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Grooms AJ, Nordmann AN, Badu-Tawiah AK. Dual Tunability for Uncatalyzed N-Alkylation of Primary Amines Enabled by Plasma-Microdroplet Fusion. Angew Chem Int Ed Engl 2023:e202311100. [PMID: 37770409 DOI: 10.1002/anie.202311100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Revised: 09/22/2023] [Accepted: 09/28/2023] [Indexed: 09/30/2023]
Abstract
The fusion of non-thermal plasma with charged microdroplets facilitates catalyst-free N-alkylation for a variety of primary amines, without halide salt biproduct generation. Significant reaction enhancement (up to >200×) is observed over microdroplet reactions generated from electrospray. This enhancement for the plasma-microdroplet system is attributed to the combined effects of energetic collisions and the presence of reactive oxygen species (ROS). The ROS (e.g., O2 ⋅- ) act as a proton sink to increase abundance of free neutral amines in the charged microdroplet environment. The effect of ROS on N-alkylation is confirmed through three unique experiments: (i) utilization of radical scavenging reagent, (ii) characterization of internal energy distribution, and (iii) controls performed without plasma, which lacked reaction acceleration. Establishing plasma discharge in the wake of charged microdroplets as a green synthetic methodology overcomes two major challenges within conventional gas-phase plasma chemistry, including the lack of selectivity and product scale-up. Both limitations are overcome here, where dual tunability is achieved by controlling reagent concentration and residence time in the microdroplet environment, affording single or double N-alkylated products. Products are readily collected yielding milligram quantities in eight hours. These results showcase a novel synthetic strategy that represents a straightforward and sustainable C-N bond-forming process.
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Affiliation(s)
- Alexander J Grooms
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH-43210, USA
| | - Anna N Nordmann
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH-43210, USA
| | - Abraham K Badu-Tawiah
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH-43210, USA
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Grooms A, Nordmann AN, Badu-Tawiah AK. Plasma-Droplet Reaction Systems: A Direct Mass Spectrometry Approach for Enhanced Characterization of Lipids at Multiple Isomer Levels. ACS MEASUREMENT SCIENCE AU 2023; 3:32-44. [PMID: 36817012 PMCID: PMC9936802 DOI: 10.1021/acsmeasuresciau.2c00051] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Revised: 09/15/2022] [Accepted: 09/15/2022] [Indexed: 06/18/2023]
Abstract
Neutral triacylglyceride (TG) lipids are critical in cellular function, signaling, and energy storage. Multiple molecular pathways control TG structure via nonselective routes making them structurally complex and analytically challenging to characterize. The presence of C=C bond positional isomers exacerbates this challenge as complete structural elucidation is not possible by conventional tandem mass spectrometric methods such as collision-induced dissociation (CID), alone. Herein, we report a custom-made coaxial contained-electrospray ionization (ESI) emitter that allows the fusion of plasma discharge with charged microdroplets during electrospray (ES). Etched capillaries were incorporated into this contained-ES emitter, facilitating the generation of reactive oxygen species (ROS) at low (3 kV) ESI voltages and allowing stable ESI ion signal to be achieved at an unprecedented high (7 kV) spray voltage. The analytical utility of inducing plasma discharge during electrospray was investigated using online ionization of neutral TGs, in situ epoxidation of unsaturation sites, and C=C bond localization via conventional CID mass spectrometry. Collisional activation of the lipid epoxide generated during the online plasma-droplet fusion experiment resulted in a novel fragmentation pattern that showed a quadruplet of diagnostic ions for confident assignment of C=C bond positions and subsequent isomer differentiation. This phenomenon enabled the identification of a novel TG lipid, composed of conjugated linoleic acid, that is isomeric with two other TG lipids naturally found in extra virgin olive oil. To validate our findings, we analyzed various standards of TG lipids, including triolein, trilinolein, and trilinolenin, and isomeric mixtures in the positive-ion mode, each of which produced the expected quadruplet diagnostic fragment ions. Further validation was obtained by analyzing standards of free fatty acids expected from the hydrolysis of the TG lipids in the negative-ion mode, together with isomeric mixtures. The chemistry governing the gas-phase fragmentation of the lipid epoxides was carefully elucidated for each TG lipid analyzed. This comprehensive shotgun lipidomic approach has the potential to impact biomedical research since it can be accomplished on readily available mass spectrometers without the need for instrument modification.
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Burris BJ, Walsh LC, Badu-Tawiah AK. Online Cross-Linking of Peptides and Proteins during Contained-Electrospray Ionization Mass Spectrometry. Anal Chem 2023; 95:1085-1094. [PMID: 36534015 DOI: 10.1021/acs.analchem.2c03791] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Recent advancements in mass spectrometry (MS) now enable all levels of protein structures to be characterized, including primary protein sequence, post-translational modifications, and three-dimensional protein conformations. However, protein conformational studies by MS require the use of many separate techniques that are performed independently of each other. Herein, we described a contained-electrospray (ES) experiment that has potential to integrate peptide/protein cross-linking with the general MS workflow. In our experiment, cross-linking of protein/peptide occurs simultaneously with ionization after analytes, and cross-linkers are sprayed from two separate ES emitters. The online cross-linking process occurring in the charged microdroplet environment was optimized using trilysine peptide and bis(sulfosuccinimidyl)suberate cross-linker. We detected the electrostatic complex between analyte and cross-linker, the mono-linked intermediate, and the fully cross-linked product, allowing us to correctly predict the sequence of reaction events in the cross-linking process. Importantly, we observed that the terminal fully cross-linked product is composed of two distinct conformations. In one form, the product involved cross-linking between two ε-NH2 amines in lysine residues, while the other conformer was formed by a reaction between one ε-NH2 amine and the N-terminus. The experimental conditions for selecting one cross-linked species over others during the online ES ionization-MS analysis have been detailed. Appropriate parameters enabled the reaction between α-lactalbumin proteins and cross-linkers using a non-denaturing spray condition. These results establish a framework for a future development in high-throughput structural MS method, where all levels of protein information can be gathered in a single experiment.
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Affiliation(s)
- Benjamin J Burris
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio43210, United States
| | - Leah C Walsh
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio43210, United States
| | - Abraham K Badu-Tawiah
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio43210, United States
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Eremin DB, Fokin VV. Dual Electrospray Ionization Enhancement of Proteins Enabled by DMSO Supercharging Reagent. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2022; 33:203-206. [PMID: 34850625 DOI: 10.1021/jasms.1c00280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Supercharging reagents assist protein ionization by producing higher charge states and increasing signal intensities, thus improving sensitivity. Described here is an approach to employ a dual-spray ionization source with DMSO as a supercharging reagent to expand in-source supercharging. Under denaturing conditions, dual-source supercharging enhances ionization up to an order of magnitude for proteins of various properties and sizes, but the effect is not uniform. Efficient mixing of solutions from two nebulizing plumes was observed, which allowed sufficient transfer of supercharging molecules to a protein. The described method and proposed mechanism require at least 2.5% of DMSO to produce visible enhancement.
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Affiliation(s)
- Dmitry B Eremin
- Bridge Institute, University of Southern California, 1002 Childs Way, Los Angeles, California 90089-3502, United States
- Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, United States
| | - Valery V Fokin
- Bridge Institute, University of Southern California, 1002 Childs Way, Los Angeles, California 90089-3502, United States
- Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, California 90089-1661, United States
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Burris BJ, Badu-Tawiah AK. Enzyme-Catalyzed Hydrolysis of Lipids in Immiscible Microdroplets Studied by Contained-Electrospray Ionization. Anal Chem 2021; 93:13001-13007. [PMID: 34524788 DOI: 10.1021/acs.analchem.1c02785] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Enzyme-catalyzed hydrolysis of lipids was monitored directly in immiscible microdroplet environments using contained-electrospray mass spectrometry. Aqueous solution of the lipase enzyme from Pseudomonas cepacia and the chloroform solution of the lipids were sprayed from separate capillaries, and the resultant droplets were merged within a reaction cavity that is included at the outlet of the contained-electrospray ionization source. By varying the length of the reaction cavity, the interaction time between the enzyme and its substrate was altered, enabling the quantification of reaction product as a function of time. Consequently, enhancement factors were estimated by comparing rate constants derived from the droplet experiment to rate constants calculated from solution-phase conditions. These experiments showed enhancement factors greater than 100 in favor of the droplet experiment. By using various lipid types, two possible mechanisms were identified to account for lipase reactivity in aerosols: in-droplet reactions for relatively highly soluble lipids and a droplet coalescence mechanism that allows interfacial reactions for the two immiscible systems.
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Affiliation(s)
- Benjamin J Burris
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
| | - Abraham K Badu-Tawiah
- Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio 43210, United States
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Sarih NM, Romero-Perez D, Bastani B, Rauytanapanit M, Boisdon C, Praneenararat T, Tajuddin HA, Abdullah Z, Badu-Tawiah AK, Maher S. Accelerated nucleophilic substitution reactions of dansyl chloride with aniline under ambient conditions via dual-tip reactive paper spray. Sci Rep 2020; 10:21504. [PMID: 33299034 PMCID: PMC7725966 DOI: 10.1038/s41598-020-78133-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 11/12/2020] [Indexed: 11/25/2022] Open
Abstract
Paper spray ionization (PSI) mass spectrometry (MS) is an emerging tool for ambient reaction monitoring via microdroplet reaction acceleration. PSI-MS was used to accelerate and monitor the time course of the reaction of dansyl chloride with aniline, in acetonitrile, to produce dansyl aniline. Three distinct PSI arrangements were explored in this study representing alternative approaches for sample loading and interaction; conventional single tip as well as two novel setups, a dual-tip and a co-axial arrangement were designed so as to limit any on-paper interaction between reagents. The effect on product abundance was investigated using these different paper configurations as it relates to the time course and distance of microdroplet travel. It was observed that product yield increases at a given distance and then decreases thereafter for all PSI configurations. The fluorescent property of the product (dansyl aniline) was used to visually inspect the reaction progress on the paper substrate during the spraying process. Amongst the variety of sample loading methods the novel dual-tip arrangement showed an increased product yield and microdroplet density, whilst avoiding any on-paper interaction between the reagents.
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Affiliation(s)
- Norfatirah Muhamad Sarih
- Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool, L69 3GJ, UK
- Department of Chemistry, Faculty of Science, University of Malaya, 50603, Kuala Lumpur, Malaysia
| | - David Romero-Perez
- Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool, L69 3GJ, UK
| | - Behnam Bastani
- Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool, L69 3GJ, UK
| | - Monrawat Rauytanapanit
- Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool, L69 3GJ, UK
- Department of Chemistry, Faculty of Science, Chulalongkorn University, Phayathai Rd, Pathumwan, Bangkok, 10330, Thailand
| | - Cedric Boisdon
- Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool, L69 3GJ, UK
| | - Thanit Praneenararat
- Department of Chemistry, Faculty of Science, Chulalongkorn University, Phayathai Rd, Pathumwan, Bangkok, 10330, Thailand
| | - Hairul Anuar Tajuddin
- Department of Chemistry, Faculty of Science, University of Malaya, 50603, Kuala Lumpur, Malaysia
| | - Zanariah Abdullah
- Department of Chemistry, Faculty of Science, University of Malaya, 50603, Kuala Lumpur, Malaysia
| | | | - Simon Maher
- Department of Electrical Engineering and Electronics, University of Liverpool, Brownlow Hill, Liverpool, L69 3GJ, UK.
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