The structural study of small heme-containing proteins, such as myoglobin, in the apo-form lacking heme has been extensively described, but the characterization and stability of the giant Glossoscolex paulistus hemoglobin (HbGp), in the absence of heme groups, has not been studied. Spectroscopic data show efficient extraction of the heme groups from the hemoglobin, with relatively small secondary and tertiary structural changes in apo-HbGp noticed compared to oxy-HbGp. Electrophoresis shows a partial precipitation of the trimer abc (significantly lower intensity of the corresponding band in the gel), due to extraction of heme groups, and the predominance of the intense monomeric d band, as well as of two linker bands. AUC and DLS data agree with SDS-PAGE in showing that the apo-HbGp undergoes dissociation into the d and abc subunits. Subunits d and abc are characterized by sedimentation coefficients and percentage contributions of 2.0 and 3.0 S and 76 and 24%, respectively. DLS data suggest that the apo-HbGp is unstable, and two populations are present in solution: one with a diameter around 6.0 nm, identified with the dissociated species, and a second one with diameter 100–180 nm, due to aggregated protein. Finally, the presence of urea promotes the exposure of the fluorescent probes, extrinsic ANS and intrinsic protein tryptophans to the aqueous solvent due to the unfolding process. An understanding of the effect of heme extraction on the stability of hemoproteins is important for biotechnological approaches such as the introduction of non-native prosthetic groups and development of artificial enzymes with designed properties.

缺乏血红素的脱辅基形式的含血红素的小蛋白（如肌红蛋白）的结构研究已得到广泛描述，但是在没有血红素基团的情况下，巨大的Glossoscolex paulistus血红蛋白（HbGp）的特征和稳定性尚未得到描述经过研究。光谱数据显示从血红蛋白中高效提取血红素基团，与氧-HbGp相比，apo-HbGp的二级和三级结构变化较小。电泳显示三聚体abc的部分沉淀（凝胶中相应谱带的强度明显降低），这是由于血红素基团的提取以及强单体d的占优势带，以及两个接头带。AUC和DLS数据与SDS-PAGE一致，表明apo-HbGp发生解离成d和abc亚基。d和abc亚基其特征是沉降系数和贡献率分别为2.0和3.0 S，76和24％。DLS数据表明，载脂蛋白HbGp不稳定，溶液中存在两个种群：一个种群的直径大约为6.0 nm，可以被解离的物种识别出来；另一个种群的直径是100-180 nm，这是由于蛋白质聚集造成的。最后，由于展开过程，尿素的存在促进了荧光探针，外部ANS和内在蛋白色氨酸暴露于水性溶剂。了解血红素提取对血红蛋白稳定性的影响对于生物技术方法很重要，例如引入非天然修复基团和开发具有设计特性的人造酶。