Microrobots that are light and agile yet require no artificial power input can be widely used in medical, military, and industrial applications. As an actuation system to drive such robots, here we report a biologically inspired bilayer structure that harnesses the environmental humidity energy, with ratchets to rectify the motion. We named this actuator-ratchet system the hygrobot. The actuator uses a hygroscopically responsive film consisting of aligned nanofibers produced by directional electrospinning, which quickly swells and shrinks in lengthwise direction in response to the change of humidity. The ratchets based on asymmetric friction coefficients rectify oscillatory bending motion in a directional locomotion. We mathematically analyzed the mechanical response of the hygrobot, which allowed not only prediction of its performance but also the optimal design to maximize the locomotion speed given geometric and environmental constraints. The hygrobot sterilized a trail across an agar plate without any artificial energy supply.

Collisional activation of 2-[(2,2,6,6-tetramethylpiperidin-1-yloxy)methyl]benzoic acid (TEMPO-Bz)-conjugated peptide cations, prepared by attaching a TEMPO-derived precursor 1 to an N-terminal amino group or a lysine side chain, resulted in the formation of radical species. The subsequent tandem mass spectrometry on the radical cations exhibited odd-electron peptide backbone dissociations in the same manner as that observed by electron capture dissociation (ECD) or electron transfer dissociation (ETD). For example, a-, x-, or z-types of ions were major fragments and the disulfide bond was readily cleaved. The TEMPO-FRIPS (free radical initiated peptide sequencing) was also applicable to characterizing even singly protonated peptides, in contrast to ECD or ETD in which only doubly or highly protonated cations are responsive. The TEMPO-FRIPS approach also has universality in that it can be used in any type of a tandem mass spectrometer.

Highlights d Discovery of JH-RE-06, a compound disrupting REV1-POL zmediated mutagenic TLS d JH-RE-06 induces REV1 dimerization to block the REV1-REV7 interaction d JH-RE-06 sensitizes tumors to cisplatin and reduces mutagenesis in vitro d JH-RE-06 suppresses tumor progression in mice and prolongs animal survival

This paper presents a technology to determine the melt viscosity of a =/supercritio-d CO, solution using a linear capillary tube die mounted on a foaming extruder. CO, was injected into the extrusion barrel and the content of CO, was varied in the range of 0 to 4 wt% using a positive displacement pump. Single-phase PS/CO, solutions were formed using a microcellular extrusion system and phase separation was prevented by maintaining a high pressure in the capillary tube die. By measuring the pressure drop through the die, the viscosity of PS/CO, solutions was determined. The experimental results indicate that the PS/CO, solution viscosity is a sensitive function of shear rate, temperature, pressure, and CO, content. A theoretical model based on the generalized Cross-Carreau model was proposed to describe the shear-thinning behavior of PS/CO, solutions at various shear rates. The zeroshear viscosity was modeled using a generalized Arrhenius equation to accommodate the effects of temperature, pressure, and CO, content. Finally, the solubility of CO, has been estimated by monitoring the pressure drop and the absolute pressure in the capillary die.

We introduce pH responsive fluorescent false neurotransmitters (pH responsive FFNs) as novel probes that act as vesicular monoamine transporter (VMAT) substrates and ratiometric fluorescent pH sensors. The development of these agents was achieved by systematic molecular design that integrated several structural elements, including the aminoethyl group (VMAT recognition), halogenated hydroxycoumarin core (ratiometric optical pH sensing in the desired pH range), and N-or C-alkylation (modulation of lipophilicity). Of fourteen compounds that were synthesized, the probe Mini202 was selected based on the highest uptake in VMAT2-transfected HEK cells and desirable optical properties. Using Mini202, we measured the pH of catecholamine secretory vesicles in PC-12 cells (pH ~ 5.9) via two-photon fluorescence microscopy. Incubation with methamphetamine led to an increase in vesicular pH (pH ~ 6.4), consistent with a proposed mechanism of action of this psychostimulant, and eventually to redistribution of vesicular content (including Mini202) from vesicles to cytoplasm. Mini202 is sufficiently bright, photostable and suitable for two-photon microscopy. This probe will enable fundamental neuroscience and neuroendocrine research as well as drug screening efforts.As part of a broad program aimed at optical imaging of metabolic and signaling enzymes in cells and tissues,1 , 2 we became interested in visualization of neurotransmission. Recently we have introduced fluorescent false neurotransmitters (FFNs), probes that act as optical tracers that provide the first means to image neurotransmitter release from individual presynaptic terminals in the brain. Monoamine neurotransmitters are accumulated in synaptic vesicles by vesicular monoamine transporter 2 (VMAT2), which translocates the monoamine (e.g., dopamine) from cytosol to the lumen of synaptic vesicles.5 Similarly, in chromaffin cells of adrenal medulla, epinephrine and norepinephrine are accumulated in secretory vesicles by a closely related protein, VMAT1 ( Figure 1). The vesicular lumen is acidic (pH ~ 5-6) due to the action of vacuolar-H + ATPase, which imports H + at the expense of ATP hydrolysis. The pH gradient between the cytoplasm and the vesicular lumen in turn provides the driving force for the accumulation of transmitters in the vesicles. Thus the pH gradient is a key parameter regulating synaptic plasticity as it controls the vesicular transmitter content and amount of transmitter released during vesicle fusion. The pH gradient between the cytosol and the vesicular lumen is ATP dependent and thus closely coupled to the metabolic state of the presynaptic terminals. Despite the importance of this parameter and great efforts focused on development of fluorescent pH indicators,6 there are currently no small molecule probes available for selective measurement of pH in synaptic or secretory vesicles. The pHsensitive synaptopHluorin protein can be used to estimate pH in synaptic vesicles of cultured neurons.7 Alternatively, construction of avidin-chimera prot...