The electron-injection energy losses of dye-sensitized solar cells (DSSCs) are among the fundamental problems hindering their successful breakthrough application. Two triazatruxene (TAT)-based sensitizers, with one containing a flexible Z-type double bond and another a rigid single bond, coded as ZL001 and ZL003, respectively, have been synthesized and applied in DSSCs to probe the energy losses in the process of electron injection. Using time-resolved laser spectroscopic techniques in the kinetic study, ZL003 with the rigid single bond promotes much faster electron injection into the conductive band of TiO2 especially in the locally excited state (hot injection), which leads to higher electron density in TiO2 and a higher V oc. The devices based on ZL003 exhibited a champion power conversion efficiency (PCE) of 13.6% with V oc = 956 mV, J sc = 20.73 mA cm–2, and FF = 68.5%, which are among the highest recorded results to date on single dye-sensitized DSSCs. An independent certified PCE of 12.4% has been obtained for devices based on ZL003.

Low-temperature-processed (100 °C) carbon paste was developed as counter electrode material in hole-conductor free perovskite/TiO2 heterojunction solar cells to substitute noble metallic materials. Under optimized conditions, an impressive PCE value of 8.31% has been achieved with this carbon counter electrode fabricated by doctor-blading technique. Electrochemical impedance spectroscopy demonstrates good charge transport characteristics of low-temperature-processed carbon counter electrode. Moreover, this carbon counter electrode-based perovskite solar cell exhibits good stability over 800 h.

The biocontrol agent Lysobacter enzymogenes produces polycyclic tetramate macrolactams (PoTeMs), including the antifungal HSAF. To elucidate the biosynthesis of the cyclic systems, we identified eleven HSAF precursors/analogues with zero, one, two, or three rings through heterologous expression of the HSAF gene cluster. A series of combinatorial gene expression and deletion experiments showed that OX3 is the "gatekeeper" responsible for the formation of the first 5-membered ring from lysobacterene A, OX1 and OX2 are responsible for formation of the second ring but with different selectivity, and OX4 is responsible for formation of the 6-membered ring. In vitro experiments showed that OX4 is an NADPH-dependent enzyme that catalyzes the reductive cyclization of 3-dehydroxy alteramide C to form 3-dehydroxy HSAF. Thus, the multiplicity of OX genes is the basis for the structural diversity of the HSAF family, which is the only characterized PoTeM cluster that involves four redox enzymes in the formation of the cyclic system.

Antifungal HSAF (heat‐stable antifungal factor, dihydromaltophilin) is a polycyclic tetramate macrolactam from the biocontrol agent Lysobacter enzymogenes. Its biosynthetic gene cluster contains only a single‐module polyketide synthase–nonribosomal peptide synthetase (PKS‐NRPS), although two separate hexaketide chains are required to assemble the skeleton. To address the unusual biosynthetic mechanism, we expressed the biosynthetic genes in two “clean” strains of Streptomyces and showed the production of HSAF analogues and a polyene tetramate intermediate. We then expressed the PKS module in Escherichia coli and purified the enzyme. Upon incubation of the enzyme with acyl‐coenzyme A and reduced nicotinamide adenine dinucleotide phosphate (NADPH), a polyene was detected in the tryptic acyl carrier protein (ACP). Finally, we incubated the polyene–PKS with the NRPS module in the presence of ornithine and adenosine triphosphate (ATP), and we detected the same polyene tetramate as that in Streptomyces transformed with the PKS‐NRPS alone. Together, our results provide evidence for an unusual iterative biosynthetic mechanism for bacterial polyketide–peptide natural products.

Development of hole transport materials (HTMs) with comprehensive passivation effects and appropriate energy levels are urgently desirable for constructing highly efficient and stable perovskite solar cells (PSCs). Herein, we report an effective interfacial molecular doping strategy and energy level regulation approach to improve the performance of PSCs with ultrasimple carbazole-based HTMs CZ-As and CZ-Py. The pyridine-substituted HTM CZ-Py exhibits a stepped energy level with perovskite and CZ-As, effective passivation of Pb2+ defect, as well as the assistance of the formation of high-quality perovskite film and hole transport layer (HTL). By utilizing CZ-Py as interfacial doping material and CZ-As as HTM, the undesired charge carrier recombination at the perovskite/HTM interface are significantly restricted. Finally, the fabricated PSCs feature an impressive power conversion efficiency (PCE) up to 23.5% and good long-term stability. This work demonstrates a facile and highly efficient way to reduce nonradiative recombination and further improve photovoltaic performance of PSCs.

Polycyclic tetramate macrolactams (PoTeMs) are a growing class of natural products with distinct structure and diverse biological activities. By promoter engineering and heterologous expression of the cryptic cbm gene cluster, four new PoTeMs, combamides A-E (1-4), were identified. Additionally, two new derivatives, combamides E (5) and F (6), were generated via combinatorial biosynthesis. Together, our findings provide a sound base for expanding the structure diversities of PoTeMs through genome mining and combinatorial biosynthesis.

Six hygrocins, polyketides of ansamycin class, were isolated from the gdmAI-disrupted Streptomyces sp. LZ35. The planar structure of hygrocins C-E (1-3) was determined by one-dimensional and two-dimensional NMR spectroscopy and high-resolution mass spectrometry. They are derivatives of hygrocin A but differ in the configuration at C-2 and the orientation of the C-3,4 double bond. Hygrocin F(4) and G(5) were shown to be isomers of hygrocin C (1) and B (6), respectively, due to the different alkyl oxygen participating in the macrolide ester linkage. Hygrocins C, D, and F were found to be toxic to human breast cancer MDA-MB-431 cells (IC50 = 0.5, 3.0, and 3.3 μM, respectively) and prostate cancer PC3 cells (IC50 = 1.9, 5.0, and 4.5 μM, respectively), while hygrocins B, E, and G were inactive.

Hygrocins are naphthoquinone ansamycins with significant antitumor activities. Here, we report the identification and characterization of the hygrocin biosynthetic gene cluster (hgc) in Streptomyces sp. LZ35. A biosynthetic pathway is proposed based on bioinformatics analysis of the hgc genes and intermediates accumulated in selected gene disruption mutants. One of the steps during the biosynthesis of hygrocins is a Baeyer–Villiger oxidation between C5 and C6, catalyzed by luciferase- like monooxygenase homologue Hgc3. Hgc3 represents the founding member of a previously uncharacterized family of enzymes acting as Baeyer–Villiger monooxygenases.