The GTPase dynamin polymerizes into a helical coat that constricts membrane necks of endocytic pits to promote their fission. However, the dynamin mechanism is still debated because constriction is necessary but not sufficient for fission. Here, we show that fission occurs at the interface between the dynamin coat and the uncoated membrane. At this location, the considerable change in membrane curvature increases the local membrane elastic energy, reducing the energy barrier for fission. Fission kinetics depends on tension, bending rigidity, and the dynamin constriction torque. Indeed, we experimentally find that the fission rate depends on membrane tension in vitro and during endocytosis in vivo. By estimating the energy barrier from the increased elastic energy at the edge of dynamin and measuring the dynamin torque, we show that the mechanical energy spent on dynamin constriction can reduce the energy barrier for fission sufficiently to promote spontaneous fission. :

No abstract

Triplet and singlet harvesting in combination with enhancing the emitter rigidity leads to a landmark value of the photoluminescence quantum yield for dissolved Cu(i) complexes.

Neutral Cu­(I) and Ag­(I) complexes with a new rigid tridentate N,P,P ligand (dmpzpp, 3,5-dimethyl-1-(2-((2-(di-o-tolyl)­phosphanyl) (o-tolyl)-phosphanyl)­phenyl)-1H-pyrazole), giving Cu­(dmpzpp)Cl 6, Cu­(dmpzpp)Br 7, Cu­(dmpzpp)I 8, Cu­(dmpzpp)­SPh 9, and Ag­(dmpzpp)I 10 with SPh = thiophenylato, were prepared and their crystal structures, TD-DFT electronic structures, and phosphorescence and thermally activated delayed fluorescence (TADF) properties were studied in detail. The photoluminescence quantum yields ΦPL of neat powder materials lie between 70 and 90% with emission colors from blue to yellow. Compound 9, with bulky ligands showing ΦPL = 90%, was used for detailed emission studies from T = 1.7 to 300 K. Up to T ≈ 70 K, 9 shows only long-lived phosphorescence with a radiative decay time of T 1 of τr(phos) = 1 ms because of weak spin–orbit coupling. Accordingly, the zero-field splittings of T 1 in three substates are < 1 cm–1 (0.1 meV). Individual decay times of 2400, 2250, and 292 μs are estimated. Presumably, the phosphorescence is essentially induced by spin–vibronic mechanisms. Up to T = 300 K, the radiative decay time decreases by more than two orders of magnitude to τr(TADF) = 5.6 μs because of the TADF effect. This short decay time is determined by the small gap of ΔE(S1–T1) = 600 cm–1 (74 meV) and the fast radiative S1 → S0 rate of 1.1 × 107 s–1 (91 ns). For fabrication of OLED devices, we applied sublimable 8 and 9 using cohost device structures. For example, with a concentration of 2 wt % of 8, a green-emitting OLED showing CIE coordinates of (0.33; 0.52), a high external quantum efficiency of up to EQE = 16.4%, and a high luminance of almost 10,000 cd m–2 could be fabricated. Strategies for designing compounds giving higher EQE are presented.