Litman G W, Good R A, Frommel D, Rosenberg A
Proc Natl Acad Sci U S A. 1970 Nov;67(3):1085-92. doi: 10.1073/pnas.67.3.1085.
Biophysical studies of intact immunoglobulins, enzymatically derived immunoglobulin subunits, and chemically derived immunoglobulin chains are reported. All the forms studied lacked optical activity associated with the alpha-helix conformation. A dichroism band centered near 217 nm, which has been assigned to the beta-sheet conformation, was present in all subunits that contained at least two covalently linked intrachain disulfide loop regions. This dichroism band could not be detected in Component II, the C-terminal 120 amino acids of the heavy chain. The reduction and alkylation of the intrachain disulfide linkages caused a large conformational change associated with short range interactions. The cleavage of the intrachain disulfide also produced a large change in the environment of two aromatic amino acids, tyrosine and tryptophan. These observations indicate some unique conformational relationships for immunoglobins which may be related to the functional demands placed on this class of macromolecule.
报道了对完整免疫球蛋白、酶促衍生的免疫球蛋白亚基和化学衍生的免疫球蛋白链的生物物理研究。所有研究的形式都缺乏与α-螺旋构象相关的光学活性。在所有包含至少两个共价连接的链内二硫键环区域的亚基中，都存在一个以217nm附近为中心的二向色性带，该带已被指定为β-折叠构象。在重链C末端的120个氨基酸的组分II中未检测到这种二向色性带。链内二硫键的还原和烷基化导致了与短程相互作用相关的大的构象变化。链内二硫键的断裂也使两种芳香族氨基酸酪氨酸和色氨酸的环境发生了很大变化。这些观察结果表明免疫球蛋白存在一些独特的构象关系，这可能与对这类大分子的功能需求有关。
