Water dynamics in bolaamphiphile hydrogels investigated by 1H NMR relaxometry and diffusometry. 2011

Martin Bastrop, and Annette Meister, and Hendrik Metz, and Simon Drescher, and Bodo Dobner, and Karsten Mäder, and Alfred Blume
Institute of Chemistry, Martin-Luther-University Halle-Wittenberg, Von-Danckelmann-Platz 4, 06120 Halle/Saale, Germany.

The dynamical properties of water in hydrogels formed by the bolaamphiphiles dotriacontane-1,32-diyl-bis[2-(trimethylammonio)ethylphosphate] (PC-C32-PC) and its head group derivative dotriacontane-1,32-diyl-bis[2-(dimethylammonio)ethylphosphate] (Me(2)PE-C32-Me(2)PE) were investigated by determining the transverse relaxation times and the mean diffusion coefficients of the water protons. T(2) distributions obtained for hydrogels containing only 1 mg/mL of PC-C32-PC or Me(2)PE-C32-Me(2)PE were found to be almost unchanged compared to that of pure deionized water. In a hydrogel containing 30 mg/mL PC-C32-PC, a small dynamical perturbation of the water molecules could be observed, since the obtained major peak in the T(2) distribution was found to be slightly broadened and shifted to lower T(2) values with respect to pure water. Moreover, a slightly decreased mean diffusion coefficient of the water molecules was determined for the hydrogel with 30 mg/mL PC-C32-PC. For 30 mg/mL Me(2)PE-C32-Me(2)PE at pH 5, the dynamical properties of water are significantly influenced by the presence of the bolaamphiphiles. Whereas the mean diffusion coefficient of water was again only slightly decreased, the relaxation behavior was found to be considerably changed. At room temperature, the major T(2) peak obtained for 30 mg/mL Me(2)PE-C32-Me(2)PE at pH 5 was significantly broadened and shifted to lower T(2) values compared to pure buffer. This broad monomodal peak becomes bimodal when the temperature is decreased to 5 °C. Increasing the temperature revealed that the structural changes of the bolaamphiphilic self-assemblies at 45 °C are reflected in the determined mean relaxation times (T(2m)). These results indicate the presence of a significant degree of structural heterogeneity in a hydrogel formed by 30 mg/mL Me(2)PE-C32-Me(2)PE at pH 5. By comparing the mean diffusion coefficients with the mean transverse relaxation times, the distance scale of these heterogeneities could be estimated to be in the range of 50 to 120-140 μm. They can most probably be ascribed to the existence of a considerable number of lamellar domains being formed besides the nanofibers in hydrogels with 30 mg/mL Me(2)PE-C32-Me(2)PE at pH 5. Upon storage, the phenomenon of syneresis was observed for this hydrogel, which corresponds to a growth of the lamellar domains to sizes between 140 and 190 μm.

UI MeSH Term Description Entries
D009682 Magnetic Resonance Spectroscopy Spectroscopic method of measuring the magnetic moment of elementary particles such as atomic nuclei, protons or electrons. It is employed in clinical applications such as NMR Tomography (MAGNETIC RESONANCE IMAGING). In Vivo NMR Spectroscopy,MR Spectroscopy,Magnetic Resonance,NMR Spectroscopy,NMR Spectroscopy, In Vivo,Nuclear Magnetic Resonance,Spectroscopy, Magnetic Resonance,Spectroscopy, NMR,Spectroscopy, Nuclear Magnetic Resonance,Magnetic Resonance Spectroscopies,Magnetic Resonance, Nuclear,NMR Spectroscopies,Resonance Spectroscopy, Magnetic,Resonance, Magnetic,Resonance, Nuclear Magnetic,Spectroscopies, NMR,Spectroscopy, MR
D011728 Pyridones Pyridine derivatives with one or more keto groups on the ring. Pyridinones
D003931 Diacetyl Carrier of aroma of butter, vinegar, coffee, and other foods. 2,3-Butanedione,Biacetyl,Diketobutane,Dimethyldiketone,Dimethylglyoxal,2,3 Butanedione
D004058 Diffusion The tendency of a gas or solute to pass from a point of higher pressure or concentration to a point of lower pressure or concentration and to distribute itself throughout the available space. Diffusion, especially FACILITATED DIFFUSION, is a major mechanism of BIOLOGICAL TRANSPORT. Diffusions
D005663 Furans Compounds with a 5-membered ring of four carbons and an oxygen. They are aromatic heterocycles. The reduced form is tetrahydrofuran. Tetrahydrofurans
D006863 Hydrogen-Ion Concentration The normality of a solution with respect to HYDROGEN ions; H+. It is related to acidity measurements in most cases by pH pH,Concentration, Hydrogen-Ion,Concentrations, Hydrogen-Ion,Hydrogen Ion Concentration,Hydrogen-Ion Concentrations
D000473 Alkanes The generic name for the group of aliphatic hydrocarbons Cn-H2n+2. They are denoted by the suffix -ane. (Grant & Hackh's Chemical Dictionary, 5th ed) Alkane
D013696 Temperature The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms. Temperatures
D014867 Water A clear, odorless, tasteless liquid that is essential for most animal and plant life and is an excellent solvent for many substances. The chemical formula is hydrogen oxide (H2O). (McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed) Hydrogen Oxide
D056004 Molecular Dynamics Simulation A computer simulation developed to study the motion of molecules over a period of time. Molecular Dynamics Simulations,Molecular Dynamics,Dynamic, Molecular,Dynamics Simulation, Molecular,Dynamics Simulations, Molecular,Dynamics, Molecular,Molecular Dynamic,Simulation, Molecular Dynamics,Simulations, Molecular Dynamics

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