RESUMO
The large open circuit voltage (VOC) loss and phase segregation are two main obstacles hindering the development of wide-bandgap perovskite solar cells (PSCs). Even though substantial progress has been made through crystallization regulation and surface modification on perovskite, the mechanism of VOC loss and phase segregation has rarely been studied. In this paper, we first investigate the halide ions distribution along the out-of-plane direction and find the initial inhomogeneous distribution of halide ions during the crystallization process is an important reason. It leads to the formation of an unfavorable potential well in PSCs, resulting in VOC loss as well as generation of strong strain exacerbating phase segregation. Through introducing melatonin (MT) into perovskite precursors, a homogeneous distribution of halide anions is realized due to the well-regulated crystallization. Consequently, the treated PSCs exhibit an optimized power conversion efficiency (PCE) of 22.88% with a VOC loss as low as 0.38 V, which are the best values for wide-bandgap PSCs up to now.
RESUMO
Campechic acids A and B are anti-invasive polyketide antibiotics isolated from Streptomyces sp. CHI93 strain. Herein we describe stereoselective synthesis of the C-16-C-30 fragment of campechic acids A and B via a biosynthesis-inspired epoxide-opening cascade and its NMR spectroscopic comparison with the authentic degradation product, resulting in configurational assignment of the C-21, C-24, C-25, and C-28 stereogenic centers and reassignment of the C-18 stereogenic center.
Assuntos
Antibacterianos/química , Compostos de Epóxi/química , Policetídeos/química , Streptomyces/química , Produtos Biológicos , Estrutura Molecular , Policetídeos/isolamento & purificação , Policetídeos/metabolismo , EstereoisomerismoRESUMO
Campechic acids A (1) and B (2), two new polyketides, were isolated from the culture extract of Streptomyces sp., and their structures were determined by NMR and MS spectroscopic analysis. Campechic acids are polyether-polyketides functionalized by two tetrahydrofuran rings, an enolized 1,3-diketone, and multiple methyl substitutions. Absolute configuration of nine stereogenic centers in 1, except for four chiral centers in the cyclic ether moieties, was determined by the 1H NMR anisotropy method in combination with chemical degradation. Campechic acids exhibited potent inhibitory effects on tumor cell invasion with IC50 values in the nanomolar to submicromolar range.
Assuntos
Antineoplásicos/isolamento & purificação , Policetídeos/isolamento & purificação , Streptomyces/química , Antineoplásicos/química , Antineoplásicos/farmacologia , Bacillus subtilis/efeitos dos fármacos , Candida albicans/efeitos dos fármacos , Ensaios de Seleção de Medicamentos Antitumorais , Escherichia coli/efeitos dos fármacos , Humanos , Concentração Inibidora 50 , México , Testes de Sensibilidade Microbiana , Micrococcus luteus/efeitos dos fármacos , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Policetídeos/química , Policetídeos/farmacologia , Microbiologia do Solo , Staphylococcus aureus/efeitos dos fármacosAssuntos
Adipócitos/efeitos dos fármacos , Adipogenia/efeitos dos fármacos , Aminoácidos/farmacologia , Descoberta de Drogas , Streptomyces/metabolismo , Adipócitos/citologia , Aminoácidos/biossíntese , Aminoácidos/química , Aminoácidos/isolamento & purificação , Animais , Fármacos Antiobesidade/química , Fármacos Antiobesidade/isolamento & purificação , Fármacos Antiobesidade/metabolismo , Fármacos Antiobesidade/farmacologia , Linhagem Celular , Hipoglicemiantes/química , Hipoglicemiantes/isolamento & purificação , Hipoglicemiantes/metabolismo , Hipoglicemiantes/farmacologia , Camundongos , Estrutura Molecular , Concentração Osmolar , Microbiologia do Solo , Streptomyces/crescimento & desenvolvimento , Streptomyces/isolamento & purificaçãoRESUMO
Akaeolide, a novel polycyclic polyketide, was isolated from the culture extract of a marine-derived actinomycete belonging to the genus Streptomyces. The planar structure of the new compound was elucidated by spectroscopic analysis including NMR and MS, and the absolute configuration was determined by X-ray crystallographic analysis of its chlorinated derivative. Akaeolide possesses a 15-membered carbocyclic framework, apparently derived from the malonate pathway, with a tetrahydrofuran ring and a ß-keto-δ-lactone unit.
Assuntos
Furanos/química , Macrolídeos/química , Policetídeos/química , Streptomyces/química , Cristalografia por Raios X , Macrolídeos/isolamento & purificação , Estrutura Molecular , Ressonância Magnética Nuclear Biomolecular , Policetídeos/isolamento & purificaçãoRESUMO
Jomthonic acid A (1), a new modified amino acid, was isolated from the culture broth of a soil-derived actinomycete of the genus Streptomyces. The structure and absolute configuration of 1 were determined by spectroscopic analyses and chemical conversion. Jomthonic acid A (1) induced differentiation of preadipocytes into mature adipocytes at 2-50 µM.
Assuntos
Adipócitos/efeitos dos fármacos , Aminoácidos/isolamento & purificação , Microbiologia do Solo , Streptomyces/química , Adipócitos/metabolismo , Aminoácidos/química , Aminoácidos/metabolismo , Estrutura Molecular , Ressonância Magnética Nuclear BiomolecularRESUMO
Abyssomicin I (1), a new modified polycyclic polyketide, was isolated from the culture extract of a soil-derived Streptomyces sp. The structure of 1 was elucidated by interpretation of NMR and other spectroscopic data. The stereochemistry of the new compound was assigned by NOE analysis, chemical derivatization, and application of the modified Mosher method. While 1 was inactive against bacteria and yeasts, the oxidized derivative 7 showed weak activities against gram-positive bacteria. Compounds 1 and 7 exhibited inhibitory effects on tumor cell invasion with IC(50) values of 11 and 0.21 µM, respectively.
