<div><div>Protons play a central role in many chemical reactions in living organisms. In some cases, a proton may be shared between two nearby molecular groups rather than being localized on just one. This phenomenon can strongly influence the properties and reactivity of biomolecules and is important for enzyme function.</div></div><div>Researchers led by Hanns Christian Schewe (IOCB Prague and Heyrovský Institute of the CAS) together with Lukáš Tomaník (UCT Prague and Fritz Haber Institute of the Max Planck Society) have now investigated proton sharing in a range of biologically relevant polycarboxylic acids dissolved in water, including several molecules related to the citric acid cycle (Krebs cycle).Using liquid-jet X-ray photoelectron spectroscopy (LJ-PES), a technique that reveals the chemical environment of atoms in molecules dissolved in water, the team was able to probe the position of protons on an ultrafast time scale. Unlike techniques such as NMR, which provide a time-averaged picture, photoelectron spectroscopy captures the instantaneous distribution of protons and can therefore distinguish more directly between localized and shared states.The results showed significant proton sharing only in maleic acid dissolved in water. In contrast, protons remained mostly localized at individual carboxylic groups in succinic acid, fumaric acid, malic acid, glutaric acid and citric acid. This suggests that proton sharing is not a common feature of these molecules when they are freely dissolved in water.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/IOCB_Prague_Cropped_part_of_the_cover_by_Schewe_et_al_with_the_use_of_Nano_Banana_2_0_2_2a408dbeb5.webp" alt="IOCB Prague: Cropped part of the cover by Schewe et al. with the use of Nano Banana 2.0: Full cover by Schewe et al. with the use of Nano Banana 2.0." srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_IOCB_Prague_Cropped_part_of_the_cover_by_Schewe_et_al_with_the_use_of_Nano_Banana_2_0_2_2a408dbeb5.webp 117w," sizes="100vw" width="1620" height="2154">The difference appears to be largely controlled by molecular geometry. In maleic acid, the two carboxylic groups are held close together, creating favorable conditions for proton sharing. More flexible molecules can adopt conformations in which the groups are farther apart, while water molecules form strong hydrogen bonds with them and favor localized protons.However, the situation may be different inside proteins. When a carboxylic acid binds in the active site of an enzyme, its shape and position can be tightly constrained. Such an environment could bring the relevant groups close enough together to promote proton sharing and thereby influence enzymatic reactions.The study highlights an important distinction: proton sharing may be rare in freely hydrated molecules but could become important when biomolecules are held in the right geometry by enzymes. It also demonstrates that LJ-PES is a powerful tool for studying proton behavior in solutions. Its ultrafast and site-specific sensitivity could in future help researchers investigate proton sharing directly in more complex chemical and biological systems.<blockquote><h4>The original article</h4><h4><a target="_blank" rel="noopener noreferrer" href="https://pubs.acs.org/jaaucr/article/6/6/3349/5084661/Proton-Sharing-in-Polycarboxylic-Acids-in-Aqueous">Proton Sharing in Polycarboxylic Acids in Aqueous Solution</a></h4>Lukáš Tomaník, Jiří Tůma, Gunnar Öhrwall, Ronny Golnak, Ngoc Lan Le Nguyen, Bruno Credidio, Harmanjot Kaur, Petr Slavíček, Bernd Winter, H. Christian Schewe<div>JACS Au, 2026, 6, 3349–3355</div><a target="_blank" rel="noopener noreferrer" href="https://doi.org/10.1021/jacsau.6c00377">https://doi.org/10.1021/jacsau.6c00377</a><h6>licenced under <a target="_blank" rel="noopener noreferrer" href="https://creativecommons.org/licenses/by/4.0/">CC-BY 4.0</a></h6></blockquote><h4>Abstract</h4>We investigate proton sharing in biologically relevant polycarboxylic acids in aqueous solutions using liquid-jet X-ray photoelectron spectroscopy. In contrast to techniques that record time-averaged proton positions, like nuclear magnetic resonance, photoelectron spectroscopy captures instantaneous proton distribution due to its ultrafast probing time scale. The method is, therefore, uniquely sensitive to the occurrence of proton sharing in an aqueous environment, as demonstrated here. We only observe significant proton sharing dynamics in maleic acid, where its monoanionic form shows a single, delocalized peak in the carbon 1s spectrum. Conversely, succinic acid, fumaric acid, malic acid, glutaric acid, and citric acid exhibit distinct peaks corresponding to separate, localized COOH and COO– groups, instead of shared protons. Our results reveal that intramolecular proton sharing in water is rather an exception for most biologically relevant polycarboxylic acids. This highlights the importance of enzyme-driven structural changes of polycarboxylic acids associated with proton sharing during metabolic processes.</div>

Proton sharing in polycarboxylic acids in aqueous solution

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Breathomics, Asthma & GC×GC: PH Stefanuto on Fighting the “Proof‑of‑Concept” Trap

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The Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences (IOCB Prague) is a leading scientific institution in the Czech Republic, recognized internationally. Its primary mission is basic research in the fields of chemical biology and medicinal chemistry, organic and material oriented chemistry, chemistry of natural compounds, biochemistry and molecular biology, physical chemistry, theoretical chemistry, and analytical chemistry. 

Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences

Analytika is a Czech company that offers and produces certified reference materials (CRM) and (ultra)pure chemicals for quality control and quality assurance in laboratories, including accredited laboratories.

Our portfolio also includes pipettes and tips, digestors, PFA labware and other equipment for analytical laboratory and trace analysis.

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Organomation, founded in 1959, designs and manufactures high-quality nitrogen evaporators and extraction systems. Known for innovation and durability, their lab instruments are used globally for efficient sample preparation with strong customer support.

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EST Analytical CENTURION Water/Soil Purge and Trap Autosampler

The EST Analytical CENTURION delivers reliable purge and trap VOC analysis with high sample capacity, robust design, and intuitive software for water and soil testing.

The CENTURION is a flexible purge and trap autosampler available in two configurations: a combined water/soil system or a water-only system. Purge and trap technology enables the extraction of volatile organic compounds (VOCs) from samples by purging them with an inert gas onto a sorbent trap, where they are concentrated and subsequently transferred into instruments such as GC or GC/MS for precise analysis.Designed for laboratories worldwide, the CENTURION enhances throughput, ensures reliable performance, and simplifies VOC sample preparation. With robust engineering and intuitive software, it helps analysts and technicians maximize efficiency and maintain consistent results across demanding workflows.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_CENTURION_Water_Soil_Purge_and_Trap_Autosampler_3_3cb7b848e1.jpg" alt="EST Analytical: CENTURION Water/Soil Purge and Trap Autosampler" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_CENTURION_Water_Soil_Purge_and_Trap_Autosampler_3_3cb7b848e1.jpg 141w," sizes="100vw" width="704" height="778"><h4>Key Features</h4><h5>Reliable Purge &amp; Trap Performance</h5><ul><li>Proven XYZ autosampler design with heavy-duty rails for stability</li><li>Separate needles for water and soil samples to prevent cross-contamination</li><li>Internal standard addition with &lt;3% RSD precision</li><li>Engineered for consistent results right from the start</li></ul><h5>Optimized Productivity</h5><ul><li>Supports up to 100 water samples and 90 soil samples</li><li>Single calibration method accommodates both water and soil matrices</li><li>Integrated optical sensors reduce vial and syringe handling errors</li><li>Includes methanol extraction capability and optional pH detection</li></ul><h5>User-Friendly Operation</h5><ul><li>Unique software for prioritizing urgent/rush samples</li><li>400:1 dilution capability for flexible workflows</li><li>Intuitive control software accessible from any PC in the lab</li><li>Programmable soil needle depth to minimize clogging</li><li>Automated hot water rinse cycle to reduce carryover</li></ul><h4>Technical Specifications</h4><ul><li>Configurations: Water/Soil purge &amp; trap system or Water-only system</li><li>Sample Capacity: 100 water samples / 90 soil samples</li><li>Dilution Capability: Up to 400:1</li><li>Carryover Control: Programmable hot water rinse</li><li>Additional Functions: Methanol extraction, pH detection (optional)</li><li>Software: Intuitive, PC-based control with rush sample handling</li></ul>

EST Analytical EVOLUTION 2 Purge and Trap Concentrator

The EST Analytical EVOLUTION 2 concentrator delivers EPA-compliant VOC analysis with patented flow control, faster cycles, and compact, user-friendly design.

Developed with direct input from laboratory users, the EVOLUTION 2 purge and trap concentrator combines USEPA compliance with high productivity, stability, and simplified maintenance. Designed for reliable VOC concentration, it delivers superior performance and minimizes downtime, making it an ideal solution for today’s demanding laboratory environments.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/EST_Analytical_EVOLUTION_2_Purge_and_Trap_Concentrator_2_b841c750b8.jpg" alt="EST Analytical: EVOLUTION 2 Purge and Trap Concentrator" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_EST_Analytical_EVOLUTION_2_Purge_and_Trap_Concentrator_2_b841c750b8.jpg 129w," sizes="100vw" width="570" height="689"><h4>Key Features</h4><h5>Engineered for Accuracy</h5><ul><li>Unique 8-port valve pathway ensures advanced moisture control</li><li>Enhanced ventilation system shortens trap cool-down times</li><li>Patented Desorb Pressure Control (DPC) for improved chromatography results</li><li>Patented Desorb Flow Control (DFC) optimized for USEPA 524 methods</li></ul><h5>Maximized Productivity</h5><ul><li>Faster trap cooling reduces cycle times</li><li>Automated signaling boosts sample throughput</li><li>Innovative flow path design minimizes sample carryover</li><li>Proven Moisture Reduction Trap (MORT) technology</li><li>Dual-mode functionality for higher output and flexibility</li></ul><h5>User-Friendly Operation</h5><ul><li>Intuitive, advanced software interface</li><li>Quick-access design with removable covers for trap maintenance</li><li>Compact footprint saves valuable bench space</li></ul><h4>Technical Specifications</h4><ul><li>Compliance: USEPA 524 and related VOC methods</li><li>Sample Pathway: 8-port valve with advanced moisture control</li><li>Patented Features: DPC (Desorb Pressure Control), DFC (Desorb Flow Control), MORT (Moisture Reduction Trap)</li><li>Productivity: Dual-mode operation, automated cycle optimization</li><li>Design: Compact footprint, easy maintenance access</li></ul>

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Proton sharing in polycarboxylic acids in aqueous solution

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