Long-range transport of giant vesicles along microtubule networks

We report on a minimal system to mimic intracellular transport of membrane-bounded, vesicular cargo. In a cell-free assay, purified kinesin-1 motor proteins were directly anchored to the membrane of giant unilamellar vesicles, and their movement studied along two-dimensional microtubule networks. Motion-tracking of vesicles with diameters of 1-3 μm revealed traveling distances up to the millimeter range. The transport velocities were identical to velocities of cargo-free motors. Using total internal reflection fluorescence (TIRF) microscopy, we were able to estimate the number of GFP-labeled motors involved in the transport of a single vesicle. We found that the vesicles were transported by the cooperative activity of typically 5-10 motor molecules. The presented assay is expected to open up further applications in the field of synthetic biology, aiming at the in vitro reconstitution of sub-cellular multi-motor transport systems. It may also find applications in bionanotechnology, where the controlled long-range transport of artificial cargo is a promising means to advance current lab-on-a-chip systems.     

Assessment of free energy predictors for ligand binding to a methyllysine histone code reader

Methyllysine histone code readers constitute a new promising group of potential drug targets. For instance, L3MBTL1, a malignant brain tumor (MBT) protein, selectively binds mono- and di-methyllysine epigenetic marks (KMe, KMe(2) ) that eventually results in the negative regulation of multiple genes through the E2F/Rb oncogenic pathway. There is a pressing need in potent and selective small-molecule probes that would enable further target validation and might become therapeutic leads. Such an endeavor would require efficient tools to assess the free energy of protein-ligand binding. However, due to an unparalleled function of the MBT binding pocket (i.e., selective binding to KMe/KMe(2) ) and because of its distinctive structure representing a small aromatic "cage," an accurate assessment of its binding affinity to a ligand appears to be a challenging task. Here, we report a comparative analysis of computationally affordable affinity predictors applied to a set of seven small-molecule ligands interacting with L3MBTL1. The analysis deals with novel ligands and targets, but applies widespread computational approaches and intuitive comparison metrics that makes this study compatible with and incremental to earlier large scale accounts on the efficiency of affinity predictors. Ultimately, this study has revealed three top performers, far ahead of the other techniques, including two scoring functions, PMF04 and PLP, along with a simulation-based method MM-PB/SA. We discuss why some methods may perform better than others on this target class, the limits of their application, as well as how the efficiency of the most CPU-demanding techniques could be optimized.     

New techniques for empirical processes of dependent data

We present a new technique for proving the empirical process invariance principle for stationary processes _(Xn)n≥0${\left(X_n\right)}_{n\ge 0}$. The main novelty of our approach lies in the fact that we only require the central limit theorem and a moment bound for a restricted class of functions _(f(Xn))n≥0${\left(f\left(X_n\right)\right)}_{n\ge 0}$, not containing the indicator functions. Our approach can be applied to Markov chains and dynamical systems, using spectral properties of the transfer operator. Our proof consists of a novel application of chaining techniques.     

Synthesis and structure of novel 4-arylhexahydro-1H,3H-pyrido[1,2-c]pyrimidine derivatives

A series of new 4-aryl-hexahydro-1H,3H-pyrido[1,2-c]pyrirnidine-1,3-dione derivatives 4a-k were prepared by catalytic hydrogenation of 4-aryl-1H,2H-pyrido[1,2-c]pyrirnidine-1,3-diones 3a-k. The structures of compounds were determined by ¹H and ¹³C nmr spectroscopy in solution. Steric hindrance caused twisting of the phenyl ring with respect to the pyridopyrimidine system, the effect was confirmed by X-ray diffraction.