Naumann D, Schultz C, Görne-Tschelnokow U, Hucho F
Robert Koch-Institut des Bundesgesundheitsamtes, Berlin, FRG.
Biochemistry. 1993 Mar 30;32(12):3162-8. doi: 10.1021/bi00063a031.
Fourier transform infrared spectroscopy (FT-IR) was used to test the secondary structure of purified acetylcholine receptor membranes from Torpedo californica. The secondary structure was estimated using the spectral features observed in the structure sensitive region of amide I and amide I' (between 1600 and 1700 cm-1), taking advantage of Fourier self-deconvolution and second-derivative techniques along with least-squares band fitting procedures. At least six different amide I' band components could be resolved in D2O and were tentatively assigned to beta-structures (1680 and 1636 cm-1), alpha-helices (1657 cm-1), aperiodic structures and/or distorted helices (1646-1648 cm-1), and turns (1690 and 1668 cm-1), respectively. The beta-band around 1637 cm-1, in particular, turned out to be complex since it reproducibly exhibited weak features near 1630 and 1627 cm-1, thereby suggesting the presence of different chain interacting beta-structures. The band near 1657 cm-1 was assigned to alpha-helices which transverse the membrane bilayers, while 1646-1648-cm-1 component was tentatively attributed to aperiodic structures and alpha-helices localized within the "globular head" of the receptor protein protruding from the membrane surface into the surrounding water. Least-squares band fitting procedures were applied in order to estimate relative amounts of secondary structures. The results suggest 36-43%, 32-33%, 14-24%, and 18-19% for beta-, alpha-helical, turn, and "rest" structures, respectively. Additionally, the temperature- and time-dependent variations of the secondary structure was tested by evaluating the changes of amide I and amide II band components of receptor membranes dispersed in H2O and D2O.(ABSTRACT TRUNCATED AT 250 WORDS)
傅里叶变换红外光谱法（FT-IR）被用于检测从加州电鳐中纯化得到的乙酰胆碱受体膜的二级结构。利用傅里叶自卷积和二阶导数技术以及最小二乘带拟合程序，根据在酰胺I和酰胺I'（1600至1700 cm-1之间）的结构敏感区域中观察到的光谱特征来估计二级结构。在D2O中至少可以分辨出六种不同的酰胺I'带成分，并初步将它们分别归属于β-结构（1680和1636 cm-1）、α-螺旋（1657 cm-1）、非周期性结构和/或扭曲螺旋（1646 - 1648 cm-1）以及转角（1690和1668 cm-1）。特别是，1637 cm-1附近的β-带结果很复杂，因为它在1630和1627 cm-1附近可重复地表现出微弱特征，这表明存在不同的链相互作用β-结构。1657 cm-1附近的带被归属于横穿膜双层的α-螺旋，而1646 - 1648 cm-1成分初步归因于非周期性结构和位于从膜表面突出到周围水中的受体蛋白“球状头部”内的α-螺旋。应用最小二乘带拟合程序来估计二级结构的相对含量。结果表明，β-结构、α-螺旋结构、转角结构和“其他”结构的相对含量分别为36 - 43%、32 - 33%、14 - 24%和18 - 19%。此外，通过评估分散在H2O和D2O中的受体膜的酰胺I和酰胺II带成分的变化，测试了二级结构随温度和时间的变化。（摘要截取自250字）
