ORIGINAL PAPER Calcium Oxalate Monohydrate www.crt-journal.org Effect of Charge State of L-Aspartic and L-Arginine Amino Acids on Morphology of Calcium Oxalate Monohydrate Crystals Yuliia Volodymyrivna Taranets,* Igor Mikhaylovich Pritula, Olga Nikolaevna Bezkrovnaya, Pavel Victorovich Mateychenko, Dmitriy Semyonovich Sofronov, and Anna Nikolaevna Puzan The influence of amino acids of different nature (L-aspartic acid (L-asp) and L-arginine (L-arg)) on the morphology and size of calcium oxalate monohydrate crystals (COM), one of the main components of pathogenic organomineral aggregates in the human organism, is studied. Addition of L-asp and L-arg is found to inhibit the processes of COM crystal growth, thereby decreasing the crystal size by more than twice compared to pure COM crystals. The increase in the concentration of L-asp and L-arg amino acids in the reaction mixture to 4 × 10 -3 m and higher leads to the appearance of individual COM crystal. At 20 × 10 -3 m concentration of the amino acid, individual crystals of size between 3 to 5 µm are mainly formed. L-asp and L-arg amino acids can block the growth of the {121} face due to the formation of hydrogen bonds, and the growth of the {100} and {010} faces by electrostatic interaction. 1. Introduction All over the world urolithiasis is one of the most widespread uro- logical diseases characterized by the formation of concrements localized, as a rule, in kidneys, urinary bladder or ureter. These stones are a result of pathogenic mineral formation in living or- ganism. According to numerous studies, pathogenic organomin- eral aggregates have a complex and heterogeneous composition. The main components of 70–80% of such stones are calcium ox- alates, in particular, monohydrate (CaC 2 O 4 ·H 2 O, COM) and di- hydrate (CaC 2 O 4 ·2H 2 O, COD). [1,2] In [3] It is believed [3] that the processes of pathogenic mineral formation in human organism are associated, first of all, with the formation of COM crystals, which represent thermodynamically the most stable phase, [4] and is, consequently, usually found in kidney stones. Y. V. Taranets, I. M. Pritula, O. N. Bezkrovnaya, P. V. Mateychenko, Institute for Single Crystals STC “Institute for Single Crystals” NAS of Ukraine Nauky Ave. 60, Kharkiv 61001, Ukraine E-mail: j.v.taranets@gmail.com D. S. Sofronov, A. N. Puzan Division of Functional Materials Chemistry STC “Institute for Single Crystals” NAS of Ukraine Nauky Ave. 60, Kharkiv 61001, Ukraine DOI: 10.1002/crat.201700133 The works aimed at determination of qualitative and quantitative phase com- position of the stones [5,6] show that, de- spite diversity of pathogenic minerals (currently about 58 kinds of the stones are known [7] ), all of them have com- mon formation regularities and con- sist of organic and inorganic matrices Among the organic components present in pathogenic aggregates, proteins de- serve special consideration because they play an important role in the processes which provide vital functions of the hu- man organism. Taking into account the fact that all proteins consist of a sequence of amino acids, it is especially impor- tant to investigate the crystallization pro- cesses and the formation of COM crystals in the presence of particular amino acids. Since amino acids dif- fer in their physicochemical properties, the features of their inter- action with the growing faces of COM crystals are also different. In the literature [8–10] special attention has been paid to acidic proteins and amino acids (L-glutamic and L-aspartic acids), which can be adsorbed on the surface of COM crystals, whereas the influence of an amino acid possessing basic properties (e. g, L-arginine), on the growth characteristics and morphology of these crystals has been considered poorly. These studies are also of considerable interest, as they enable to establish a relation- ship between the properties of amino acids and the mecha- nism of their interaction with the growing faces of pathogenic organomineral aggregates of COM. Therefore, the aim of our work was to study the effect of amino acids (L-aspartic acid and L-arginine) having different nature on the peculiarities of the growth and morphology of COM crystals. 2. Experimental Section COM crystals were prepared from chemically pure calcium chlo- ride CaCl 2 and potassium oxalate K 2 C 2 O 4 ·Н 2 O salts. Chemically pure L-aspartic acid (L-asp) and L-arginine (L-arg) amino acids were used in the capacity of organic additives, and distilled water was used as the solvent. COM crystals were synthesized by the method closest to the physiological conditions. [11,12] The ratio of molar concentrations Cryst. Res. Technol. 2018, 1700133 C  2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1700133 (1 of 7)