A fluorescent probe for selective detection of boric acids and its application for screening the conversion of the Suzuki-Miyaura coupling reaction.

Boric acid (B(OH)3) plays an important physiological role and is widely used as a food preservative and an antiseptic. Various colorimetric, fluorescent probes have been developed to detect boric acid; however, most of them could not discriminate boric acid over boronic acids (R-B(OH)2) or are limited to boronic acid sensors. Therefore, the development of boric acid-selective probes is necessary. Herein, a salicylimine-based fluorophore, Di-OH, was designed that showed selective fluorescence response to boric acid over boronic acid. Its fluorescence response to boric acid showed a large fluorescence turn-on signal up to 140 fold and excellent selectivity with various analytes. Furthermore, since boric acid is generated in proportion to the consumed boronic acid derivatives during reactions involving oraganoboron compounds, Di-OH allowed the determination of the conversion of the Suzuki-Miyaura coupling reaction using fluorescence spectroscopy and its correlation with the GC conversion was confirmed.

Turn-On Fluorescent pH Probes for Monitoring Alkaline pHs Using Bis[2-(2'-hydroxyphenyl)benzazole] Derivatives.

For surveilling human health, industries, and the environment, pH monitoring is important. Numerous studies on fluorescent probes have been conducted to monitor various pH ranges. However, fluorescent probes that are capable of sensing alkaline regions are rare. In this study, we propose turn-on-type fluorescent probes for detecting alkaline pHs using bis[2-(2'-hydroxyphenyl)benzazole] (bis(HBX)) derivatives. These probes have high pKa values (from 9.7 to 10.8) and exhibit strong fluorescence intensity and color changes at alkaline pHs. Probes derived from bis(HBX) exhibit good photostability, reversibility, and anti-interference toward pH variations, which can be identified as a certain fluorescence change toward a basic pH. Therefore, compounds would be advantageous to use fluorescent probes for monitoring alkaline pH changes.

Ratiometric Strategy Based on Intramolecular Internal Standard for Reproducible and Simultaneous Fingerprint Recognition of Diols via 19F NMR Spectroscopy.

19F NMR spectroscopy has been widely used as a convenient and noninvasive analytical technique for understanding complex natural phenomena at the atomic level. However, current NMR referencing techniques are most optimized for 1H NMR, which causes some limitations while referencing heteronuclear NMR. Despite its promising advantages, 19F NMR spectroscopy often exhibits large variations in experimental results and lacks consistency compared with 1H NMR. Herein, we propose a new strategy to improve the consistency of 19F NMR referencing using an internal standard method. As a proof-of-concept, BA-Py-TFP was applied as a sensor for diols via 19F NMR spectroscopy. This strategy proved to be a robust and reproducible referencing method with acceptable deviation (ΔδF = 43-58 ppb) across diverse NMR spectrometers at different institutions. In particular, this new strategy allows reliable fingerprint recognition for analytes and enables qualitative and quantitative analyses of mixtures of multiple analytes simultaneously. The high recovery rates for d-glucose in the human serum matrix suggest its potential suitability for a diverse range of applications, such as in diabetes-related diagnostics.

Metal-Free, Rapid, and Highly Chemoselective Reduction of Aromatic Nitro Compounds at Room Temperature.

In this study, we developed a metal-free and highly chemoselective method for the reduction of aromatic nitro compounds. This reduction was performed using tetrahydroxydiboron [B2(OH)4] as the reductant and 4,4'-bipyridine as the organocatalyst and could be completed within 5 min at room temperature. Under optimal conditions, nitroarenes with sensitive functional groups, such as vinyl, ethynyl, carbonyl, and halogen, were converted into the corresponding anilines with excellent selectivity while avoiding the undesirable reduction of the sensitive functional groups.

Investigation of a benzodiazaborine library to identify new pH-responsive fluorophores.

The detection of pH is important owing to its significance in various processes, such as clinical and industrial processes. Numerous fluorescent pH probes have been developed using a variety of fluorophores; however, most are only suitable for application in a narrow pH range (between 5 and 8) owing to the lack of diversity of the pH-sensitive units. Furthermore, probes suitable for sensing high pHs have rarely been studied despite the importance of reliable detection of high pH in various industrial processes. In this study, we prepared a benzodiazaborine (bDAB) library consisting of 238 different bDABs through combinatorial synthesis to investigate their suitability as fluorescent pH probes. Informed by the results of a fluorescence-based, high-throughput screening of the library, we identified four bDABs that exhibit promising pH-sensitive ratiometric fluorescence responses. Their pKas vary significantly, ranging from 7.29 to 12.44, indicating their suitability for the detection of basic pHs even in extremely basic environments (pH > 10). Furthermore, their fluorescence responses show high stability, anti-interference, and reversibility under various pH conditions.

Hypoxia-inducible factor 2α is a novel inhibitor of chondrocyte maturation.

Hypoxic environment is essential for chondrocyte maturation and longitudinal bone growth. Although hypoxia-inducible factor 1 alpha (Hif-1α) has been known as a key player for chondrocyte survival and function, the function of Hif-2α in cartilage is mechanistically and clinically relevant but remains unknown. Here we demonstrated that Hif-2α was a novel inhibitor of chondrocyte maturation through downregulation of Runx2 stability. Mechanistically, Hif-2α binding to Runx2 inhibited chondrocyte maturation by Runx2 degradation through disrupting Runx2/Cbfß complex formation. The Hif-2α-mediated-Runx2 degradation could be rescued by Cbfß transfection due to the increase of Runx2/Cbfß complex formation. Consistently, mesenchymal cells derived from Hif-2α heterozygous mice were more rapidly differentiated into hypertrophic chondrocytes than those of wild-type mice in a micromass culture system. Collectively, these findings demonstrate that Hif-2α is a novel inhibitor for chondrocyte maturation by disrupting Runx2/Cbfß complex formation and consequential regulatory activity.

Colorimetric discrimination of nucleoside phosphates based on catalytic signal amplification strategy and its application to related enzyme assays.

Selective detection of adenosine monophosphate (AMP) and adenosine diphosphate (ADP) which are less charged molecules than adenosine triphosphate (ATP) or pyrophosphate (PPi) in aqueous solution has been considered challenging because AMP and ADP have relatively low binding affinity for phosphate receptors. In this study, colorimetric discrimination of nucleoside phosphates was achieved based on catalytic signal amplification through the activation of artificial peroxidase. This method showed high selectivity for AMP and ADP over ATP and PPi, unlike previous phosphate sensors that use Zn2+-dipicolylamine-based receptors. High selectivity of the suggested method allowed discrimination of AMP in aqueous solution by the naked eye, and the detection limit was estimated to be 0.5 µM. Mechanism analysis revealed AMP acted as activators in the peroxidation cycle of the Mn2(bpmp)/ABTS/H2O2 system despite having relatively low binding affinity. Additionally, high selectivity and quantitative signal amplification allowed for the development of colorimetric phosphodiesterase and a small molecule kinase assay method. The newly proposed method offers direct, real-time, and quantitative analysis of enzyme activities and inhibition, and is expected to be further applied to high-throughput screening of inhibitors.

Ligand-free Suzuki-Miyaura cross-coupling with low Pd content: rapid development by a fluorescence-based high-throughput screening method.

Suzuki-Miyaura (SM) cross-coupling is one of the most effective strategies for carbon-carbon bond formation, but previous methods have several drawbacks, such as the requirement of complicated ligands, toxic organic solvents, and high-content-Pd catalysts. Thus, in this study, a highly efficient SM cross-coupling was developed using metal oxide catalysts: 0.02 mol% Pd, aqueous solvent, no ligand, and room temperature. Metal oxides containing low Pd content (ppm scale) were prepared by a simple co-precipitation method and used as a catalyst for the SM reaction. A fluorescence-based high-throughput screening (HTS) method was developed for the rapid evaluation of catalytic activity and reaction conditions. Among the various metal oxides, Pd/Fe2O3 showed the highest activity for the SM reaction. After further optimization by HTS, various biaryl compounds were obtained under optimal conditions: Pd/Fe2O3 (0.02 mol% Pd) in aqueous ethanol at mild temperature without any ligands.

Photocatalytic carbocarboxylation of styrenes with CO2 for the synthesis of γ-aminobutyric esters.

Metal-free photoredox-catalyzed carbocarboxylation of various styrenes with carbon dioxide (CO2) and amines to obtain γ-aminobutyric ester derivatives has been developed (up to 91% yield, 36 examples). The radical anion of (2,3,4,6)-3-benzyl-2,4,5,6-tetra(9H-carbazol-9-yl)benzonitrile (4CzBnBN) possessing a high reduction potential (-1.72 V vs. saturated calomel electrode (SCE)) easily reduces both electron-donating and electron-withdrawing group-substituted styrenes.

Antifibrosis treatment by inhibition of VEGF, FGF, and PDGF receptors improves bladder wall remodeling and detrusor overactivity in association with modulation of C-fiber afferent activity in mice with spinal cord injury.

AIMS: Spinal cord injury (SCI) above the sacral level causes bladder dysfunction and remodeling with fibrosis. This study examined the antifibrotic effects using nintedanib, an inhibitor of vascular endothelial growth factor, fibroblast growth factor, and platelet-derived growth factor receptors, on detrusor overactivity (DO) and bladder fibrosis, as well as the modulation mechanisms of C-fiber afferent pathways. METHODS: Thirty female C57BL/6 mice were divided into group A (spinal intact), group B (SCI with vehicle), and group C (SCI with nintedanib). At 2 weeks after SCI, vehicle or 50 mg/kg nintedanib was administered subcutaneously for 2 weeks. Then, cystometry was conducted, followed by RT-PCR measurements of fibrosis-related molecules, muscarinic, ß-adrenergic, TRP and purinergic receptors in the bladder or L6-S1 dorsal root ganglia (DRG). Trichrome stain and Western blot analysis of transforming growth factor-beta and fibronectin were performed in the bladder. TRPV1 expression in L6 DRG was measured by immunohistochemistry. RESULTS: In cystometry, intercontraction intervals, nonvoiding contractions, voided volume, and voiding efficiency were significantly improved in group C versus group B. RT-PCR, Western blotting, and trichrome staining revealed the fibrotic changes in the bladder of group B, which was improved in group C. Increased messenger RNA levels of TRPV1, TRPA1, P2X2 , and P2X3 in DRG of group B were significantly decreased in group C. TRPV1 immunoreactivity in DRG was increased in group B, but decreased in group C. CONCLUSIONS: Nintedanib improves storage and voiding dysfunctions and bladder fibrosis in SCI mice. Also, nintedanib-induced improvement of DO is associated with reduced expression of C-fiber afferent markers, suggesting the modulation of bladder C-fiber afferent activity.

Transition-Metal-Free Borylation of Aryl Bromide Using a Simple Diboron Source.

In this study, we developed a simple transition-metal-free borylation reaction of aryl bromides. Bis-boronic acid (BBA), was used, and the borylation reaction was performed using a simple procedure at a mild temperature. Under mild conditions, aryl bromides were converted to arylboronic acids directly without any deprotection steps and purified by conversion to trifluoroborate salts. The functional group tolerance was considerably high. The mechanism study suggested that this borylation reaction proceeds via a radical pathway.

Enantioselective Alkynylation of Trifluoromethyl Ketones Catalyzed by Cation-Binding Salen Nickel Complexes.

Cation-binding salen nickel catalysts were developed for the enantioselective alkynylation of trifluoromethyl ketones in high yield (up to 99 %) and high enantioselectivity (up to 97 % ee). The reaction proceeds with substoichiometric quantities of base (10-20 mol % KOt-Bu) and open to air. In the case of trifluoromethyl vinyl ketones, excellent chemo-selectivity was observed, generating 1,2-addition products exclusively over 1,4-addition products. UV-vis analysis revealed the pendant oligo-ether group of the catalyst strongly binds to the potassium cation (K+ ) with 1:1 binding stoichiometry (Ka =6.6×105 m-1 ).

Co-functionalization with phosphate and carboxylate on polydiacetylene for colorimetric detection of calcium ions in serum.

In this study, co-functionalization with phosphate and carboxylate on polydiacetylene (PDA) was proposed to detect calcium ions in serum, inspired by biologically abundant phosphate-calcium ion and carboxylate-calcium ion binding. The cooperative interaction of calcium ions with phosphate and carboxylate in PDA induced the change of electronic properties in the backbone without aggregation of liposomes, accompanied by blue-to-purple color transition. The cooperative effect through the introduction of mixed ligands facilitated the selective detection of calcium ions over magnesium ions, which was a source of major interference in many calcium ion probes, and in the presence of major serum metal ions. The sensor system exhibited highly sensitive detection of calcium ions with an estimated limit of detection of 0.97 µM. In addition, the detection method was employed to determine the concentration of calcium ions in various serums.

Cavitation Damage Characteristics of Shot Peened ALBC3 Alloy.

Copper alloys have widely used for marine plants, ship building equipment, and renewable energy facilities under marine environment due to its excellent castability, durability, and corrosion resistance. In this study, the surface of ALBC3 alloy was modified with shot peening time to improve the strength and cavitation characteristics. For evaluation of cavitation resistance, cavitation experiments for the non-shot peened and shot-peened specimens were performed to investigate the extent of damage and determine the weight loss. As a result, the shot peened ALBC3 alloys improved cavitation resistance. In particular, the shot peening time of 3.5 min was considered to be the optimum shot peening condition since it presented an improvement of 35.7% in cavitation resistance.

Development of a Simple Assay Method for Adenosine Deaminase via Enzymatic Formation of an Inosine-Tb3+ Complex.

Adenosine deaminase (ADA), which catalyzes the irreversible deamination of adenosine to inosine, is related to various human diseases such as tuberculous peritonitis and leukemia. Therefore, the method used to detect ADA activity and screen the effectiveness of various inhibitor candidates has important implications for the diagnosis treatment for various human diseases. A simple and rapid assay method for ADA, based on the enzymatic formation of a luminescent lanthanide complex, is proposed in this study. Inosine, an enzymatic product of ADA with stronger sensitization efficiency for Tb3+ than adenosine, produced a strong luminescence by forming an inosine-Tb3+ complex, and it enabled the direct monitoring of ADA activity in real-time. By introducing only Tb3+ to adenosine and ADA in the buffer, the enhancement of luminescence enabled the detection of a low concentration of ADA (detection limit 1.6 U/L). Moreover, this method could accurately determine the inhibition efficiency (IC50) of the known ADA inhibitor, erhythro-9-(2-hydroxy-3-nonyl)adenine (EHNA), and the inhibition of ADA could be confirmed by the naked eye. Considering its simplicity, this assay could be extended to the high-throughput screening of various ADA inhibitor candidates.

Development of Human Serum Albumin Selective Fluorescent Probe Using Thieno[3,2-b]pyridine-5(4H)-one Fluorophore Derivatives.

The level of human serum albumin (HSA) in biological fluids is a key health indicator and its quantitative determination has great clinical importance. In this study, we developed a selective and sensitive fluorescent HSA probe by fluorescence-based high-throughput screening of a set of fluorescent thieno[3,2-b]pyridine-5(4H)-one derivatives against major plasma proteins: HSA, bovine serum albumin (BSA), globulin, fibrinogen, and transferrin. The fluorophore chosen finally (4) showed noticeable fluorescence enhancement in the presence of HSA (160-fold increase), and it exhibited rapid response, high sensitivity (detection limit 8 nM), and the ability to clearly distinguish HSA from BSA in pH 9 buffer condition. Moreover, the probe could be applicable to detect trace amounts of HSA in an artificial urine sample; further, it might be applied to the determination of the HSA concentration in complex biological samples for pre-clinical diagnosis.

A colorimetric chemosensor for heptanal with selectivity over formaldehyde and acetaldehyde through synergistic interaction of hydrophobic interactions and oxime formation.

Aldehydes with long alkyl chains are important biomarkers, but chemosensors for the detection of the aldehydes have been rarely reported. Herein, a chemosensor based on hydroxylamine-functionalized polydiacetylene (PDA) was developed for the selective detection of heptanal, which contains a long alkyl chain. The hydroxylamine group of PDA reacts with the aldehyde group of heptanal, while hydrophobic interactions between the alkyl chains of PDA and heptanal occur simultaneously. As a result, synergistic interactions with the aldehyde group and alkyl chain on heptanal allowed for the selective detection of heptanal over formaldehyde and acetaldehyde, which do not contain long alkyl chains. The consequent perturbation of the backbone by the synergistic interactions induced a blue-to-purple color transition, allowing for colorimetric detection by the naked eye. The chemosensor had an estimated detection limit of 4.8 µM. In addition, the sensor system was applied to determine heptanal concentrations in serum samples.

An [Mn2(bpmp)]3+ complex as an artificial peroxidase and its applications in colorimetric pyrophosphate sensing and cascade-type pyrophosphatase assay.

The development of artificial peroxidases has attracted great interest because of their applications in various fields such as the chemical industry and biosensing. In this study, 2,6-bis[(bis(2-pyridylmethyl)amino)-methyl]-4-methylphenol (H-bpmp) complexes with various transition metal ions have been investigated as artificial peroxidases. Among these metal complexes, the [Mn2(bpmp)]3+ complex showed the highest peroxidase-like activity as determined by a colorimetric assay using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) and H2O2. The peroxidase-like activity was inhibited by pyrophosphate (PPi), which blocked the active site of the [Mn2(bpmp)]3+ complex. Based on this phenomenon, the ABTS/H2O2/[Mn2(bpmp)]3+ system could be applied for the detection of PPi, which could be achieved selectively by visual observation with a detection limit of 130 nM. Moreover, the addition of pyrophosphatase (PPase) to the [Mn2(bpmp)]3+ complex blocked by PPi resulted in the recovery of the peroxidase-like activity of the [Mn2(bpmp)]3+ complex due to the hydrolysis of PPi. Hence, the enzyme cascade reaction of the PPase and [Mn2(bpmp)]3+ complex allowed the real-time colorimetric assay of PPase.

Paper-Based Colorimetric Sensor System for High-Throughput Screening of C-H Borylation.

A paper-based colorimetric sensor system (PBCSS) was developed to detect the amount of bis(pinacolato)diboron (B2 Pin2 ) and applied as a high-throughput screening protocol in Ir-catalyzed C-H borylation. First, 96 ligands were screened for the borylation of benzene, and then 12 of them were selected and tested for five substrates. These reaction mixtures were spotted in the PBCSS, showing a blue-violet color. The value of the gray scale of each reaction was obtained from these colored spots and converted to the extent of conversion of B2 Pin2 . The extents of conversion of B2 Pin2 obtained from the PBCSS showed good correlation with those obtained from gas chromatography analysis. In addition, the modified conversion using blank data showed good correlation with the yield of products.

Core Binding Factor ß Plays a Critical Role During Chondrocyte Differentiation.

Core binding factor ß (Cbfß) is a partner protein of Runx family transcription factors with minimally characterized function in cartilage. Here we address the role of Cbfß in cartilage by generating chondrocyte-specific Cbfß-deficient mice (Cbfb(Δch/Δch) ) from Cbfb-floxed mice crossed with mice expressing Cre from the Col2a1 promoter. Cbfb(Δch/Δch) mice died soon after birth and exhibited delayed endochondral bone formation, shorter appendicular skeleton length with increased proliferative chondrocytes, and nearly absent hypertrophic chondrocyte zones. Immunohistochemical and quantitative real-time PCR analyses showed that the number and size of proliferative chondrocytes increased and the expression of chondrocyte maturation markers at the growth plates, including Runx2, osterix, and osteopontin, significantly diminished in Cbfb(Δch/Δch) mice compared to wild type mice. With regard to signaling pathways, both PTHrP-Ihh and BMP signaling were compromised in Cbfb(Δch/Δch) mice. Mechanistically, Cbfß deficiency in chondrocytes caused a decrease of protein levels of Runx transcription factors by accelerating polyubiquitination-mediated proteosomal degradation in vitro. Indeed, Runx2 and Runx3, but not Runx1, decreased in Cbfb(Δch/Δch) mice. Collectively, these findings indicate that Cbfß plays a critical role for chondrocyte differentiation through stabilizing Runx2 and Runx3 proteins in cartilage.