The transformation of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayers from the gel (Lβ') to the fluid (Lα) phase involves an intermediate ripple (Pβ') phase forming a few degrees below the main transition temperature (Tm). While the exact cause of bilayer rippling is still debated, the presence of amphiphilic molecules, pH, and lipid bilayer architecture are all known to influence (pre)transition behavior. In particular, fatty acid chains interact with hydrophobic lipid tails, while the carboxylic groups simultaneously participate in proton transfer with interfacial water in the polar lipid region which is controlled by the pH of the surrounding aqueous medium. The molecular-level variations in the DPPC ripple phase in the presence of 2% palmitic acid (PA) were studied at pH levels 4.0, 7.3, and 9.1, where PA is fully protonated, partially protonated, or fully deprotonated. Bilayer thermotropic behavior was investigated by differential scanning calorimetry (DSC) and Fourier-transform infrared (FTIR) spectroscopy which agreed in their characterization of (pre)transition at pH of 9.1, but not at pH 4.0 and especially not at 7.3. Owing to the different insertion depths of protonated and deprotonated PA, along with the ability of protonated PA to undergo flip-flop in the bilayer, these two forms of PA show a different hydration pattern in the interfacial water layer. Finally, these results demonstrated the hitherto undiscovered potential of FTIR spectroscopy in the detection of the events occurring at the surface of lipid bilayers that obscure the low-cooperativity phase transition explored in this work.

• Klíčová slova
• 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) lipid bilayers, DSC and FTIR spectroscopy, Palmitic acid (PA), Ripple phase, pH-dependent (de)protonation,
• MeSH
• 1,2-dipalmitoylfosfatidylcholin * analogy a deriváty   MeSH
• diferenciální skenovací kalorimetrie MeSH
• koncentrace vodíkových iontů MeSH
• kyselina palmitová * chemie   MeSH
• lipidové dvojvrstvy * chemie   MeSH
• molekulární struktura MeSH
• protony MeSH
• spektroskopie infračervená s Fourierovou transformací MeSH
• teplota MeSH
• změna skupenství MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• 1,2-dipalmitoylfosfatidylcholin * MeSH
• colfosceril palmitate MeSH Prohlížeč
• kyselina palmitová * MeSH
• lipidové dvojvrstvy * MeSH
• protony MeSH

Procyanidins, contained in many products abundant in human diet, exhibit high biological activity. However, this activity has not been fully explained at cellular and molecular levels. In this study, we determine the mechanism of interaction of procyanidin B3 with model lipid membrane. This mechanism was established on the basis of changes induced by B3 in the physical properties of lipid bilayer. The changes were investigated using steady state and time-resolved fluorescence, DSC, and FTIR. We show that procyanidin B3 causes changes in the arrangement of the polar heads of lipids, order of their acyl chains and the main lipid phase transition temperature. Furthermore, its presence in the membrane leads to a reduction in membrane dipole potential. Procyanidin B3 is anchored to membrane via hydrogen bonds formed between its OH groups and the PO2- and CO groups of lipids, causing changes in both hydrophilic and hydrophobic regions of the membrane.

• Klíčová slova
• DMPC, FTIR, Fluidity, Hydration, Order parameter, Procyanidin B(3), Procyanidin B(3) (CID 146798),
• MeSH
• 2-naftylamin analogy a deriváty   chemie   MeSH
• biflavonoidy chemie   MeSH
• diferenciální skenovací kalorimetrie MeSH
• dihydropyridiny chemie   MeSH
• dimyristoylfosfatidylcholin chemie   MeSH
• fluorescenční spektrometrie MeSH
• hydrofobní a hydrofilní interakce MeSH
• katechin chemie   MeSH
• laurany chemie   MeSH
• lipidové dvojvrstvy chemie   MeSH
• proantokyanidiny chemie   MeSH
• spektroskopie infračervená s Fourierovou transformací MeSH
• teplota MeSH
• termodynamika MeSH
• vodíková vazba MeSH
• změna skupenství MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 2-naftylamin MeSH
• 2,6-dimethyl-1,4-dihydropyridine-3,5-dicarboxylic acid monomethyl ester MeSH Prohlížeč
• biflavonoidy MeSH
• dihydropyridiny MeSH
• dimyristoylfosfatidylcholin MeSH
• katechin MeSH
• laurany MeSH
• laurdan MeSH Prohlížeč
• lipidové dvojvrstvy MeSH
• proantokyanidiny MeSH
• procyanidin B3 MeSH Prohlížeč

Analysis of C cross-polarization magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), Fourier transform infrared (FTIR), and X-ray powder diffraction data of trospium chloride (TCl) products crystallized from different mixtures of water-ethanol [φ(EtOH) = 0.5-1.0] at various temperatures (0°C, 20°C) and initial concentrations (saturated solution, 30%-50% excess of solvent) revealed extensive structural variability of TCl. Although (13) C CP/MAS NMR spectra indicated broad variety of structural phases arising from molecular disorder, temperature-modulated DSC identified presence of two distinct components in the products. FTIR spectra revealed alterations in the hydrogen bonding network (ionic hydrogen bond formation), whereas the X-ray diffraction reflected unchanged unit cell parameters. These results were explained by a two-component character of TCl products in which a dominant polymorphic form is accompanied by partly separated nanocrystalline domains of a secondary phase that does not provide clear Bragg reflections. These phases slightly differ in the degree of molecular disorder, in the quality of crystal lattice and hydrogen bonding network. It is also demonstrated that, for the quality control of such complex products, (13) C CP/MAS NMR spectroscopy combined with factor analysis (FA) can satisfactorily be used for categorizing the individual samples: FA of (13) C CP/MAS NMR spectra found clear relationships between the extent of molecular disorder and crystallization conditions. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci 102:1235-1248, 2013.

• MeSH
• benziláty chemie   MeSH
• diferenciální skenovací kalorimetrie MeSH
• difrakce rentgenového záření MeSH
• krystalizace MeSH
• magnetická rezonanční spektroskopie MeSH
• nortropany chemie   MeSH
• prášková difrakce MeSH
• spektroskopie infračervená s Fourierovou transformací MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• benziláty MeSH
• nortropany MeSH
• trospium chloride MeSH Prohlížeč

The paper specifies the electrostatic spinning process of specific polymeric materials, such as polyvinylidene fluoride (PVDF), polyamide-6 (PA6, Nylon-6) and their combination PVDF/PA6. By combining nanofibers from two different materials during the spinning process, new structures with different mechanical, chemical, and physical properties can be created. The materials and their combinations were subjected to several measurements: scanning electron microscopy (SEM) to capture topography; contact angle of the liquid wettability on the sample surface to observe hydrophobicity and hydrophilicity; crystallization events were determined by differential scanning calorimetry (DSC); X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FT-IR) to describe properties and their changes at the chemical level. Furthermore, for the electrical properties of the sample, the dielectric characteristics and the piezoelectric coefficient were measured. The advantage of the addition of co-polymers was to control the properties of PVDF samples and understand the reasons for the changed functionality. The innovation point of this work is the complex analysis of PVDF modification caused by mixing with nylon PA6. Here we emphasize that the application of nylon during the spin influences the properties and structure (polarization, crystallization) of PVDF.

• Klíčová slova
• DSC, FTIR, PA6, PVDF, Raman spectroscopy, SEM, XPS, electrostatic spinning, nanofibers, permittivity,
• Publikační typ
• časopisecké články MeSH

Three polymorphic modifications of bis(N-phenylbiguanidium(1+)) oxalate are reported, and their characterization is discussed in this paper. The non-centrosymmetric bis(N-phenylbiguanidium(1+)) oxalate (I), which was obtained from an aqueous solution at 313K, belongs to the monoclinic space group Cc (a=6.2560(2)Å, b=18.6920(3)Å, c=18.2980(5)Å, β=96.249(1)°, V=2127.0(1)Å(3), Z=4, R=0.0314 for 4738 observed reflections). The centrosymmetric bis(N-phenylbiguanidium(1+)) oxalate (II) was obtained from an aqueous solution at 298K and belongs to the monoclinic space group P21/n (a=6.1335(3)Å, b=11.7862(6)Å, c=14.5962(8)Å, β=95.728(2)°, V=1049.90(9)Å(3), Z=4, R=0.0420 for 2396 observed reflections). The cooling of the centrosymmetric phase (II) leads to the formation of bis(N-phenylbiguanidium(1+)) oxalate (III) (a=6.1083(2)Å, b=11.3178(5)Å, c=14.9947(5)Å, β=93.151(2)°, V=1035.05(8)Å(3), Z=4, R=0.0345 for 2367 observed reflections and a temperature of 110K), which also belongs to the monoclinic space group P21/n. The crystal structures of the three characterized phases are generally based on layers of isolated N-phenylbiguanidium(1+) cations separated by oxalate anions and interconnected with them by several types of N-H(...)O hydrogen bonds. The observed phases generally differ not only in their crystal packing but also in the lengths and characteristics of their hydrogen bonds. The thermal behaviour of the prepared compounds was studied using the DSC method in the temperature range from 90K up to a temperature near the melting point of each crystal. The bis(N-phenylbiguanidium(1+)) oxalate (II) crystals exhibit weak reversible thermal effects on the DSC curve at 147K (heating run). Further investigation of this effect, which was assigned to the isostructural phase transformation, was performed using FTIR, Raman spectroscopy and X-ray diffraction analysis in a wide temperature range.

• Klíčová slova
• N-Phenylbiguanide salts, Polymorphism, Second harmonic generation, Thermal behaviour, Vibrational spectroscopy, X-ray diffraction,
• Publikační typ
• časopisecké články MeSH

This study is focused on the characterization and investigation of polyvinylidene fluoride (PVDF) nanofibers from the point of view of macro- and nanometer level. The fibers were produced using electrostatic spinning process in air. Two types of fibers were produced since the collector speed (300 rpm and 2000 rpm) differed as the only one processing parameter. Differences in fiber's properties were studied by scanning electron microscopy (SEM) with cross-sections observation utilizing focused ion beam (FIB). The phase composition was determined by Fourier-transform infrared spectroscopy (FTIR) and Raman spectroscopy. The crystallinity was determined by differential scanning calorimetry (DSC), and chemical analysis of fiber's surfaces and bonding states were studied using X-ray photoelectron spectroscopy (XPS). Other methods, such as atomic force microscopy (AFM) and piezoelectric force microscopy (PFM), were employed to describe morphology and piezoelectric response of single fiber, respectively. Moreover, the wetting behavior (hydrophobicity or hydrophilicity) was also studied. It was found that collector speed significantly affects fibers alignment and wettability (directionally ordered fibers produced at 2000 rpm almost super-hydrophobic in comparison with disordered fibers spun at 300 rpm with hydrophilic behavior) as properties at macrolevel. However, it was confirmed that these differences at the macrolevel are closely connected and originate from nanolevel attributes. The study of single individual fibers revealed some protrusions on the fiber's surface, and fibers spun at 300 rpm had a core-shell design, while fibers spun at 2000 rpm were hollow.

• Klíčová slova
• AFM, DSC, FIB, FTIR, PFM, PVDF, Raman spectroscopy, SEM, STEM, XPS, core-shell, electrostatic spinning, hollow, hydrophilic, hydrophobic, nanofibers,
• Publikační typ
• časopisecké články MeSH

Porous carbons, originated from resorcinol-formaldehyde (RF) gels, show high application potential. However, the kinetics and mechanism of RF condensation are still not well described. In this work, different methods (dynamic light scattering-DLS, Fourier transform infrared spectroscopy-FTIR, low field 1H nuclear magnetic resonance relaxometry-1H-NMR, and differential scanning calorimetry-DSC) were used to follow the isothermal RF condensation of mixtures varying in catalyst content (Na2CO3) and reactant concentration. The applicability and results obtained by the methods used differ significantly. The changes in functional groups can be followed by FTIR only at very early stages of the reaction. DLS enables the estimate of the growth of particles in reaction solution, but only before the solution becomes more viscous. Following the relaxation of 1H nuclei in water during RF condensation brings a different view on the system-this technique follows the properties of the present water that is gradually captured in polymeric gel. From this side, the process behaves similarly to the nucleation reaction, which is in contradiction to the n-order mechanism confirmed by other techniques. The widest range of applicability was found for DSC measurement of the freezing/melting behavior of the reaction mixture, which is possible to use without any limitations until full solidification. Furthermore, this approach enables us to follow the gradual formation and development of the gel through the intermediate undergoing glass transition.

• Klíčová slova
• 1H-NMR relaxometry, DLS, DSC, FTIR, resorcinol-formaldehyde, sol-gel kinetics,
• Publikační typ
• časopisecké články MeSH

The method of inclusion of various additives into a polymer depends highly on the material in question and the desired effect. In the case of this paper, nitride salts were introduced into polyvinylidene fluoride fibers prepared by electrospinning. The resulting changes in the structural, chemical and electrical properties of the samples were observed and compared using SEM-EDX, DSC, XPS, FTIR, Raman spectroscopy and electrical measurements. The observed results displayed a grouping of parameters by electronegativity and possibly the molecular mass of the additive salts. We virtually demonstrated elimination of the presence of the γ-phase by addition of Mg(NO3)2, Ca(NO3)2, and Zn(NO3)2 salts. The trend of electrical properties to follow the electronegativity of the nitrate salt cation is demonstrated. The performed measurements of nitrate salt inclusions into PVDF offer a new insight into effects of previously unstudied structures of PVDF composites, opening new potential possibilities of crystalline phase control of the composite and use in further research and component design.

• Klíčová slova
• EDX, FTIR, PVDF, Raman spectroscopy, XPS, XRD, nitrate salt, permittivity,
• Publikační typ
• časopisecké články MeSH

The ability of arginine-rich peptides to cross the lipid bilayer and enter cytoplasm, unlike their lysine-based analogues, is intensively studied in the context of cell-penetrating peptides. Although the experiments have not yet reconstructed their internalization mechanism, the computational studies have shown that the type or charge of lipid polar groups is one of the crucial factors in their translocation. In order to gain more detailed insight into the interaction of guanidinium (Gdm+) and ammonium (NH4+) cations, as important building blocks in arginine and lysine amino acids, with lipid bilayers, we conducted the experimental and computational study that tackles this phenomenon. The adsorption of Gdm+ and NH4+ on lipid bilayers prepared from a zwitterionic (DPPC) and an anionic (DPPS) lipid was examined by thermoanalytic and spectroscopic techniques. Using temperature-dependent UV-Vis spectroscopy and DSC calorimetry we determined the impact of Gdm+ and NH4+ on the thermotropic properties of lipid bilayers. FTIR data, along with molecular dynamics simulations, unraveled the molecular-level details on the nature of their interactions, showing the proton transfer between NH4+ and DPPS, but not between Gdm+ and DPPS. The findings originated from this work imply that Gdm+ and NH4+ form qualitatively different interactions with lipids of different charge which is reflected in the physico-chemical interactions that arginine-and lysine-based peptides establish at a complex and chemically heterogeneous environment such as the biological membrane.

• Klíčová slova
• 1,2-Dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-Dipalmitoyl-sn-glycero-3-phosphoserine (DPPS), Guanidinium (Gdm(+)) and ammonium (NH(4)(+)) cations, Molecular dynamics (MD) simulations, Spectroscopic (UV–Vis, FTIR) and calorimetric (DSC) study,
• MeSH
• arginin MeSH
• fosfatidylseriny chemie   MeSH
• guanidin MeSH
• kalorimetrie MeSH
• kationty MeSH
• lecitiny MeSH
• lipidové dvojvrstvy * chemie   MeSH
• lysin MeSH
• penetrační peptidy * MeSH
• simulace molekulární dynamiky MeSH
• spektrální analýza MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• arginin MeSH
• fosfatidylseriny MeSH
• guanidin MeSH
• kationty MeSH
• lecitiny MeSH
• lipidové dvojvrstvy * MeSH
• lysin MeSH
• penetrační peptidy * MeSH

Surfaces of iron oxide of ferrimagnetic magnetite (Fe3O4) nanoparticles (MNPs) prepared by Massart's method and their functionalized form (f-MNPs) with succinic acid, L-arginine, oxalic acid, citric acid, and glutamic acid were studied by dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FTIR-S), UV-vis, thermogravimetric analysis (TGA)/differential scanning calorimetry (DSC), X-ray photoelectron spectroscopy (XPS), and reflection electron energy loss spectroscopy (REELS). The XPS analysis of elements and their chemical states at the surface of MNPs and f-MNPs revealed differences in chemical bonding of atoms, content of carbon-oxygen groups, iron oxide forms, iron oxide magnetic properties, adsorbed molecules, surface coverage, and overlayer thickness, whereas the Auger parameters (derived from XPS and Auger spectra) and elastic and inelastic scattering probabilities of electrons on atoms and valence band electrons (derived from REELS spectra) indicated modification of surface charge redistribution, electronic, and optical properties. These modified properties of f-MNPs influenced their biological properties. The surfaces biocompatible for L929 cells showed various cytotoxicity for HeLa cells (10.8-5.3% of cell death), the highest for MNPs functionalized with oxalic acid. The samples exhibiting the largest efficiency possessed smaller surface coverage and thickness of adsorbed molecules layers, the highest content of oxygen and carbon-oxygen functionalizing groups, the highest ratio of lattice O2- and OH- to C sp2 hybridizations on MNP surface, the highest ratio of adsorbed O- and OH- to C sp2 hybridizations on adsorbed molecule layers, the closest electronic and optical properties to Fe3O4, and the lowest degree of admolecule polymerization. This high cytotoxicity was attributed to interaction of cells with a surface, where increased content of oxygen groups, adsorbed O-, and OH- may play the role of additional adsorption and catalytic sites and a large content of adsorbed molecule layers of carboxylic groups facilitating Fenton reaction kinetics leading to cell damage.

• Klíčová slova
• DLS, FTIR-S, HeLa cells, REELS, TGA/DSC, XPS, biocompatible acid functionalization, ferrimagnetic magnetite (Fe3O4) magnetic nanoparticles,
• Publikační typ
• časopisecké články MeSH