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An N-annulated indenoperylene electron-donor decorated with photochemically inactive segments is synthesized and further conjugated via triple bond with electron-acceptor benzothiadiazolylbenzoic acid for a metal-free donor/acceptor dye. Without use of any coadsorbate, the judiciously tailored indenoperylene dye achieves a high-power conversion efficiency of 12.5% under irradiance of 100 mW cm(-2) AM1.5G sunlight.

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A metal-free organic dye-sensitized solar cell attains 13% power conversion efficiency under AM1.5G full sunlight.

Native human Abs represent attractive drug candidates; however, the low frequency of B cells expressing high-quality Abs has posed a barrier to discovery. Using a novel single-cell phenotyping technology, we have overcome this barrier to discover human Abs targeting the conserved but poorly immunogenic central motif of respiratory syncytial virus (RSV) G protein. For the entire cohort of 24 subjects with recent RSV infection, B cells producing Abs meeting these stringent specificity criteria were rare, <10 per million. Several of the newly cloned Abs bind to the RSV G protein central conserved motif with very high affinity (Kd 1–24 pM). Two of the Abs were characterized in detail and compared with palivizumab, a humanized mAb against the RSV F protein. Relative to palivizumab, the anti-G Abs showed improved viral neutralization potency in vitro and enhanced reduction of infectious virus in a prophylaxis mouse model. Furthermore, in a mouse model for postinfection treatment, both anti-G Abs were significantly more effective than palivizumab at reducing viral load. The combination of activity in mouse models for both prophylaxis and treatment makes these high-affinity human-derived Abs promising candidates for human clinical testing.

Transcription-generated DNA supercoiling plays a decisive role in a promoter relay mechanism for the coordinated expression of genes in the Salmonella typhimurium ilvIH-leuO-leuABCD gene cluster. A similar mechanism also operates to control expression of the genes in the Escherichia coli ilvIH-leuO-leuABCD gene cluster. However, the mechanism underlying the DNA supercoiling effect remained elusive. A bacterial gene silencer AT8 was found to be important for the repression state of the leuO gene as part of the promoter relay mechanism. In this communication, we demonstrated that the gene silencer AT8 is a nucleation site for recruiting histone-like nucleoid structuring protein to form a cis-spreading nucleoprotein filament that is responsible for silencing of the leuO gene. With a DNA geometric similarity rather than a DNA sequence specificity, the E. coli gene silencer EAT6 was capable of replacing the histone-like nucleoid structuring protein nucleation function of the S. typhimurium gene silencer AT8 for the leuO gene silencing. The interchangeability between DNA geometrical elements for supporting the silencing activity in the region is consistent with a previous finding that a neighboring transcription activity determines the outcome of the gene silencing activity. The geometric requirement, which was revealed for this silencing activity, explains the decisive role of transcription-generated DNA supercoiling found in the promoter relay mechanism.DNA supercoiling has been known to play important roles in transcriptional regulation (1-7). By using a bacterial transcription regulation model system, we have demonstrated that transcription-generated DNA supercoiling is a crucial driven force that triggers the sequential activation of genes in the Salmonella typhimurium ilvIH-leuO-leuABCD gene cluster (8 -12). This rather complex sequential gene activation process was named the promoter relay mechanism (11, 12). The exact molecular detail that underlies the effect of transcription-generated DNA supercoiling on the sequential activation of genes at this locus remains unclear. The direct DNA supercoiling effect on activating promoters of genes in this region has been ruled out. Instead, the effect appears to mediate through cis-elements within the locus control regions (LCRs 1 illustrated in Fig. 1) located between genes in the ilvIH-leuO-leuABCD gene cluster (8).Although not ruling out the possible involvement of other cis-acting elements in the transcription regulation, we have identified two cis-elements in the LCR-I that are important for the promoter relay mechanism as follows: a bacterial gene silencer, termed AT8; and a LeuO protein-binding site, termed AT7 (13, 14). The bacterial gene silencer AT8-mediated transcriptional silencing is integral to the gene expression regulation and is responsible for the repressed state of the leuO gene. LeuO protein-mediated derepression, which relieves the repression of leuO gene, is also a crucial part of the promoter relay mechanism. Transcription-generated DNA supercoili...

Conjugated polymers are regarded as promising candidates for dopant-free hole-transport materials (HTMs) in efficient and stable perovskite solar cells (PSCs). Thus far, the vast majority of polymeric HTMs feature structurally complicated benzo­[1,2-b:4,5-b’]­dithiophene (BDT) analogs and electron-withdrawing heterocycles, forming a strong donor–acceptor (D–A) structure. Herein, a new class of phenanthrocarbazole (PC)-based polymeric HTMs (PC1, PC2, and PC3) has been synthesized by inserting a PC unit into a polymeric thiophene or selenophene chain with the aim of enhancing the π–π stacking of adjacent polymer chains and also to efficiently interact with the perovskite surface through the broad and planar conjugated backbone of the PC. Suitable energy levels, excellent thermostability, and humidity resistivity together with remarkable photoelectric properties are obtained via meticulously tuning the conformation and elemental composition of the polymers. As a result, PSCs containing PC3 as dopant-free HTM show a stabilized power conversion efficiency (PCE) of 20.8% and significantly enhanced longevity, rendering one of the best types of PSCs based on dopant-free HTMs. Subsequent experimental and theoretical studies reveal that the planar conformation of the polymers contributes to an ordered and face-on stacking of the polymer chains. Furthermore, introduction of the “Lewis soft” selenium atom can passivate surface trap sites of perovskite films by Pb–Se interaction and facilitate the interfacial charge separation significantly. This work reveals the guiding principles for rational design of dopant-free polymeric HTMs and also inspires rational exploration of small molecular HTMs.

We have previously demonstrated that sequential activation of the bacterial ilvIH-leuO-leuABCD gene cluster involves a promoter-relay mechanism. In the current study, we show that the final activation of the leuABCD operon is through a transcriptional derepression mechanism. The leuABCD operon is transcriptionally repressed by the presence of a 318-base pair AT-rich upstream element. LeuO is required for derepressing the repressed leuABCD operon. Deletion analysis of the repressive effect of the 318-bp element has led to the identification of a 72-bp AT-rich (78% A؉T) DNA sequence element, AT4, which is capable of silencing a number of unrelated promoters in addition to the leuABCD promoter. AT4-mediated gene silencing is orientation-independent and occurs within a distance of 300 base pairs. Furthermore, an increased gene-silencing effect was observed with a tandemly repeated AT4 dimer. The possible mechanism of AT4-mediated gene silencing in bacteria is discussed.The leu-500 mutation is an A to G transition in the Ϫ10 region of the promoter of the Salmonella typhimurium leuABCD operon (1). The transcriptional activity of the mutant promoter is DNA supercoiling-dependent (2). The mechanism whereby the leu-500 promoter (pleu-500) is activated in the topA mutants is intriguing (3-7). Previous studies using a plasmid system have demonstrated that activation of plasmidborne pleu-500 in topA mutants requires an upstream transcriptional activity transcribing away from pleu-500 (8 -11). This notion has been confirmed in a recent study using the chromosomal setting (12). Transcriptional activation of the ilvIH promoter (pilvIH) located 1.9 kilobases upstream of pleu-500 was shown to be responsible for pleu-500 activation (5). Transcription-driven DNA supercoiling (13) has been suggested to play a role in this long-range promoter-promoter interaction.The intervening promoter that relays the distant interaction between pilvIH and pleu-500 is the leuO promoter (pleuO). In addition to transcriptional activity from pleuO, the leuO gene product, LeuO, is also required to provide a trans-acting function for activation of pleu-500 (6). It appears that the functional pleuO (or other replaced promoter) and LeuO are coupled in activating pleu-500. The molecular basis for pleu-500 activation by the combined action of pleuO and LeuO is still a mystery.There is a stretch of 434 base pairs (bp) 1 that is AT-rich DNA flanked by the divergently arrayed leuO and leuABCD (14). Besides the promoter sequences of the flanking genes, the function of the remaining 318-bp AT-rich (69% AϩT) DNA is unknown (illustrated in Fig. 1). By monitoring pleu-500 activation, we found that the 318-bp AT-rich intervening DNA appears to repress the short-range interaction (11) between the two flanking promoters. Interestingly, LeuO relieves the repression. The repressive effect of the AT-rich intervening DNA on the short-range promoter-promoter interaction (pleuO and pleu-500) could potentially be due to anchoring of the AT-rich DNA to a large mass, which re...