Impurity effects of protein oligomer for protein crystallization and crystal quality

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In this study, impurity effects on the growth of protein (hen egg white lysozyme) crystals have been studied using in-situ atomic force microscopy (AFM) and fluorescent microscopy (FM). The main results are as follows;1. Development of solution exchange system for AFM observations.We successively developed a solution exchange system to observe adsorption process of protein molecules by using AFM.2. Observation of adsorption process of protein on crystal surfaces.The adsorption of (pure) lysozyme to crystal surfaces has been directly observed by using the system described above.3. Morphology changes of protein crystals induced by a protein impurityWe observed surfaces of tetragonal lysozyme crystals contaminated by ovotransferrin, which has rather larger molecular weight than that of lysozyme by AFM, and revealed that ovotransferrin preferentially adsorbs on the (101). FM observation also showed that the density of the impurities near the (101) surface is relatively higher than the other region. These results explain the morphological changes of protein crystals induced by the lysozyme crystals.