Weaver M L, Qiu S R, Friddle R W, Casey W H, De Yoreo J J
Deptartment of Chemistry and Department of Geology, University of California, Davis, California, 95616.
Cryst Growth Des. 2010;10(7):2954-2959. doi: 10.1021/cg901626a.
Using in situ atomic force microscopy (AFM), we investigate the inhibition of calcium oxalate monohydrate (COM) step growth by aspartic acid-rich peptides and find that the magnitude of the effect depends on terrace lifetime. We then derive a time dependent step-pinning model in which average impurity spacing depends on the terrace lifetime as given by the ratio of step spacing to step speed. We show that the measured variation in step speed is well fit by the model and allows us to extract the characteristic peptide adsorption time. The model also predicts that a crossover in the timescales for impurity adsorption and terrace exposure leads to bistable growth dynamics described mathematically by a catastrophe. We observe this behavior experimentally both through the sudden drop in step speed to zero upon decrease of supersaturation as well as through fluctuations in step speed between the two limiting values at the point where the catastrophe occurs. We discuss the model's general applicability to macromolecular modifiers and biomineral phases.
我们使用原位原子力显微镜（AFM）研究了富含天冬氨酸的肽对一水合草酸钙（COM）台阶生长的抑制作用，发现这种效应的大小取决于平台寿命。然后我们推导了一个时间相关的台阶钉扎模型，其中平均杂质间距取决于平台寿命，其关系由台阶间距与台阶速度的比值给出。我们表明，模型能很好地拟合测量到的台阶速度变化，并使我们能够提取特征肽吸附时间。该模型还预测，杂质吸附和平台暴露时间尺度的交叉会导致由突变数学描述的双稳态生长动力学。我们通过在过饱和度降低时台阶速度突然降至零以及在突变发生点处台阶速度在两个极限值之间波动这两种情况，从实验上观察到了这种行为。我们讨论了该模型对大分子改性剂和生物矿相的一般适用性。
