Dislocation-Actuated Growth and Inhibition of Hexagonal l‑Cystine Crystallization at the Molecular Level

• Published in: Crystal growth & design 2015-02, Vol.15 (2), p.921-934
• Main Authors: Shtukenberg, Alexander G, Poloni, Laura N, Zhu, Zina, An, Zhihua, Bhandari, Misha, Song, Pengcheng, Rohl, Andrew L, Kahr, Bart, Ward, Michael D
• Format: Article
• Language: English
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/cg501485e

Crystallization of l-cystine is a critical process in the pathogenesis of kidney stone formation in cystinuria, a disorder affecting more than 20 000 individuals in the United States alone. In an effort to elucidate the crystallization of l-cystine and the mode of action of tailored growth inhibitors that may constitute effective therapies, real-time in situ atomic force microscopy has been used to investigate the surface micromorphology and growth kinetics of the {0001} faces of l-cystine at various supersaturations and concentrations of the growth inhibitor l-cystine dimethylester (CDME). Crystal growth is actuated by screw dislocations on the {0001} l-cystine surface, producing hexagonal spiral hillocks that are a consequence of six interlacing spirals of anisotropic molecular layers. The high level of elastic stress in the immediate vicinity around the dislocation line results in a decrease in the step velocities and a corresponding increase in the spacing of steps. The kinetic curves acquired in the presence of CDME conform to the classical Cabrera–Vermilyea model. Anomalous birefringence in the {101̅0} growth sectors, combined with computational modeling, supports a high fidelity of stereospecific binding of CDME, in a unique orientation, exclusively at one of the six crystallographically unique projections on the {101̅0} plane.