<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

Autumn has already turned the leaves into vibrant shades, and with the end of the year approaching, we would like to thank you - before the first snowflakes arrive - for your trust, cooperation, and continued interest in our products and services.As a long-standing distributor of Thermo Scientific Finnpipette products, we know that the accuracy and reliability of laboratory results often begin with seemingly small details. 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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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Characterization of polymers (Watrex)

Watrex Prague offers laboratory characterization of polymers using GPC.

<h4>WI08112 – Determination of Molecular Weight Distribution of Polymeric Materials</h4><ul><li>Determination by GPC method in water and THF, or optionally in other solvents upon request.</li><li>Each set of measurements requires calibration (WI08113).</li><li>Price: 3,300 CZK excl. VAT</li></ul><h4>WI08113 – Calibration for Molecular Weight Distribution of Polymeric Materials</h4><ul><li>Calibration using dextran, polymaltotriose, or polystyrene standards for GPC molecular weight distribution determination.</li><li>Price: 4,500 CZK excl. VAT</li></ul><img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Watrex_GPC_separace_polymeru_na_kolone_Watrex_Delta_Gel_47ce92deaa.jpg" alt="Watrex: GPC separation of polymers on Watrex DeltaGel column" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Watrex_GPC_separace_polymeru_na_kolone_Watrex_Delta_Gel_47ce92deaa.jpg 213w," sizes="100vw" width="1385" height="1018"><blockquote><h3>Services – Laboratory</h3>The Watrex Analytical Laboratory will be happy to perform any of our standard analyses, custom analyses, or assist you with method development.We specialize primarily in liquid chromatography techniques and are ready to meet a wide range of requirements—from method development and optimization, through validation and verification of external methods, to training and troubleshooting.Our laboratory also manufactures and packs its own chromatographic columns and guard columns for basic HPLC modes (reversed phase, normal phase, ion chromatography, and ion exclusion chromatography).<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Watrex_Analyticka_laborator_fc8862fba5.jpg" alt="Watrex: Analytical Laboratory" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Watrex_Analyticka_laborator_fc8862fba5.jpg 245w," sizes="100vw" width="1569" height="637"></blockquote>

Analytical Services for Building Materials (Watrex Laboratory)

Comprehensive analysis of building materials by ion chromatography and gravimetry – salts, moisture, lime, gypsum, density, and absorption testing by Watrex Laboratory.

<h5>WI08101 – Determination of Water-Soluble Salts in Building Materials</h5><ul><li>Determination of chlorides, nitrates, and sulfates in aqueous extract using ion chromatography. Requires approx. 1 g of a homogeneous sample.</li><li>Price: 600 CZK excl. VAT</li></ul><h5>WI08102 – Determination of Moisture in Building Materials</h5><ul><li>Gravimetric method after drying the sample to constant weight. Moisture content is expressed in mass %. Requires at least 10 g of sample in sealed packaging.</li><li>Price: 300 CZK excl. VAT</li></ul><h5>WI08103 – Determination of Lime Content in Lime Mortars</h5><ul><li>After acid digestion, Ca and Mg content is determined to calculate CaCO₃ and MgCO₃. Sand content determined gravimetrically. Not suitable for cement mortars. Requires approx. 5 g of sample.</li><li>Price: 1,275 CZK excl. VAT</li></ul><h5>WI08104 – Semi-Quantitative Determination of Gypsum in Building Materials</h5><ul><li>Based on solubility differences of gypsum and alkaline sulfates. Requires approx. 11 g of sample.</li><li>Price: 1,100 CZK excl. VAT</li></ul><h5>WI08105 – Determination of Bulk Density of Building Materials</h5><ul><li>Performed using quartz sand displacement. Requires 30–50 cm³ of sample in pieces 2–4 cm.</li><li>Price: 440 CZK excl. VAT</li></ul><h5>WI08109 – Determination of Hygroscopic Moisture in Building Materials</h5><ul><li>Gravimetric method after equilibrium at 100% RH and drying at 105 °C for 2 hours. Requires approx. 10 g of sample.</li><li>Price: 440 CZK excl. VAT</li></ul><h5>WI08114 – Determination of Water Absorption of Building Materials</h5><ul><li>Gravimetric method from weight difference between dried and water-saturated sample. Bulk density determined simultaneously. Requires 30–50 cm³ of sample in pieces 2–4 cm.</li><li>Price: 4,495 CZK excl. VAT</li></ul><blockquote>10% discount when submitting 3 or more samples at once.</blockquote><blockquote><h3>Services – Laboratory</h3>The Watrex Analytical Laboratory will be happy to perform any of our standard analyses, custom analyses, or assist you with method development.We specialize primarily in liquid chromatography techniques and are ready to meet a wide range of requirements—from method development and optimization, through validation and verification of external methods, to training and troubleshooting.Our laboratory also manufactures and packs its own chromatographic columns and guard columns for basic HPLC modes (reversed phase, normal phase, ion chromatography, and ion exclusion chromatography).<img src="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/Watrex_Analyticka_laborator_fc8862fba5.jpg" alt="Watrex: Analytical Laboratory" srcset="https://storage.googleapis.com/labrulez-bucket-strapi-h3hsga3/thumbnail_Watrex_Analyticka_laborator_fc8862fba5.jpg 245w," sizes="100vw" width="1569" height="637"></blockquote>

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Proton sharing in polycarboxylic acids in aqueous solution

Equip Your Laboratory for Autumn at a Better Price