1D Chiral Enantiomer Lead-Free Perovskites Induced Chiralopical Activity and Photoelectric Response.

Chirality is a fascinating geometrical concept with widespread applications in biology, chemistry, and materials. Incorporating chirality into hybrid perovskite materials can induce novel physical properties (chiral optical activity, nonlinear optics, etc.). Hybrid lead-free or lead-substituted perovskite materials, as representatives of perovskites, have been widely used in fields such as photovoltaics, sensors, catalysis, and detectors. However, the successful introduction of chirality into hybrid lead-free perovskites, which can enable their potential applications in areas such as circularly polarized light photodetectors, memories, and spin transistors, remains a challenging research topic. Here, we synthesized two new chiral lead-free perovskites, [(R)-2-methylpiperazine][BiI5] and [(S)-2-methylpiperazine][BiI5]. The material possesses a perovskite structure with a one-dimensional (1D) arrangement, denoted as ABX5. This structure is composed of chiral cations, specifically methylpiperazine, and endless chains of [BiI3] along the a-axis. These chains are assembled from distorted coplanar [BiI5]2- octahedra. The testing results revealed that (R)-1 and (S)-1 have narrow band gaps (Eg-R = 2.016 eV, Eg-S = 1.964 eV), high photoelectric response, and long carrier lifetime [R = 4.94 µs (τ), S = 7.85 µs (τ)]. It is worth noting that 1D chiral lead-free perovskites (R)-1 and (S)-1, which are synthesized in this study with narrow band gaps, high photoelectric response, and long carrier lifetime, have the potential to serve as alternative materials for the perovskite layer in future iterations of lead-free perovskite solar cells. Moreover, this research will inspire the preparation of multifunctional, lead-free perovskites.

Precise Design of Molecular Ferroelectrics with High TC and Tunable Band Gap by Molecular Modification.

Molecular ferroelectric materials are widely applied in piezoelectric converters, non-volatile memorizers, and photovoltaic devices due to their advantages of adjustable structure, lightweight, easy processing, and environmental friendliness. However, designing multifunctional molecular ferroelectrics with excellent properties has always been a great challenge. Herein, a multiaxial molecular ferroelectric is successfully designed by modifying the quasi-spherical cation dabco with CuBr2 to obtain halogenated [Bretdabco]CuBr4 (Bretdabco = N-bromoethyl-N'-diazabicyclo [2.2.2]octane), which crystallizes in polar point groups (C6). Typical ferroelectric behaviors featured by the P-E hysteresis loop and switched ferroelectric domain are exhibited. Notably, the molecular ferroelectric shows a high TC of 460 K, which is rare in the field and could greatly expand the application range of this material. In addition, the band gap is adjustable through the regulation of halogen. Both the UV absorption spectra and theoretical calculations indicate that the molecular ferroelectrics belong to a direct band gap (2.14 eV) semiconductor. This tunable and narrow band gap semiconductor molecular ferroelectric material with high TC can be utilized more effectively in the study of optoelectronics and sensors, including piezoelectric energy harvesters. This research may provide a promising approach for the development of multiaxial molecular ferroelectrics with a tiny band gap and high TC.

Clinical significance of circulating tumor cells in predicating the outcomes of patients with colorectal cancer.

BACKGROUND: Relapse and metastasis of patients with Colorectal Cancer (CRC) is the major obstacle to the long-term life of patients. Its mechanisms remain defined. METHODS: A total of 48 CRC patients were enrolled and 68 samples were obtained from the peripheral blood of patients before or after treatments in this study. Twenty non-cancer patients were also detected as a negative control. Circulating Tumor Cells (CTCs), including Epithelial CTCs (eCTCs), Mesenchymal (MCTCs), and epithelial/mesenchymal mixed phenotypes (mixed CTCs), were identified by CanPatrolTM CTC enrichment and RNA in situ hybridization. The relationship between CTCs number and Progression-Free Survival (PFS) or Overall Survival (OS) was evaluated. RESULTS: Thirty-four of 48 patients (70.8%) were found to have positive CTCs. Total CTCs and MCTCs in the post-treatment had a significant correlation PFS and OS. When total CTCs or MCTCs in 5 mL blood of patients were more than 6 CTCs or 5 MCTCs, PFS of the patients was significantly shorter (p < 0.05) than that in patients with less than 6 CTCs or 5 MCTCs. The patients with > 5 CTCs count changes were found to exhibit poor PFS and OS rates (p < 0.05). CONCLUSION: Total CTCs and MCTCs number detection in patients with colorectal cancer was very useful biomarker for predicting the prognosis of patients. Higher CTCs or MCTCs had poorer PFS and OS rates.

Clinical significance of circulating tumor cells in predicating the outcomes of patients with colorectal cancer

Abstract Background: Relapse and metastasis of patients with Colorectal Cancer (CRC) is the major obstacle to the long-term life of patients. Its mechanisms remain defined. Methods: A total of 48 CRC patients were enrolled and 68 samples were obtained from the peripheral blood of patients before or after treatments in this study. Twenty non-cancer patients were also detected as a negative control. Circulating Tumor Cells (CTCs), including Epithelial CTCs (eCTCs), Mesenchymal (MCTCs), and epithelial/ mesenchymal mixed phenotypes (mixed CTCs), were identified by CanPatrolTM CTC enrichment and RNA in situ hybridization. The relationship between CTCs number and Progression-Free Survival (PFS) or Overall Survival (OS) was evaluated. Results: Thirty-four of 48 patients (70.8%) were found to have positive CTCs. Total CTCs and MCTCs in the post-treatment had a significant correlation PFS and OS. When total CTCs or MCTCs in 5 mL blood of patients were more than 6 CTCs or 5 MCTCs, PFS of the patients was significantly shorter (p < 0.05) than that in patients with less than 6 CTCs or 5 MCTCs. The patients with > 5 CTCs count changes were found to exhibit poor PFS and OS rates (p < 0.05). Conclusion: Total CTCs and MCTCs number detection in patients with colorectal cancer was very useful biomarker for predicting the prognosis of patients. Higher CTCs or MCTCs had poorer PFS and OS rates.

Design, synthesis and biological evaluation of pyridinylmethylenepiperidine derivatives as potent 5-HT1F receptor agonists for migraine therapy.

Migraine is a common neurovascular disease which has been classified as the sixth most disabling disorder. Current migraine therapy was triptans, however, riptans can cause contraction of blood vessels. Therefore, novel drugs without cardiovascular effects emerged, such as CGRP and selective 5-HT1F receptor agonists. In this work, a series of pyridinylmethylenepiperidine derivatives were designed, synthesized and evaluated for their 5-HT1F receptor agonist activity. The results in vitro showed that compound C1-C6 displayed potent agonist activities compared with positive drug lasmiditan. Pharmacokinetic properties in rat indicated that 2,4,6-trifluoro-N-(6-(fluoro(1-methylpiperidin-4-ylidene)methyl)pyridin-2-yl)benzamide (C5) possessed high AUC and good bioavailability. In two rodent models of migraine, C5 significantly inhibited dural plasma protein extravasation and c-fos expression in the trigeminal nucleus caudalis. Moreover, C5 showed no effect on vasoconstriction. Through these studies, we identified C5 as a potent 5-HT1F receptor agonist for migraine therapy.

Pyruvate kinase from Plasmodium falciparum: Structural and kinetic insights into the allosteric mechanism.

During its intra-erythrocytic growth phase, the malaria parasite Plasmodium falciparum relies heavily on glycolysis for its energy requirements. Pyruvate kinase (PYK) is essential for regulating glycolytic flux and for ATP production, yet the allosteric mechanism of P. falciparum PYK (PfPYK) remains poorly understood. Here we report the first crystal structure of PfPYK in complex with substrate analogues oxalate and the ATP product. Comparisons of PfPYK structures in the active R-state and inactive T-state reveal a 'rock-and-lock' allosteric mechanism regulated by rigid-body rotations of each subunit in the tetramer. Kinetic data and structural analysis indicate glucose 6-phosphate is an activator by increasing the apparent maximal velocity of the enzyme. Intriguingly, the trypanosome drug suramin inhibits PfPYK, which points to glycolysis as a set of potential therapeutic targets against malaria.

Stereoselective Phenylselenoglycosylation of Glycals Bearing a Fused Carbonate Moiety toward the Synthesis of 2-Deoxy-ß-galactosides and ß-Mannosides.

A phenylselenoglycosylation reaction of glycal derivatives mediated by diphenyl diselenide and phenyliodine(III) bis(trifluoroacetate) under mild conditions is described. Stereoselective glycosylation has been achieved by installing fused carbonate on those glycals. 3,4-O-Carbonate galactals and 2,3-O-carbonate 2-hydroxyglucals are converted into corresponding glycosides in good yields with excellent ß-selectivity, resulting in 2-phenylseleno-2-deoxy-ß-galactosides and 2-phenylseleno-ß-mannosides which are good precursors of 2-deoxy-ß-galactosides and ß-mannosides, respectively.

Crystal structure and catalytic mechanism of the essential m1G37 tRNA methyltransferase TrmD from Pseudomonas aeruginosa.

The tRNA (m1G37) methyltransferase TrmD catalyzes m1G formation at position 37 in many tRNA isoacceptors and is essential in most bacteria, which positions it as a target for antibiotic development. In spite of its crucial role, little is known about TrmD in Pseudomonas aeruginosa (PaTrmD), an important human pathogen. Here we present detailed structural, substrate, and kinetic properties of PaTrmD. The mass spectrometric analysis confirmed the G36G37-containing tRNAs Leu(GAG), Leu(CAG), Leu(UAG), Pro(GGG), Pro(UGG), Pro(CGG), and His(GUG) as PaTrmD substrates. Analysis of steady-state kinetics with S-adenosyl-l-methionine (SAM) and tRNALeu(GAG) showed that PaTrmD catalyzes the two-substrate reaction by way of a ternary complex, while isothermal titration calorimetry revealed that SAM and tRNALeu(GAG) bind to PaTrmD independently, each with a dissociation constant of 14 ± 3 µM. Inhibition by the SAM analog sinefungin was competitive with respect to SAM (Ki = 0.41 ± 0.07 µM) and uncompetitive for tRNA (Ki = 6.4 ± 0.8 µM). A set of crystal structures of the homodimeric PaTrmD protein bound to SAM and sinefungin provide the molecular basis for enzyme competitive inhibition and identify the location of the bound divalent ion. These results provide insights into PaTrmD as a potential target for the development of antibiotics.

Six1 is negatively correlated with poor prognosis and reduces 5-fluorouracil sensitivity via attenuating the stemness of hepatocellular carcinoma cells.

The promoting roles of transcriptional factor six1 have been shown in various tumors, such as breast cancer and colorectal Cancer. However, its roles in hepatocellular carcinoma (HCC) cell stemness and chemotherapeutic sensitivity are never been revealed. In the present study, we showed that six1 expression was negatively correlated the overall survival of HCC patients and significantly increased in HCC tissues. Analysis on normal hepatic cells and HCC cells obtained the consistent result. Functional experiments revealed that six1 knockdown enhanced 5-fluorouracil (5-FU) sensitivity and reduced the stemness of HCC cells. Additionally, six1 knockdown partially reversed 5-FU resistance and attenuated the stemness in 5-FU-resistant HCC cells. Furthermore, we demonstrated that six1 directly bound to sox2 (a stemness master regulator) promoter, enhanced its transcription and expression. Overexpression of sox2 rescued the inhibitory effects of six1 knockdown on the stemness and 5-FU sensitivity of HCC cells. Thus, our work identified a novel six1/sox2 axis in regulating the stemness of HCC cells.

Pyruvate Kinase Regulates the Pentose-Phosphate Pathway in Response to Hypoxia in Mycobacterium tuberculosis.

In response to the stress of infection, Mycobacterium tuberculosis (Mtb) reprograms its metabolism to accommodate nutrient and energetic demands in a changing environment. Pyruvate kinase (PYK) is an essential glycolytic enzyme in the phosphoenolpyruvate-pyruvate-oxaloacetate node that is a central switch point for carbon flux distribution. Here we show that the competitive binding of pentose monophosphate inhibitors or the activator glucose 6-phosphate (G6P) to MtbPYK tightly regulates the metabolic flux. Intriguingly, pentose monophosphates were found to share the same binding site with G6P. The determination of a crystal structure of MtbPYK with bound ribose 5-phosphate (R5P), combined with biochemical analyses and molecular dynamic simulations, revealed that the allosteric inhibitor pentose monophosphate increases PYK structural dynamics, weakens the structural network communication, and impairs substrate binding. G6P, on the other hand, primes and activates the tetramer by decreasing protein flexibility and strengthening allosteric coupling. Therefore, we propose that MtbPYK uses these differences in conformational dynamics to up- and down-regulate enzymic activity. Importantly, metabolome profiling in mycobacteria reveals a significant increase in the levels of pentose monophosphate during hypoxia, which provides insights into how PYK uses dynamics of the tetramer as a competitive allosteric mechanism to retard glycolysis and facilitate metabolic reprogramming toward the pentose-phosphate pathway for achieving redox balance and an anticipatory metabolic response in Mtb.

Thienopyrimidinone Derivatives That Inhibit Bacterial tRNA (Guanine37-N1)-Methyltransferase (TrmD) by Restructuring the Active Site with a Tyrosine-Flipping Mechanism.

Among the >120 modified ribonucleosides in the prokaryotic epitranscriptome, many tRNA modifications are critical to bacterial survival, which makes their synthetic enzymes ideal targets for antibiotic development. Here we performed a structure-based design of inhibitors of tRNA-(N1G37) methyltransferase, TrmD, which is an essential enzyme in many bacterial pathogens. On the basis of crystal structures of TrmDs from Pseudomonas aeruginosa and Mycobacterium tuberculosis, we synthesized a series of thienopyrimidinone derivatives with nanomolar potency against TrmD in vitro and discovered a novel active site conformational change triggered by inhibitor binding. This tyrosine-flipping mechanism is uniquely found in P. aeruginosa TrmD and renders the enzyme inaccessible to the cofactor S-adenosyl-l-methionine (SAM) and probably to the substrate tRNA. Biophysical and biochemical structure-activity relationship studies provided insights into the mechanisms underlying the potency of thienopyrimidinones as TrmD inhibitors, with several derivatives found to be active against Gram-positive and mycobacterial pathogens. These results lay a foundation for further development of TrmD inhibitors as antimicrobial agents.

Backbone resonance assignment for the full length tRNA-(N1G37) methyltransferase of Pseudomonas aeruginosa.

Bacterial tRNA (guanine37-N1)-methyltransferase (TrmD) plays important roles in translation, making it an important target for the development of new antibacterial compounds. TrmD comprises two domains with the N-terminal domain binding to the S-adenosyl-L-methionine (SAM) cofactor and the C-terminal domain critical for tRNA binding. Bacterial TrmD is functional as a dimer. Here we report the backbone NMR resonance assignments for the full length TrmD protein of Pseudomonas aeruginosa. Most resonances were assigned and the secondary structure for each amino acid was determined according to the assigned backbone resonances. The availability of the assignment will be valuable for exploring molecular interactions of TrmD with ligands, inhibitors and tRNA.

Targeting the Bacterial Epitranscriptome for Antibiotic Development: Discovery of Novel tRNA-(N1G37) Methyltransferase (TrmD) Inhibitors.

Bacterial tRNA modification synthesis pathways are critical to cell survival under stress and thus represent ideal mechanism-based targets for antibiotic development. One such target is the tRNA-(N1G37) methyltransferase (TrmD), which is conserved and essential in many bacterial pathogens. Here we developed and applied a widely applicable, radioactivity-free, bioluminescence-based high-throughput screen (HTS) against 116350 compounds from structurally diverse small-molecule libraries to identify inhibitors of Pseudomonas aeruginosa TrmD ( PaTrmD). Of 285 compounds passing primary and secondary screens, a total of 61 TrmD inhibitors comprised of more than 12 different chemical scaffolds were identified, all showing submicromolar to low micromolar enzyme inhibitor constants, with binding affinity confirmed by thermal stability and surface plasmon resonance. S-Adenosyl-l-methionine (SAM) competition assays suggested that compounds in the pyridine-pyrazole-piperidine scaffold were substrate SAM-competitive inhibitors. This was confirmed in structural studies, with nuclear magnetic resonance analysis and crystal structures of PaTrmD showing pyridine-pyrazole-piperidine compounds bound in the SAM-binding pocket. Five hits showed cellular activities against Gram-positive bacteria, including mycobacteria, while one compound, a SAM-noncompetitive inhibitor, exhibited broad-spectrum antibacterial activity. The results of this HTS expand the repertoire of TrmD-inhibiting molecular scaffolds that show promise for antibiotic development.

Backbone resonance assignment for the N-terminal region of bacterial tRNA-(N1G37) methyltransferase.

Bacterial tRNA (guanine37-N1)-methyltransferase (TrmD) is an important antibacterial target due to its essential role in translation. TrmD has two domains connected with a flexible linker. The N-terminal domain (NTD) of TrmD contains the S-adenosyl-L-methionine (SAM) cofactor binding site and the C-terminal domain is critical for tRNA binding. Here we report the backbone NMR resonance assignments for NTD of Pseudomonas aeruginosa TrmD. Its secondary structure was determined based on the assigned resonances. Relaxation analysis revealed that NTD existed as dimers in solution. NTD also exhibited thermal stability in solution. Its interactions with SAM and other compounds suggest it can be used for evaluating SAM competitive inhibitors by NMR.

Allosteric pyruvate kinase-based "logic gate" synergistically senses energy and sugar levels in Mycobacterium tuberculosis.

Pyruvate kinase (PYK) is an essential glycolytic enzyme that controls glycolytic flux and is critical for ATP production in all organisms, with tight regulation by multiple metabolites. Yet the allosteric mechanisms governing PYK activity in bacterial pathogens are poorly understood. Here we report biochemical, structural and metabolomic evidence that Mycobacterium tuberculosis (Mtb) PYK uses AMP and glucose-6-phosphate (G6P) as synergistic allosteric activators that function as a molecular "OR logic gate" to tightly regulate energy and glucose metabolism. G6P was found to bind to a previously unknown site adjacent to the canonical site for AMP. Kinetic data and structural network analysis further show that AMP and G6P work synergistically as allosteric activators. Importantly, metabolome profiling in the Mtb surrogate, Mycobacterium bovis BCG, reveals significant changes in AMP and G6P levels during nutrient deprivation, which provides insights into how a PYK OR gate would function during the stress of Mtb infection.

Synthesis and cytotoxicity evaluation of naphthalimide derived N-mustards.

A series of N-mustards, which was conjugated to mono- or bis-naphthalimides with a flexible amine link, were synthesized and evaluated for cytotoxicity against five cancer cell lines (HCT-116, PC-3, U87 MG, Hep G2 and SK-OV-3). Several compounds displayed better activities than the control compound amonafide. Further evaluations by fluorescence spectroscopy studies and DNA-interstrand cross-linking assays revealed that the derivatives showed both alkylating and intercalating properties. Among the derivatives, the bis-naphthalimide N-mustard derivative 11b was found to exhibit the highest cytotoxic activity and DNA cross-linking ability. Both 11b and 7b induce HCT-116 cell apoptosis by S phase arrest.

Pyruvate kinases have an intrinsic and conserved decarboxylase activity.

The phosphotransfer mechanism of PYKs (pyruvate kinases) has been studied in detail, but the mechanism of the intrinsic decarboxylase reaction catalysed by PYKs is still unknown. 1H NMR was used in the present study to follow OAA (oxaloacetate) decarboxylation by trypanosomatid and human PYKs confirming that the decarboxylase activity is conserved across distantly related species. Crystal structures of TbPYK (Trypanosoma brucei PYK) complexed with the product of the decarboxylase reaction (pyruvate), and a series of substrate analogues (D-malate, 2-oxoglutarate and oxalate) show that the OAA analogues bind to the kinase active site with similar binding modes, confirming that both decarboxylase and kinase activities share a common site for substrate binding and catalysis. Decarboxylation of OAA as monitored by NMR for TbPYK has a relatively low turnover with values of 0.86 s-1 and 1.47 s-1 in the absence and presence of F26BP (fructose 2,6-bisphosphate) respectively. Human M1PYK (M1 isoform of PYK) has a measured turnover value of 0.50 s-1. The X-ray structures explain why the decarboxylation activity is specific for OAA and is not general for α-oxo acid analogues. Conservation of the decarboxylase reaction across divergent species is a consequence of piggybacking on the conserved kinase mechanism which requires a stabilized enol intermediate.

Pre-, peri-, and postoperative oral administration of branched-chain amino acids for primary liver cancer patients for hepatic resection: a systematic review.

Pre-, peri-, and postoperative oral administration of branched-chain amino acids (BCAA) to patients with primary liver cancer (PLC) during hepatic resection (HR) remains controversial. The aim of this systematic review was to evaluate the efficacy and safety of this practice. Seven literature databases were systematically searched for randomized controlled trials (RCTs) that reported pre-, peri-, and postoperative oral administration of BCAA for PLC patients during HR. Three RCTs were included in a meta-analysis in which risk ratios (RRs) and 95% confidence intervals (95% CIs) were calculated. The 2 groups showed similar recurrence rates (RR = 1.03, 95% CI 0.78 to 1.36) and similar overall survival (RR = 0.91, 95% CI 0.71 to 1.18). Adverse events related to oral administration of BCAA were more than the control group, including nausea, vomiting, diarrhea, abdominal distension, abdominal pain, and hypertension. However, all adverse reactions disappeared after symptomatic treatment. The available evidence suggests that although pre-, peri-, and postoperative oral BCAA for patients with PLC is safe, it is of questionable clinical value. More RCTs are warranted to explore this question definitively.

Structures of pyruvate kinases display evolutionarily divergent allosteric strategies.

The transition between the inactive T-state (apoenzyme) and active R-state (effector bound enzyme) of Trypanosoma cruzi pyruvate kinase (PYK) is accompanied by a symmetrical 8° rigid body rocking motion of the A- and C-domain cores in each of the four subunits, coupled with the formation of additional salt bridges across two of the four subunit interfaces. These salt bridges provide increased tetramer stability correlated with an enhanced specificity constant (k cat/S 0.5). A detailed kinetic and structural comparison between the potential drug target PYKs from the pathogenic protists T. cruzi, T. brucei and Leishmania mexicana shows that their allosteric mechanism is conserved. By contrast, a structural comparison of trypanosomatid PYKs with the evolutionarily divergent PYKs of humans and of bacteria shows that they have adopted different allosteric strategies. The underlying principle in each case is to maximize (k cat/S 0.5) by stabilizing and rigidifying the tetramer in an active R-state conformation. However, bacterial and mammalian PYKs have evolved alternative ways of locking the tetramers together. In contrast to the divergent allosteric mechanisms, the PYK active sites are highly conserved across species. Selective disruption of the varied allosteric mechanisms may therefore provide a useful approach for the design of species-specific inhibitors.

`In crystallo' substrate binding triggers major domain movements and reveals magnesium as a co-activator of Trypanosoma brucei pyruvate kinase.

The active site of pyruvate kinase (PYK) is located between the AC core of the enzyme and a mobile lid corresponding to domain B. Many PYK structures have already been determined, but the first `effector-only' structure and the first with PEP (the true natural substrate) are now reported for the enzyme from Trypanosoma brucei. PEP soaked into crystals of the enzyme with bound allosteric activator fructose 2,6-bisphosphate (F26BP) and Mg(2+) triggers a substantial 23° rotation of the B domain `in crystallo', resulting in a partially closed active site. The interplay of side chains with Mg(2+) and PEP may explain the mechanism of the domain movement. Furthermore, it is apparent that when F26BP is present but PEP is absent Mg(2+) occupies a position that is distinct from the two canonical Mg(2+)-binding sites at the active site. This third site is adjacent to the active site and involves the same amino-acid side chains as in canonical site 1 but in altered orientations. Site 3 acts to sequester Mg(2+) in a `priming' position such that the enzyme is maintained in its R-state conformation. In this way, Mg(2+) cooperates with F26BP to ensure that the enzyme is in a conformation that has a high affinity for the substrate.