Protein phosphatase 2A (PP2A) accounts for the majority of total Ser/Thr phosphatase activities in most cell types and regulates many biological processes. PP2A holoenzymes contain a scaffold A subunit, a catalytic C subunit, and one of the regulatory/targeting B subunits. How the B subunit controls PP2A localization and substrate specificity, which is a crucial aspect of PP2A regulation, remains poorly understood. The kinetochore is a critical site for PP2A functioning, where PP2A orchestrates chromosome segregation through its interactions with BubR1. The PP2A-BubR1 interaction plays important roles in both spindle checkpoint silencing and stable microtubule-kinetochore attachment. Here we present the crystal structure of a PP2A B56-BubR1 complex, which demonstrates that a conserved BubR1 LxxIxE motif binds to the concave side of the B56 pseudo-HEAT repeats. The BubR1 motif binds to a groove formed between B56 HEAT repeats 3 and 4, which is quite distant from the B56 binding surface for PP2A catalytic C subunit and thus is unlikely to affect PP2A activity. In addition, the BubR1 binding site on B56 is far from the B56 binding site of shugoshin, another kinetochore PP2A-binding protein, and thus BubR1 and shugoshin can potentially interact with PP2A-B56 simultaneously. Our structural and biochemical analysis indicates that other proteins with the LxxIxE motif may also bind to the same PP2A B56 surface. Thus, our structure of the PP2A B56-BubR1 complex provides important insights into how the B56 subunit directs the recruitment of PP2A to specific targets.Electronic supplementary materialThe online version of this article (doi:10.1007/s13238-016-0283-4) contains supplementary material, which is available to authorized users.

TiO 2 loaded with crystalline nano silver (c-Ag/TiO 2 ) was successfully synthesized by a one-step low-temperature hydrothermal method in aqueous solution using tetra-n-butyl titanate and AgNO 3 as precursors. The structure and morphology were characterized by Auger electron spectroscopy (AES), X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-Vis absorption spectra (UV-Vis) and fluorescence spectra (FS). The photocatalytic activity was tested with photocatalytic degradation of hydrogen sulfide (H 2 S) gas. The results show that the nano silver particles of Ag/TiO 2 prepared by the one-step lowtemperature hydrothermal method are crystalline, while they are amorphous when prepared by the conventional UV reduction deposition method (a-Ag/TiO 2 ). The photocatalytic activity of the c-Ag/TiO 2 prepared by the hydrothermal method was found to have a significant improvement for H 2 S degradation, being more than 2 times over that of the a-Ag/TiO 2 prepared by the conventional method.

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Ultratrace molecular detections are vital for precancer diagnosis, forensic analysis, and food safety. Superhydrophobic (SH) surface-enhanced Raman scattering (SERS) sensors are regarded as an ideal approach to improve detection performance by concentrating analyte molecules within a small volume. However, due to the low adhesion of SH surfaces, the analyte droplet is prone to rolling, making it hard to deposit molecules on a predetermined position. Furthermore, the sediment with a very small area on the SH-SERS surface is difficult to be captured even with a Raman microscope. In this study, femtosecond laser fabricated hybrid SH/hydrophobic (SH/HB) surfaces are successfully applied to realize a rapid and highly sensitive SERS detection. By modulating dual surface structures and wetting behaviors, the analyte molecules can be enriched at the edge of HB pattern. This improves the convenience and speed of Raman test. On a hybrid SH/HB SERS substrate with a circular HB pattern at 300-µm-diameter, a femtomolar level (10−14 M) of rhodamine 6G can be detected by using analyte volumes of just 5 µL. The SERS enhancement factor can reach 5.7×108 and a good uniformity with a relative standard deviation of 6.98% is achieved. Our results indicate that the laser fabrication of hybrid SERS sensor offers an efficient and cost-effective approach for ultratrace molecular detection.

A novel spatial double-pulse laser ablation scheme is investigated to enhance the processing quality and efficiency for nanosecond laser ablation of silicon substrate. During the double-pulse laser ablation, two splitted laser beams simultaneously irradiate on silicon surface at a tunable gap. The ablation quality and efficiency are evaluated by both scanning electron microscope and laser scanning confocal microscope. As tuning the gap distance, the ablation can be significantly enhanced if the spatial interaction between the two splitted laser pulses is optimized. The underlying physical mechanism for the interacting spatial double-pulse enhancement effect is attributed to the redistribution of the integrated energy field, corresponding to the temperature field. This new method has great potential applications in laser micromachining of functional devices at higher processing quality and faster speed.