Taming of Singlet Oxygen: Towards Artificial Oxygen Carriers Based on 1,4-Dialkylnaphthalenes

Naphthalene endoperoxides are known as convenient sources of singlet oxygen (O₂, ¹Δ_g), which is the major product of endoperoxide cycloreversion reaction. However, their potential as carriers of ground-state molecular oxygen (O₂, ³Σ_g) similar to artificial oxygen carriers remains largely unexplored. This is due to the extreme reactivity and cytotoxic effects of the released singlet oxygen. We now report that a compound with a bimodular design, which incorporates an endoperoxide and an efficient physical quencher of singlet oxygen, 1,4-diazabicyclo[2.2.2]octane (DABCO), produces exclusively ground-state molecular oxygen. This result, coupled with the fact that oxygen release rates from endoperoxides are highly amenable to fine-tuning in a very broad range, and open to targeting by ligand attachment, raises the potential of these compounds far above any comparable chemical, or even biochemical sources. In cell culture experiments, we showed that the addition of the endoperoxide-quencher conjugate can enhance and sustain cell proliferation.     

Structure of methylphenylhydrazone form of 2-(2-methylphenylazo)-1,3-indandione

The molecule crystallizes in a ketohydrazone tautomeric form. The tautomeric form is stabilized by a strong intramolecular hydrogen bond of 2.709(2) Å binding the 3-oxo to the nearest nitrogen atom in the azine chain. The compound crystallizes in the monoclinic space group P2_l/c witha=7.0470(4),b=11.3090(9),c=16.2250(4) Å, =90.310(3)°, V=1293.0(1) ų, Z=4,Dx=1.3576 g cm^–3 and (Cu-K)=7.03 cm^–1. The molecule is nearly planar not regarding the methyl group; the small deviations from planarity are indicative of intramolecular interactions between the phenylazo group and indandione group. Some of the bond lengths and angles found in the molecule are distorted due to resonance, -electron delocalization and strain. The relation between these chemical effects and structural results are discussed.     

Crystal and molecular structure of [rac-1S,2S,-3S,4R]methyl 2-benzoyl-3,4-dimethyl-4-phenylcyclobutane-1-carboxylate,C21H22O3

The structure of the title compound C₂₁H₂₂O₃, was determined by X-rays.Minr=322.4, monoclinic, space groupP2₁/a,a=11.960(2),b=14.275(3),c=10.858(2) Å,=103.20(2)°,V _c =1804.8 ų,Z=4,D _x =1.223 Mg m^–3. CuK radiation (graphite crystal monochromator,=1.54184 Å),(CuK)=6.53 cm^–1,F(000)=688, T=290 K. Final conventionalR factor=0.050,R _w =0.069 for 1679 unique reflections and 284 variables. The structure was solved usingMultan.     

Intramolecular hydrogen bonding and tautomerism in N-(3-pyridil)-2-oxo-1-naphthylidenemethylamine

N-(3-pyridil)-2-oxo-1-naphthylidenemethylamine (C₁₆H₁₂N₂O) was studied by elemental analysis, IR, ¹H NMR, and UV–visible techniques and X-ray diffraction methods. The UV–visible spectrum of the compound was investigated in solutions effect polarity. The polarity of the some solvents was modifierly the additional (CF₃COOH) and [(C₂H₅)₃N]. The compound is in tautomeric equilibrium (phenol-imine O–H···N and keto-amine O···H–N forms) in polar and nonpolar solvents. The keto-amine form is observed in basic solutions of DMSO, ethanol, chloroform, benzene, cyclohexane, and in acidic solutions of chloroform and benzene, but not in acidic solutions of DMSO and ethanol. The compound crystallizes in the monoclinic, space group P2₁/a with a = 7.010(5) Å, b = 13.669(4) Å, c = 12.764(4) Å, = 101.23(4)°, V = 1199.6(10) ų, Z = 4, D _c = 1.375 g/cm³, (Mo K) = 0.088 mm^–1, R = 0.045 for 1658 reflections [I > 2(I)]. The title compound is not planar two Schiff base moieties A [C1–C11, O1] and B [N1, C12, C13, N2, C14, C15, C16] are inclined at an angle of 27.4(1)° reflecting mainly the twist about C12–N1 [C11–C12–N1–C13, 29.7(2)°]. There is a strong intramolecular hydrogen bond (O–H···N) of 2.529(2) Å.     

Detection of Variation in Long-Term Micropropagated Mature Pistachio via DNA-Based Molecular Markers

Determination of genetic stability of in vitro-grown plantlets is needed for safe and large-scale production of mature trees. In this study, genetic variation of long-term micropropagated mature pistachio developed through direct shoot bud regeneration using apical buds (protocol A) and in vitro-derived leaves (protocol B) was assessed via DNA-based molecular markers. Randomly amplified polymorphic DNA (RAPD), inter-simple sequence repeat (ISSR), and amplified fragment length polymorphism (AFLP) were employed, and the obtained PIC values from RAPD (0.226), ISSR (0.220), and AFLP (0.241) showed that micropropagation of pistachio for different periods of time resulted in “reasonable polymorphism” among donor plant and its 18 clones. Mantel’s test showed a consistence polymorphism level between marker systems based on similarity matrices. In conclusion, this is the first study on occurrence of genetic variability in long-term micropropagated mature pistachio plantlets. The obtained results clearly indicated that different marker approaches used in this study are reliable for assessing tissue culture-induced variations in long-term cultured pistachio plantlets.     

Remote‐Controlled Release of Singlet Oxygen by the Plasmonic Heating of Endoperoxide‐Modified Gold Nanorods: Towards a Paradigm Change in Photodynamic Therapy

The photodynamic therapy of cancer is contingent upon the sustained generation of singlet oxygen in the tumor region. However, tumors of the most metastatic cancer types develop a region of severe hypoxia, which puts them beyond the reach of most therapeutic protocols. More troublesome, photodynamic action generates acute hypoxia as the process itself diminishes cellular oxygen reserves, which makes it a self‐limiting method. Herein, we describe a new concept that could eventually lead to a change in the 100 year old paradigm of photodynamic therapy and potentially offer solutions to some of the lingering problems. When gold nanorods with tethered endoperoxides are irradiated at 808 nm, the endoperoxides undergo thermal cycloreversion, resulting in the generation of singlet oxygen. We demonstrate that the amount of singlet oxygen produced in this way is sufficient for triggering apoptosis in cell cultures.     

Simultaneous Identification of Spectral Properties and Sizes of Multiple Particles in Solution with Subnanometer Resolution

We report an unsurpassed solution characterization technique based on analytical ultracentrifugation, which demonstrates exceptional potential for resolving particle sizes in solution with sub‐nm resolution. We achieve this improvement in resolution by simultaneously measuring UV/Vis spectra while hydrodynamically separating individual components in the mixture. By equipping an analytical ultracentrifuge with a novel multi‐wavelength detector, we are adding a new spectral discovery dimension to traditional hydrodynamic characterization, and amplify the information obtained by orders of magnitude. We demonstrate the power of this technique by characterizing unpurified CdTe nanoparticle samples, avoiding tedious and often impossible purification and fractionation of nanoparticles into apparently monodisperse fractions. With this approach, we have for the first time identified the pure spectral properties and band‐gap positions of discrete species present in the CdTe mixture.     

Palladium‐catalyzed Suzuki reaction using 1,3‐dialkylbenzimidazol‐2‐ylidene ligands in aqueous media

From readily available starting compounds, six functionalized 1,3‐dialkylbenzimidazolium salts ( 2a–c and 4a–c ) have been prepared and characterized by conventional spectroscopic methods and elemental analyses. A highly effective, easy to handle, and environmentally benign process for palladium‐mediated Suzuki cross‐coupling was developed. The in situ prepared three‐component systems Pd(OAc)₂/1,3‐dialkylbenzimidazolium chlorides and Cs₂CO₃ catalyze quantitatively the Suzuki cross‐coupling of deactivated aryl chlorides. © 2004 Wiley Periodicals, Inc. Heteroatom Chem 15:419–423, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20034     

An inhibition type amperometric biosensor based on tyrosinase enzyme for fluoride determination

In this study, a new biosensor based on the inhibition of tyrosinase for the determination of fluoride is described. To construct the biosensor tyrosinase was immobilized by using gelatine and cross-linking agent glutaraldehyde on a Clark type dissolved oxygen (DO) probe covered with a teflon membrane which is sensitive for oxygen. The phosphate buffer (50 mM, pH 7.0) at 30 °C were established as providing the optimum working conditions. The method is based on the measurement of the decreasing of dissolved oxygen level of the interval surface that related to fluoride concentration added into reaction medium in the presence of catechol. Inhibitor effect of fluoride results in decrease in dissolved oxygen concentration. The biosensor response depends linearly on fluoride concentration between 1.0 and 20 μM with a response time of 3 min.In the characterization studies of the biosensor some parameters such as reproducibility, substrate specificity and storage stability were carried out. From the experiments, the average value (x), Standard deviation (S.D) and coefficient of variation (C.V %) were found as 10.5 μM, ± 0.57 μM, 5.43%, respectively for 10 μM fluoride standard.     

A location–allocation heuristic for the capacitated multi-facility Weber problem with probabilistic customer locations

The capacitated multi-facility Weber problem is concerned with locating m facilities in the Euclidean plane, and allocating their capacities to n customers at minimum total cost. The deterministic version of the problem, which assumes that customer locations and demands are known with certainty, is a non-convex optimization problem and difficult to solve. In this work, we focus on a probabilistic extension and consider the situation where the customer locations are randomly distributed according to a bivariate distribution. We first present a mathematical programming formulation, which is even more difficult than its deterministic version. We then propose an alternate location–allocation local search heuristic generalizing the ideas used originally for the deterministic problem. In its original form, the applicability of the heuristic depends on the calculation of the expected distances between the facilities and customers, which can be done for only very few distance and probability density function combinations. We therefore propose approximation methods which make the method applicable for any distance function and bivariate location distribution.