Koenig S H, Brown R D, Spiller M, Chakrabarti B, Pande A
IBM T.J. Watson Research Center, Yorktown Heights, New York 10598.
Biophys J. 1992 Mar;61(3):776-85. doi: 10.1016/S0006-3495(92)81882-9.
From analyses of the magnetic field dependence of 1/T1 (NMRD profiles) of water protons in solutions of calf lens alpha-crystallin at several concentrations, we find two regimes of solute behavior in both cortical and nuclear preparations. Below approximately 15% vol/vol protein concentration, the solute molecules appear as compact globular proteins of approximately 1,350 (cortical) and approximately 1,700 (nuclear) kD. At higher concentrations, the effective solute particle size increases, reversibly, as evidenced by the appearance of spectra-like 14N peaks in the NMRD profiles and a change in the field and temperature dependence of 1/T1. At these higher concentrations, the profiles are very similar to those of calf gamma II-crystallin, a crystallin that undergoes an analogous transition near approximately 15% protein (Koenig, S. H., C.F. Beaulieu, R. D. Brown III, and M. Spiller, 1990. Biophys. J. 57:461-469). By comparison with recent analyses of NMRD results for solutions of immobilized proteins as models for the transition from protein solutions to tissue (Koenig, S. H., and R. D. Brown III. 1991. Prog. NMR Spectr. 22:487-567), we argue that alpha-crystallin solute behaves as aggregates approximately greater than 50,000 kD as protein concentration is progressively increased above 15%. Finally, the concentration dependence of the NMRD profiles of alpha- and gamma II-crystallin can readily explain recent osmotic pressure data, in particular the intersection of the respective pressure curves at approximately 23% vol/vol (Vérétout, F., and A. Tardieu. 1989. Eur. Biophys. J. 17:61-68).
通过对几种浓度的小牛晶状体α-晶状体蛋白溶液中水质子的1/T1（NMRD谱）的磁场依赖性分析，我们发现在皮质和核制剂中溶质行为存在两种状态。在大约15%体积/体积的蛋白质浓度以下，溶质分子表现为约1350（皮质）和约1700（核）kD的紧密球状蛋白质。在较高浓度下，有效溶质粒径可逆增加，这由NMRD谱中类似光谱的14N峰的出现以及1/T1的场和温度依赖性变化所证明。在这些较高浓度下，谱与小牛γII-晶状体蛋白的谱非常相似，γII-晶状体蛋白在约15%蛋白质附近经历类似转变（Koenig，S.H.，C.F. Beaulieu，R.D. Brown III和M. Spiller，1990. Biophys. J. 57:461 - 469）。通过与最近对固定化蛋白质溶液作为从蛋白质溶液到组织转变模型的NMRD结果分析（Koenig，S.H.和R.D. Brown III. 1991. Prog. NMR Spectr. 22:487 - 567）进行比较，我们认为随着蛋白质浓度逐渐增加到15%以上，α-晶状体蛋白溶质表现为约大于50,000 kD的聚集体。最后，α-和γII-晶状体蛋白的NMRD谱的浓度依赖性可以很容易地解释最近的渗透压数据，特别是各自压力曲线在约23%体积/体积处的交点（Vérétout，F.和A. Tardieu. 1989. Eur. Biophys. J. 17:61 - 68）。
