Neoglycolipids Micelle-like Structures as a Basis for Drug Delivery Systems

Targeted drug delivery is one of the most promising tasks of nanomedicine, as this is a real way to increase the effectiveness of therapeutic effects against many diseases. In this regard, the development of new inexpensive highly effective stimulating and non-immunogenic drug delivery systems (DDS) is of great importance. In this work new molecular candidates were proposed and studied for the creation of such systems based on the use of new compounds, neoglycolipids. It is shown that these compounds are capable of self-association in aqueous solutions and can serve as potential carriers of drug compounds with targeted delivery determined by their terminal groups (in particular, glycans). The processes of their associates formation and features of their structure are investigated. The results show that these selforganizing nanoscale systems can be used as a basis for developing new drug delivery systems. Keywords: neoglycolipids, micelle-like structures, small-angle X-ray scattering, molecular dynamics simulatio

Effect of Buffer Composition on Conformational Flexibility of N-Terminal Fragments of Dps and the Nature of Interactions with DNA. Small-Angle X-Ray Scattering Study

The DNA-binding protein Dps plays a key role in the formation of Dps–DNA crystalline arrays in living bacterial cells, which allows bacteria to survive under stress conditions and under the influence of various adverse factors. Such genome-protective mechanisms can lead to the emergence of bacterial resistance to antibiotics and other drugs. Elucidation of the fundamental biochemical, genetic, and structural basis of the resistance is of primary importance for the development of strategies for combating and preventing bacterial resistance, as well as the elaboration of innovative therapeutic approaches. Conformational characteristics of Dps and its N-terminal fragments responsible for the nature of interactions of this protein with DNA in solution were studied by small-angle scattering

Tetrameric Structures of Inorganic CBS-Pyrophosphatases from Various Bacterial Species Revealed by Small-Angle X-ray Scattering in Solution

Quaternary structure of CBS-pyrophosphatases (CBS-PPases), which belong to the PPases of family II, plays an important role in their function ensuring cooperative behavior of the enzymes. Despite an intensive research, high resolution structures of the full-length CBS-PPases are not yet available making it difficult to determine the signal transmission path from the regulatory to the active center. In the present work, small-angle X-ray scattering (SAXS) combined with size-exclusion chromatography was applied to determine the solution structures of the full-length wild-type CBS-PPases from three different bacterial species. Previously, in the absence of an experimentally determined full-length CBS-PPase structure, a homodimeric model of the enzyme based on known crystal structures of the CBS domain and family II PPase without this domain has been proposed. Our SAXS analyses demonstrate, for the first time, the existence of stable tetramers in solution for all studied CBS-PPases from different sources. Our findings show that further studies are required to establish the functional properties of these enzymes. This is important not only to enhance our understanding of the relation between CBS-PPases structure and function under normal conditions but also because some human pathogens harbor this class of enzymes

Formation of High-Order Structures in Solution by CBS-Pyrophosphatase from D. hafniense

To solve the question about the oligomeric state of wild-type CBS-pyrophosphatase (CBS-PPase) from D. hafniense, this enzyme has been studied using two independent structural methods: small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryoTEM). The formation of stable high-order structures (large helical associates) in a concentrated protein solution has been observed for the first time. It is also shown for the first time that the formation of these structures is a reversible process and the protein passes to the tetramer form (in which it usually exists in diluted solutions) at ligand attachment. The obtained results are important for understanding the functional features of CBS-PPase (in particular, gaining insight into the pathogenesis of some diseases)

The Effect of Cationic Polylysine on the Release of an Encapsulated Substance from pH-Sensitive Anionic Liposomes

The formation of complexes from anionic liposomes with a pH-sensitive molecular switch (flipid) and a cationic polypeptide (polylysine) embedded in the membrane with a degree of polymerization of 90, 660, and 1360 was investigated. Liposomes in the complex retain their integrity in a buffer solution with a pH of 7; The resulting complexes are resistant to dissociation in a physiological solution containing 0.15 M NaCl. Lowering the pH of the solution to 5 causes the formation of defects in the lipid bilayer by changing the conformation of the flipid, which leads to the release of the encapsulated substance from the liposomes into the surrounding solution. In this case, complexation increases both the rate of release of the encapsulated substance and the amount of the substance moving from the liposomes to the external solution. The results obtained are of interest for encapsulation and controlled drug delivery

Spatial organization of Dps and DNA–Dps complexes

DNA co-crystallization with Dps family proteins is a fundamental mechanism, which preserves DNA in bacteria from harsh conditions. Though many aspects of this phenomenon are well characterized, the spatial organization of DNA in DNA–Dps co-crystals is not completely understood, and existing models need further clarification. To advance in this problem we have utilized atomic force microscopy (AFM) as the main structural tool, and small-angle X-scattering (SAXS) to characterize Dps as a key component of the DNA-protein complex. SAXS analysis in the presence of EDTA indicates a significantly larger radius of gyration for Dps than would be expected for the core of the dodecamer, consistent with the N-terminal regions extending out into solution and being accessible for interaction with DNA. In AFM experiments, both Dps protein molecules and DNA–Dps complexes adsorbed on mica or highly oriented pyrolytic graphite (HOPG) surfaces form densely packed hexagonal structures with a characteristic size of about 9 nm. To shed light on the peculiarities of DNA interaction with Dps molecules, we have characterized individual DNA–Dps complexes. Contour length evaluation has confirmed the non-specific character of Dps binding with DNA and revealed that DNA does not wrap Dps molecules in DNA–Dps complexes. Angle analysis has demonstrated that in DNA–Dps complexes a Dps molecule contacts with a DNA segment of ~6 nm in length. Consideration of DNA condensation upon complex formation with small Dps quasi-crystals indicates that DNA may be arranged along the rows of ordered protein molecules on a Dps sheet