher Inc.) spectrometer was used for MALDI–MS measurements, using the UV laser source at λmax = 337.2 nm. An overall mass range of m/z 100–1000 was scanned simultaneously in the Orbitrap analyzer in presence of inner standard (Figs. 1 and 2; m/z 283). The ImageQuest 1.0.1 program package was used. The extracted MS spectra (without the MS peaks of the inner standard) and processing of the ion chromatograms was performed using AMDIS 2.71 (2012) and SeeMS 3.0.11.565.0 (2017), respectively. The laser energy values were ∈ 14.8–15.5 μJ. The numbers of averaged laser shots lies ∈ 18–80, the MALDI flow rate values were ∈ 25.01–25.08, the corresponding elapsed scan time range lies ∈ 18.0–2.50 s, respectively.
Introduction: Provides an overview of the power of mass spectrometry in qualitative and quantitative analysis while identifying the lack of accurate quantitative models for 3D structural determination.
1. Experimental: Details the chemical synthesis of the analyte, instrumentation specifications for MS and HPLC, and the specific sample preparation techniques used for both MALDI and ESI measurements.
2. Results and discussion: Presents the qualitative and quantitative analysis of experimental MALDI and ESI mass spectrometric data, applying the stochastic dynamics approach and verifying results through chemometric testing.
3. Theoretical data: Connects experimental findings with high-accuracy quantum chemical computations to validate diffusion parameters and reaction energetics via the Arrhenius formalism.
Conclusion: Synthesizes the core findings, confirming the validity of the proposed stochastic model equations across different sample preparations and highlighting the impact on structural analytical chemistry.
Stochastic dynamics, mass spectrometry, quantification, MALDI-MS, ESI-MS, diffusion parameters, chemometrics, DFT, molecular modeling, 3D structural determination, ion intensity, signal processing, quantum chemistry, Arrhenius approximation, thermodynamic modeling
The work focuses on developing a new quantitative methodology for MALDI mass spectrometry by utilizing stochastic dynamics to model the temporal behavior of analyte ion intensities.
The research spans analytical chemistry, physical chemistry, and computational/theoretical chemistry, specifically aiming to link experimental MS data with quantum chemical modeling.
The central question is whether the MALDI-MS method can effectively serve as a prospective approach for the accurate quantitative analysis of reaction kinetics, diffusion, and 3D structural determination of analytes.
The study employs stochastic dynamics, specifically the Box-Müller method, alongside non-linear regression, chemometric ANOVA tests, and high-level quantum chemical computations like DFT and ab initio methods.
The main body presents experimental results from mass spectrometric measurements, validates these through statistical and theoretical models, and discusses the correlation between experimental diffusion parameters and quantum chemical predictions.
Key terms include stochastic dynamics, mass spectrometry, quantification, MALDI-MS, ESI-MS, diffusion parameters, and chemometrics.
The study proposes using nonlinear model equations that account for the stochastic nature of random intensity variations caused by sample heterogeneity and non-uniform analyte distribution.
Validation is achieved by comparing experimental diffusion parameters with those derived from quantum chemical modeling, utilizing the Arrhenius approximation to connect activation enthalpy and diffusion.
It serves as an independent methodology used to benchmark the diffusion parameters obtained via the new stochastic dynamics approach, demonstrating significant statistical correlation.
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