Department of Chemistry, Iowa State University, Ames, Iowa 50011, USA.
J Am Chem Soc. 2010 Jul 7;132(26):9197-205. doi: 10.1021/ja103658h.
A number of arylamides have been synthesized and found to exhibit potent antimicrobial activities against a broad spectrum of Gram-positive and Gram-negative bacteria while exhibiting low toxicity toward eukaryotic cells. These facially amphiphilic foldamers have a relatively rigid intramolecular hydrogen-bonded arylamide as a framework, which places trifluormethyl versus positively charged amino and guanidino groups along opposite faces of the elongated molecule, facilitating interactions with lipid membranes. To better understand the mechanism of action of these antimicrobial foldamers, we have investigated the lipid interaction, depth of insertion, orientation, and dynamics of an arylamide, PMX30016, using (31)P and (19)F solid-state NMR spectroscopy. Static (31)P NMR line shapes of lipid membranes with a range of compositions indicate that PMX30016 does not disrupt the lamellar order of the lipid bilayer but perturbs the lipid headgroup conformation. This headgroup perturbation, manifested as systematic (31)P chemical shift anisotropy increases, is consistent with the well documented "electrometer" effect of lipid membranes in response to the addition of positive charges to membrane surfaces. Paramagnetic relaxation enhancement experiments indicate that the arylamide inserts into the membrane-water interface, just below the headgroup region. Measurement of (19)F-(19)F dipolar couplings within each CF(3) moiety revealed that PMX30016 is oriented with the molecular plane 20 degrees and 30 degrees from the membrane normal of neutral and anionic bilayers, respectively, and the long molecular axis lies parallel to the membrane plane. Thus, this arylamide inserts into the bilayer in a knife-like fashion, consistent with previous vibrational spectroscopy results. Moreover, (19)F NMR line shapes indicate that this molecular knife undergoes fast uniaxial rotation around the bilayer normal. These results suggest that antimicrobial arylamides destabilize anionic lipid membranes primarily by altering the membrane electric potential profile, and the spinning molecular knife may additionally create transient defects in the lipid membrane. Compared to typical antimicrobial peptides, this arylamide has more subtle effects on and is less disruptive of the structure of lipid bilayers.
已经合成了许多芳酰胺，并发现它们对革兰氏阳性和革兰氏阴性细菌表现出广谱的强大抗菌活性，同时对真核细胞的毒性较低。这些具有面状两亲性的折叠体具有相对刚性的分子内氢键芳酰胺作为框架，将三氟甲基与带正电荷的氨基和胍基基团放置在拉长分子的相对面上，促进与脂膜的相互作用。为了更好地了解这些抗菌折叠体的作用机制，我们使用（31）P 和（19）F 固态 NMR 光谱研究了芳酰胺 PMX30016 与脂质的相互作用、插入深度、取向和动力学。具有一系列组成的脂质膜的静态（31）P NMR 线形状表明，PMX30016 不会破坏脂质双层的层状有序性，但会扰乱脂质头基构象。这种头基扰动表现为系统的（31）P 化学位移各向异性增加，与众所周知的脂质膜对膜表面添加正电荷的“静电计”效应一致。顺磁弛豫增强实验表明芳酰胺插入到膜-水界面，刚好在头基区域下方。在每个 CF(3) 部分内测量（19）F-(19)F 偶极耦合表明，PMX30016 以分子平面与中性和阴离子双层的膜法线成 20 度和 30 度的角度取向，并且长分子轴平行于膜平面。因此，这种芳酰胺以刀状插入双层，与先前的振动光谱结果一致。此外，（19）F NMR 线形状表明，这种分子刀围绕膜法线进行快速单轴旋转。这些结果表明，抗菌芳酰胺主要通过改变膜电势分布来破坏阴离子脂质膜，而旋转的分子刀还可能在脂质膜中产生瞬时缺陷。与典型的抗菌肽相比，这种芳酰胺对脂质双层的结构影响更为微妙，破坏程度也较小。
