<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. 

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Linde Acetylene for Flame Photometry - Gas Cylinder

Linde Acetylene ≥99.6% for flame photometry and AAS. High-efficiency fuel gas delivering stable flame conditions for analytical and industrial applications.

Acetylene for flame photometry from Linde is a highly efficient fuel gas supplied at approximately 99.6% purity, dissolved in acetone or DMF (dimethylformamide). This dissolved form ensures safe storage and handling by stabilizing the gas within a porous mass inside the cylinder.Acetylene offers the highest flame temperature among commonly used fuel gases and provides rapid heating. These properties make it suitable for both analytical and industrial applications. In analytical chemistry, it is widely used as a fuel gas for flame photometry and atomic absorption spectrometry (AAS), ensuring stable flame conditions and accurate measurements.Thanks to specially designed cylinders, acetylene supplied by Linde meets the strictest industrial safety standards and ensures reliable operation.<h4>Key Features</h4><ul><li>Highest efficiency among fuel gases</li><li>High purity (~≥ 99.6%) for analytical applications</li><li>Dissolved in acetone or DMF for safe handling</li><li>Stable and high-temperature flame</li><li>Suitable for analytical and industrial use</li><li>Complies with strict safety standards</li></ul><h4>Technical Specifications</h4><ul><li>Gas: acetylene (C₂H₂)</li><li>Purity: approx. ≥ 99.6% (photometry grade)</li><li>Supply form: dissolved in acetone or DMF in gas cylinder</li></ul><h4>Applications</h4><h5>Analytical Applications:</h5><ul><li>Fuel gas for flame photometry</li><li>Fuel gas for atomic absorption spectrometry (AAS)</li></ul><h5>Industrial Applications:</h5><ul><li>Flame welding and brazing</li><li>Oxy-fuel cutting</li><li>Heat treatment (e.g., carburizing)</li><li>Flame heating and hot forming</li><li>Flame cleaning, hardening, and straightening</li></ul><h5>Other Applications:</h5><ul><li>Glass industry (e.g., separation layer formation)</li></ul>

Linde Acetylene Pure – Gas Cylinder

Linde Acetylene ≥98.5% for welding, cutting, and heating. Highly efficient fuel gas with the highest flame temperature and rapid heating performance.

Pure acetylene from Linde is a highly efficient fuel gas supplied at a purity of ≥ 98.5%, dissolved in acetone. This form ensures safe storage and handling by stabilizing the gas within a porous mass inside the cylinder.Acetylene provides the highest flame temperature among commonly used fuel gases and delivers rapid heating performance. When combined with oxygen, it offers outstanding technological properties, making it suitable for a wide range of industrial applications.Its unique characteristics make it ideal not only for welding and cutting but also for metallurgical processes (e.g., carburizing) and glass manufacturing.<h4>Key Features</h4><ul><li>Highest efficiency among fuel gases</li><li>Purity ≥ 98.5%</li><li>Dissolved in acetone for safe handling</li><li>Very fast heating capability</li><li>Stable and high-temperature flame</li><li>Versatile industrial applications</li></ul><h4>Technical Specifications</h4><ul><li>Gas: acetylene (C₂H₂)</li><li>Purity: ≥ 98.5%</li><li>Supply form: dissolved in acetone in gas cylinder</li><li>Cylinder type:<ul><li>1.8 kg</li><li>4 kg</li><li>7 kg</li><li>8 kg</li><li>10 kg</li></ul></li></ul><h4>Applications</h4><ul><li>Flame welding and brazing</li><li>Oxy-fuel cutting</li><li>Flame heating</li><li>Flame gouging</li><li>Flame hardening</li><li>Flame cleaning and straightening</li><li>Hot forming</li></ul><h5>Additional applications:</h5><ul><li>Metallurgy (e.g., surface carburizing)</li><li>Glass industry (e.g., separation layer formation)</li></ul>

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

Proton sharing in polycarboxylic acids in aqueous solution

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