The combined use of mass spectrometry and spectroscopy in analytical chemistry offers a powerful approach to obtaining comprehensive chemical information with improved efficiency and reduced sample consumption. This article overviews this hyphenated technique and explores its potential applications in various fields.
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Combining Mass Spectrometry and Spectroscopy: A Comprehensive Approach for Chemical and Structural Analysis
Mass spectrometry identifies chemical substances by separating their gaseous ions based on their mass-to-charge ratios. On the other hand, spectroscopy studies the absorption and emission of radiation by matter to identify the elements and molecules based on their ability to reflect, absorb or emit radiant energy.
Mass spectrometry and spectroscopy techniques complement each other by providing different types of information. For example, mass spectrometry offers molecular weight and structural details through fragmentation patterns, while spectroscopy (IR or Raman) identifies functional groups and analyzes molecular properties.
Their combined use enables a comprehensive approach to obtain detailed chemical and structural information about target samples. As a result, it reduces sample consumption, minimizes the risk of losing crucial chemical information, and enables efficient analyte identification.
Synergistic Applications of Mass Spectrometry and Spectroscopy
Enhanced Metabolite Detection and Annotation
Metabolomics is a powerful tool that identifies small molecules in complex biological samples, aiding research in numerous fields.
Nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry are the two primary techniques used in metabolomics. While NMR spectroscopy is noninvasive, it has limited sensitivity and signal overlap, whereas MS is destructive but offers high sensitivity. However, by combining these two techniques, researchers can achieve more comprehensive coverage of the metabolome, increase the accuracy of metabolite identification, and enable the structural characterization of new metabolites.
Combining mass spectrometry and spectroscopy techniques has greatly enhanced metabolomics by overcoming the limitations of each technique, providing more comprehensive coverage of the metabolome, and improving identification accuracy for known and unknown metabolites.
Advancing Insight into Protein Oxidation and Post-Translational Modifications
Protein oxidation is a post-translational modification that can lead to various effects, such as impairments of cell growth and loss of enzymatic activity. In addition, oxidized proteins can be toxic if not eliminated or repaired, but many of the biological roles of these oxidized forms are still unknown.
Combining mass spectrometry and spectroscopy provides a valuable tool for the structural characterization of larger peptides and can have commercial implications in developing methods for identifying and repairing oxidized proteins.
A study published in Physical Chemistry Chemical Physics focuses on identifying the final products of oxidation for small model peptides containing a thioether function using IR multiple photon dissociation spectroscopy and tandem mass spectrometry.
By combining mass spectrometry and spectroscopy techniques, researchers gained new insights into protein oxidation, including the oxidation of thioether functions and the mechanisms of intramolecular electron transfer in peptides. In addition, this approach enabled them to better characterize oxidized protein residues and identify new tools for studying key steps in protein oxidation.
Analyzing Complex Mixtures in Food Science for Authenticity and Regulatory Compliance
The combination of mass spectrometry and spectroscopy techniques enables the analysis of complex mixtures and the identification of specific compounds, with implications in food science, pharmaceuticals, and environmental monitoring. It also aids regulatory bodies in enforcing labeling laws and detecting fraud in food products.
In a study published in Food Chemistry, researchers developed a reliable and efficient method to characterize and quantify blends of Arabica and Robusta coffees, which are often degraded by substituting the more expensive Arabica beans with cheaper Robusta beans.
To achieve this, they combined paper spray mass spectrometry and attenuated total reflectance Fourier transform infrared spectroscopy and employed partial least squares (PLS) regression to build a multivariate model.
The resulting model was robust and accurately predicted the composition of coffee blends, with quinic acid, trigonelline, sugars, and chlorogenic acids suggested as discriminant markers between Arabica and Robusta species.
This technique provides valuable insights into the composition of coffee blends and has commercial implications for ensuring the authenticity of food products.
Enhancing Insight into Protein-RNA Complexes and Gene Regulation
RNA plays a crucial role in gene regulation, and defining RNA-protein interactions is important to comprehend molecular mechanisms and find therapies for related diseases. However, determining the structure of protein-RNA complexes remains challenging due to the complexity of the process.
Traditional structural biology has relied on NMR spectroscopy and X-ray crystallography methods. However, the emergence of integrative structural biology methods, combining multiple biophysical techniques such as mass spectrometry, cryo-electron microscopy, and nuclear magnetic resonance spectroscopy, is now recognized as a promising approach for describing the genome-wide positioning of RNA-binding proteins and their domains.
Hybrid approaches combining mass spectrometry and spectroscopy techniques have improved our understanding of the structural biology of protein-RNA complexes. For example, they have revealed insights into RNA methylation enzymes, RNA-binding proteins, RNP assembly pathways, conformational diversity, and protein-RNA interface hydration.
These approaches have allowed researchers to investigate RNA-protein interactions with enhanced efficiency and precision, providing a more comprehensive understanding of the molecular mechanisms involved in gene regulation.
Dynamic Single-Cell Analysis
Combining mass spectrometry and spectroscopy techniques improves single-cell analysis by providing complementary molecular composition and dynamics information.
Spectroscopy techniques can monitor changes in cells' fluorescence or absorbance spectra, indicating changes in the concentration or conformation of specific molecules. Mass spectrometry can detect and quantify the levels of specific biomolecules, even at very low concentrations.
A study published in the journal Analyst employed the dual use of optical spectroscopy and MALDI mass spectrometry for dynamic analysis of single algal cells. The combination of mass spectrometry and spectroscopy techniques enabled monitoring of the adenosine triphosphate ratio to adenosine diphosphate as astaxanthin accumulates in cells.
Overlaying the information gathered from spectroscopy and mass spectrometry enabled the revelation of metabolic events during encystment.
This integrated approach can improve our understanding of complex biological processes and facilitate biotechnological applications, such as algae farming.
Characterizing Reduced Metal Complexes with Non-Innocent Ligands
The dual use of mass spectrometry and spectroscopy has enhanced trace component analysis in complicated mixes, the optimization of catalytic processes and the design of new drugs by illustrating the localization of electrons in metal complexes containing non-innocent ligands.
In a study published in Physical Chemistry Chemical Physics, researchers combined electron capture dissociation mass spectrometry with infrared multiple photon dissociation action spectroscopy to form, select, and characterize reduced metal complexes containing non-innocent ligands.
The combined use of mass spectrometry and spectroscopy allowed the researchers to obtain a useful electronic description of the product radicals, which provided significant information on the native protein structure.
This combination provides a particularly advantageous approach when studying radical complexes that are highly reactive in solution and simplifies interpreting any metal-ligand interactions essential to catalytic processes.
Future Outlooks
Future developments in the combined mass spectrometry and spectroscopy techniques are expected to influence analytical chemistry. These developments include integrating data analysis techniques, enhanced ionization procedures, improved imaging technologies, and applying these techniques to medicine, environmental monitoring, and food industries. Such advancements will improve sensitivity, accuracy, and speed in analyzing complex samples, enabling a better understanding of various materials' chemical and structural properties.
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References and Further Reading
Assis, C., Pereira, H. V., Amador, V. S., Augusti, R., de Oliveira, L. S., & Sena, M. M. (2019). Combining mid infrared spectroscopy and paper spray mass spectrometry in a data fusion model to predict the composition of coffee blends. Food Chemistry. https://doi.org/10.1016/j.foodchem.2018.12.044
Bhinderwala, F., Wase, N., DiRusso, C., & Powers, R. (2018). Combining mass spectrometry and NMR improves metabolite detection and annotation. Journal of Proteome Research. https://doi.org/10.1021/acs.jproteome.8b00567
Fagerer, S. R., Schmid, T., Ibáñez, A. J., Pabst, M., Steinhoff, R., Jefimovs, K., ... & Zenobi, R. (2013). Analysis of single algal cells by combining mass spectrometry with Raman and fluorescence mapping. Analyst. https://doi.org/10.1039/C3AN01135F
Katari, M., de La Garanderie, E. P., Nicol, E., Steinmetz, V., van der Rest, G., Carmichael, D., & Frison, G. (2015). Combining gas phase electron capture and IRMPD action spectroscopy to probe the electronic structure of a metastable reduced organometallic complex containing a non-innocent ligand. Physical Chemistry Chemical Physics. https://doi.org/10.1039/C5CP01501D
Leitner, A., Dorn, G., & Allain, F. H. T. (2019). Combining mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy for integrative structural biology of protein–RNA complexes. Cold Spring Harbor Perspectives in Biology. https://doi.org/10.1101/cshperspect.a032359
Scuderi, D., Ignasiak, M. T., Serfaty, X., De Oliveira, P., & Levin, C. H. (2015). Tandem mass spectrometry and infrared spectroscopy as a tool to identify peptide oxidized residues. Physical Chemistry Chemical Physics. https://doi.org/10.1039/C5CP03223G
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