Manufacturing 6-[18F]Fluoro-L-DOPA via Flow Chemistry-Enhanced Photoredox Radiofluorination.

In this study, we introduce a practical methodology for the synthesis of PET probes by seamlessly combining flow chemistry with photoredox radiofluorination. The clinical PET tracer 6-[18F]FDOPA was smoothly prepared in a 24.3% non-decay-corrected yield with over 99.0% radiochemical purity (RCP) and enantiomeric excess (ee), notably by a simple cartridge-based purification. The flow chemistry-enhanced photolabeling method supplies an efficient and versatile solution for the synthesis of 6-[18F]FDOPA and for more PET tracer development.

Chelator boosted tumor-retention and pharmacokinetic properties: development of 64Cu labeled radiopharmaceuticals targeting neurotensin receptor.

PURPOSE: Accumulating evidence suggests that neurotensin (NTS) and neurotensin receptors (NTSRs) play key roles in lung cancer progression by triggering multiple oncogenic signaling pathways. This study aims to develop Cu-labeled neurotensin receptor 1 (NTSR1)-targeting agents with the potential for both imaging and therapeutic applications. METHOD: A series of neurotensin receptor antagonists (NRAs) with variable propylamine (PA) linker length and different chelators were synthesized, including [64Cu]Cu-CB-TE2A-iPA-NRA ([64Cu]Cu-4a-c, i = 1, 2, 3), [64Cu]Cu-NOTA-2PA-NRA ([64Cu]Cu-4d), [64Cu]Cu-DOTA-2PA-NRA ([64Cu]Cu-4e, also known as [64Cu]Cu-3BP-227), and [64Cu]Cu-DOTA-VS-2PA-NRA ([64Cu]Cu-4f). The series of small animal PET/CT were conducted in H1299 lung cancer model. The expression profile of NTSR1 was also confirmed by IHC using patient tissue samples. RESULTS: For most of the compounds studied, PET/CT showed prominent tumor uptake and high tumor-to-background contrast, but the tumor retention was strongly influenced by the chelators used. For previously reported 4e, [64Cu]Cu-labeled derivative showed initial high tumor uptake accompanied by rapid tumor washout at 24 h. The newly developed [64Cu]Cu-4d and [64Cu]Cu-4f demonstrated good tumor uptake and tumor-to-background contrast at early time points, but were less promising in tumor retention. In contrast, our lead compound [64Cu]Cu-4b demonstrated 9.57 ± 1.35, 9.44 ± 2.38 and 9.72 ± 4.89%ID/g tumor uptake at 4, 24, and 48 h p.i., respectively. Moderate liver uptake (11.97 ± 3.85, 9.80 ± 3.63, and 7.72 ± 4.68%ID/g at 4, 24, and 48 h p.i.) was observed with low uptake in most other organs. The PA linker was found to have a significant effect on drug distribution. Compared to [64Cu]Cu-4b, [64Cu]Cu-4a had a lower background, including a greatly reduced liver uptake, while the tumor uptake was only moderately reduced. Meanwhile, [64Cu]Cu-4c showed increased uptake in both the tumor and the liver. The clinical relevance of NTSR1 was also demonstrated by the elevated tumor expression in patient tissue samples. CONCLUSIONS: Through the side-by-side comparison, [64Cu]Cu-4b was identified as the lead agent for further evaluation based on its high and sustained tumor uptake and moderate liver uptake. It can not only be used to efficiently detect NTSR1 expression in lung cancer (for diagnosis, patient screening, and treatment monitoring), but also has the great potential to treat NTSR-positive lesions once chelating to the beta emitter 67Cu.

Telomere-to-telomere genome of the allotetraploid legume Sesbania cannabina reveals transposon-driven subgenome divergence and mechanisms of alkaline stress tolerance.

Alkaline soils pose an increasing problem for agriculture worldwide, but using stress-tolerant plants as green manure can improve marginal land. Here, we show that the legume Sesbania cannabina is very tolerant to alkaline conditions and, when used as a green manure, substantially improves alkaline soil. To understand genome evolution and the mechanisms of stress tolerance in this allotetraploid legume, we generated the first telomere-to-telomere genome assembly of S. cannabina spanning ∼2,087 Mb. The assembly included all centromeric regions, which contain centromeric satellite repeats, and complete chromosome ends with telomeric characteristics. Further genome analysis distinguished A and B subgenomes, which diverged approximately 7.9 million years ago. Comparative genomic analysis revealed that the chromosome homoeologs underwent large-scale inversion events (>10 Mb) and a significant, transposon-driven size expansion of the chromosome 5A homoeolog. We further identified four specific alkali-induced phosphate transporter genes in S. cannabina; these may function in alkali tolerance by relieving the deficiency in available phosphorus in alkaline soil. Our work highlights the significance of S. cannabina as a green tool to improve marginal lands and sheds light on subgenome evolution and adaptation to alkaline soils.

The BR signaling pathway regulates primary root development and drought stress response by suppressing the expression of PLT1 and PLT2 in Arabidopsis thaliana.

Introduction: With the warming global climate, drought stress has become an important abiotic stress factor limiting plant growth and crop yield. As the most rapidly drought-sensing organs of plants, roots undergo a series of changes to enhance their ability to absorb water, but the molecular mechanism is unclear. Results and methods: In this study, we found that PLT1 and PLT2, two important transcription factors of root development in Arabidopsis thaliana, are involved in the plant response to drought and are inhibited by BR signaling. PLT1- and PLT2-overexpressing plants showed greater drought tolerance than wild-type plants. Furthermore, we found that BZR1 could bind to the promoter of PLT1 and inhibit its transcriptional activity in vitro and in vivo. PLT1 and PLT2 were regulated by BR signaling in root development and PLT2 could partially rescue the drought sensitivity of bes1-D. In addition, RNA-seq data analysis showed that BR-regulated root genes and PLT1/2 target genes were also regulated by drought; for example, CIPK3, RCI2A, PCaP1, PIP1;5, ERF61 were downregulated by drought and PLT1/2 but upregulated by BR treatment; AAP4, WRKY60, and AT5G19970 were downregulated by PLT1/2 but upregulated by drought and BR treatment; and RGL2 was upregulated by drought and PLT1/2 but downregulated by BR treatment. Discussion: Our findings not only reveal the mechanism by which BR signaling coordinates root growth and drought tolerance by suppressing the expression of PLT1 and PLT2 but also elucidates the relationship between drought and root development. The current study thus provides an important theoretical basis for the improvement of crop yield under drought conditions.

11C, 12C and 13C-Cyanation of Electron-Rich Arenes via Organic Photoredox Catalysis.

As a non-invasive imaging technology, positron emission tomography (PET) plays a crucial role in personalized medicine, including early diagnosis, patient screening, and treatment monitoring. The advancement of PET research depends on the discovery of new PET agents, which requires the development of simple and efficient radiolabeling methods in many cases. As bioisosteres for halogen and carbonyl moieties, nitriles are important functional groups in pharmaceutical and agrochemical compounds. Here, we disclose a mild organophotoredox-catalyzed method for efficient cyanation of a broad spectrum of electron-rich arenes, including abundant and readily available veratroles and pyrogallol trimethyl ethers. Notably, the transformations not only are compatible with various affordable 12C and 13C-cyanide sources, but also could be applied to carbon-11 synthons to incorporate [11C]nitriles into arenes. The aryl [11C]nitriles can be further derivatized to [11C]carboxylic acids, [11C]amides, and [11C]alkyl amines. The newly developed reaction can serve as a powerful tool for generating new PET agents.

Development of [18F]F-5-OMe-Tryptophans through Photoredox Radiofluorination: A New Method to Access Tryptophan-Based PET Agents.

Although various radiolabeled tryptophan analogs have been developed to monitor tryptophan metabolism using positron emission tomography (PET) for various human diseases including melanoma and other cancers, their application can be limited due to the complicated synthesis process. In this study, we demonstrated that photoredox radiofluorination represents a simple method to access novel tryptophan-based PET agents. In brief, 4-F-5-OMe-tryptophans (l/d-T13) and 6-F-5-OMe-tryptophans (l/d-T18) were easily synthesized. The 18F-labeled analogs were produced by photoredox radiofluorination with radiochemical yields ranging from 2.6 ± 0.5% to 32.4 ± 4.1% (3 ≤ n ≤ 5, enantiomeric excess ≥ 99.0%) and over 98.0% radiochemical purity. Small animal imaging showed that l-[18F]T13 achieved 9.58 ± 0.26%ID/g tumor uptake and good contrast in B16F10 tumor-bearing mice (n = 3). Clearly, l-[18F]T13 exhibited prominent tumor uptake, warranting future evaluations of its potential usage in precise immunotherapy monitoring.

Bicyclol Alleviates Streptozotocin-induced Diabetic Cardiomyopathy By Inhibiting Chronic Inflammation And Oxidative Stress.

PURPOSE: Diabetic cardiomyopathy (DCM) is a common and severe complication of diabetes. Inflammation and oxidative stress play important roles in DCM development. Bicyclol is a hepatoprotective drug in China that exerts anti-inflammatory effects by inhibiting the MAPK and NF-κB pathways to prevent obesity-induced cardiomyopathy. Our purpose was to explore the effect and mechanism of bicyclol on DCM. METHODS: A type 1 diabetes mouse model was established using C57BL/6 mice by intraperitoneal injection of STZ. The therapeutic effect of bicyclol was evaluated in both heart tissues of diabetic mice and high concentration of glucose (HG)-stimulated H9c2 cells. RESULTS: We showed that bicyclol significantly attenuated diabetes-induced cardiac hypertrophy and fibrosis, which is accompanied by the preservation of cardiac function in mice. In addition, bicyclol exhibited anti-inflammatory and anti-oxidative effects both in vitro and in vivo. Furthermore, bicyclol inhibited the hyperglycemia-induced activation of MAPKs and NF-κB pathways, while upregulating the Nrf-2/HO-1 pathway to exhibit protective effects. CONCLUSION: Our data indicate that bicyclol could be a promising cardioprotective agent in the treatment of DCM.

Direct C-H Radiocyanation of Arenes via Organic Photoredox Catalysis.

Innovative labeling methods to incorporate the short-lived positron emitter carbon-11(11C) into bioactive molecules are attractive for positron emission tomography (PET) tracer discovery. Herein, we report a direct C-H radiocyanation method that incorporates [11C]cyanide (11CN-) to a series of functional electron-rich arenes via photoredox catalysis. This photoredox-mediated radiocyanation can proceed in an aerobic environment and is not moisture sensitive, which allows for ease of reaction setup and for scalable synthesis of 11C-aryl nitriles from readily available precursors.

ERECTA regulates seed size independently of its intracellular domain via MAPK-DA1-UBP15 signaling.

Seed size is determined by the coordinated growth of the embryo, endosperm, and integument. Growth of the integument is initiated by signal molecules released from the developing endosperm or embryo. Although recent studies have identified many components that regulate seed size by controlling integument growth, the upstream signals and the signal transduction pathway that activate these components after double fertilization are unclear. Here, we report that the receptor-like kinase ERECTA (ER) controls seed size by regulating outer integument cell proliferation in Arabidopsis thaliana. Seeds from er mutants were smaller, while those from ER-overexpressing plants were larger, than those of control plants. Different from its role in regulating the development of other organs, ER regulates seed size via a novel mechanism that is independent of its intracellular domain. Our genetic and biochemical data show that a MITOGEN-ACTIVATED PROTEIN KINASE (MAPK) signaling pathway comprising MAPK-KINASE 4/5, MAPK 3/6 (MPK3/6), DA1, and UBIQUITIN SPECIFIC PROTEASE 15 (UBP15) functions downstream of ER and modulates seed size. MPK3/6 phosphorylation inactivates and destabilizes DA1 to increase the abundance of UBP15, promoting outer integument cell proliferation and increasing seed size. Our study illustrates a nearly completed ER-mediated signaling pathway that regulates seed size and will help uncover the mechanism that coordinates embryo, endosperm, and integument growth after double fertilization.

The Synthesis and Initial Evaluation of MerTK Targeted PET Agents.

MerTK (Mer tyrosine kinase), a receptor tyrosine kinase, is ectopically or aberrantly expressed in numerous human hematologic and solid malignancies. Although a variety of MerTK targeting therapies are being developed to enhance outcomes for patients with various cancers, the sensitivity of tumors to MerTK suppression may not be uniform due to the heterogeneity of solid tumors and different tumor stages. In this report, we develop a series of radiolabeled agents as potential MerTK PET (positron emission tomography) agents. In our initial in vivo evaluation, [18F]-MerTK-6 showed prominent uptake rate (4.79 ± 0.24%ID/g) in B16F10 tumor-bearing mice. The tumor to muscle ratio reached 1.86 and 3.09 at 0.5 and 2 h post-injection, respectively. In summary, [18F]-MerTK-6 is a promising PET agent for MerTK imaging and is worth further evaluation in future studies.

Heat Shock-Induced Accumulation of the Glycogen Synthase Kinase 3-Like Kinase BRASSINOSTEROID INSENSITIVE 2 Promotes Early Flowering but Reduces Thermotolerance in Arabidopsis.

Brassinosteroids (BRs) are essential plant growth- and development-regulating phytohormones. When applied exogenously, BRs ameliorate heat shock (HS)-induced cell damage and enhance plant thermotolerance; however, the molecular mechanism by which BRs regulate plant thermotolerance is unknown. In this study, by analyzing the thermotolerance of a series of BR signaling mutants and plants that overexpressed different BR signaling components, we obtained comprehensive data showing that BRASSINOSTEROID INSENSITIVE 2 (BIN2) plays a major role in mediating the crosstalk between BR signaling and plant HS responses. By RNA-Seq, 608 HS- and BIN2-regulated genes were identified. An analysis of the 1-kb promoter sequences of these genes showed enrichment of an abscisic acid (ABA) INSENSITIVE 5 (ABI5)-binding cis-element. Physiological studies showed that thermotolerance was reduced in bin2-1 mutant and ABI5-OX plants but increased in the abi5 mutant, and that the abi5 mutation could recover the thermotolerance of bin2-1 plants to a wild-type level, suggesting that ABI5 functions downstream of BIN2 in regulating plant thermotolerance. Further, HS treatment increased the cellular abundance of BIN2. Both bin2-1 mutant and BIN2-OX plants showed early flowering, while the BIN2 loss-of-function mutant bin2-3 bil1 bil2 flowered late. Given these findings, we propose that under HS conditions plants increase BIN2 activity to promote early flowering and ensure species survival; however, this reduces the thermotolerance and survivability of individual plants partially by activating ABI5.

Potassium Iodide Nanoparticles Enhance Radiotherapy against Breast Cancer by Exploiting the Sodium-Iodide Symporter.

Iodine has shown promise in enhancing radiotherapy. However, conventional iodine compounds show fast clearance and low retention inside cancer cells, limiting their application as a radiosensitizer. Herein, we synthesize poly(maleic anhydride-alt-1-octadecene) coated KI nanoparticles (PMAO-KI NPs) and evaluate their potential for enhancing radiotherapy. Owing to the polymer coating, the KI core of PMAO-KI NPs is not instantly dissolved in aqueous solutions but slowly degraded, allowing for controlled release of iodide (I-). I- is transported into cells via the sodium iodide symporter (NIS), which is upregulated in breast cancer cells. Our results show that PMAO-KI NPs can enhance radiation-induced production of reactive oxygen species such as hydroxyl radicals. When tested in vitro with MCF-7 cells, PMAO-KI NPs promote radiation-induced DNA double-strand breaks and lipid peroxidation, causing a drop in cancer cell viability and reproductivity. When tested in MCF-7 bearing mice, PMAO-KI NPs show significant radiosensitizing effects, leading to complete tumor eradication in 80% of the treated animals without inducing additional toxicity. Overall, our strategy exploits electrolyte nanoparticles to deliver iodide into cancer cells through NIS, thus promoting radiotherapy against breast cancer.

Development of Novel 18F-PET Agents for Tumor Hypoxia Imaging.

Tumor hypoxia is a major factor responsible for tumor progression, metastasis, invasion, and treatment resistance, leading to low local tumor control and recurrence after radiotherapy in cancers. Here,18F-positron emission tomography (PET) probes are developed for visualizing viable hypoxic cells in biopsies. Pimonidazole derivatives and nitroimidazole-based agents bearing sulfonyl linkers were evaluated. A small-animal PET study showed that the tumor uptake of [18F]-23 [poly(ethylene glycols) (PEG)-sulfonyl linker] of 3.36 ± 0.29%ID/g was significantly higher (P < 0.01) than that of [18F]-20 (piperazine-linker tracer, 2.55 ± 0.49%ID/g) at 2 h postinjection in UPPL tumors. The tumor-to-muscle uptake ratio of [18F]-23 (2.46 ± 0.48 at 2 h pi) was well improved compared with that of [18F]-FMISO (1.25 ± 0.14 at 2 h pi). A comparable distribution pattern was observed between ex vivo autoradiography of [18F]-23 and pimonidazole staining of the neighboring slice, indicating that [18F]-23 is a promising PET agent for hypoxia imaging.

Enantioselective Sensing in the Fluorous Phase for Catalyst Screening: Application of a Racemic Fluorescent Probe.

A perfluoroalkyl ketone-based molecular probe was found to show highly enantioselective fluorescent enhancement in the fluorous phase when treated with an amino alcohol generated from the asymmetric reaction of a meso-epoxide with an alkyl amine. The two enantiomeric probes (R)- and (S)-2 were used to screen catalysts for this asymmetric reaction. The use of the probe in the fluorous phase allowed the fluorescent sensing of the products to be conducted away from the other reaction components with minimized interference. It was further found that when (R)- or (S)-2 was used to determine the enantiomeric composition of the amino alcohol product, there was a large nonlinear effect. That is, only when one enantiomer of the substrate was in excess was there a large fluorescence enhancement for the chirality-matched probe-substrate interaction. This allowed the racemic probe rac-2 to be used to evaluate the asymmetric induction in the catalyst screening. The catalyst screening using the fluorescent probes led to the discovery of a more enantioselective and efficient method for the desymmetrization of 1,2-epoxycyclohexane with iPrNH2 to form the corresponding chiral amino alcohol. This work presents a novel method to conduct catalyst screening for asymmetric synthesis and has potential to become a high-throughput process.

Design and synthesis of sinomenine isoxazole derivatives via 1,3-dipolar cycloaddition reaction.

A novel structure of sinomenine isoxazole derivatives is synthesised from sinomenine hydrochloride and aromatic aldehydes and requires six steps. 19 target compounds have been obtained in good yields. The sinomenine hydrochloride transforms to 4-alkynyl sinomenine, which is a key intermediate product to synthesise the target sinomenine isoxazole compounds, after a neutralisation reaction with ammonia and substitution reaction with 3-chloropropyne. Another key intermediate product is 1,3-dipole, which can be obtained from aromatic aldehyde. After treatment with hydroxylamine hydrochloride and then sodium carbonate solution, aromatic aldehyde is converted to aldehyde oxime, which reacts with N-chlorosuccinimide (NCS) to afford aryl hydroximino chloride. 1,3-Dipole is eventually formed in situ while triethylamine (TEA) in DMF is added dropwise. Then 4-alkynyl sinomenine is added to provide the sinomenine isoxazole derivative via 1,3-dipolar cycloaddition reaction as the key step. All the target compounds are characterised by melting point, 1H NMR, 13C NMR, HRMS and FT-IR spectroscopy.

Determining the concentration and enantiomeric composition of histidine using one fluorescent probe.

A chemoselective as well as enantioselective fluorescent probe has been developed to determine both the concentration and enantiomeric composition of the biologically important amino acid histidine by measuring the fluorescence responses when excited at two different wavelengths.

A near-IR Fluorescent Probe for Enantioselective Recognition of Amino Acids in Aqueous Solution.

A novel BINOL-based near-IR fluorescent probe was designed and synthesized by incorporating a rhodamine-like dye. In the presence of Zn(II), this compound was found to exhibit highly enantioselective fluorescence enhancement at λemi > 730 nm and λexc = 690 nm when treated with 14 common amino acids in aqueous solution. An enantioselective fluorescence enhancement ratio up to 163 was observed. The mechanism of the fluorescence response of this probe was investigated by various spectroscopic methods.

Mechanistic Study on a BINOL-Coumarin-Based Probe for Enantioselective Fluorescent Recognition of Amino Acids.

A detailed investigation was conducted on the reaction of a 1,1'-bi-2-naphthol-coumarin-based fluorescent probe with amino acids. On the basis of the studies, including fluorescence spectroscopy, 1H NMR, UV-vis, mass spectroscopy, single-crystal X-ray analysis, and molecular modeling, it was found that the distinctively different fluorescent responses of the probe toward the amino acid at the two excitation wavelengths are due to two different reaction pathways that generate different intermediates and products.

Sulfonation of 3,3'-Diformyl-BINOL for Enantioselective Fluorescent Recognition of Amino Acids in Water.

Reaction of (R)-3,3'-diformyl-1,1'-bi-2-naphthol with concentrated sulfuric acid gives the corresponding 6,6'-disulfonated compound (R)-2 selectively. This provides a simple and efficient method to convert a water-insoluble compound to a water-soluble fluorescent probe. It is found that (R)-2 in combination with Zn2+ shows a highly enantioselective fluorescent response toward various amino acids in the aqueous HEPES buffer solution at pH 7.4. For example, an enantioselective fluorescence enhancement ratio [ef=ΔID /ΔIL ] up to 35.8 is observed for the recognition of asparagine. NMR and mass spectroscopic investigations are conducted to explore the reaction of (R)-2 with asparagine.

Excitation of One Fluorescent Probe at Two Different Wavelengths to Determine the Concentration and Enantiomeric Composition of Amino Acids.

When a novel fluorescent probe made of BINOL and coumarin is excited at λ1 = 365 nm in a neutral buffer solution, it shows fluorescence enhancement at 465 nm in the presence of an amino acid with a very small difference between the two enantiomers. When excited at λ2 = 467 nm, it shows highly enantioselective fluorescence enhancement at 534 nm. This allows the determination of both concentration and enantiomeric composition of amino acids.