Ito Seya, Imura Tomohiro, Fukuoka Tokuma, Morita Tomotake, Sakai Hideki, Abe Masahiko, Kitamoto Dai
Faculty of Science and Technology, Tokyo University of Science, Yamazaki 2641, Noda, Chiba 278-8510, Japan.
Colloids Surf B Biointerfaces. 2007 Aug 1;58(2):165-71. doi: 10.1016/j.colsurfb.2007.03.003. Epub 2007 Mar 12.
Kinetic studies on the interactions between self-assembled monolayers of mannosylerythritol lipids (MELs), which are glycolipid biosurfactants abundantly produced by microorganisms, and various classes of immunoglobulins including human IgG, IgA, and IgM were performed using surface plasmon resonance (SPR). The effect of the MEL structure on the binding behavior of HIgG was examined. Assembled monolayers of MEL-A having two acetyl groups on the headgroup gave a high affinity (K(d)=1.7x10(-6)M) toward HIgG, while those of MEL-B or MEL-C having only one acetyl group at C-6' or C-4' position gave little affinity. Our kinetic analysis revealed that the binding manner of HIgG, HIgA (K(d)=2.4x10(-7)M), and HIgM (K(d)=2.2x10(-7)M) to the assembled monolayers of MEL-A is not the monovalent mode but the bivalent mode, and both the first and second rate association constants (k(a1), k(a2)) increase with an increase in the number of antibody binding sites, while those for dissociation (k(d1), k(d2)) changed little. Moreover, we succeeded in directly observing great amounts of HIgG, HIgA, and HIgM bound to MEL-A monolayers using atomic force microscopy (AFM). Finally, we found that MEL-A assembled monolayer binds toward various IgG derived from mouse, pig, rabbit, horse, goat, rat, and bovine as well as human IgG (HIgG), and the only exception was sheep IgG. These results clearly demonstrate that MEL-A assembled monolayers would be useful as noble affinity ligand system for various immunoglobulins.
甘露糖赤藓糖醇脂（MELs）是微生物大量产生的糖脂生物表面活性剂，利用表面等离子体共振（SPR）对其自组装单分子层与包括人IgG、IgA和IgM在内的各类免疫球蛋白之间的相互作用进行了动力学研究。研究了MEL结构对人IgG结合行为的影响。头基上有两个乙酰基的MEL - A组装单分子层对人IgG具有高亲和力（K(d)=1.7×10(-6)M），而在C - 6'或C - 4'位置只有一个乙酰基的MEL - B或MEL - C组装单分子层则几乎没有亲和力。我们的动力学分析表明，人IgG、人IgA（K(d)=2.4×10(-7)M）和人IgM（K(d)=2.2×10(-7)M）与MEL - A组装单分子层的结合方式不是单价模式而是二价模式，一级和二级速率缔合常数（k(a1)，k(a2)）均随着抗体结合位点数量的增加而增加，而解离常数（k(d1)，k(d2)）变化不大。此外，我们利用原子力显微镜（AFM）成功直接观察到大量结合在MEL - A单分子层上的人IgG、人IgA和人IgM。最后，我们发现MEL - A组装单分子层能与人IgG（HIgG）以及源自小鼠、猪、兔、马、山羊、大鼠和牛的各种IgG结合，唯一的例外是绵羊IgG。这些结果清楚地表明，MEL - A组装单分子层可作为用于各种免疫球蛋白的新型亲和配体系统。
