Preparation of liposomal formulations containing water-soluble drugs in the form of lipophilic prodrugs in their lipid bilayer is of considerable interest. Previously, we synthesized doxorubicin dioleoyl glyceride and oleoyl conjugates intended for incorporation into fluid-phase liposomal bilayers. In this work, we studied the behavior of lipid conjugates in bilayers prepared from palmitoyl oleoyl phosphatidylcholine and dimyristoyl phosphatidylcholine using methods of fluorescence spectroscopy and molecular modeling. The conjugates were shown to have limited mobility in lipid bilayers, which can be explained by the formation of hydrogen bonds between the doxorubicin aglycone and the lipid phosphate groups. In the liposome membrane, lipophilic conjugates also tend to form clusters through interaction of doxorubicin moieties. Oleoyl chains stretch in parallel to the acyl residues of phospholipids. Due to the formation of a larger number of hydrogen bonds, the oleoyl conjugates interacted with the bilayer more effectively than the dioleoyl glyceride counterparts. These properties of doxorubicin conjugates can affect both the possibility of their incorporation into the lipid bilayer (from the therapeutic effect point of view) and intracellular release of the antibiotic drug by means of enzymolysis.
The growing problem of antibiotic resistance in medicine raises the attention to antimicrobial substances that act on non-protein molecules, which have more conservative structure comparing to proteins or peptides. One of the most promising and studied targets is lipid II — the participant of the bacterial cell wall biosynthetic pathway. Lipid II is present in the bacterial membrane only and has a conservative chemical structure. There are several classes of natural antibiotics acting on lipid II, some of which block the peptidoglycan synthesis by formation of a strong complex with lipid II, and others have an additional bactericidal mechanism involved a violation of the membrane integrity. This review examines the prospects for using such antibacterial substances as new drugs to combat antibiotic-resistant pathogens. The main emphasis is made on the studies of membrane-embedded lipid II structure and molecular mechanisms of its recognition by water-soluble antibiotics, and also on computer modelling of their interaction.
The synthesis of phosphoramidite reagents and solid-phase supports for the preparation of oligonucleotides labeled on various locations within the oligonucleotide chain (including multiple modification) with biotin, lipoic acid, amino group and terminal acetylene, is described. The efficiency of the reagents and solid supports is confirmed by the synthesis of corresponding modified oligonucleotides.