Wagner Avital, Hill Adam, Lemcoff Tali, Livne Eynav, Avtalion Noam, Casati Nicola, Kariuki Benson M, Graber Ellen R, Harris Kenneth D M, Cruz-Cabeza Aurora J, Palmer Benjamin A
Department of Chemistry, Ben-Gurion University of the Negev, Be'er Sheba 8410501, Israel.
Department of Chemical Engineering, The University of Manchester, Manchester M13 9PL, U.K.
Chem Mater. 2024 Sep 1;36(18):8910-8919. doi: 10.1021/acs.chemmater.4c01771. eCollection 2024 Sep 24.
Many spectacular optical phenomena in animals are produced by reflective assemblies of guanine crystals. The crystals comprise planar H-bonded layers of π-stacked molecules with a high in-plane refractive index. By preferentially expressing the highly reflective π-stacked (100) crystal face and controlling its cross-sectional shape, organisms generate a diverse array of photonic superstructures. Recently, it was found that biogenic guanine crystals are composites, containing high quantities of hypoxanthine and xanthine in a molecular alloy. Here, we crystallized guanine in the presence of these dopants and used computations to rationalize their influence on the crystal morphology and energy. Exceptional quantities of hypoxanthine are incorporated into kinetically favored solid solutions, indicating that fast crystallization kinetics underlies the heterogeneous compositions of biogenic guanine crystals. We find that weakening of H-bonding interactions by additive incorporation elongates guanine crystals along the stacking direction-the opposite morphology of biogenic crystals. However, by modulation of the strength of competing in-plane H-bonding interactions, additive incorporation strongly influences the cross-sectional shape of the crystals. Our results suggest that small-molecule H-bond disrupting additives may be simultaneously employed with π-stack blocking additives to generate reflective platelet crystal morphologies exhibited by organisms.
动物体内许多引人注目的光学现象是由鸟嘌呤晶体的反射组件产生的。这些晶体由具有高面内折射率的π堆积分子的平面氢键层组成。通过优先表达高反射性的π堆积（100）晶面并控制其横截面形状，生物体产生了各种各样的光子超结构。最近，人们发现生物源鸟嘌呤晶体是一种复合材料，在分子合金中含有大量的次黄嘌呤和黄嘌呤。在这里，我们在这些掺杂剂存在的情况下使鸟嘌呤结晶，并通过计算来解释它们对晶体形态和能量的影响。大量的次黄嘌呤被掺入动力学有利的固溶体中，这表明快速结晶动力学是生物源鸟嘌呤晶体异质组成的基础。我们发现，通过添加掺杂剂削弱氢键相互作用会使鸟嘌呤晶体沿堆积方向伸长，这与生物源晶体的形态相反。然而，通过调节竞争的面内氢键相互作用的强度，添加掺杂剂会强烈影响晶体横截面的形状。我们的结果表明，小分子氢键破坏添加剂可以与π堆积阻断添加剂同时使用，以产生生物体所呈现的反射片状晶体形态。
