Morphology And Structure Of Calcium Oxalate Monohydrate (COM) Crystals In Banana Plants And In Vitro Modulation Of Nucleation And Growth Of COM Crystals By Small Organic Molecules

Calcium oxalate (CaOx) crystals/biominerals are distributed among all photosynthetic plants families. CaOx biomineralization process is not a simple and random chemical precipitation of endogenously synthesized oxalic acid and environmentally derived Ca ions. In vivo calcium oxalate monohydrate (COM) formation is precisely controlled by biomacromolecules through the exquisite bio-regulation mechanisms. In this study, we have investigated morphology and structure of COM in banana plants, and in vitro COM crystallization inhibition in the presence of relevant organic molecules by combining SEM, XRD and FTIR, which may give molecular mechanisms of COM crystallization modulations by organic acids. The main results are summarized as follows:1. In Musa sapientum plants the needle-like COM crystals are formed in vacuoles of idioblasts with140-250μm in length and3μm in width. In addition, crystals develop within an organic matrix which consists of two structural phases including water-soluble and detergent-soluble matrix. According to SDS-PAGE results, the water-soluble matrix contains a series of proteins/peptides with a broad range of apparent molecular weights of182,93,86,65,49and19kDa. Detergent-soluble matrix includes related proteins with molecular weights of182,93,86,65,49,18and17kDa.2. In vitro experiments showed that sodium citrate significantly inhibited the nucleation of COM through increasing induction times. In the presence of10,50or500μmol/L sodium citrate, the induction time was decreased to1,63or228min,respectively. Moreover, the growth of the (101) face of COM was inhibited, and morphological changes of the (101) face were obvious with increasing the concentrations of sodium citrate.3. D/L-glutamate significantly inhibited the nucleation of COM through increasing induction times. The presence of200,400or600μmol/L D/L-glutamate decreased the induction time to16,53or126min for D-glutamate, and41,102or106min for L-glutamate, respectively. Moreover, the growth of the (101) face of COM was inhibited, and morphological changes of the (101) face were obvious with increasing the concentrations of D/L-glutamate.4. D/L-aspartic acid significantly inhibited the nucleation of COM through increasing induction times. The presence of100or200μmol/L D-aspartic acid decreased the induction time to6or42min; In the presence of1,50or100μmol/L L-aspartic acid, the induction time was decreased to9,114or171min, respectively. Moreover, the growth of the (101) face of COM was inhibited, morphological changes were significant with increasing the concentrations of D/L-aspartic acid.