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The synthesis of (Z)-4-(4-nitrobenzylidene)-2-phenyloxazol-5(4H)-one, which is a potent immunomodulator and tyrosinase inhibitor, is described as an experiment for an upper-division undergraduate organic chemistry laboratory course. This compound is produced via an Erlenmeyer-Plöchl reaction in the absence of any additional solvents and is isolated without need of preparative chromatography, yielding up to 97% of product. [ABSTRACT FROM AUTHOR]

The fluorescence of a rhodamine X dye covalently linked to the 5′ terminus of a 25-mers thymine oligodeoxynucleotide (dT25-ROX), adsorbed on the shell of thermo-responsive core-shell polymer particles, was used to probe the polarity, mobility, and distribution of the oligodeoxynucleotides (ODNs) in the shell. The particles have a glassy core of poly(methyl methacrylate) (PMMA) with a 67-nm radius, and a thermoresponsive shell of poly(N-isopropyl acrylamide) (PNIPAM) whose thickness changes from 42 nm at 11 °C to 5 nm at 45 °C. The variation in polarity of the shell with temperature was obtained both from the lifetimes and from the solvatochromic shifts of the dye and shows a sharp transition at the volume phase transition temperature (TVPT) of the PNIPAM shell. Förster resonance energy transfer (FRET) between dT25-ROX and a malachite green (MG)-labeled ODN (dT25-MG) was used to obtain the distribution of the ODNs in the thermoresponsive shell. Our results show that at 23 °C (below TVPT) the ODNs are distributed inside the shell, sensing an environment similar to water. At this temperature, the PNIPAM shell is composed of hydrated chains with high mobility, as probed by the fluorescence anisotropy of dT25-ROX. By increasing the temperature above TVPT, the shell collapses and the chain mobility drastically slows down owing to the anchoring of the ODN to the dense shell of PNIPAM. Furthermore, FRET shows that the ODNs are absorbed on the 5-nm-thick collapsed shell but extend into the water. The polarity probed by the ROX averages the dyes distributed in the interior of the particle shell and in water, with 60 % of the dyes outside the particle shell (i.e., sensing pure water). Another indication that above the TVPT most of the ODNs are oriented with the dye toward the water phase is that the mobility of the dye covalently bound to the ODNs is identical in water and in the collapsed particle shell. The hybridization efficiency between an ODN supported in the particle shell (by adsorbing the ODN below TVPT and subsequently increasing the temperature above TVPT) and the complementary ODN in solution is identical to that of hybridization in water. This result opens good perspectives toward the use of the core-shell thermoresponsive nanoparticles as supports in DNA bioassays. [ABSTRACT FROM AUTHOR]

Gold nanoclusters (AuNCs) with fluorescence in the Near Infrared (NIR) by both one- and two-photon electronic excitation were incorporated in mesoporous silica nanoparticles (MSNs) using a novel one-pot synthesis procedure where the condensation polymerization of alkoxysilane monomers in the presence of the AuNCs and a surfactant produced hybrid MSNs of 49 nm diameter. This method was further developed to prepare 30 nm diameter nanocomposite particles with simultaneous NIR fluorescence and superparamagnetic properties, with a core composed of superparamagnetic manganese (II) ferrite nanoparticles (MnFe2O4) coated with a thin silica layer, and a shell of mesoporous silica decorated with AuNCs. The nanocomposite particles feature NIR-photoluminescence with 0.6% quantum yield and large Stokes shift (290 nm), and superparamagnetic response at 300 K, with a saturation magnetization of 13.4 emu g−1. The conjugation of NIR photoluminescence and superparamagnetic properties in the biocompatible nanocomposite has high potential for application in multimodal bioimaging. [ABSTRACT FROM AUTHOR]

The article informs that designs of dye laser can be identified with the help of Förster resonance energy transfer. It mentions the benefits of laser dyes which include deep tissue penetration, low photoinduced damage and reduced interference from the autofluorescence of biological samples. It presents a figure of a polymer core-shell nanoparticle which has been loaded with rhodamine and Nile blue dyes.

The phototransformation of aryl chlorides adsorbed on MFI zeolites is markedly different from that observed in solution and other solid surfaces such as silica. The formation of radical cations and the constraints imposed by the channels shift the reactivity from the C−Cl bond to the O−R bond. Irradiation generates kinetically stabilized intermediates that can be characterized using conventional steady-state spectroscopic techniques, and these intermediates can be used as ordinary chemical reagents. [ABSTRACT FROM AUTHOR]

Mitochondria metabolism is an emergent target for the development of novel anticancer agents. It is amply recognized that strategies that allow for modulation of mitochondrial function in specific cell populations need to be developed for the therapeutic potential of mitochondria-targeting agents to become a reality in the clinic. In this work, we report dipolar and quadrupolar quinolizinium and benzimidazolium cations that show mitochondria targeting ability and localized light-induced mitochondria damage in live animal cells. Some of the dyes induce a very efficient disruption of mitochondrial potential and subsequent cell death under two-photon excitation in the Near-infrared (NIR) opening up possible applications of azonia/azolium aromatic heterocycles as precision photosensitizers. The dipolar compounds could be excited in the NIR due to a high two-photon brightness while exhibiting emission in the red part of the visible spectra (600–700 nm). Interaction with the mitochondria leads to an unexpected blue-shift of the emission of the far-red emitting compounds, which we assign to emission from the locally excited state. Interaction and possibly aggregation at the mitochondria prevents access to the intramolecular charge transfer state responsible for far-red emission. Molecules that target mitochondria have promising applications as anticancer agents. Here quinolizinium and benzimidazolium cations are shown to deactivate mitochondria through two-photon absorption in the near infrared range. [ABSTRACT FROM AUTHOR]

The synthesis of two triads with two porphyrinyl units linked by oligopyridine derivatives and a new β-functionalized porphyrin-dihydroazepine is described. One of the porphyrin-oligopyridine triads has a quinquepyridine unit connecting the porphyrins β-pyrrolic positions, while the other one has an asymmetric quaterpyridine with one of the pyridines fused to the porphyrin. All compounds have fluorescence emission quantum yields in the range of meso-tetraphenylporphyrin (16-22%). [ABSTRACT FROM AUTHOR]

Chargedmolecules based on the quinolizinum cation have potentialapplications as labels in fluorescence imaging in biological mediaunder nonlinear excitation. A systematic study of the linear and nonlinearphotophysics of derivatives of the quinolizinum cation substitutedby either dimethylaniline or methoxyphenyl electron donors is performed.The effects of donor strength, conjugation length, and symmetry inthe two-photon emission efficiency are analyzed in detail. The bestperforming nonlinear fluorophore, with two-photon absorption crosssections of 1140 GM and an emission quantum yield of 0.22, is characterizedby a symmetric D-π-A+-π-D architecture basedon the methoxyphenyl substituent. Application of this molecule asa fluorescent marker in optical microscopy of living cells revealedthat, under favorable conditions, the fluorophore can be localizedin the cytoplasmatic compartment of the cell, staining vesicular shapeorganelles. At higher dye concentrations and longer staining times,the fluorophore can also penetrate into the nucleus. The nonlinearlyexcited fluorescence lifetime imaging shows that the fluorophore lifetimeis sensitive to its location in the different cell compartments. Usingfluorescence lifetime microscopy, a multicolor map of the cell isdrafted with a single dye. [ABSTRACT FROM AUTHOR]

Fluorescent probes, coumarin 153 (C153) and octadecylrhodamine B (ORB), were used to study the self-assembly in water of poly(N-decylacrylamide)-block-poly(N,N-diethylacrylamide), (PDcA11-block-PDEA295; Mn = 40 300 g mol−1; Mw/Mn = 1.01). From the variation of both the fluorescence intensity and the solvatochromic shifts of C153 with polymer concentration, the critical micelle concentration (CMC) was determined as 1.8 ± 0.1 μM. On the other hand, steady-state anisotropy measurements showed the presence of premicellar aggregates below the CMC. Time-resolved fluorescence anisotropy evidenced that ORB is located in the premicellar aggregates and the micelle core, while C153 is partitioned between the aggregates and the water phase. The micelle core contains both semicrystalline and amorphous regions. In the semicrystalline regions the probes cannot rotate, while in the amorphous regions the rotational correlation times correlate well with the hydrodynamic volume of the probes. The amorphous region of the micelle core is relatively fluid, reflecting the large free-volume accessible to the probes. [ABSTRACT FROM AUTHOR]