<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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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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Watrex SCS 205 GPC Sample cleanup system

The Watrex Streamline SCS 205 Sample Clean-up System is designed for GPC sample pretreatment.

Sample clean-up is an essential method for many routine chromatography applications. One of the most common cases is analysis of polyaromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and pesticides in complex mixtures.The initial step is an isolation of hydrophobic (lipophilic) components from the rest of the sample mixture by gel-permeation chromatography (GPC).In such configuration, triglycerides (700-900Da) can be isolated from low molecular (200-300Da) PAHs, PCBs or pesticides using GPC steric exclusion. SCS 205 is a dedicated system for GPC sample pretreatment. SCS 205 includes an isocratic pump double piston pump, manual injector with preparative sample loop, PAH/PCB preparative column (200mg sample loading capacity), fraction collector and start-up kit. .The entire system is controlled from a TFT touch display through intuitive screens.After injection and GPC separation, the purified sample (PAHs, PCBs etc.) is captured by an automated fraction collection usinga3-way motorized switching valve. The timing of the collection is predetermined from the elution profile of the pollutants.<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Watrex_Watrex_SCS_205_Sample_cleanup_system_column_7dce4f25e0.jpg" alt="Watrex: Watrex SCS 205 Sample cleanup system - column"><h3>FEATURES</h3><ul><li>High performance pollutant izolation from complex matrices</li><li>Eluent flexibility</li><li>Easy programmable</li><li>Easy installation &amp; Simple operation</li></ul><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Watrex_Watrex_SCS_205_Sample_cleanup_system_schema_ad45276ad0.jpg" alt="Watrex: Watrex SCS 205 Sample cleanup system - schema"><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Watrex_Watrex_SCS_205_Sample_cleanup_system_graph_10ce455cc3.jpg" alt="Watrex: Watrex SCS 205 Sample cleanup system - graph"><h3>TECHNICAL SPECIFICATION</h3><ul><li>Sampling System: manual valve</li><li>Sample volume: 2 mL loop</li><li>Fraction collection: 50mL flask</li><li>Collection time programming: alternating valve switching to waste/collect/waste</li><li>Display: 4-character</li></ul><h3>Ordering information:</h3><h5>PN/Component:</h5><ul><li>SCS205-001 SCS 205 Sample Clean-up System (Price 8 627 € ex VAT)</li><li>WI02077 WATREX 250x16 mm PAH Prep column, 10 um</li><li>DGD.3008 WATREX 300x8 mm DeltaGel Mixed-D column, 5 um</li><li>DGB.25020 WATREX 250x20 mm DeltaGel Mixed-B column, 5 um</li></ul>You can also visit this product on the <a target="_blank" rel="noopener noreferrer" href="https://watrex.com/obchod/chromatography/dedicated-instruments/scs-205-sample-clean-up-system/?utm_source=labrulez&amp;utm_medium=propagace&amp;utm_campaign=labrulez_produkty">Watrex website</a>.

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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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