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The trans isomers of fatty acids are found in human adipose tissue. These isomers have been linked with deleterious health effects (e.g., coronary artery disease). In this study, we performed molecular dynamics simulations to investigate the structures and dynamic properties of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylcholine (POPC) and 1-palmitoyl-2-elaidoyl sn-glycero-3-phosphatidylcholine (PEPC) lipid bilayers. The geometry of the olefinic bond and membrane packing effects significantly influenced the conformations and dynamics of the two C-C single bonds adjacent to the olefinic bond. For the PEPC lipid, the two C-C single bonds adjacent to the olefinic bond adopted mainly nonplanar skew-trans and planar cis-trans motifs; although the cis conformation featured relatively strong steric repulsion, it was stabilized through membrane packing because its planar structure is more suitable for membrane packing. Moreover, membrane packing effects stabilized the planar transition state for conformational conversion to a greater extent than they did with the nonplanar transition state, thereby affecting the dynamics of conformational conversion. The rotational motions of the first neighboring C-C single bonds were much faster than those of typical saturated C-C single bonds; in contrast, the rotational motions of the second neighboring C-C single bonds were significantly slower than those of typical saturated torsion angles. The packing of PEPC lipids is superior to that of POPC lipids, leading to a smaller area per lipid, a higher order parameter and a smaller diffusion coefficient. The distinct properties of POPC and PEPC lipids result in PEPC lipids forming microdomains within a POPC matrix.

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This work analyses the effects of polarization and pressure in caesium 6S–8S two-photon spectroscopy. The linewidth was broadened and the frequency was shifted by a change of polarization states. The frequency shift and the linewidth broadening of the caesium 6S–8S two-photon transition were measured as a function of laser power using one single-frequency Ti:sapphire ring cavity laser, two caesium cells and two quarter-wave plates to ensure polarization states of light, and we showed that the linewidth cannot be evaluated just by fitting data to a Lorentzian shape. As determined by fitting the data to a Voigt profile, the natural linewidth is independent of the polarization states of the pump beams, the laser power and the pressure. Caesium 6S–8S two-photon transitions pumped by a circularly polarized beam have narrower linewidths and smaller shifts than those pumped by a linearly polarized beam. The light shift obtained by pumping with the circularly polarized beam is −6.75(57) Hz (mW mm−2)−1, and that obtained by pumping with a linearly polarized beam is −7.25(45) Hz (mW mm−2)−1. These results agree closely with theoretical calculations. The pressure shift is −588(387) Hz mPa−1. This work shows how to evaluate two-photon transitions with a Voigt profile, and then helps us to understand two-photon transitions with different polarization states, and improve the signal quality obtained when they are used as frequency markers.

An efficient and low-cost method for the synthesis of 4-substituted quinolin-2-(1H)-ones has been developed. In the presence of TBHP, the cobalt(ii)-catalyzed carbocyclization reactions of arylethenyl substituted α-bromo-N-phenylacetamides, involving sequential 6-exo-trig radical cyclization, t-butylperoxy radical cross-coupling reaction and the base-promoted ionic Kornblum-DeLaMare reaction, produced 4-benzoylquinolin-2-(1H)-ones. A variety of useful functional groups such as methoxy, fluoro, chloro, bromo, methoxycarbonyl, and cyano groups, are compatible with the reaction conditions. This strategy was further applied to arylethynyl substituted α-bromo-N-phenylacetamides, and 4-benzylquinolin-2-(1H)-ones were formed effectively.