Synthesis and Characterization of Naphthalenediimide-Functionalized Flavin Derivatives

Two acceptor–acceptor dyads have been synthesized featuring a flavin moiety and a naphthalenediimide (NDI) unit. The NDI unit is linked to the flavin through a short spacer group via either the N(3) or N(10) positions of the flavin. We have investigated the UV-Vis and redox properties of these multi-electron accepting systems which indicate that these materials display the collective properties of their component systems. Fluorescence spectroscopy measurements have revealed that their emission properties are dominated by the flavin unit

Correction: Zainalabdeen, N., et al., Synthesis and Characterization of Naphthalenediimide-Functionalized Flavin Derivatives. Int. J. Mol. Sci. 2013, 14, 7468–7479.

Note: In lieu of an abstract, this is an excerpt from the first page. In the original version of the manuscript [1] some of the analytical data for compounds 1 and 2 were incorrect. The correct NMR data are presented below. The authors apologize for any inconvenience this may have caused to the readers of this journal. Compound 1: 1H NMR (500 MHz, DMSO-d6) δ 11.64 (s, 1H), 8.73 (s, 4H), 8.57 (d, J = 1.4 Hz, 1H), 8.16 (dd, J = 8.9, 1.4 Hz, 1H), 7.81 (d, J = 8.5 Hz, 2H), 7.64 (d, J = 8.5 Hz, 2H), 6.99 (d, J = 8.9 Hz, 1H), 4.08 (t, J = 7.0 Hz, 2H), 3.28 (m, 2H), 1.69 (quin, J = 7.0 Hz, 2H), 1.33 (m, 8H), 0.86 (t, J = 6.8 Hz, 3H). 13C NMR (125 MHz, DMSO-d6) δ 162.6 (2xC = 0), 162.3 (2xC = 0), 158.9, 155.1, 151.9, 140.8, 136.6, 136.1, 135.2, 133.7, 131.1 (2xC), 130.5 (4xC), 130.3 (q, J = 4 Hz), 128.6 (q, J = 4 Hz), 128.4 (2xC), 126.6, 126.5 (2xC), 126.4 (q, J = 31 Hz), 126.3 (2xC), 126.2, 123.2 (q, J = 271 Hz), 117.8, 39.9, 30.9, 28.5, 28.3, 27.1, 26.3, 21.9, 13.7. Compound 2: 1H NMR (500 MHz, CDCl3) δ 8.77 (s, 4H), 8.58 (d, J = 1.4 Hz, 1H), 8.03 (dd, J = 9.1, 1.4 Hz, 1H), 7.87 (d, J = 8.4 Hz, 2H), 7.76 (d, J = 9.1 Hz, 1H), 7.27 (d, J = 8.4 Hz, 2H), 5.37 (s, 2H), 4.61 (br s, 2H), 4.19 (t, 2H), 2.47 (sept, J = 6.7 Hz, 1H), 1.74 (m, 2H), 1.47–1.23 (m, 10H), 1.07 (d, J = 6.7 Hz, 6H), 0.87 (t, J = 6.9 Hz, 3H). 13C NMR (125 MHz, CDCl3) δ 163.1 (2xC = O), 162.9 (2xC = O), 159.0, 155.0, 149.9, 138.9, 137.5, 135.2, 134.9, 134.3, 131.7 (2xC), 131.5 (2xC), 131.2 (q, J = 4 Hz), 131.1 (4xC), 130.9 (q, J = 4 Hz), 128.6 (2xC), 127.1 (2xC), 127.0 (q, J = 28 Hz), 126.8 (2xC), 123.1 (q, J = 270 Hz), 116.9, 51.5, 44.9, 41.2, 31.9, 29.4, 29.3, 28.2, 27.6, 27.2, 22.8, 20.2 (2xC), 14.2

Structural phase transition and ferromagnetism in monodisperse 3 nm FePt particles

FePt nanoparticles with a size of 3 nm and thermally stable room-temperature ferromagnetism are investigated. The monodisperse nanoparticles were prepared by chemical synthesis and a salt-matrix annealing technique. Structural and magnetic characterizations confirmed the phase transition from the disordered face-centered cubic structure to the L10 structure with the chemical ordering parameter of 0.62±0.05. Analysis in blocking temperature and fitting of temperature dependence of switching field reveals that the transformed 3 nm nanoparticles have a magnetic anisotropy constant of (2.8±0.2) x 106 J/m3, smaller than those for the bigger particles and the fully ordered L10 bulk phase

Solvatochromic probes for detecting hydrogen-bond-donating solvents

Hydrogen bonding heavily influences conformations, rate of reactions, and chemical equilibria. The development of a method to monitor hydrogen bonding interactions independent of polarity is challenging as both are linked. We have developed two solvatochromic dyes that detect hydrogen-bond-donating solvents. The unique solvatochromism of the triazine architecture has allowed the development of probes that monitor hydrogen-bond-donating species including water

Recognition-Mediated Assembly of Quantum Dot Polymer Conjugates with Controlled Morphology

We have demonstrated a polymer mediated “bricks and mortar” method for the self-assembly of quantum dots (QDs). This strategy allows QDs to self-assemble into structured aggregates using complementary three-point hydrogen bonding. The resulting nanocomposites have distinct morphologies and inter-particle distances based on the ratio between QDs and polymer. Time resolved photoluminescence measurements showed that the optical properties of the QDs were retained after self-assembly

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Aromatic stacking interactions in flavin model systems

Flavins feature multiple attributes that explain their widespread occurrence in nature, including photostability, reversible electrochemistry, and especially the tunability of their optical, electronic, and redox properties by supramolecular interactions and modification of their chemical structure. Flavins are important redox cofactors for enzymatic catalysis and are central to a wide variety of processes, including biosynthesis, electron transport, photosynthesis, and DNA repair. The wide range of processes catalyzed by flavins makes them promising leads for synthetic catalysts. Their properties are also relevant to organic electronic and optoelectronic devices, where they have the potential to serve as photoactive electron carriers, a very uncommon property in current photovoltaic systems. In flavoenzymes, the flavin cofactor binds to the active site of the apoenzyme through noncovalent interactions. These interactions regulate cofactor recognition and tune the redox behavior of the flavin cofactor. In this Account, we describe the creation of host guest systems based on small molecule, polymer, and nanoparticle scaffolds that explore the role of aromatic stacking on the redox properties of the flavin and provide insight into flavoenzyme function. We also describe the creation of synthetic flavin-based interlocked structures featuring aromatic stacking interactions, along with the use of aromatic stacking to direct self-assembly of flavin-based materials. The interplay between redox events and aromatic stacking interactions seen in these synthetic models is important for fundamental understanding of biological systems including the flavoenzymes. The precise control of aromatic interactions and binding of flavins not only underpins their biological activity but gives them the potential to be developed into novel organic optoelectronic materials based on tuned synthetic flavin receptor assemblies. In a broader context, the redox properties of the flavin provide a very concise tool for looking at the role of electronics in aromatic stacking, an issue of general importance in biological and supramolecular chemistry.</p

One-Pot Green Synthesis of Fe₃O₄/MoS₂ 0D/2D Nanocomposites and Their Application in Noninvasive Point-of-Care Glucose Diagnostics

We report a novel synthesis of Fe₃O₄/MoS₂ zero-dimensional (0D)/two-dimensional (2D) nanocomposites. When bulk MoS₂ is exfoliated in the presence of thiol-functionalized Fe₃O₄ nanoparticles in water, the latter anchor on the exfoliated MoS₂ nanosheets because of thiol affinity toward MoS₂, resulting in the Fe₃O₄/MoS₂ nanocomposites. The one-pot reaction, room temperature processing, and use of aqueous solvents make the synthesis process facile and ecofriendly. Because of the unique 0D/2D morphology, Fe₃O₄/MoS₂ nanocomposites show significantly higher peroxidase-like catalytic activity compared to Fe₃O₄ nanoparticles or MoS₂ nanosheets alone. The enhanced catalytic activity has been used to detect glucose levels down to 2.4 μM in absorbance measurements. Application toward noninvasive point-of-care glucose diagnostics has been explored by developing paper-based “dip and use” test strips that show colorimetric response in the presence of glucose. To achieve this, Fe₃O₄/MoS₂ nanocomposites along with other active sensing elements are printed onto paper via a desktop inkjet printer and cut into strips. When dipped into solutions of various glucose concentrations, the test strips allow colorimetric detection of glucose concentrations in a qualitative and quantitative manner. To demonstrate practical usage, we have shown that the Fe₃O₄/MoS₂ nanocomposite-based glucose test strips are sufficient to distinguish between normal (healthy) and higher (diabetic) glucose concentrations with the naked eye. Because of the simple and ecofriendly preparation and sensing efficacy with low limit of detection, Fe₃O₄/MoS₂ nanocomposites show promise in noninvasive point-of-care medical diagnostics

Magnetoferritin enhances T₂ contrast in magnetic resonance imaging of macrophages

Imaging of immune cells has wide implications in understanding disease progression and staging. While optical imaging is limited in penetration depth due to light properties, magnetic resonance (MR) imaging provides a more powerful tool for the imaging of deep tissues where immune cells reside. Due to poor MR signal to noise ratio, tracking of such cells typically requires contrast agents. This report presents an in-depth physical characterization and application of archaeal magnetoferritin for MR imaging of macrophages - an important component of the innate immune system that is the first line of defense and first responder in acute inflammation. Magnetoferritin is synthesized by loading iron in apoferritin in anaerobic condition at 65 °C. The loading method results in one order of magnitude enhancement of r1 and r2 relaxivities compared to standard ferritin synthesized by aerobic loading of iron at room temperature. Detailed characterizations of the magnetoferritin revealed a crystalline core structure that is distinct from previously reported ones indicating magnetite form. The magnetite core is more stable in the presence of reducing agents and has higher peroxidase-like activities compared to the core in standard loading. Co-incubation of macrophage cells with magnetoferritin in-vitro shows significantly higher enhancement in T2-MRI contrast of the immune cells compared to standard ferritin.Nanyang Technological UniversityThis work was supported by NTU-Northwestern Institute for Nano-medicine located at the International Institute for Nanotechnology, Northwestern University, USA and the Nanyang Technological Univer-sity, Singapore (Grant No. M4081504.F40.706022)