Hidden Hypoxanthine Neighborhoods in β-Guanine
- 1School of Renewable Energy
- 2Inner Mongolia University of Technology
- 3Independent researcher
Abstract
Biogenic guanine crystals can incorporate substantial hypoxanthine (Hpx) while retaining the βguanine lattice, but whether the lattice discriminates both dopant identity and local neighborhood remains unresolved. Here, periodic DFT, site-anchored cluster cross-checks, symmetry-complete pair enumeration, and GIPAW 13C calculations connect these two levels of incorporation to experimentally testable observables. In a dry 6.25% fixed-cell model, N7H-Hpx is 21.78 kcal mol ¹ lower in electronic energy than N9H-Hpx; three cluster treatments preserve a 17.40–18.25 ⁻¹ lower in electronic energy than N9H-Hpx; three cluster treatments preserve a 17.40–18.25 kcal mol ¹ preference. A pure-crystal calibration excluding the embedded-Hpx resonance ⁻¹ lower in electronic energy than N9H-Hpx; three cluster treatments preserve a 17.40–18.25 predicts C5 shifts of 115.98 ppm for N7H and 127.94 ppm for N9H, placing N7H-Hpx in the experimentally reported 115–116 ppm region. At 12.5% substitution, 120 site pairs reduce to 13 symmetry-distinct orbits. Fifteen representatives were relaxed, and the corrected orbit means span 2.407 kcal mol ¹, with an adjacent in-plane orbit lowest; independent starts for four low- ⁻¹ lower in electronic energy than N9H-Hpx; three cluster treatments preserve a 17.40–18.25 energy motifs preserve this minimum. Fixed-geometry 700 eV reevaluation in a 4 × 2 × 1 association cycle gives adjacent- and far-pair association energies of −1.2219 and +0.0189 kcal mol ¹. Across four GIPAW pair models, C5 remains comparatively stable, whereas C6/C8 report ⁻¹ lower in electronic energy than N9H-Hpx; three cluster treatments preserve a 17.40–18.25 local arrangement: adjacent and separated motifs yield C8 splittings of 2.854 and 0.037 ppm. Together, the calculations show that the tested β-guanine lattice models discriminate both metabolite identity and relative placement. The resulting ¹³C signatures provide experimentally testable markers of how biologically supplied purine mixtures may become locally organized during biomineralization.
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BibTeX
@misc{hu2026hidden,
title = {{Hidden Hypoxanthine Neighborhoods in β-Guanine}},
author = {He Hu and Li Yi},
howpublished = {ChemRxiv},
year = {2026},
month = sep,
doi = {10.26434/chemrxiv.15008518/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008518/v1},
note = {CC BY},
}
RIS
TY - UNPB
TI - Hidden Hypoxanthine Neighborhoods in β-Guanine
AU - He Hu
AU - Li Yi
PY - 2026
DA - 2026/09/08
PB - ChemRxiv
DO - 10.26434/chemrxiv.15008518/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008518/v1
AB - Biogenic guanine crystals can incorporate substantial hypoxanthine (Hpx) while retaining the βguanine lattice, but whether the lattice discriminates both dopant identity and local neighborhood remains unresolved. Here, periodic DFT, site-anchored cluster cross-checks, symmetry-complete pair enumeration, and GIPAW 13C calculations connect these two levels of incorporation to experimentally testable observables. In a dry 6.25% fixed-cell model, N7H-Hpx is 21.78 kcal mol ¹ lower in electronic energy than N9H-Hpx; three cluster treatments preserve a 17.40–18.25 ⁻¹ lower in electronic energy than N9H-Hpx; three cluster treatments preserve a 17.40–18.25 kcal mol ¹ preference. A pure-crystal calibration excluding the embedded-Hpx resonance ⁻¹ lower in electronic energy than N9H-Hpx; three cluster treatments preserve a 17.40–18.25 predicts C5 shifts of 115.98 ppm for N7H and 127.94 ppm for N9H, placing N7H-Hpx in the experimentally reported 115–116 ppm region. At 12.5% substitution, 120 site pairs reduce to 13 symmetry-distinct orbits. Fifteen representatives were relaxed, and the corrected orbit means span 2.407 kcal mol ¹, with an adjacent in-plane orbit lowest; independent starts for four low- ⁻¹ lower in electronic energy than N9H-Hpx; three cluster treatments preserve a 17.40–18.25 energy motifs preserve this minimum. Fixed-geometry 700 eV reevaluation in a 4 × 2 × 1 association cycle gives adjacent- and far-pair association energies of −1.2219 and +0.0189 kcal mol ¹. Across four GIPAW pair models, C5 remains comparatively stable, whereas C6/C8 report ⁻¹ lower in electronic energy than N9H-Hpx; three cluster treatments preserve a 17.40–18.25 local arrangement: adjacent and separated motifs yield C8 splittings of 2.854 and 0.037 ppm. Together, the calculations show that the tested β-guanine lattice models discriminate both metabolite identity and relative placement. The resulting ¹³C signatures provide experimentally testable markers of how biologically supplied purine mixtures may become locally organized during biomineralization.
ER -