NMR investigations of interactions between anesthetics and lipid bilayers

Interactions between anesthetics (lidocaine and short chain alcohols) and lipid membranes formed by dimyristoylphosphatidylcholine (DMPC) were studied using NMR spectroscopy. The orientational order of lidocaine was investigated using deuterium NMR on a selectively labelled compound whereas segmental ordering in the lipids was probed by two-dimensional 1H-13C separated local field experiments under magic-angle spinning conditions. In addition, trajectories generated in molecular dynamics (MD) computer simulations were used for interpretation of the experimental results. Separate simulations were carried out with charged and uncharged lidocaine molecules. Reasonable agreement between experimental dipolar interactions and the calculated counterparts was observed. Our results clearly show that charged lidocaine affects significantly the lipid headgroup. In particular the ordering of the lipids is increased accompanied by drastic changes in the orientation of the P-N vector in the choline group

Nonfatal Injuries 1 Week After Hurricane Sandy — New York City Metropolitan Area, October 2012

On October 29, 2012, Hurricane Sandy (Sandy) made landfall in densely populated areas of New York, New Jersey, and Connecticut. Flooding affected 51 square miles (132 square kilometers) of New York City (NYC) and resulted in 43 deaths, many caused by drowning in the home, along with numerous storm-related injuries. Thousands of those affected were survivors of the World Trade Center (WTC) disaster of September 11, 2001 (9/11) who had previously enrolled in the WTC Health Registry (Registry) cohort study. To assess Sandy-related injuries and associated risk factors among those who lived in Hurricane Sandy-flooded areas and elsewhere, the NYC Department of Health and Mental Hygiene surveyed 8,870 WTC survivors, who had provided physical and mental health updates 8 to 16 months before Sandy. Approximately 10% of the respondents in flooded areas reported injuries in the first week after Sandy; nearly 75% of those had more than one injury. Injuries occurred during evacuation and clean-up/repair of damaged or destroyed homes. Hurricane preparation and precautionary messages emphasizing potential for injury hazards during both evacuation and clean-up or repair of damaged residences might help mitigate the occurrence and severity of injury after a hurricane

Nuclear spin relaxation and translational diffusion study of Benzene-Hexa-n-alkanoat

The molecular dynamics of benzene-hexa-n-heptanoate (BHA7) have been studied in the isotropic liquid phase by multified carbon-13 nuclear spin relaxation of a carboxyl carbon labeled compound. The experimental data are analyzed with a dynamical model based on the assumption of three trypes of motion: a fast internal motion in the aliphatic chains, a slow overall reorientation of the molecule, and an intermediate process connected with the flexibility of the carboxyl group. The first two motions occur clearly on different time scales, whereas the last process is not time scale separated from the global molecular tumbling. Preciously reported carbon-13 line shapes in the mesophase and in the solid state of BHA7 were used for vertification of the results. Measurements of translational diffusion coefficients in isotropic and ordered phases of BHA6 and BHA7 were performed using 1H pulsed field gradient NMR spin-echo techniques

Heteronuclear dipolar recoupling in solid-state nuclear magnetic resonance by amplitude-, phase-, and frequency-modulated Lee-Goldburg cross-polarization

This paper presents a theoretical, numerical, and experimental study of phase- and frequency-switched Lee-Goldburg cross-polarization (FSLG-CP) under magic-angle spinning conditions. It is shown that a well-defined amplitude modulation of one of the two radio-frequency (rf) fields in the FSLG-CP sequence results in highly efficient heteronuclear dipolar recoupling. The recoupled dipolar interaction is gamma-encoded and, under ideal conditions, the effective spin Hamiltonian is equivalent to that in continuous-wave Lee-Goldburg CP. In practice, however, FSLG-CP is less susceptible to rf field mismatch and inhomogeneity, and provides better suppression of (1)H spin diffusion. The performance of FSLG-CP is experimentally demonstrated on liquid-crystalline samples exhibiting motionally averaged dipolar couplings

13C NMR studies of columnar liquid crystals

Many materials composed of disc-shaped molecules exhibit thermotropic liquid crystalline phases. Most of the mesophases formed by these molecules display an architecture where the molecules are stacked into columns, which in turn form two-dimensional arrays. These columnar phases, which have gained much attention due to the potentially important practical applications, particularly in electronics and display technology, are currently under active studies by various experimental techniques, including nuclear magnetic resonance (NMR). Carbon-13 NMR spectroscopy is an increasingly important tool in studies of columnar liquid crystals. The method is a useful complement to the traditional 2H NMR approach, which requires isotopic labeling and may be difficult to realize due to problems with spectral assignment and overlap. By employing advanced 13C NMR methods developed during the last decade, it is now possible to extract very detailed information on molecular structure, order and dynamics from multi-dimensional 13C NMR experiments in oriented as well as in unoriented mesophases under both static and magic-angle spinning (MAS) conditions. In this chapter, we demonstrate applications of recently developed NMR methods to columnar liquid crystals. Several techniques are considered; in particular we describe experimental methods for signal enhancement, spectral assignment, determination of the chemical shift anisotropies, and measurement of dipolar couplings. The efficiency and accuracy of the various approaches are also discussed