Abstract
The calixarene derivative used in this study (tetra-p-guanidinoethylcalix[4]arene) shows in vitro activity against different Gram-positive and Gram-negative bacteria. The interaction between bacterial cell membranes and the water-soluble calixarene was investigated using model lipids spread as monomolecular films at the air–water interface. Compression and adsorption experiments, as well as Brewster angle microscopy, polarization modulation-infrared reflection–absorption spectroscopy and computer modeling permitted understanding of the intra- and intermolecular interaction in several lipid-calixarene systems. Because the affinity of the calixarene derivative for the membranes may be linked to the interaction with negative charges, phosphatidylglycerols were used as model lipids; the phosphatidylglycerols contained saturated or unsaturated hydrocarbon chains with different lengths. It was showed that the affinity of the calixarene for the monolayer depends on the structure of the phosphatidylglycerols side chains. This observation may be of interest for a further development of new antibiotics.
Highlights
New effective antibiotics with precise antimicrobial and cell-penetrating activities are urgently needed to address the mounting resistance challenge
The profiles of the isotherms corresponding to DLPG, DMPG, DOPG and DPPG are similar up to 45 mNÁmÀ1; DSPG differs from the other four films, as it shows a plateau at 30 mNÁmÀ1
Based on the compression and the adsorption experiments we propose that below 30 mN mÀ1 CX1 is intercalated between the DSPG molecules [14]
Summary
Calixarenes are considered as versatile platforms for synthesizing bioactive agents [1]. These organic macrocyclic molecules contain a series of phenolic units linked through methylene bridges at the ortho-position to the hydroxyl group present on the aromatic moiety [2]. It was shown in the literature that different calixarene derivatives interact with lipid bilayers and modify their properties [3]. This observation is important for engineering molecular structures with an affinity towards bacterial membrane. Among different calix[4]arene derivatives synthesized in our group, some have antibacterial properties [4,5,6]. The impact of CX1 on bacterial membranes was observed in vitro using microscopy [10], electrophoretic mobility [10], and membrane permeability
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