Influence of the concentration of phosphatidylcholine (PC) in the solution of 0.5mol.L-1 CaCl2 on the crystal structure of CaCO3 has been studied by means of X-ray diffeaction method.When the concentration of PC is below its CMC, the calcite CaCO3 is formed. It advantageous that CaCl2 reacts with Na2CO3 so as to form vaterite CaCO3 in the lipesome composed of PC more than in the water. The arnount of vaterite CaCO3 formed is increased with increase of con-centration of PC. But if the concentration of PC is so increased as to form liquid crystal, then the amount of vaterite decreases obviously. The reason for the difference of crystal type formed has been discussed in the paper.
In this paper, the mimetic biomineralization of CaC2O4 in lecithin water(PC H2O) ordered systems has been discussed. First, the effect of the aggregation state of PC aqueous solutions on the crystal structure of CaC2O4 has been studied. In all experiments, the only precipitated crystal forms obtained are calcium oxalate monohydrate(COM) and calcium oxalate dihydrate(COD). It have been shown that the relative amount of COD in PC H2O systems is much higher than that of in H2O system, and furthermore the aggregation state of PC influences the composition of coprecipitations to some extent. When PC distributing in aqueous solution as single molecules, it acts as inhibitor of COM , and then favors the formation of COD. While PC in micelle existence, the relative amount of COM increases , but is still lower than that of in H2O system . And when PC aggregates as vesicles, COD forms predominantly. Second, the morphology of CaC2O4 obtained in different reaction systems under different conditions has been also investigated. In H2O system, we observed thin, plate like crystals with serrated edges underISL(low ionic strength) condition and oriented clusters under ISH(high ionic strength) condition. Crystals with two layers arrangement were obtained in micelleordered PC H2O system under ISL condition. And in vesicle ordered PC H2O system, clusters with butterfly like shape were observed. The results obtained revealed a complex dependence of calcium oxalate formation,crystal growth, structure and morphology on the aggregation state of PC H2O systems.
