Lipidverankerte Oligonucleotide zur Bildung stabiler Doppelhelices in Membrandomänen

Guanosine Nucleolipids: Synthesis, Characterization, Aggregation and X-Ray Crystallographic Identification of Electricity-Conducting G-Ribbons

The lipophilization of β-d-riboguanosine (1) with various symmetric as well as asymmetric ketones is described (→3a-3f). The formation of the corresponding O-2',3'-ketals is accompanied by the appearance of various fluorescent by-products which were isolated chromatographically as mixtures and tentatively analyzed by ESI-MS spectrometry. The mainly formed guanosine nucleolipids were isolated and characterized by elemental analyses, ¹ H-, ¹³ C-NMR and UV spectroscopy. For a drug profiling, static topological polar surface areas as well as ¹⁰ logP_OW values were calculated by an increment-based method as well as experimentally for the systems 1-octanol-H₂ O and cyclohexane-H₂ O. The guanosine-O-2',3'-ketal derivatives 3b and 3a could be crystallized in (D₆ )DMSO - the latter after one year of standing at ambient temperature. X-ray analysis revealed the formation of self-assembled ribbons consisting of two structurally similar 3b nucleolipid conformers as well as integrated (D₆ )DMSO molecules. In the case of 3a ⋅ DMSO, the ribbon is formed by a single type of guanosine nucleolipid molecules. The crystalline material 3b ⋅ DMSO was further analyzed by differential scanning calorimetry (DSC) and temperature-dependent polarization microscopy. Crystallization was also performed on interdigitated electrodes (Au, distance, 5 μm) and visualized by scanning electron microscopy. Resistance and amperage measurements clearly demonstrate that the electrode-bridging 3b crystals are electrically conducting. All O-2',3'-guanosine ketals were tested on their cytostatic/cytotoxic activity towards phorbol 12-myristate 13-acetate (PMA)-differentiated human THP-1 macrophages as well as against human astrocytoma/oligodendroglioma GOS-3 cells and against rat malignant neuroectodermal BT4Ca cells.

Triazole-tailored guanosine dinucleosides as biomimetic ion channels to modulate transmembrane potential

A “click” ion channel platform has been established by employing a clickable guanosine azide or alkyne with covalent spacers. The resulting guanosine derivatives modulated the traffic of ions across the phospholipid bilayer, exhibiting a variation in conductance spanning three orders of magnitude (pS to nS). Förster resonance energy transfer studies of the dansyl fluorophore with the membrane binding fluorophore Nile red revealed that the dansyl fluorophore is deeply embedded in the phospholipid bilayer. Complementary cytosine can inhibit the conductance of the supramolecular guanosine channels in the phospholipid bilayers.

DNA-based micelles: synthesis, micellar properties and size-dependent cell permeability

Functional nanomaterials based on molecular self-assembly hold great promise for applications in biomedicine and biotechnology. However, their efficacy could be a problem and can be improved by precisely controlling the size, structure, and functions. This would require a molecular engineering design capable of producing monodispersed functional materials characterized by beneficial changes in size, shape, and chemical structure. To address this challenge, we have designed and constructed a series of amphiphilic oligonucleotide molecules. In aqueous solutions, the amphiphilic oligonucleotide molecules, consisting of a hydrophilic oligonucleotide covalently linked to hydrophobic diacyllipid tails, spontaneously self-assemble into monodispersed, three-dimensional micellar nanostructures with a lipid core and a DNA corona. These hierarchical architectures are results of intermolecular hydrophobic interactions. Experimental testing further showed that these types of micelles have excellent thermal stability and their size can be fine-tuned by changing the length of the DNA sequence. Moreover, in the micelle system, the molecular recognition properties of DNA are intact, thus, our DNA micelles can hybridize with complimentary sequences while retaining their structural integrity. Importantly, when interacting with cell membranes, the highly charged DNA micelles are able to disintegrate themselves and insert into the cell membrane, completing the process of internalization by endocytosis. Interestingly, the fluorescence was found accumulated in confined regions of cytosole. Finally, we show that the kinetics of this internalization process is size-dependent. Therefore, cell permeability, combined with small sizes and natural nontoxicity are all excellent features that make our DNA-micelles highly suitable for a variety of applications in nanobiotechnology, cell biology, and drug delivery systems.