Fluorescence quenching detection of peanut agglutinin based on photoluminescent silole-core carbosilane dendrimer peripherally functionalized with lactose

A glycocluster peripherally functionalized with a lactose (Lac: Galβ1→4Glcβ1–) derivative possessing a silole moiety as a luminophore was synthesized. The photoluminescence spectrum of the glycocluster showed extremely strong emission at 474 nm and the absolute quantum yield was estimated to be 92% in distilled water. The emission intensity was decreased by increasing the amount of peanut agglutinin (PNA), a lactose-binding lectin, and plots of the relative fluorescence intensity revealed a decline of 95% in emission intensity. Fluorescence quenching of the glycocluster upon mixing with PNA could be easily observed by the naked eye under UV irradiation, whereas no distinct change in fluorescence properties of the glycocluster was observed when wheat germ agglutinin (WGA) was employed.     

Enzyme‐Free Quinone Crosslinking Reaction for Proteins: A Macromolecular Characterization Study Using Gelatin

To mimic the quinone hardening of extracellular proteins in invertebrates, we investigated an enzyme‐free crosslinking of gelatin by HQ in a neutral aqueous phase. The mixture was rapidly transformed to a yellowish brown, thermally and mechanically stable hydrogel in the presence of a simple copper(II) salt. A dehydrated thin film made of the mixture was flexible, tough, and showed a large ultimate breaking force. Physicochemical examination of the gel suggested that the basic amino acid residues (lysine, hydroxylysine, and histidine) of the protein were modified by the quinone ring to form 2–6 crosslinks per protein. The enzyme‐free crosslinking reaction is discussed with consideration of a copper(II) ion‐catalyzed oxidation of HQ and the hydroquinone/protein adducts.

     

β-Galactosidase fluorescence probe with improved cellular accumulation based on a spirocyclized rhodol scaffold

We identified a rhodol bearing a hydroxymethyl group (HMDER) as a suitable scaffold for designing fluorescence probes for various hydrolases. HMDER shows strong fluorescence at physiological pH, but phenolic O-alkylation of HMDER results in a strong preference for the spirocyclic form, which has weak fluorescence. As a proof of concept, we utilized this finding to develop a new fluorescence probe for β-galactosidase. This probe has favorable characteristics for imaging in biological samples: it has good cellular permeability, and its hydrolysis product is well-retained intracellularly. It could rapidly and clearly visualize β-galactosidase activity in cultured cells and in Drosophila melanogaster tissue, which has rarely been achieved with previously reported fluorescence probes.     

Development of an Si-rhodamine-based far-red to near-infrared fluorescence probe selective for hypochlorous acid and its applications for biological imaging

A far-red to near-infrared (NIR) fluorescence probe, MMSiR, based on Si-rhodamine, was designed and synthesized for sensitive and selective detection of HOCl in real time. MMSiR and its oxidized product SMSiR have excellent properties, including pH-independence of fluorescence, high resistance to autoxidation and photobleaching, and good tissue penetration of far-red to NIR fluorescence emission. The value of MMSiR was confirmed by real-time imaging of phagocytosis using a fluorescence microscope. wsMMSiR, a more hydrophilic derivative of MMSiR, permitted effective in vivo imaging of HOCl generation in a mouse peritonitis model. This probe is expected to be a useful tool for investigating the wide range of biological functions of HOCl.     

Molecular dynamics simulations of nucleation from vapor to solid composed of Lennard-Jones molecules

We performed molecular dynamics (MD) simulations of nucleation from vapor at temperatures below the triple point for systems consisting of 10(4)-10(5) Lennard-Jones (L-J) type molecules in order to test nucleation theories at relatively low temperatures. Simulations are performed for a wide range of initial supersaturation ratio (S(0) ? 10-10(8)) and temperature (kT = 0.2-0.6ε), where ε and k are the depth of the L-J potential and the Boltzmann constant, respectively. Clusters are nucleated as supercooled liquid droplets because of their small size. Crystallization of the supercooled liquid nuclei is observed after their growth slows. The classical nucleation theory (CNT) significantly underestimates the nucleation rates (or the number density of critical clusters) in the low-T region. The semi-phenomenological (SP) model, which corrects the CNT prediction of the formation energy of clusters using the second virial coefficient of a vapor, reproduces the nucleation rate and the cluster size distributions with good accuracy in the low-T region, as well as in the higher-T cases considered in our previous study. The sticking probability of vapor molecules onto the clusters is also obtained in the present MD simulations. Using the obtained values of sticking probability in the SP model, we can further refine the accuracy of the SP model.     

Simple method for preparing superhydrophobic paper: spray-deposited hydrophobic silica nanoparticle coatings exhibit high water-repellency and transparency

Superhydrophobic and transparent coatings are deposited onto paper by spraying alcohol suspensions of SiO(2) nanoparticles. Superhydrophobicity depends on the aggregation states of nanoparticles, which are determined by the type of alcohol used in the suspensions. The superhydrophobicity of the paper is maintained after touching the paper with a bare finger.     

A practical strategy to create near-infrared luminescent probes: conversion from fluorescein-based sensors

Luminescent lanthanide complexes incorporating Yb(3+) and Nd(3+) are attracting much attention as imaging agents, but there have been few practical methods to make responsive sensors with these complexes. Here, we introduce a general strategy to synthesize near-infrared luminescent probes by conjugating a Yb(3+) chelate to established fluorescein-based probes. As the first demonstration, we present a complex, based on the green-emitting probe DAF-4, that responds to nitric oxide (NO) in aqueous solution with a significant increase in luminescence intensity at 980 nm.     

A long-lived luminescent probe to sensitively detect arylamine N-acetyltransferase (NAT) activity of cells

Arylamine N-acetyltransferase (NAT) is an important phase II metabolizing enzyme that influences drug efficacy and adverse effects. Here, we report a long-lived luminescent lanthanide complex as a probe for NAT, employing an intraligand photoinduced electron transfer strategy. The probe shows approximately 100-fold increase of luminescence upon N-acetylation catalyzed by NAT, with relatively high specificity for NAT2 over NAT1. It is the first NAT probe that is suitable for sensitive, homogeneous, and rapid detection of NAT activity of recombinant enzyme or cell lysate, and is expected to be useful for drug discovery and clinical diagnosis.     

Possibility of scanning electron microscope observation and energy dispersive X-ray analysis in microscale region of insulating samples using diluted ionic liquid

The possibility of scanning electron microscope (SEM) observation and energy dispersive X-ray (EDX) spectrometry analysis in microscale regions of insulating samples using diluted ionic liquid was investigated. It is possible to obtain clear secondary electron images of insulating samples such as a rock and mineral at 5,000 times magnification by dropping 10 μL of 1 wt% of 1-ethyl-3-methylimidazolium acetate (EMI-CH?COO) diluted with ethanol onto the samples. We also obtained EDX spectra of the samples in microscale regions (~5 μm2) without overlapping EDX spectra of other minerals with different composition. It might be possible to perform quantitative analysis of the samples if a method that does not need standard samples is applied or an X-ray detector sensitive for light elements was attached. The method of dropping 1 wt% EMI-CH?COO diluted with ethanol onto insulating samples is useful for SEM observation, EDX analysis in microscale regions, and the preservation of scarce rock and mineral samples because ionic liquid can be easily removed with acetone.     

Rhodium-catalyzed asymmetric coupling reaction of allylic ethers with arylboronic acids

An asymmetric allylic substitution of simple allylic ethers with arylboronic acids in the presence of a rhodium(I)/(R)-DTBM-SEGPHOS catalyst has been developed. The reactions proceeded smoothly at room temperature to give the corresponding branch products with excellent regioselectivities and good to excellent enantioselectivities.