ABSTRACT
Dynamic nuclear polarization has been developed to overcome the limitations of the inherently low signal intensity of NMR spectroscopy. This technique promises to be particularly useful for solid-state NMR spectroscopy where the signals are broadened over a larger frequency range and most investigations rely on recording low gamma nuclei. To extend the range of possible investigations, a triple-resonance flat-coil solid-state NMR probe is presented with microwave irradiation capacities allowing the investigation of static samples at temperatures of 100 K, including supported lipid bilayers. The probe performance allows for two-dimensional separated local field experiments with high-power Lee-Goldberg decoupling and cross-polarization under simultaneous irradiation from a gyrotron microwave generator. Efficient cooling of the sample turned out to be essential for best enhancements and line shape and necessitated the development of a dedicated cooling chamber. Furthermore, a new membrane-anchored biradical is presented, and the geometry of supported membranes was optimized not only for good membrane alignment, handling, stability, and filling factor of the coil but also for heat and microwave dissipation. Enhancement factors of 17-fold were obtained, and a two-dimensional PISEMA spectrum of a transmembrane helical peptide was obtained in less than 2 h.
Subject(s)
Lipid Bilayers , Nuclear Magnetic Resonance, Biomolecular/methods , Peptides/chemistry , Magnetic Resonance SpectroscopyABSTRACT
Atherosclerosis results in the narrowing of arterial blood vessels and this causes significant changes in the endogenous shear stress between healthy and constricted arteries. Nanocontainers that can release drugs locally with such rheological changes can be very useful. Here, we show that vesicles made from an artificial 1,3-diaminophospholipid are stable under static conditions but release their contents at elevated shear stress. These vesicles have a lenticular morphology, which potentially leads to instabilities along their equator. Using a model cardiovascular system based on polymer tubes and an external pump to represent shear stress in healthy and constricted vessels of the heart, we show that drugs preferentially release from the vesicles in constricted vessels that have high shear stress.
Subject(s)
Cardiovascular System/drug effects , Drug Delivery Systems , Ethanolamines , Nanostructures/chemistry , Phospholipids/chemistry , Arteries/drug effects , Arteries/pathology , Ethanolamines/chemical synthesis , Ethanolamines/chemistry , Ethanolamines/pharmacology , Humans , Lipids/chemistry , Rheology , Stress, MechanicalABSTRACT
Despite almost hundred years of dedicated research, the synthesis of phospholipids remains a challenge. Here, we briefly review important trends and point out possible future directions that might lead to interesting new probes for the membrane environment. An improved liposome purification and concentration protocol rounds up the article.