ABSTRACT
In organic photovoltaics (OPVs), determining the energy-level alignment of a donor and an acceptor is particularly important since the interfacial energy gap between the highest occupied molecular orbital (HOMO) level of a donor and the lowest unoccupied molecular orbital (LUMO) level of an acceptor (E-E) gives the theoretical maximum value of the open-circuit voltage (VOC). To increase the E-E, non-fullerene acceptors, which have a lower electron affinity (EA) than C60, are receiving increasing attention. In this study, we investigated the energy-level alignment at the interface of a boron chloride subphthalocyanine (SubPc) donor and a halogenated SubPc (Cl6SubPc) acceptor using soft X-ray spectroscopy techniques. The estimated E-E of Cl6SubPc/SubPc was 1.95 eV, which was significantly higher than that of 1.51 eV found at the interface of C60/SubPc. This increased E-E was the origin of the enhanced VOC in OPVs. Additionally, we studied the molecular orientation of Cl6SubPc using angle-dependent X-ray absorption spectroscopy. The highly disordered Cl6SubPc molecules result in low carrier mobility, which contributes to the lower short-circuit current density of the Cl6SubPc acceptor OPVs than the C60 acceptor OPVs.
ABSTRACT
Mitochondrial dysfunction has been suggested as a causal factor for insulin resistance and diabetes. Previously we have shown a decrease of mitochondrial DNA (mtDNA) content in tissues of diabetic patients. The mitochondrial proteins, which regulate the mitochondrial biogensis, including transcription and replication of mtDNA, are encoded by nuclear DNA. Despite the potential function of the proteins bound to the D-loop region of mtDNA in regulating mtDNA transcription/replication, only a few proteins are known to bind the D-loop region of mtDNA. The functional association of these known proteins with insulin resistance is weak. In this study, we applied proteomic analysis to identify a group of proteins (proteome) that physically bind to D-loop DNA of mtDNA. We amplified D-loop DNA (1.1 kb) by PCR and conjugated the PCR fragments to CNBr-activated sepharose. Mitochondria fractions were isolated by both differential centrifugation and Optiprep-gradient ultracentrifugation. The D-loop DNA binding proteome fractions were enriched via this affinity chromatography and analyzed by SDS-PAGE. The proteins on the gel were transferred onto PVDF membrane and the peptide sequences of each band were subsequently analyzed by capillary reverse-phase liquid chromatography/tandem mass spectrometry (RPLC/MS/MS). We identified many D-loop DNA binding proteins, including mitochondrial transcription factor A (mtTFA, Tfam) and mitochondrial single-stranded DNA binding protein (mtSSBP) which were known to bind to mtDNA. We also report the possibility of novel D-loop binding proteins such as histone family proteins and high-mobility group proteins.
