Ringstad Lovisa, Andersson Nordahl Emma, Schmidtchen Artur, Malmsten Martin
Department of Pharmacy, Uppsala University, SE-751 23 Uppsala, Sweden.
Biophys J. 2007 Jan 1;92(1):87-98. doi: 10.1529/biophysj.106.088161. Epub 2006 Oct 6.
The effect of peptide hydrophobicity and charge on peptide interaction with model lipid bilayers was investigated for the C3a-derived peptide CNY21 by fluorescence spectroscopy, circular dichroism, ellipsometry, z-potential, and photon correlation spectroscopy measurements. For both zwitterionic and anionic liposomes, the membrane-disruptive potency for CNY21 variants increased with increasing net positive charge and mean hydrophobicity and was completely lost on elimination of all peptide positive charges. Analogous effects of elimination of the peptide positive net charge in particular were found regarding bacteria killing for both Pseudomonas aeruginosa and Bacillus subtilis. The peptides, characterized by moderate helix content both in buffer and when attached to the liposomes, displayed high adsorption for the net positively charged peptide variants, whereas adsorption was non-measurable for the uncharged peptide. That electrostatically driven adsorption represents the main driving force for membrane disruption in lipid systems was also demonstrated by a drastic reduction in both liposome leakage and peptide adsorption with increasing ionic strength, and this salt inactivation can be partly avoided by increasing the peptide hydrophobicity. This increased electrolyte resistance translates also to a higher antibacterial effect for the hydrophobically modified variant at high salt concentration. Overall, our findings demonstrate the importance of the peptide adsorption and resulting peptide interfacial density for membrane-disruptive effects of these peptides.
通过荧光光谱法、圆二色性、椭圆偏振法、ζ电位和光子相关光谱测量，研究了C3a衍生肽CNY21的肽疏水性和电荷对其与模型脂质双层相互作用的影响。对于两性离子脂质体和阴离子脂质体，CNY21变体的膜破坏效力随着净正电荷和平均疏水性的增加而增强，并且在消除所有肽正电荷后完全丧失。特别是在对铜绿假单胞菌和枯草芽孢杆菌的杀菌作用方面，也发现了消除肽正净电荷的类似效果。这些肽在缓冲液中以及附着在脂质体上时均具有适度的螺旋含量，对于带正电荷的肽变体表现出高吸附性，而对于不带电荷的肽则无法测量到吸附。脂质体泄漏和肽吸附均随着离子强度的增加而急剧降低，这也证明了静电驱动的吸附是脂质系统中膜破坏的主要驱动力，并且通过增加肽的疏水性可以部分避免这种盐失活。这种增加的电解质抗性在高盐浓度下也转化为疏水修饰变体更高的抗菌效果。总体而言，我们的研究结果证明了肽吸附以及由此产生的肽界面密度对这些肽的膜破坏作用的重要性。
