title: Impurity effects on lysozyme crystal growth.
abstract: Atomic force microscopy (AFM) and X-ray diffraction experiments have been combined to study the correlation between impurity incorporation, crystal surface morphology and crystal quality. Hen egg-white lysozyme has been used as a model protein, and covalently bound lysozyme dimer as a model impurity. AFM observation of the [101] crystal face revealed that the crystal surface clearly became rough when 5% impurity was added, and the steps disappeared as the impurity concentration increased to 10%. The crystal quality was evaluated by four factors: maximum resolution limit, <I>/<sigmaI>, Rmerge, and overall B factor. In every index, the crystal quality tended to degrade as the impurity concentration increased. The B-factor dropped significantly at 5% impurity; at the same time the step roughening was observed. This strongly suggested that the impurity incorporation affected the step growth mechanism and degraded the crystal quality.
authors.affiliation: Space Utilization Research Center, National Space Development agency of Japan. yoshizaki.izumi@nasda.go.jp
authors.forename: Izumi
authors.initials: I
authors.lastname: Yoshizaki
authors.forename: Akio
authors.initials: A
authors.lastname: Kadowaki
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Iimura
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Igarashi
authors.forename: Shinichi
authors.initials: S
authors.lastname: Yoda
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Komatsu
mesh_terms: D003460:Crystallization / Q000379:methods*; D019281:Dimerization; D046911:Macromolecular Substances; D018625:Microscopy, Atomic Force / Q000379:methods*; D009113:Muramidase / Q000032:analysis* / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D011786:Quality Control; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013499:Surface Properties; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D046911:Macromolecular Substances; C421864:hen egg lysozyme; D009113:Muramidase