<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.

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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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Linde REDLINE Pressure Regulators C 200/1 & C 200/2

REDLINE C 200 pressure regulators provide precise and stable gas control up to 6.0 purity, ideal for laboratory, analytical, and research applications.

The REDLINE C 200 series pressure regulators (models C 200/1 single-stage and C 200/2 dual-stage) are designed for precise control of non-corrosive gases with purity levels up to 6.0 (99.9999%), as well as gas mixtures containing low concentrations of corrosive components.These regulators ensure excellent pressure stability, high accuracy, and preservation of gas purity, making them ideal for demanding laboratory, analytical, and research applications.The C 200/1 single-stage version is suitable for applications with stable inlet pressure, such as gases supplied in liquid phase. The C 200/2 dual-stage version is specifically designed for systems where inlet pressure fluctuates, ensuring highly stable outlet pressure even under changing conditions.<h4>Key Features</h4><ul><li>High precision pressure regulation for analytical applications</li><li>Suitable for high-purity gases up to grade 6.0 (99.9999%)</li><li>Excellent outlet pressure stability (especially dual-stage version)</li><li>Designed to maintain gas purity and minimize contamination</li><li>Wide range of configurable outlet pressure ranges</li><li>Flexible configuration with multiple valve and purging options</li><li>Robust and reliable design for laboratory and R&amp;D environments</li></ul><h4>Technical Specifications</h4><ul><li>Inlet pressure: up to 230 bar</li><li>Outlet pressure ranges:<ul><li>C 200/1 (single-stage): 3 / 6 / 10 / 14 / 16 / 28 / 35 / 50 / 100 / 200 bar</li><li>C 200/2 (dual-stage): 1 / 3 / 6 / 10 / 14 bar</li></ul></li><li>Gas compatibility:<ul><li>Non-corrosive gases up to purity 6.0</li><li>Gas mixtures with low corrosive content</li></ul></li><li>Inlet connections:<ul><li>According to DIN 477 and gas specification</li></ul></li><li>Outlet connections:<ul><li>Compression fittings</li><li>Hose nozzles</li></ul></li></ul><h4>Available Configurations</h4><h5>Models</h5><ul><li>C 200/1 (Single-stage) Designed for applications with stable inlet pressure</li><li>C 200/2 (Dual-stage) Designed for fluctuating inlet pressure with maximum outlet stability</li></ul><h4>Optional Equipment</h4><ul><li>Shut-off valve (Type A)</li><li>Needle valve (Type B)</li><li>High-pressure side purge (Type P)</li><li>Inert/external gas purge (Type TP)</li><li>Purge manifold (Type EP)</li><li>Post-purge (Type DP – available only for C 200/2)</li></ul><h4>Applications</h4><ul><li>Laboratory gas supply systems</li><li>Analytical instrumentation (e.g., GC, LC, MS workflows)</li><li>Research and development environments</li><li>High-purity gas distribution systems</li><li>Any application requiring stable pressure and contamination-free gas delivery</li></ul>

Linde REDLINE Pressure Regulators C 300/1 & C 300/2

REDLINE C 300 pressure regulators provide precise and stable gas control up to 6.0 purity, ensuring reliability for laboratory, analytical, and research applications.

The REDLINE C 300 series pressure regulators (models C 300/1 single-stage and C 300/2 dual-stage) are designed for precise control of non-corrosive gases with purity levels up to 6.0 (99.9999%), as well as gas mixtures containing low concentrations of corrosive components.Thanks to their robust design and high-quality manufacturing, these regulators provide excellent pressure stability, accuracy, and long-term reliability. They are particularly well suited for demanding laboratory, analytical, and research applications where maintaining gas purity and consistent pressure is critical.The C 300/1 single-stage regulator is recommended for applications with relatively stable inlet pressure, such as gases supplied in liquid phase. The C 300/2 dual-stage version is intended for systems with fluctuating inlet pressure, ensuring highly stable outlet pressure and improved control under varying operating conditions.<h4>Key Features</h4><ul><li>Precise and stable pressure regulation for analytical workflows</li><li>Compatible with high-purity gases up to grade 6.0 (99.9999%)</li><li>Dual-stage version provides superior outlet pressure stability</li><li>Designed to maintain gas purity and minimize contamination risks</li><li>Wide range of adjustable outlet pressure settings</li><li>Modular design with multiple optional valve and purge configurations</li><li>High reliability for continuous laboratory and R&amp;D operation</li></ul><h4>Technical Specifications</h4><ul><li>Inlet pressure: up to 300 bar</li><li>Outlet pressure ranges:<ul><li>C 300/1 (single-stage): 3 / 6 / 10 / 14 / 16 / 28 / 35 / 50 / 100 / 200 bar</li><li>C 300/2 (dual-stage): 1 / 3 / 6 / 10 / 14 bar</li></ul></li><li>Gas compatibility:<ul><li>Non-corrosive gases up to purity 6.0</li><li>Gas mixtures with low corrosive content</li></ul></li><li>Inlet connections:<ul><li>According to DIN 477 and gas specification</li></ul></li><li>Outlet connections:<ul><li>Compression fittings</li><li>Hose nozzles</li></ul></li></ul><h4>Available Configurations</h4><h5>Models</h5><ul><li>C 300/1 (Single-stage) Designed for applications with stable inlet pressure</li><li>C 300/2 (Dual-stage) Designed for fluctuating inlet pressure with maximum outlet pressure stability</li></ul><h4>Optional Equipment</h4><ul><li>Shut-off valve (Type A)</li><li>Needle valve (Type B)</li><li>High-pressure side purge (Type P)</li><li>Inert gas purge (Type TP)</li><li>Purge manifold (Type EP)</li><li>Post-purge (Type DP – available only for C 300/2)</li></ul><h4>Applications</h4><ul><li>Analytical instrumentation (e.g., GC, LC, MS systems)</li><li>Laboratory gas supply systems</li><li>Research and development environments</li><li>High-purity gas distribution systems</li><li>Applications requiring precise pressure control and contamination-free gas delivery</li></ul>

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Proton sharing in polycarboxylic acids in aqueous solution

Equip Your Laboratory for Autumn at a Better Price