Abnormal high density lipoprotein metabolism may contribute to the increased atherosclerosis associated with diabetes and insulin resistance. The ATP-binding cassette transporter ABCA1 mediates cholesterol transport from tissue macrophages to apoA-I, the major high density lipoprotein protein component. Because fatty acids are elevated in diabetes, we examined the effects of fatty acids on ABCA1 activity in cultured macrophages. Results showed that unsaturated fatty acids markedly inhibited ABCA1-mediated cholesterol and phospholipid efflux from macrophages when ABCA1 was induced by a cAMP analog. This was accompanied by a reduction in the membrane content of ABCA1 and a decrease in apoA-I binding to whole cells and to ABCA1. In contrast, saturated fatty acids had no effect on these processes. Fatty acids did not alter ABCA1 mRNA abundance or incorporation of methionine into ABCA1, indicating that decreased ABCA1 transcription, enhanced mRNA decay, or impaired translation efficiency did not account for these inhibitory effects. Unsaturated fatty acids, however, increased ABCA1 turnover when protein synthesis was blocked by cycloheximide. We conclude that unsaturated fatty acids reduce the macrophage ABCA1 content by enhancing its degradation rate. These findings raise the possibility that an increased supply of unsaturated fatty acids in the artery wall promotes atherogenesis by impairing the ABCA1 cholesterol secretory pathway in macrophages.Atherosclerotic cardiovascular disease is the leading cause of morbidity and mortality in diabetes (1, 2). Patients with type 2 diabetes have disorders in lipid metabolism, including elevated serum triglycerides and below normal levels of high density lipoprotein (HDL) 1 (2-4). Low HDL levels are a major risk factor for cardiovascular disease (5), raising the possibility that abnormal HDL metabolism plays a role in the increased atherosclerosis associated with diabetes.It is widely believed that HDL protects against atherosclerosis by promoting clearance of excess cholesterol from macrophages of the artery wall. This clearance is facilitated by an ATP-binding cassette transporter called ABCA1 (6, 7), which mediates transport of cellular cholesterol and phospholipids to lipid-poor HDL apolipoproteins. Mutations in ABCA1 cause Tangier disease (8 -11), a severe HDL deficiency syndrome characterized by deposition of sterols in tissue macrophages and prevalent atherosclerosis (12, 13). It is therefore feasible that factors associated with diabetes impair the activity of this lipid secretory pathway, leading to accumulation of sterols in arterial macrophages and to enhanced atherogenesis.ABCA1 expression by macrophages is highly regulated. Cholesterol loading of macrophages markedly increases ABCA1 mRNA abundance and protein levels (11, 14), consistent with a transporter that functions to rid cells of excess cholesterol. This gene regulation is mediated by nuclear liver X receptors (LXR␣ and LXR␤) and retinoid X receptor (RXR) (15-18), which form heterodimers that are activated b...

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The influence of grain boundaries (GBs) on charge carrier lifetimes in methylammonium lead triiodide perovskite (MAPbI3) remains unclear. Some experiments suggest that GBs promote rapid nonradiative decay and deteriorate device performance, while other measurements indicate that charge recombination happens primarily in non-GB regions and that GBs facilitate charge separation and collection. By combining time-domain density functional theory and nonadiabatic (NA) molecular dynamics, we demonstrate that charge separation and localization happening at MAPbI3 GBs due to symmetry breaking suppresses charge recombination. Even though GBs lower the MAPbI3 bandgap and charge localization enhances interactions with phonons, electron–hole separation decreases the NA coupling, and the excited state lifetime remains virtually unchanged compared to the pristine perovskite. Our study rationalizes how GBs can have a positive influence on perovskite optoelectronic properties and advances fundamental understanding of charge carrier dynamics in these fascinating materials.

Ethylene (C 2 H 4 ) and propylene (C 3 H 6 ) are important energy sources and raw materials in the chemical industry. Storage and separation of C 2 H 4 and C 3 H 6 are vital to their practical application. Metal–organic frameworks (MOFs) having adjustable structures and pore environments are promising candidates for C 3 H 6 /C 2 H 4 separation. Herein, we obtained a Cu-based MOF synthesized by H 3 TTCA and pyrazine ligands. By adding different functional groups on the ligands within the MOFs, their pore environments are adjusted, and thus, the C 3 H 6 storage capacity and C 3 H 6 /C 2 H 4 separation efficiency are improved. Eventually, the fluoro- and methyl-functionalized iso-MOF-4 exhibits a better gas storage and C 3 H 6 /C 2 H 4 separation performance compared with iso-MOF-1 (nonfunctionalized), iso-MOF-2 (fluoro-functionalized), and iso-MOF-3 (methyl-functionalized). A record-high C 3 H 6 uptake of 293.6 ± 2.3 cm 3 g –1 (273 K, 1 atm) is achieved using iso-MOF-4 . Moreover, iso-MOF-4 shows excellent repeatability, and only 3.5% of C 3 H 6 storage capacities decrease after nine cycles. Employing Grand Canonical Monte Carlo (GCMC) simulations, it is indicated that iso-MOF-4 preferentially adsorbs C 3 H 6 rather than C 2 H 4 at low pressure. Single-crystal X-ray diffraction on C 3 H 6 -adsorbed iso-MOF-4 crystals precisely demonstrates the adsorption positions and arrangement of C 3 H 6 molecules in the framework, which is consistent with the theoretical simulations. Remarkably, gas sorption isotherms, molecular simulations, and breakthrough experiments comprehensively demonstrate that this unique MOF material exhibits highly efficient C 3 H 6 /C 2 H 4 separation. Additionally, iso-MOF-4 also possesses efficient separation of C 3 H 8 /CH 4 and C 2 H 6 /CH ...

Three versatile amino-functionalized InIII/AlIII/ZrIV-MOFs with high-physicochemical stability for gas storage/separation, water purification and catalysis.

The separation of ethylene (C 2 H 4 )from amixture of ethane (C 2 H 6 ), ethylene (C 2 H 4 ), and acetylene (C 2 H 2 )a t normal temperature and pressure is as ignificant challenge. The sieving effect of pores is powerless due to the similar molecular size and kinetic diameter of these molecules.W e report an ew modification method based on as table ftw topological Zr-MOF platform (MOF-525). Introduction of acyclopentadiene cobalt functional group led to new ftw-type MOFs materials (UPC-612 and UPC-613), which increase the host-guest interaction and achieve efficient ethylene purification from the mixture of hydrocarbon gases.T he high performance of UPC-612 and UPC-613 for C 2 H 2 /C 2 H 4 / C 2 H 6 separation has been verified by gas sorption isotherms, density functional theory (DFT), and experimentally determined breakthrough curves.T his work provides ao ne-step separation of the ternary gas mixture and can further serve as ablueprint for the design and construction of function-oriented porous structures for such applications.

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In plants, clathrin-mediated endocytosis (CME) is dependent on the function of clathrin and its accessory heterooligomeric adaptor protein complexes, ADAPTOR PROTEIN2 (AP-2) and the TPLATE complex (TPC), and is negatively regulated by the hormones auxin and salicylic acid (SA). The details for how clathrin and its adaptor complexes are recruited to the plasma membrane (PM) to regulate CME, however, are poorly understood. We found that SA and the pharmacological CME inhibitor tyrphostin A23 reduce the membrane association of clathrin and AP-2, but not that of the TPC, whereas auxin solely affected clathrin membrane association, in Arabidopsis (Arabidopsis thaliana). Genetic and pharmacological experiments revealed that loss of AP2m or AP2s partially affected the membrane association of other AP-2 subunits and that the AP-2 subunit AP2s, but not AP2m, was required for SA-and tyrphostin A23-dependent inhibition of CME. Furthermore, we show that although AP-2 and the TPC are both required for the PM recruitment of clathrin in wild-type cells, the TPC is necessary for clathrin PM association in AP-2-deficient cells. These results indicate that developmental signals may differentially modulate the membrane recruitment of clathrin and its core accessory complexes to regulate the process of CME in plant cells.