Wilson S M, Makinen M W
Proc Natl Acad Sci U S A. 1980 Feb;77(2):944-8. doi: 10.1073/pnas.77.2.944.
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.
通过使用电子显微镜进行动力学研究，已确定了脱氧镰状血红蛋白结晶过程中的中间体和限速步骤。在缓慢搅拌的脱氧血红蛋白S溶液中[庞弗里，J. & 施泰因哈特，J.（1977年）《分子生物学杂志》112卷，359 - 375页]，观察到依次出现直径约为210埃的纤维、排列整齐的纤维束、直径约为470埃的“粗”纤维以及微晶。只有直径约为210埃的纤维和排列整齐的纤维束被认定为纤维向晶体转变过程中在动力学上重要的中间体。将从缓慢搅拌的脱氧血红蛋白S溶液中获得的微观晶种添加到仅由纤维和血红蛋白单体组成的溶液中，会导致结晶比对照溶液更快。在排列整齐的纤维束形成后添加晶种不会改变结晶的整体动力学。结果表明，纤维的排列是结晶过程中的限速步骤，并导致形成晶体生长的成核位点。
