The Increased Release Kinetics of Quercetin from Superparamagnetic Nanocarriers in Dialysis.

The actual cumulative mass of released quercetin from nanoparticles within the dialysis membrane was determined under the influence of external stationary and alternating magnetic fields. We have shown that the control of the release kinetics of quercetin from MNPs, i.e.

The Fine-Tuned Release of Antioxidant from Superparamagnetic Nanocarriers under the Combination of Stationary and Alternating Magnetic Fields.

Superparamagnetic magnetite nanoparticles (MNPs) with excellent biocompatibility and negligible toxicity were prepared by solvothermal method and stabilized by widely used and biocompatible polymer poly(ethylene glycol) PEG-4000 Da. The unique properties of the synthesized MNPs enable them to host the unstable and water-insoluble quercetin as well as deliver and localize quercetin directly to the desired site. The chemical and physical properties were validated by X-ray powder diffraction (XRPD), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), superconducting quantum interference device (SQUID) magnetometer, FTIR spectroscopy and dynamic light scattering (DLS).

Flavonol clustering in model lipid membranes: DSC, AFM, force spectroscopy and MD simulations study.

We here report on flavonols (myricetin (MCE) and its glycoside myricitrin (MCI)) - 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) membrane interactions focusing on the effects of flavonol clustering on the membrane thermotropic and nanomechanical properties. Atomic force microscopy (AFM), force spectroscopy (FS) and differential scanning calorimetry (DSC) together with molecular dynamics (MD) simulations provided a consistent picture of flavonol - DMPC membrane interactions. DMPC membrane as a supported lipid bilayer preserved its integrity even at higher flavonol molar fraction x.

The Structural Integrity of the Model Lipid Membrane during Induced Lipid Peroxidation: The Role of Flavonols in the Inhibition of Lipid Peroxidation.

The structural integrity, elasticity, and fluidity of lipid membranes are critical for cellular activities such as communication between cells, exocytosis, and endocytosis. Unsaturated lipids, the main components of biological membranes, are particularly susceptible to the oxidative attack of reactive oxygen species. The peroxidation of unsaturated lipids, in our case 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), induces the structural reorganization of the membrane.

Comparative study of the effects of ortho-, meta- and para-carboranes (CBH) on the physicochemical properties, cytotoxicity and antiviral activity of uridine and 2'-deoxyuridine boron cluster conjugates.

In this study, a series of uridine (U) and 2'-deoxyuridine (dU) conjugates containing an isomeric ortho-, meta- or para-carborane cluster (CBH) attached at C-5 through an ethynyl linker were synthesized. The effect of carborane cluster isomerism on the conjugate syn/anti conformation, molar extinction coefficient, lipophilicity, susceptibility to phosphorylation (by TK1, TK2 and dCK), cytotoxicity and antiviral activity was evaluated. A strong effect of the boron cluster modification on the syn/anti equilibrium of the modified nucleosides was observed.

Enhanced Protection of Biological Membranes during Lipid Peroxidation: Study of the Interactions between Flavonoid Loaded Mesoporous Silica Nanoparticles and Model Cell Membranes.

Flavonoids, polyphenols with anti-oxidative activity have high potential as novel therapeutics for neurodegenerative disease, but their applicability is rendered by their poor water solubility and chemical instability under physiological conditions. In this study, this is overcome by delivering flavonoids to model cell membranes (unsaturated DOPC) using prepared and characterized biodegradable mesoporous silica nanoparticles, MSNs. Quercetin, myricetin and myricitrin have been investigated in order to determine the relationship between flavonoid structure and protective activity towards oxidative stress, i.

Neurotoxic Effect of Ethanolic Extract of Propolis in the Presence of Copper Ions is Mediated through Enhanced Production of ROS and Stimulation of caspase-3/7 Activity.

Elevated amounts of copper are considered to be contributing factor in the progression of neurodegenerative diseases as they promote oxidative stress conditions. The aim of our study was to examine the effects of ethanolic extract of propolis (EEP) against copper-induced neuronal damage. In cultured P19 neuronal cells, EEP exacerbated copper-provoked neuronal cell death by increasing the generation of reactive oxygen species (ROS) and through the activation of caspase-3/7 activity.

Infrared spectroscopy of flavones and flavonols. Reexamination of the hydroxyl and carbonyl vibrations in relation to the interactions of flavonoids with membrane lipids.

Detailed vibrational assignments for twelve flavonoids (seven flavones (flavone, 3- and 5-hydroxyflavone, chrysin, apigenin, fisetin and luteolin) and five flavonols (galangin, kaempferol, quercetin, morin and myricetin)) have been made based on own and reported experimental data and calculations at the B3LYP/6-31+G(d,p) level of theory. All the molecules are treated in a uniform way by using the same set of redundancy-free set of internal coordinates. A generalized harmonic mode mixing is used to corroborate the vibrational characteristics of this important class of molecules.

Refractive Index Mixing Rules and Excess Infrared Spectra of Binary Mixtures.

Three refractive index mixing rules, Arago-Biot, Lorentz-Lorenz, and Newton, are generalized to complex refractive index and used to define infrared (IR) spectra of the corresponding ideal liquid mixtures. Using the measured optical constants n and k for acetonitrile-water mixtures (Bertie and Lan, 1997) the excess absorbances, A=  A -  A, are calculated. Relying upon the well-established properties of the acetonitrile-water mixtures, the interpretation of the excess absorbances is established that is essentially based on the understanding of a liquid as a set of oscillators.

Ligand-Dependent Nanoparticle Clustering within Lipid Membranes Induced by Surrounding Medium.

The interactions between hydrophobic or semihydrophobic gold and silver nanoparticles (NPs) and a dimyristoylphosphatidylcholine (DMPC) bilayer as a model cell membrane in two ionic solutions result in the structural reorganization within the bilayer manifested as locally increased nanomechanical compaction in the vicinity of NP clusters as well as changed overall thermotropic properties. The effects of NP surface charge and hydrophobicity were examined using AFM imaging, force spectroscopy and IR spectroscopy. The NP clustering occurred during hydration process of dry films containing both the DMPC molecules and the NPs by the mechanism in which the number of bilayer deformations was reduced by NP clustering.

Ionic strength and composition govern the elasticity of biological membranes. A study of model DMPC bilayers by force- and transmission IR spectroscopy.

Infrared (IR) spectroscopy was used to quantify the ion mixture effect of seawater (SW), particularly the contribution of Mg(2+) and Ca(2+) as dominant divalent cations, on the thermotropic phase behaviour of 1,2-dimyristoyl-sn-glycero-3-posphocholine (DMPC) bilayers. The changed character of the main transition at 24 °C from sharp to gradual in films and the 1 °C shift of the main transition temperature in dispersions reflect the interactions of lipid headgroups with the ions in SW. Force spectroscopy was used to quantify the nanomechanical hardness of a DMPC supported lipid bilayer (SLB).

Experimental and theoretical study of the cation binding properties of macrocyclic dehydrodibenzopyrido[15]annulenes.

The UV/Vis titration measurements, vibrational and NMR spectroscopy of isomeric dehydrodibenzopyrido[15]annulenes (DBPA) 1 and 2 clearly show that under proper conditions these macrocycles can achieve fast, quantitative and unselective binding of metal ions. The macrocycle 1 is an example of a hindered amine 2,6-bis(R)pyridine and its isomer 2 of a non-hindered amine 3,5-bis(R)pyridine. The protonation stoichiometry for both 1 and 2 was assumed to be DBPA:H(+)=1:1 and the formation constants logK=4.

The study of secondary effects in vibrational and hydrogen bonding properties of 2- and 3-ethynylpyridine and ethynylbenzene by IR spectroscopy.

Weak hydrogen bonds formed by 2- and 3-ethynylpyridine and ethynylbenzene with trimethylphosphate and phenol were characterized by IR spectroscopy and DFT calculations (B3LYP/6-311++G(d, p)). The structure and stability of ethynylpyridines and ethynylbenzene in the gas phase and in the complexes with trimethylphosphate and phenol are discussed in terms of geometry and electronic charge redistribution. Anharmonic effects are taken into account when calculating vibrational wavenumbers of these systems what lead to partial improvement of agreement with experiment.

Intramolecular resonance-assisted hydrogen bonds: a theoretical description by means of atomic charges and charge fluxes.

The characterization of intramolecular H-bonds in terms of atomic charges and charge fluxes (at the B3LYP/cc-pVTZ level of theory) has been extended to the case of the so called resonance-assisted (RA) H-bonds. A quadratic correlation between the charge fluxes φH and the molecular IR absorption coefficients E that includes the entire family of the studied systems (31 of them) containing both intra- and intermolecular hydrogen bonds (O-H···O/N) confirmed the critical importance of the charge fluxes on the IR intensity enhancements. Since they reflect changing of the atomic charge distribution during the normal modes of vibrations, the dynamic nature of hydrogen bonding properties has been re-emphasized.

Characterization of intramolecular hydrogen bonds by atomic charges and charge fluxes.

The electronic charge redistribution and the infrared intensities of the two types of intramolecular hydrogen bonds, O-H···O and O-H···π, of o-hydroxy- and o-ethynylphenol, respectively, together with a set of related intermolecular hydrogen bond complexes are described in terms of atomic charges and charge fluxes derived from atomic polar tensors calculated at the B3LYP/cc-pVTZ level of theory. The polarizable continuum model shows that both the atomic charges and charge fluxes are strongly dependent on solvent. It is shown that their values for the OH bond in an intramolecular hydrogen bond are not much different from those for the "free" OH bond, but the changes are toward the values found for an intermolecular hydrogen bond.

Thermal analysis of paracetamol polymorphs by FT-IR spectroscopies.

A simple IR spectroscopy based methodology in routine screening studies of polymorphism is proposed. Reflectance and transmittance temperature-dependent IR measurements (coupled with the 2D-IR data presentation and the baseline analysis) offer a positive identification of each polymorphic phase, therefore allowing simple and rapid monitoring of the measured system. Applicability and flexibility of the methodology was demonstrated on the measurement of the model polymorphic compound paracetamol under various conditions (including geometric constraints and elevated pressure).

Determination of phase transition temperatures by the analysis of baseline variations in transmittance infrared spectroscopy.

A simple method for obtaining phase transition temperatures is proposed. It is based on absolute variations of a baseline in a temperature-dependent mid-infrared transmittance spectral data set recorded for a sample KBr pellet. The method is rapid, inexpensive, and completely free of any personal bias.

Hydrogen bonding in 1,1'-Bi-2-naphthol within the polarizable continuum model.

Intra- and intermolecular hydrogen bonding of 1,1'-bi-2-naphthol in a series of solvents and in solid phase has been investigated by means of mid-IR spectroscopy and DFT reaction field calculations. The polarizable continuum model has been used to estimate the relative stability of isomers differing in the positions of the hydroxyl groups. The height of the potential barriers between them was also calculated and the corresponding transition states characterized.

ESI-MS studies of mixed-ligand Fe(II) complexes containing 1,10-phenanthroline and 1,10-phenanthroline-5,6-dione as ligands.

In order to monitor the progression of the synthesis and the separation of novel mixed-ligand iron complexes containing 1,10-phenanthroline, 1,10-phenanthroline-5,6-dione, and NCS- as ligands all products were mass analyzed by electrospray ionization ion trap MS/MS. The spectra of methanol (MeOH), acetonitrile (ACN), water, and ethanol (EtOH) solutions were collected and the results were compared. It was detected under applied electrospray ionization mass spectrometry (ESI-MS) conditions that MeOH, water, and EtOH formed solvent clusters around the free or complexed 1,10-phenanthroline-5,6-dione.

Raman study of structural relaxation and boson peak in amorphous films of adamantane.

Low-frequency Raman scattering was used to study amorphous solid films of adamantane, a globular non-polar hydrocarbon molecule. As evidenced by its spectral characteristics this type of disorder is different from the orientational disorder found in the room temperature plastic phase by the absence of the translational order as well. This gives rise to the boson peak related to acoustic phonons which gradually disappears upon heating with simultaneous emerging of the phonon line at 50 cm-1 which characterizes the low-temperature ordered phase of adamantane.

Vibrational study of the Fe(phen)2(NCS)2 spin-crossover complex by density-functional calculations.

The geometries and vibrational frequencies of an iron(II) spin-crossover complex Fe(phen)2(NCS)2 in the low- and high-spin states have been calculated using DFT (BP86 functional with 6-311G* + Wachters + f, 6-31G* and LANL2DZ basis sets). A redundancy-free set of internal coordinates has been defined and used to obtain a valence force field. The use of the symmetry coordinates of a perfect octahedron as internal coordinates for the FeN6 framework of the complex has enabled the description of the stretching-bending couplings.

Raman Spectroscopy of Three Average-Valence Dicopper Cryptates: Evidence for Copper-Copper Bonding.

Comparison of the X-ray structures of two pairs of dicopper(I) and dicopper(1.5) cryptates provides evidence (over 0.5 Å contraction of the internuclear distance in one pair) for copper-copper bond formation.