Investigating the Role of pH and Counterions in the Intrinsic Fluorescence of Solid-State L-Lysine
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| Main Authors: | , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866917123306029056 |
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| author | Monti, Marta Cimmino, Luca Mirón, Gonzalo Díaz Diaferia, Carlo Banerjee, Debarshi Stella, Martina Vitagliano, Luigi Accardo, Antonella Hassanali, Ali |
| author_facet | Monti, Marta Cimmino, Luca Mirón, Gonzalo Díaz Diaferia, Carlo Banerjee, Debarshi Stella, Martina Vitagliano, Luigi Accardo, Antonella Hassanali, Ali |
| contents | There is currently a growing interest in understanding the origins of intrinsic fluorescence as a way to design non-invasive probes for biophysical processes. In this regard, understanding how pH influences fluorescence in non-aromatic biomolecular assemblies is key to controlling their optical properties in realistic cellular conditions. Here, we combine experiments and theory to investigate the pH-dependent emission of solid-state L-Lysine (Lys). Lys aggregates prepared at different pH values using HCl and H$_2$SO$_4$ exhibit protonation- and counterion-dependent morphology and fluorescence, as shown by microscopy and steady-state measurements. We find an enhancement in the fluorescence moving from acidic to basic conditions. To uncover the molecular origin of these trends, we performed non-adiabatic molecular dynamics simulations on three Lys crystal models representing distinct protonation states. Our simulations indicate that enhanced protonation under acidic conditions facilitates non-radiative decay via proton transfer, whereas basic conditions favor radiative decay. Our combined experimental-theoretical work highlights pH and counterion identity as key factors tuning fluorescence in Lys assemblies, offering insights for designing pH responsive optical materials based on non-aromatic amino acids. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2507_19241 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Investigating the Role of pH and Counterions in the Intrinsic Fluorescence of Solid-State L-Lysine Monti, Marta Cimmino, Luca Mirón, Gonzalo Díaz Diaferia, Carlo Banerjee, Debarshi Stella, Martina Vitagliano, Luigi Accardo, Antonella Hassanali, Ali Chemical Physics Biological Physics There is currently a growing interest in understanding the origins of intrinsic fluorescence as a way to design non-invasive probes for biophysical processes. In this regard, understanding how pH influences fluorescence in non-aromatic biomolecular assemblies is key to controlling their optical properties in realistic cellular conditions. Here, we combine experiments and theory to investigate the pH-dependent emission of solid-state L-Lysine (Lys). Lys aggregates prepared at different pH values using HCl and H$_2$SO$_4$ exhibit protonation- and counterion-dependent morphology and fluorescence, as shown by microscopy and steady-state measurements. We find an enhancement in the fluorescence moving from acidic to basic conditions. To uncover the molecular origin of these trends, we performed non-adiabatic molecular dynamics simulations on three Lys crystal models representing distinct protonation states. Our simulations indicate that enhanced protonation under acidic conditions facilitates non-radiative decay via proton transfer, whereas basic conditions favor radiative decay. Our combined experimental-theoretical work highlights pH and counterion identity as key factors tuning fluorescence in Lys assemblies, offering insights for designing pH responsive optical materials based on non-aromatic amino acids. |
| title | Investigating the Role of pH and Counterions in the Intrinsic Fluorescence of Solid-State L-Lysine |
| topic | Chemical Physics Biological Physics |
| url | https://arxiv.org/abs/2507.19241 |