Schümann M, Dathe M, Wieprecht T, Beyermann M, Bienert M
Institute of Molecular Pharmacology, Berlin, Germany.
Biochemistry. 1997 Apr 8;36(14):4345-51. doi: 10.1021/bi962304x.
Fluorescence energy transfer (FET) from [Trp16]-magainin-2-amide (Trp-Mag) and [D-Ala15,D-Trp16]magainin-2-amide (DD-Trp-Mag) to N(alpha)-dansyl-magainin-2-amide (DNS-Mag) was used to study the association of magainin 2 analogs bound to phosphatidylglycerol vesicles. As shown by circular dichroism and fluorescence spectroscopy, the all-L-analogs exist in a helical conformation and are completely bound to the lipid membrane. The observed FET between Trp-Mag and DNS-Mag is rather small and increases with the DNS-Mag surface concentration. The experimentally determined transfer efficiency is lower than predicted for monomeric magainin analogs randomly distributed exclusively at the outer leaflet of lipid vesicles. These observations can be explained by two different models of spatial distribution for the monomeric magainin analogs. The first model takes into account translocation of magainin which might result in a uniform distribution of magainin at the inner and outer vesicle leaflets. The second model assumes that at least one shell of lipids exists between two magainin molecules, thus reducing the probability of direct contact. Both models explain the measured FET without any contribution of stable associates of magainin analogs. Furthermore, for Trp-Mag and DD-Trp-Mag, an identical energy transfer efficiency was observed, although the nonhelical double-D substituted analog should have a significantly reduced association tendency resulting in decreased FET. Our conclusion that the observed FET is not the result of magainin association is confirmed by the equivalence of the measured energy transfer efficiencies.
利用从[色氨酸16]-蛙皮素-2-酰胺（Trp-Mag）和[D-丙氨酸15，D-色氨酸16]蛙皮素-2-酰胺（DD-Trp-Mag）到N（α）-丹磺酰基-蛙皮素-2-酰胺（DNS-Mag）的荧光能量转移（FET）来研究与磷脂酰甘油囊泡结合的蛙皮素2类似物的缔合情况。圆二色性和荧光光谱表明，所有L型类似物均以螺旋构象存在，并完全结合于脂质膜上。观察到的Trp-Mag与DNS-Mag之间的FET相当小，且随DNS-Mag表面浓度的增加而增大。实验测定的转移效率低于仅随机分布在脂质囊泡外小叶的单体蛙皮素类似物的预测值。这些观察结果可以用单体蛙皮素类似物的两种不同空间分布模型来解释。第一个模型考虑了蛙皮素的易位，这可能导致蛙皮素在囊泡内、外小叶均匀分布。第二个模型假设在两个蛙皮素分子之间至少存在一层脂质壳，从而降低了直接接触的概率。两种模型都解释了所测量的FET，而无需蛙皮素类似物稳定缔合体的任何贡献。此外，对于Trp-Mag和DD-Trp-Mag，观察到相同的能量转移效率，尽管非螺旋双取代类似物的缔合趋势应显著降低，从而导致FET降低。我们关于观察到的FET不是蛙皮素缔合结果的结论通过测量的能量转移效率的等效性得到了证实。
