<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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KNAUER RF-20A Fluorescence Detector

High-sensitivity fluorescence detector for HPLC with 200–650 nm wavelength range, ≥1200 S/N ratio, fast 10 ms response, and excellent trace-level detection performance.

The KNAUER RF-20A Fluorescence Detector is a highly sensitive fluorescence detector designed for demanding HPLC applications requiring exceptional selectivity and trace-level detection. Covering a wavelength range from 200 to 650 nm, the RF-20A delivers outstanding sensitivity, excellent reproducibility, and reliable operation for both routine and advanced chromatographic analyses.With a signal-to-noise ratio of at least 1200 for the water Raman band, the detector is ideally suited for trace-level determinations in pharmaceutical, environmental, food, and biochemical applications. A fast 10 ms response time supports high-speed chromatography without compromising chromatographic resolution. Time-programmed wavelength switching allows optimal excitation and emission settings throughout the run, enabling highly sensitive multi-component analysis.<h3>Key Features</h3><ul><li>High-sensitivity fluorescence detector for HPLC applications</li><li>Wavelength range from 200 to 650 nm</li><li>Signal-to-noise ratio ≥1200 (water Raman band)</li><li>Excellent performance for trace-level analysis</li><li>Fast 10 ms response time</li><li>Time-programmable wavelength switching</li><li>Multi-component analysis at optimal wavelengths</li><li>Long-life xenon lamp (approx. 2,000 hours)</li><li>Front-accessible lamp and flow cell</li><li>No optical adjustment required after lamp replacement</li><li>Minimal maintenance requirements</li><li>Stand-alone operation via keypad and display</li><li>Compatible with ClarityChrom®, OpenLAB®, and PurityChrom® software</li><li>Easy integration into existing LC systems</li></ul><h3>Technical Specifications</h3><h4>Detection System</h4><ul><li>Detection channels: 1</li><li>Number of signals: 1</li><li>Light source: Xenon lamp</li><li>Wavelength range: 200–650 nm</li><li>Spectral bandwidth: 20 nm</li><li>Wavelength accuracy: ±2 nm</li><li>Wavelength precision: ±0.2 nm</li></ul><h4>Sensitivity</h4><ul><li>Signal-to-noise ratio: ≥1200 (water Raman band)</li><li>Sensitivity settings:<ul><li>HIGH (×1)</li><li>MED (×32)</li><li>LOW (×1024)</li></ul></li></ul><h4>Flow Cell</h4><ul><li>Standard flow cell included</li><li>Flow cell volume: 12 µL</li><li>Wetted materials:<ul><li>SUS316L stainless steel</li><li>PTFE</li><li>Quartz</li></ul></li></ul><h4>Signal Processing</h4><ul><li>Response time: 10 ms</li><li>Gain settings: ×1, ×4, ×16</li></ul><h4>Functions</h4><ul><li>Autozero function</li><li>Baseline shift function</li><li>Time-programmed wavelength switching</li></ul><h4>Communication</h4><ul><li>RS-232 interface</li><li>Analog output</li><li>Software control</li><li>Stand-alone operation via keypad and display</li></ul><h4>Environmental Conditions</h4><ul><li>Operating temperature: 4–35 °C</li><li>Relative humidity: 20–85% (non-condensing)</li></ul><h4>Power and Dimensions</h4><ul><li>Power supply: AC 220–240 V</li><li>Frequency: 50/60 Hz</li><li>Power consumption: 400 VA</li><li>Dimensions (W × H × D): 260 × 210 × 420 mm</li><li>Weight: 16 kg</li></ul><h3>Applications</h3><ul><li>Pharmaceutical analysis</li><li>Impurity profiling</li><li>Environmental monitoring</li><li>Food and beverage testing</li><li>Amino acid analysis</li><li>Vitamin analysis</li><li>PAH analysis</li><li>Biomolecule detection</li><li>Trace contaminant determination</li><li>Research and quality control laboratories</li></ul>

KNAUER RF-20Axs Fluorescence Detector

High-sensitivity fluorescence detector with 200–750 nm range, temperature-controlled flow cell, ≥2000 S/N ratio, and exceptional performance for trace-level HPLC analysis.

The KNAUER RF-20Axs Fluorescence Detector is the high-performance version of the <a target="_blank" rel="noopener noreferrer" href="https://lcms.labrulez.com/products/2430">RF-20A fluorescence detector</a> series, designed for laboratories requiring maximum sensitivity, exceptional reproducibility, and advanced validation capabilities. Covering a wavelength range from 200 to 750 nm, the detector supports both routine and demanding high-performance HPLC applications.With a signal-to-noise ratio of at least 2000 for the water Raman band, the RF-20Axs is ideally suited for trace-level analysis. The temperature-controlled flow cell with integrated cooling function ensures outstanding stability, reproducibility, and sensitivity, even during long analytical sequences. The detector’s fast 10 ms response time supports ultra-fast chromatography without compromising chromatographic resolution.The RF-20Axs enables highly sensitive multi-component analysis through programmable wavelength switching during a chromatographic run. An integrated low-pressure mercury lamp allows convenient verification of wavelength accuracy, supporting validation and compliance requirements. Both the xenon lamp and flow cell are easily accessible from the front panel, and lamp replacement requires no optical adjustment. Combined with a lamp lifetime of approximately 2,000 hours, this minimizes downtime and operating costs.<h3>Key Features</h3><ul><li>High-sensitivity fluorescence detector for HPLC applications</li><li>Wavelength range from 200 to 750 nm</li><li>Signal-to-noise ratio ≥2000 (water Raman band)</li><li>Designed for trace-level analysis</li><li>Temperature-controlled flow cell with cooling function</li><li>Fast 10 ms response time</li><li>Programmable wavelength switching during analysis</li><li>Simultaneous multi-component analysis at optimal wavelengths</li><li>Integrated low-pressure mercury lamp for wavelength verification</li><li>Long-life xenon lamp with approximately 2,000 operating hours</li><li>Front-accessible lamp and flow cell</li><li>No optical realignment required after lamp replacement</li><li>Advanced validation and support functions</li><li>Stand-alone operation via keypad and display</li><li>Compatible with ClarityChrom®, OpenLAB®, and PurityChrom® software</li><li>Easy integration into virtually any LC system</li></ul><h3>Technical Specifications</h3><h4>Detection System</h4><ul><li>Detection channels: 2</li><li>Number of signals: 2</li><li>Light source:<ul><li>Xenon lamp</li><li>Low-pressure mercury lamp for wavelength accuracy verification</li></ul></li><li>Wavelength range: 200–750 nm</li><li>Spectral bandwidth: 20 nm</li><li>Wavelength accuracy: ±2 nm</li><li>Wavelength precision: ±0.2 nm</li></ul><h4>Sensitivity</h4><ul><li>Signal-to-noise ratio: ≥2000 (water Raman band)</li><li>Sensitivity settings:<ul><li>HIGH (×1)</li><li>MED (×32)</li><li>LOW (×1024)</li></ul></li></ul><h4>Flow Cell</h4><ul><li>Standard flow cell included</li><li>Temperature-controlled flow cell</li><li>Integrated cooling function</li><li>Flow cell volume: 12 µL</li><li>Wetted materials:<ul><li>SUS316L stainless steel</li><li>PTFE</li><li>Quartz</li></ul></li></ul><h4>Signal Processing</h4><ul><li>Response time: 10 ms</li><li>Gain settings: ×1, ×4, ×16</li></ul><h4>Functions</h4><ul><li>Autozero function</li><li>Baseline shift function</li><li>Time-programmed wavelength switching</li><li>Wavelength accuracy verification using integrated mercury lamp</li></ul><h4>Communication</h4><ul><li>RS-232 interface</li><li>Analog output</li><li>Software control</li><li>Stand-alone operation via keypad and display</li></ul><h4>Environmental Conditions</h4><ul><li>Operating temperature: 4–35 °C</li><li>Relative humidity: 20–85% (non-condensing)</li></ul><h4>Power and Dimensions</h4><ul><li>Power supply: AC 220–240 V</li><li>Frequency: 50/60 Hz</li><li>Power consumption: 400 VA</li><li>Dimensions (W × H × D): 260 × 210 × 420 mm</li><li>Weight: 18 kg</li></ul><h3>Applications</h3><ul><li>Trace-level pharmaceutical analysis</li><li>Impurity profiling</li><li>Environmental monitoring</li><li>Food safety testing</li><li>Amino acid analysis</li><li>Vitamin analysis</li><li>PAH analysis</li><li>Biomolecule detection</li><li>Fluorescent labeling applications</li><li>Research and quality control laboratories</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

Equip Your Laboratory for Autumn at a Better Price