Polar auxin transport is unique to plants and coordinates their growth and development1,2. The PIN-FORMED (PIN) auxin transporters exhibit highly asymmetrical localizations at the plasma membrane and drive polar auxin transport3,4; however, their structures and transport mechanisms remain largely unknown. Here, we report three inward-facing conformation structures of Arabidopsis thaliana PIN1: the apo state, bound to the natural auxin indole-3-acetic acid (IAA), and in complex with the polar auxin transport inhibitor N-1-naphthylphthalamic acid (NPA). The transmembrane domain of PIN1 shares a conserved NhaA fold5. In the substrate-bound structure, IAA is coordinated by both hydrophobic stacking and hydrogen bonding. NPA competes with IAA for the same site at the intracellular pocket, but with a much higher affinity. These findings inform our understanding of the substrate recognition and transport mechanisms of PINs and set up a framework for future research on directional auxin transport, one of the most crucial processes underlying plant development.
China's aging population is experiencing an urban–rural inversion phenomenon in that the rural population is aging faster. This is normal worldwide as studies have found that urban–rural differences in population aging have universal and phase characteristics. However, China's population aging presents a “polarization trend,” that is, the aging speed of areas with a deep aging degree is faster. In this paper, we try to test whether China's current urban–rural difference in population aging is rational if considered with China's current economic and social development. We adopted the four‐quadrant map analysis method and compare China with major developed and developing countries with key indicators. Data were mainly collected from databases by country, including the Statistical Yearbook, World Bank Database, and United Nations Database. Results show that urban–rural differences in China's aging population are significantly ahead of economic development and urbanization; this imbalance can explain the greater urban–rural disparity and the “polarization trend” in China's population. Results indicate that population aging's urban–rural differences are not necessarily exhibiting universal and phased characteristics in China. What's worse, the imbalanced population aging situation will make the rural poverty and the inter‐generational conflict more prominently. Public policies are necessary to deal with the current imbalance situation.
In this manuscript, the generation of an optical vortex beam with high order and reconfigurable orbital angular momentum (OAM) is studied. Multi-waveguide holographic gratings (MWHG) are deployed to generate OAM beams with high order. The generation of the OAM beam with an order l from +4 to +8 is demonstrated by numerical simulations, and the generated OAM order is manipulable and configurable by incident phase. The working bandwidths of the MWHG for different OAM orders are at the level of 40 nm. This work could provide valuable references for practical implementation of OAM in integrated optics.
A counter-surface plasmon polariton lens (CSPPL) is proposed to perform stable nanoparticle trapping by providing up to 120k b T optical potential depth. The optical potential depth is related to the incident angle and phase difference of the light incident on two gratings of CSPPL. The depth of optical potential can be manipulated with negligible displacement by the incident angle less than 20°. Both the depth and the center position of the optical potential well can be manipulated by the incident phase difference. The study of stable and manipulatable optical potential on the CSPPL promotes the integration of optical tweezers.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.