The main task of the research is to acquire fundamental knowledge about the effect of polymer structure on the physicochemical properties of films. A novel meta-material that can be used in manufacturing sensor layers was developed as a model. At the first stage, poly(sodium 4-styrenesulfonate) (PNaSS) cross-linked microspheres are synthesized (which are based on strong polyelectrolytes containing sulfo groups in each monomer unit), and at the second stage, PNaSS@PEDOT microspheres are formed. The poly(3,4-ethylenedioxythiophene) (PEDOT) shell was obtained by the acid-assisted self-polymerization of the monomer; this process is biologically safe and thus suitable for biomedical applications. The suitability of electrochemical impedance spectroscopy for E. coli detection was tested; it was revealed that the attached bacterial wall was destroyed upon application of constant oxidation potential (higher than 0.5 V), which makes the PNaSS@PEDOT microsphere particles promising materials for the development of antifouling coatings. Furthermore, under open-circuit conditions, the walls of E. coli bacteria were not destroyed, which opens up the possibility of employing such meta-materials as sensor films. Scanning electron microscopy, X-ray photoelectron spectroscopy, water contact angle, and wide-angle X-ray diffraction methods were applied in order to characterize the PNaSS@PEDOT films.
- MeSH
- Bridged Bicyclo Compounds, Heterocyclic chemistry MeSH
- Escherichia coli * MeSH
- Microspheres MeSH
- Polymers * chemistry MeSH
- Publication type
- Journal Article MeSH
The influence of maltose-modified poly(propylene imine) (PPI) dendrimers on dimyristoylphosphatidylcholine (DMPC) or dimyristoylphosphatidylcholine/dimyristoylphosphatidylglycerol (DMPC/DMPG) (3%) liposomes was studied. Fourth generation (G4) PPI dendrimers with primary amino surface groups were partially (open shell glycodendrimers - OS) or completely (dense shell glycodendrimers - DS) modified with maltose residues. As a model membrane, two types of 100nm diameter liposomes were used to observe differences in the interactions between neutral DMPC and negatively charged DMPC/DMPG bilayers. Interactions were studied using fluorescence spectroscopy to evaluate the membrane fluidity of both the hydrophobic and hydrophilic parts of the lipid bilayer and using differential scanning calorimetry to investigate thermodynamic parameter changes. Pulsed-filed gradient NMR experiments were carried out to evaluate common diffusion coefficient of DMPG and DS PPI in D2O when using below critical micelle concentration of DMPG. Both OS and DS PPI G4 dendrimers show interactions with liposomes. Neutral DS dendrimers exhibit stronger changes in membrane fluidity compared to OS dendrimers. The bilayer structure seems more rigid in the case of anionic DMPC/DMPG liposomes in comparison to pure and neutral DMPC liposomes. Generally, interactions of dendrimers with anionic DMPC/DMPG and neutral DMPC liposomes were at the same level. Higher concentrations of positively charged OS dendrimers induced the aggregation process with negatively charged liposomes. For all types of experiments, the presence of NaCl decreased the strength of the interactions between glycodendrimers and liposomes. Based on NMR diffusion experiments we suggest that apart from electrostatic interactions for OS PPI hydrogen bonds play a major role in maltose-modified PPI dendrimer interactions with anionic and neutral model membranes where a contact surface is needed for undergoing multiple H-bond interactions between maltose shell of glycodendrimers and surface membrane of liposome.
- MeSH
- Dendrimers chemistry metabolism MeSH
- Diphenylhexatriene chemistry MeSH
- Calorimetry, Differential Scanning MeSH
- Dimyristoylphosphatidylcholine chemistry metabolism MeSH
- Membrane Fluidity MeSH
- Fluorescence Polarization MeSH
- Phosphatidylglycerols chemistry metabolism MeSH
- Hydrophobic and Hydrophilic Interactions MeSH
- Lipid Bilayers chemistry metabolism MeSH
- Liposomes chemistry metabolism MeSH
- Magnetic Resonance Spectroscopy MeSH
- Maltose chemistry metabolism MeSH
- Membrane Lipids chemistry metabolism MeSH
- Polypropylenes chemistry metabolism MeSH
- Static Electricity MeSH
- Hydrogen Bonding MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
Combining the unique properties of peptides as versatile tools for nano- and biotechnology with lead halide perovskite nanoparticles can bring exceptional opportunities for the development of optoelectronics, photonics, and bioelectronics. As a first step towards this challenge sub 10 nm methylammonium lead bromide perovskite colloidal nanoparticles have been synthetizes using commercial cyclic peptide Cyclo(RGDFK), containing 5 amino acids, as a surface stabilizer. Perovskite nanoparticles passivated with Cyclo(RGDFK) possess charge transfer from the perovskite core to the peptide shell, resulting in lower photoluminescence quantum yields, which however opens a path for the application where charge transfer is favorable.
- MeSH
- Inorganic Chemicals chemistry MeSH
- Peptides, Cyclic chemistry MeSH
- Luminescence * MeSH
- Nanoparticles chemistry MeSH
- Lead chemistry MeSH
- Oxides chemistry MeSH
- Semiconductors * MeSH
- Calcium Compounds chemistry MeSH
- Titanium chemistry MeSH
- Publication type
- Journal Article MeSH
- Research Support, Non-U.S. Gov't MeSH
ConspectusMagnetic resonance techniques represent a fundamental class of spectroscopic methods used in physics, chemistry, biology, and medicine. Electron paramagnetic resonance (EPR) is an extremely powerful technique for characterizing systems with an open-shell electronic nature, whereas nuclear magnetic resonance (NMR) has traditionally been used to investigate diamagnetic (closed-shell) systems. However, these two techniques are tightly connected by the electron-nucleus hyperfine interaction operating in paramagnetic (open-shell) systems. Hyperfine interaction of the nuclear spin with unpaired electron(s) induces large temperature-dependent shifts of nuclear resonance frequencies that are designated as hyperfine NMR shifts (δHF).Three fundamental physical mechanisms shape the total hyperfine interaction: Fermi-contact, paramagnetic spin-orbit, and spin-dipolar. The corresponding hyperfine NMR contributions can be interpreted in terms of through-bond and through-space effects. In this Account, we provide an elemental theory behind the hyperfine interaction and NMR shifts and describe recent progress in understanding the structural and electronic principles underlying individual hyperfine terms.The Fermi-contact (FC) mechanism reflects the propagation of electron-spin density throughout the molecule and is proportional to the spin density at the nuclear position. As the imbalance in spin density can be thought of as originating at the paramagnetic metal center and being propagated to the observed nucleus via chemical bonds, FC is an excellent indicator of the bond character. The paramagnetic spin-orbit (PSO) mechanism originates in the orbital current density generated by the spin-orbit coupling interaction at the metal center. The PSO mechanism of the ligand NMR shift then reflects the transmission of the spin polarization through bonds, similar to the FC mechanism, but it also makes a substantial through-space contribution in long-range situations. In contrast, the spin-dipolar (SD) mechanism is relatively unimportant at short-range with significant spin polarization on the spectator atom. The PSO and SD mechanisms combine at long-range to form the so-called pseudocontact shift, traditionally used as a structural and dynamics probe in paramagnetic NMR (pNMR). Note that the PSO and SD terms both contribute to the isotropic NMR shift only at the relativistic spin-orbit level of theory.We demonstrate the advantages of calculating and analyzing the NMR shifts at relativistic two- and four-component levels of theory and present analytical tools and approaches based on perturbation theory. We show that paramagnetic NMR effects can be interpreted by spin-delocalization and spin-polarization mechanisms related to chemical bond concepts of electron conjugation in π-space and hyperconjugation in σ-space in the framework of the molecular orbital (MO) theory. Further, we discuss the effects of environment (supramolecular interactions, solvent, and crystal packing) and demonstrate applications of hyperfine shifts in determining the structure of paramagnetic Ru(III) compounds and their supramolecular host-guest complexes with macrocycles.In conclusion, we provide a short overview of possible pNMR applications in the analysis of spectra and electronic structure and perspectives in this field for a general chemical audience.
- Publication type
- Journal Article MeSH
A freeze-drying method enabling solubilization of hydrophobic species in aqueous solutions of native hyaluronan is described. The method is based on opening the access to supposed hydrophobic patches on hyaluronan by disturbing its massive hydration shell. Hydrophobic and/or polarity-sensitive fluorescence probes were used as hydrophobic models or indicators of interactions with hydrophobic patches. Fluorescence parameters specific to individual probes confirmed the efficiency of the freeze-drying method. This work is the first step in developing biocompatible and biodegradable carriers for hydrophobic drugs with targeted distribution of the active compound from native, chemically non-modified hyaluronan.
... Structure and function are correlated at all levels of biological organization 9 -- Organisms are open ... ... Context of Life 25 -- Matter consists of chemical elements in pure form and in combinations called compounds ... ... CHAPTER 4 -- Carbon and the Molecular Diversity of Life 53 -- Organic chemistry is the study of carbon compounds ... ... plant disease: science as a process 324 -- Most viruses consist of a genome enclosed in a protein shell ... ... from the three embryonic germ layers 973 -- Amniote embryos develop in a fluid-filled sac within a shell ...
Fourth edition 1206, 32 stran : ilustrace ; 29 cm
