Multimodal fluorescence modulation using molecular photoswitches and upconverting nanoparticles

The intensity and colour of the light emitted from upconverting nanoparticles is controlled by the state of photoresponsive dithienylethene ligands decorated onto the surface of the nanoparticles. By selectively activating one or both ligands in a mixed, 3-component system, a multimodal read-out of the emitted light is achieved.     

The Phloroglucinols of Dryopteris aitoniana PICHI SERM. (Dryopteridaceae,Pteridophyta)

The phenolic compounds of the fern Dryopteris aitoniana were analyzed by improved methods avoiding alcaline reagents and contact with unbuffered SiO₂, which can cause deterioration. We confirmed the presence of five of the formerly (1971) reported six compounds, while the sixth, formerly incorrectly assumed to be aspidin (based on a spot in TLC), has now been isolated as cristals (TR-1579). It has the empirical formula C₂₇H₅₂O₂, but its structure is still unknown. Five other compounds were isolated in pure form, tetra-albaspidin BBBB ( 25 -BBBB) a known but rare phloroglucinol, and four new compounds: penta-albaspidin BBBBB ( 37 -BBBBB), hexa-albaspidin BBBBBB ( 38 -BBBBBB), tetraflavaspidic acid BBBB ( 26 -BBBB) and hexaflavaspidic acid BBBBBB ( 39 -BBBBBB). The structures were established by degradation NMR and partly by field-desorption and fast-atom-bombardment (FAB) mass spectra. The oligoflavaspidic acids are very unstable compounds, deteriorating during isolation procedures using the older ‘standard method’.     

Identification of mechanical properties of arteries with certification of global optimality

In this study, we consider identification of parameters in a non-linear continuum-mechanical model of arteries by fitting the models response to clinical data. The fitting of the model is formulated as a constrained non-linear, non-convex least-squares minimization problem. The model parameters are directly related to the underlying physiology of arteries, and correctly identified they can be of great clinical value. The non-convexity of the minimization problem implies that incorrect parameter values, corresponding to local minima or stationary points may be found, however. Therefore, we investigate the feasibility of using a branch-and-bound algorithm to identify the parameters to global optimality. The algorithm is tested on three clinical data sets, in each case using four increasingly larger regions around a candidate global solution in the parameter space. In all cases, the candidate global solution is found already in the initialization phase when solving the original non-convex minimization problem from multiple starting points, and the remaining time is spent on increasing the lower bound on the optimal value. Although the branch-and-bound algorithm is parallelized, the overall procedure is in general very time-consuming.

     

Modification of the CHARMM force field for DMPC lipid bilayer

The CHARMM force field for DMPC lipids was modified in order to improve agreement with experiment for a number of important properties of hydrated lipid bilayer. The modification consists in introduction of a scaling factor 0.83 for 1-4 electrostatic interactions (between atoms separated by three covalent bonds), which provides correct transgauche ratio in the alkane tails, and recalculation of the headgroup charges on the basis of HF/6-311(d,p) ab-initio computations. Both rigid TIP3P and flexible SPC water models were used with the new lipid model, showing similar results. The new model in a 75 ns simulation has shown a correct value of the area per lipid at zero surface tension, as well as good agreement with the experiment for the electron density, structure factor, and order parameters, including those in the headgroup part of lipids.