Lipid exchange promotes fusion of model protocells

Vesicle fusion is an important process underlying cell division, transport, and membrane trafficking. In phospholipid systems, a range of fusogens including divalent cations and depletants have been shown to induce adhesion, hemifusion, and then full content fusion between vesicles. This works shows that these fusogens do not perform the same function for fatty acid vesicles, which are used as model protocells (primitive cells). Even when fatty acid vesicles appear adhered or hemifused to each other, the intervening barriers between vesicles do not rupture. This difference is likely because fatty acids have a single aliphatic tail, and are more dynamic than their phospholipid counterparts. To address this, we postulate that fusion could instead occur under conditions, such as lipid exchange, that disrupt lipid packing. Using both experiments and molecular dynamics simulations, we verify that fusion in fatty acid systems can indeed be induced by lipid exchange. These results begin to probe how membrane biophysics could constrain the evolutionary dynamics of protocells.Comment: 15 pages, 7 figure

Optical excitations of a self assembled artificial ion

By use of magneto-photoluminescence spectroscopy we demonstrate bias controlled single-electron charging of a single quantum dot. Neutral, single, and double charged excitons are identified in the optical spectra. At high magnetic fields one Zeeman component of the single charged exciton is found to be quenched, which is attributed to the competing effects of tunneling and spin-flip processes. Our experimental data are in good agreement with theoretical model calculations for situations where the spatial extent of the hole wave functions is smaller as compared to the electron wave functions.Comment: to be published in Physical Review B (rapid communication

Neurologically Plausible Distinctions in Cognition Relevant to Drug Use Etiology and Prevention

This article outlines several distinctions in cognition and related topics in emotion that receive support from work in cognitive neuroscience and have important implications for prevention: implicit cognition, working memory, nonverbal memory, and neurobiological systems of habit. These distinctions have not been widely acknowledged or applied in drug use prevention research, despite their neural plausibility and the availability of methods to make this link. The authors briefly review the basis for the distinctions and indicate general implications and assessment possibilities for prevention researchers conducting large-scale field trials. Subsequently, the article outlines a connectionist framework for specific applications in prevention interventions. These possibilities begin the attempt to derive useful fusions of normally distinct areas of prevention and cognitive neuroscience, in the spirit of a transdisciplinary approach