Promotion Of Crystallization Kinetics Of Calcium Oxalates By N-Terminus Peptides Of Calcium Oxalate Raphides In Banana (Musa Spp.)

Calcium oxalate crystals are widespread in all kinds of higher plants. Different plants present different specific forms of calcium oxalate crystals, such as square crystal, cylindrical crystal, raphide crystal. That suggest the formation of calcium oxalate crystals in plants are controlled by biological macromolecules. The study found that the banana plant of calcium oxalate raphides within 14 k Da protein, its form and self-assembly nanowire, template included the formation of raphides. By synthesis the peptide（MENLTASEIAG）（11-mer MG） from the amidogen terminus protein, and combined with nucleation and the dynamics growth of calcium oxalate research by in situ atomic force microscopy（AFM）. we investigated the impact on COM crystal nucleation and growth by amidogen terminus 14 k Da.（1） In order to provides suitable samples for COM surface research by AFM, we synthesized COM in silica-gel and clay-gel. The results showed crystals are clear and tufted in silica-gel. The largest size（length is about 1000 microns, the width is about 137 microns） COM crystals（010） surface was got when the experiment conditions as follows: silica-gel, 50 °C, the concentration of K₂C₂O₄ and Ca（NO₃）₂ were 0.75 mol·L-1, 30 d. But AFM experiments show that the growth of the crystal surface disorder and unable to find the growth of spiral, therefore should not be used for the surface kinetics experiment under AFM. Crtstals are not transparent and gray in caly-gel. The length is about 522 microns, the width is about 250 microns of COM（010） surface was got when the experiment conditions as follows: clay-gel, 62 °C, the concentration of K₂C₂O₄ and Ca（NO₃）₂ were 0.75 mol·L-1, 60 d. In the same experiment system, add 20 g Na Cl into clay-gel, the largest size（length is about 815 microns, the width is about 268 microns） COM crystals（-101） surface was got. AFM experiments show that can find the growth of spiral on crystals（010） and（-101） surface which were synthesized in clay-gel.（2） The effect of 11-mer MG peptide on COM nucleation crystallization under Na Cl or KCl background electrolyte suggest: the various concentrations of peptide can promote COM nucleation, but there was no significant difference between different protein concentration. Under Na Cl background electrolyte induction time was significantly higher than under KCl system. The morphology of COM crystals which formed in Na Cl and KCl background electrolyte are the rules of the hexagon and the diamond. These suggest that the presence of KCl and 11-mer MG can promoting COM nucleation.（3） By means of AFM study on COM surface growth in nanoscale. The various concentrations of peptide promote the speed of the step at different supersaturations（ σ = 0.266,σ = 0.508,σ = 0.816）. σ=0.266, it promote the strongest at 1 n M concentrations of peptide on（010） plane. [0-2-1] direction steps movement speed increased by 1.8 times and [100] direction steps movement speed increased by 1 times. So the promote effect is remarkable at low saturaration and low protein peptide concentration on COM surface growth. And this phenomenon may be due to the steps of 11-mer MG peptide make steps local higher degree of supersaturation, the increase of desolvation degree at crystal surface or ions clung to the lattice, such as lowering the activation energy.