No abstract

Modifiers are commonly used in natural, biological, and synthetic crystallization to tailor the growth of diverse materials. Here, we identify tautomers as a new class of modifiers where the dynamic interconversion between solute and its corresponding tautomer(s) produces native crystal growth inhibitors. The macroscopic and microscopic effects imposed by inhibitor-crystal interactions reveal dual mechanisms of inhibition where tautomer occlusion within crystals that leads to natural bending, tunes elastic modulus, and selectively alters the rate of crystal dissolution. Our study focuses on ammonium urate crystallization and shows that the keto-enol form of urate, which exists as a minor tautomer, is a potent inhibitor that nearly suppresses crystal growth at select solution alkalinity and supersaturation. The generalizability of this phenomenon is demonstrated for two additional tautomers with relevance to biological systems and pharmaceuticals. These findings offer potential routes in crystal engineering to strategically control the mechanical or physicochemical properties of tautomeric materials.

The solubility of 4-(hydroxymethyl) benzoic acid (p-HMBA) in nine pure solvents (water, methanol, ethanol, 1-propanol, 2-propanol, ethyl formate, ethyl acetate, isopropyl acetate, and butyl acetate) and two different binary solvents (methanol + water and ethanol + water) was measured by a gravimetric method at temperatures ranging from 283.15 to 323.15 K under atmospheric pressure (p = 0.1 MPa). The results reveal that the solubility of p-HMBA increases with increasing temperature in all investigated solvents. Under an isothermal condition, the solubility of p-HMBA increases monotonously with the increase of the mole fraction of methanol in binary solvents of methanol and water. However, the solubility of p-HMBA increases first and then decreases with the increase of ethanol in the binary solvent mixtures of ethanol and water and reaches its maximum value when the mole fraction of ethanol is 0.8. The solubility data were correlated with the modified Apelblat equation and λh model. All of the models gave satisfactory correlation results. The results presented in this paper would be helpful to the further crystallization and separation process of p-HMBA.

The pathological mineralization of calcium oxalate monohydrate (COM) crystals in vivo inevitably brings renal injury wherein natural macromolecules play an indispensable role in regulating the process. However, the role of...