Accession Number : ADA306807

Title :   Atomic Force Microscopy of Insulin Single Crystals: Direct Visualization of Molecules and Crystal Growth.

Descriptive Note : Technical rept.,

Corporate Author : MINNESOTA UNIV MINNEAPOLIS DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE

Personal Author(s) : Yip, Christopher M. ; Ward, Michael D.

PDF Url : ADA306807

Report Date : 08 APR 1996

Pagination or Media Count : 30

Abstract : Atomic force microscopy performed on single crystals of three different polymorphs of bovine insulin revealed molecularly smooth (001) layers separated by steps whose heights reflect the dimensions of single insulin hexamer. Whereas contact mode imaging caused etching that prevented molecular-scale resolution, tapping mode imaging in solution provided molecular-scale contrast the enabled determined of lattice parameters and polymorph identification while simultaneously enabling real-time examination of growth modes and assessment of crystal quality. Crystallization proceeds layer-by-layer in which the protein molecules assemble homoepitaxially with nearly perfect orientational and translational commensurism. Tapping mode imaging also revealed insulin aggregates attached to the (001) faces, their incorporation into growing terraces, and their role in defect formation. These observations demonstrate that tapping mode imaging is ideal for real-time in situ investigation of the crystallization of soft protein crystals of relatively small proteins such as insulin, which cannot withstand the lateral shear forces exerted by the scanning robe in conventional imaging modes

Descriptors :   *CRYSTALS, *MICROSCOPY, *BOVINES, *CRYSTAL GROWTH, MOLECULES, PROTEINS, SINGLE CRYSTALS, CRYSTALLIZATION, ETCHING, AGGREGATES(MATERIALS), QUALITY, IMAGES, POLYMORPHISM, INSULIN, GROWTH(PHYSIOLOGY).

Subject Categories : Biochemistry
      Biology
      Optics

Distribution Statement : APPROVED FOR PUBLIC RELEASE