we test this hypothesis directly by using a combination of fluorescence lifetime imaging of order sensitive probes with microinjection and selective quenching. Our results show that in live cell plasma membranes, inner leaflet order is slightly, but significantly, lower compared to the outer leaflet. The magnitude of the difference is smaller than expected from compositional asymmetry, suggesting that strong coupling between leaflets in asymmetric membranes prevents high lipid order differentials. We also find that a loss of membrane asymmetry during phospholipid scrambling or apoptosis drastically reduces the order of the plasma membrane and eliminates the order differences between leaflets. Finally, we observe that these biophysical differences are important for cell physiology, as inhibition of lipid scrambling suppresses the functional activation of immune cells. These findings document the biophysical asymmetry of the plasma membrane and suggest an important role for this asymmetry in cell function.
We analysed perovskite CH3NH3PbI3-xClx inverted planner structure solar cellwith nickel oxide (NiO) and spiro-MeOTAD as hole conductors. This structure isfree from electron transport layer. The thickness is optimized for NiO andspiro-MeOTAD hole conducting materials and the devices do not exhibit anysignificant variation for both hole transport materials. The back metal contactwork function is varied for NiO hole conductor and observed that Ni and Cometals may be suitable back contacts for efficient carrier dynamics. The solarphotovoltaic performance showed a linear decrease in efficiency with increasingtemperature. The electron affinity and band gap of transparent conducting oxideand NiO layers are varied to understand their impact on conduction and valenceband offsets. A range of suitable band gap and electron affinity values arefound essential for efficient device performance.
Protein arginine methyltransferase 6 (PRMT6) catalyzes asymmetric dimethylation of histone H3 at arginine 2 (H3R2me2a). This mark has been reported to associate with silent genes. Here, we use a cell model of neural differentiation, which upon PRMT6 knockout exhibits proliferation and differentiation defects. Strikingly, we detect PRMT6-dependent H3R2me2a at active genes, both at promoter and enhancer sites. Loss of H3R2me2a from promoter sites leads to enhanced KMT2A binding and H3K4me3 deposition together with increased target gene transcription, supporting a repressive nature of H3R2me2a. At enhancers, H3R2me2a peaks co-localize with the active enhancer marks H3K4me1 and H3K27ac. Here, loss of H3R2me2a results in reduced KMT2D binding and H3K4me1/H3K27ac deposition together with decreased transcription of associated genes, indicating that H3R2me2a also exerts activation functions. Our work suggests that PRMT6 via H3R2me2a interferes with the deposition of adjacent histone marks and modulates the activity of important differentiation-associated genes by opposing transcriptional effects.
Membrane proteins play an important role in maintaining the structure and physiology of an organism. Despite their significance, spectroscopic studies involving membrane proteins remain challenging due to the difficulties in mimicking their native lipid bilayer environment. Membrane mimetic systems such as detergent micelles, liposomes, bicelles, nanodiscs, lipodisqs have improved the solubility and folding properties of the membrane proteins for structural studies, however, each mimetic system suffers from its own limitations. In this study, using three different lipid environments, vesicles were titrated with styrene-maleic acid (StMA) copolymer leading to a homogeneous SMALP system (∼10 nm) at a weight ratio of 1:1.5 (vesicle: StMA solution). A combination of Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) was used to characterize these SMALPs. We used a controlled synthesis mechanism to synthesize StMA based block copolymers called reversible addition-fragmentation chain transfer polymerization (RAFT) SMALPs. Incorporation of the Voltage Sensor Domain of KCNQ1 (Q1-VSD) into RAFT SMALPs indicates that this is a promising application of this system to study membrane proteins using different biophysical techniques. V165C in Q1-VSD corresponding to the hydrophobic region was incorporated into the SMALP system. Continuous Wave-Electron Paramagnetic Resonance (CW-EPR) line shape analysis showed line shape broadening, exposing a lower rigid component and a faster component of the spin label.