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.

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.

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 ).

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.

A direct assay of butyrylcholinesterase activity using a fluorescent substrate.

In this study, we report a direct fluorometric assay for butyrylcholinesterase (BChE) activity and screening of its inhibitor, using a fluorescent substrate. 2-(2-(5,6-Dimethoxy-1,3-dioxoisoindolin-2-yl)acetoxy)-N,N,N-trimethylethan-1-ammonium iodide (1) was hydrolyzed by BChE, and its fluorescence was quenched by an intramolecular photoinduced electron transfer process. The resulting change in fluorescence provided a facile method for real-time BChE activity testing. Remarkably, 1 was selectively hydrolyzed by BChE, even in the presence of excess acetylcholinesterase, thereby facilitating the specific monitoring of BChE activity. This assay method is also useful for screening potential BChE inhibitors. Given its simplicity, selectivity, and higher assay speed, this method may be extended to high-throughput screening of BChE inhibitors and relevant drug discovery.

Analysis of the effect of inert gas on alveolar/venous blood partial pressure by using the operator splitting method.

This study aims to investigate how inert gas affects the partial pressure of alveolar and venous blood using a fast and accurate operator splitting method (OSM). Unlike previous complex methods, such as the finite element method (FEM), OSM effectively separates governing equations into smaller sub-problems, facilitating a better understanding of inert gas transport and exchange between blood capillaries and surrounding tissue. The governing equations were discretized with a fully implicit finite difference method (FDM), which enables the use of larger time steps. The model employed partial differential equations, considering convection-diffusion in blood and only diffusion in tissue. The study explores the impact of initial arterial pressure, breathing frequency, blood flow velocity, solubility, and diffusivity on the partial pressure of inert gas in blood and tissue. Additionally, the effects of anesthetic inert gas and oxygen on venous blood partial pressure were analyzed. Simulation results demonstrate that the high solubility and diffusivity of anesthetic inert gas lead to its prolonged presence in blood and tissue, resulting in lower partial pressure in venous blood. These findings enhance our understanding of inert gas interaction with alveolar/venous blood, with potential implications for medical diagnostics and therapies.

High-Throughput Approach for Facile Access to Hetero-Dinuclear Synergistic Metal Complex for H2O2 Activation and Its Implications.

Hetero-dinuclear synergic catalysis is a promising approach for improving catalytic performance. However, employing it is challenging because the design principles for the metal complex are still not well understood. Further, these complexes have a broader set of possibilities than mononuclear or homometallic systems, increasing the time and effort required to understand them. In this study, we explored a high-throughput approach to obtain a new hetero-dinuclear synergistic metal complex for H2O2 activation. From the 1152 combinations of metal complex candidates obtained by changing three variables (metal ions, unsymmetrical dinucleating ligands, and pH), the lead complex (L3-(Ni, Co)), which has the highest peroxidase activity, was derived using colorimetric parallel analysis. A series of control experiments revealed that L3 plays a crucial role in the formation of active L3-(Ni, Co) complexes, Co2+ acts as a catalytic center, and Ni2+ serves as an assistant catalytic site within L3-(Ni, Co). In addition, the catalytic efficiency of L3-(Ni, Co), which was 125 times that of the homo-bimetallic complex (L3-(Co, Co)), revealed clear hetero-bimetallic synergism in the buffer. The ultraviolet-visible study and electron paramagnetic resonance-based spin-trap experiment provided mechanistic insight into H2O2 activation by the intermediate, which was found to be induced by the reaction of L3-(Ni, Co) and H2O2. Moreover, the intermediate could act as a donor of the hydroperoxyl radical (•OOH) in the buffer. Furthermore, L3-(Ni, Co) demonstrated potential for application as a signal transducer for H2O2 in an enzyme-coupled cascade assay that can be used for the colorimetric detection of glucose.