Young N M, Williams R E
Int J Pept Protein Res. 1982 Mar;19(3):243-50. doi: 10.1111/j.1399-3011.1982.tb03033.x.
The circular dichroism spectra of the monomer, dimer and tetramer forms of MOPC 167 mouse IgA are reported. The spectra were very similar in the aromatic region (250-310 nm) but the intensity of the negative band at 217 nm, arising from the peptide backbone, was higher in the dimer and tetramer (-4600 degree cm2 dmol-1) than in the monomer (-3400 degree cm2 dmol-1). When monomer and dimer IgA were exposed to concentrations of guanidine hydrochloride around 1.3 m, the 217 nm band increased in intensity, twofold in the case of the monomer, and solutions of the dimer became turbid, indicating aggregation of the proteins and formation of a cross-beta-structure. At concentrations of guanidine hydrochloride of above 2.3 M both proteins were similarly denatured, indicating that dimerization through J chain does not alter the stability of IgA. The aggregating effect of guanidine hydrochloride did not occur with samples of human IgA1 and IgA2 and may be related to the unusual CH1 domain of mouse IgA.
报道了MOPC 167小鼠IgA单体、二聚体和四聚体形式的圆二色光谱。这些光谱在芳香区域（250 - 310 nm）非常相似，但由肽主链产生的217 nm处负带的强度，在二聚体和四聚体中（-4600度·厘米²·dmol⁻¹）高于单体（-3400度·厘米²·dmol⁻¹）。当单体和二聚体IgA暴露于约1.3 m的盐酸胍浓度时，217 nm带的强度增加，单体情况下增加了两倍，并且二聚体溶液变得浑浊，表明蛋白质聚集并形成了交叉β结构。在盐酸胍浓度高于2.3 M时，两种蛋白质都发生了类似的变性，这表明通过J链的二聚化不会改变IgA的稳定性。盐酸胍的聚集作用在人IgA1和IgA2样品中未发生，可能与小鼠IgA不寻常的CH1结构域有关。
