Critical adhesion areas of cells on micro-nanopatterns

Cell adhesion to extracellular matrices(ECM)is critical to physiological and pathological processes as well as biomedical and biotechnological applications.It has been known that a cell can adhere on an adhesive microisland only over a critical size.But no publication has concerned critical adhesion areas of cells on microislands with nanoarray decoration.Herein,we fabricated a series of micro-nanopatterns with different microisland sizes and arginine-glycine-aspartate(RGD)nanospacings on a nonfouling poly(ethylene glycol)background.Besides reproducing that nanospacing of RGD,a ligand of its receptor integrin(a membrane protein),significantly influences specific cell adhesion on bioactive nanoarrays,we confirmed that the concept of critical adhesion area originally suggested in studies of cells on micropatterns was justified also on the micro-nanopatterns,yet the latter exhibited more characteristic behaviors of cell adhesion.We found increased critical adhesion areas of human mesenchymal stem cells(hMSCs)on nanoarrayed microislands with increased RGD nanospacings.However,the numbers of nanodots with respect to the critical adhesion areas were not a constant.A unified interpretation was then put forward after combining nonspecific background adhesion and specific cell adhesion.We further carried out the asymptotic analysis of a series of micro-nanopatterned surfaces to obtain the effective RGD nanospacing on unpatterned free surfaces with densely grafted RGD,which could be estimated nonzero but has never been revealed previously without the assistance of the micro-nanopatterning techniques and the corresponding analysis.

Hydrothermal Synthesis and Phase-, Morphology-Evolution Mechanism of Lead Titanate Nanostructures Assisted with Tetramethylammonium Hydroxide

Lead titanate nanostructures with different phases and morphologies, layered hexagonal PbTiO2（CO3）0.3- （NO3）0.35（OH） nanosheets, pyrochlore Pb2Ti2O6 nanodendites, pre-perovskite PbTiO3 nanofibres and perovskite PbTiO3 nanoplates, have been synthesized via a conventional hydrothermal route assisted with different concentra- tions of tetramethylammonium hydroxide （TMAH）. X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and high-resolution TEM （HRTEM） were employed to characterize the phase, morphology and growth behavior of the synthesized samples. The results reveal that at low TMAH concen- tration the obtained samples are mainly of PbTiO2（CO3）o.3（NO3）0.35（OH） nanosheets. With the TMAH concentration increasing, the obtained samples change to pyrochlore Pb2Ti2O6 nanodendites, pre-perovskite PbTiO3 nanofibres and perovskite PbTiO3 nanoplates in turn. With the basis of the experimental results, the phase- and morpholo- gy-evolution mechanism of the lead titanate nanostructures is discussed by combining the analysis of the lattice structure feature and the properties of TMAH.

IRESfinder:Identifying RNA internal ribosome entry site in eukaryotic cell using framed k-mer features

In eukaryotic cells, initiation of protein translation is to recruit the ribosome to a specific mRNA, which is generally dependent on the 5＇ cap structure. However, protein translation can also be initiated in a cap-independent manner by using a cis-regulatory element termed the internal ribosome entry site （IRES）. The first experimentally validated IRES was reported in the poliovirus （Pelletier and Sonenberg, 1988）. Then eukaryotic cellular mRNAs were also validated to contain IRES elements.