Heredia Alejandro, van der Strate Han J, Delgadillo Ivonne, Basiuk Vladimir A, Vrieling Engel G
Departamento de Química de Radiaciones y Radioquímica, Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Circuito Exterior C.U. Apdo. Postal 70-543, 04510 México, DF, México.
Chembiochem. 2008 Mar 3;9(4):573-84. doi: 10.1002/cbic.200700313.
Biologically formed silica is produced at ambient conditions under the control of molecular and physicochemical processes that are apparently integrated in biosilica morphogenesis, but the mechanisms are not yet fully understood. With the recent identification of small polypeptides and proteins that are encapsulated inside the biosilica and functional in silica polymerization in vitro, it is of importance to determine whether interactions between inorganic silica species and these organic compounds occur in vivo. A time-resolved analysis of valve formation in synchronously growing cells of the diatom species Navicula pelliculosa enabled us to characterize the relevant chemical bonds by attenuated total reflectance Fourier-transformed infrared (ATR-FTIR) spectroscopy. Typically, inorganic bonds of Si-O-Si (bands at 1058, 843 cm(-1)), Si-OH (3689 cm(-1)), and P=O (1239 cm(-1)) and organic bonds of proteinaceous matter (with the amide I and II bands at 1642 and 1543 cm(-1), respectively) were positively identified during one cycle of valve formation. The observed variations in FTIR band intensity and location represented specific interactions between organic and inorganic molecules during the major silicification event, during which stretching of the Si-O bonds was predominantly noticed. The experimentally obtained frequencies (nu) of the major bonds corresponded to those that were obtained by MM+ and PM3 FTIR simulations for organo-silica interactions based on biomolecules that are proposed to be involved in biosilica formation. The results indicated that hydrogen bonds originated from interactions, albeit weak, between organic phosphate or amine groups to the inorganic hydroxyl groups or oxygen atoms from the silicic acid and/or silica. The existence of covalent P-O-Si bonds and electrostatic interactions could not be excluded. These interactions clearly suggest that biomolecules actively contribute to the silica polymerization process during valve formation in N. pelliculosa, and also might act comparably in other diatoms species in which similar biomolecules have been identified.
生物形成的二氧化硅是在环境条件下，受分子和物理化学过程控制而产生的，这些过程显然整合在生物二氧化硅形态发生过程中，但其机制尚未完全明了。随着最近发现一些小的多肽和蛋白质被包裹在生物二氧化硅内部且在体外二氧化硅聚合过程中发挥作用，确定无机硅物种与这些有机化合物在体内是否发生相互作用变得至关重要。对硅藻物种微小舟形藻同步生长细胞中瓣膜形成的时间分辨分析，使我们能够通过衰减全反射傅里叶变换红外（ATR-FTIR）光谱对相关化学键进行表征。通常，在瓣膜形成的一个周期中，可明确鉴定出Si-O-Si（1058、843 cm⁻¹处的谱带）、Si-OH（3689 cm⁻¹）和P=O（1239 cm⁻¹）的无机键，以及蛋白质物质的有机键（酰胺I和II谱带分别位于1642和1543 cm⁻¹）。观察到的FTIR谱带强度和位置变化代表了主要硅化事件期间有机和无机分子之间的特定相互作用，在此期间主要观察到Si-O键的伸缩。实验获得的主要键的频率（ν）与基于拟参与生物二氧化硅形成的生物分子的有机-二氧化硅相互作用的MM+和PM3 FTIR模拟所获得的频率相对应。结果表明，氢键源于有机磷酸基团或胺基团与硅酸和/或二氧化硅的无机羟基或氧原子之间的相互作用，尽管较弱。不能排除共价P-O-Si键和静电相互作用的存在。这些相互作用清楚地表明，生物分子在微小舟形藻瓣膜形成过程中积极促进二氧化硅聚合过程，并且在已鉴定出类似生物分子的其他硅藻物种中可能也发挥类似作用。
