Electron microscope study of the kinetics of the fiber-to-crystal transition of sickle cell hemoglobin.

AUTOR(ES)

Wilson, S M

RESUMO

The intermediates and the rate-limiting step in the crystallization of deoxygenated sickle hemoglobin have been determined by a kinetic study with the use of electron microscopy. In slowly stirred solutions of deoxygenated hemoglobin S [Pumphrey, J. & Steinhardt, J. (1977) J. Mol. Biol. 112, 359--375], the sequential appearance of fibers have a diameter of approximately equal to 210 A, bundles of aligned fibers in well-ordered arrays, "thick" fibers of approximately equal to 470 A diameter, and microcrystals is observed. Only the fibers having a diameter of approximately equal to 210 A and bundles of aligned fibers are assigned as kinetically important intermediates of the fiber-to-crystal transition. Addition of microscopic seed crystals obtained from slowly stirred solutions of deoxyhemoglobin S to a solution composed of only fibers and hemoglobin monomers results in more rapid crystallization than in control solutions. Addition of seed crystals after the formation of bindles of aligned fibers does not alter the overall kinetics of crystallization. The results demonstrate that alignment of fibers is the rate-limiting step in the crystallization process and results in formation of nucleation sites for crystal growth.

Documentos Relacionados

• Thermodynamic studies of polymerization of deoxygenated sickle cell hemoglobin.
• Dichloromethane as an antisickling agent in sickle cell hemoglobin.
• Ligand-linked phase changes in a biological system: applications to sickle cell hemoglobin.
• Accelerated autoxidation and heme loss due to instability of sickle hemoglobin.
• X-ray diffraction studies of fibers and crystals of deoxygenated sickle cell hemoglobin.