Novel Hybrid Benzoazacrown Ligand as a Chelator for Copper and Lead Cations: What Difference Does Pyridine Make

A synthetic procedure for the synthesis of azacrown ethers with a combination of pendant arms has been developed and the synthesized ligand, characterized by various techniques, was studied. The prepared benzoazacrown ether with hybrid pendant arms and its complexes with copper and lead cations were studied in terms of biomedical applications. Similarly to a fully acetate analog, the new one binds both cations with close stability constants, despite the decrease in both constants. The calculated geometry of the complexes correlate with the data from X-ray absorption and NMR spectroscopy. Coordination of both cations differs due to the difference between the ionic radii. However, these chelation modes provide effective shielding of cations in both cases, that was shown by the stability of their complexes in the biologically relevant media towards transchelation and transmetallation.     

Novel NIR-Phosphorescent Ir(III) Complexes: Synthesis,Characterization and Their Exploration as Lifetime-Based O2 Sensors in Living Cells

A series of [Ir(N^C)₂(N^N)]⁺ NIR-emitting orthometalated complexes (1–7) has been prepared and structurally characterized using elemental analysis, mass-spectrometry, and NMR spectroscopy. The complexes display intense phosphorescence with vibrationally structured emission bands exhibiting the maxima in the range 713–722 nm. The DFT and TD DFT calculations showed that the photophysical characteristics of these complexes are largely determined by the properties of the metalating N^C ligands, with their major contribution into formation of the lowest S₁ and T₁ excited states responsible for low energy absorption and emission, respectively. Emission lifetimes of 1–7 in degassed methanol solution vary from 1.76 to 5.39 µs and show strong quenching with molecular oxygen to provide an order of magnitude lifetime reduction in aerated solution. The photophysics of two complexes (1 and 7) were studied in model physiological media containing fetal bovine serum (FBS) and Dulbecco’s Modified Eagle Medium (DMEM) to give linear Stern-Volmer calibrations with substantially lower oxygen-quenching constants compared to those obtained in methanol solution. These observations were interpreted in terms of the sensors’ interaction with albumin, which is an abundant component of FBS and cell media. The studied complexes displayed acceptable cytotoxicity and preferential localization, either in mitochondria (1) or in lysosomes (7) of the CHO-K1 cell line. The results of the phosphorescence lifetime imaging (PLIM) experiments demonstrated considerable variations of the sensors’ lifetimes under normoxia and hypoxia conditions and indicated their applicability for semi-quantitative measurements of oxygen concentration in living cells. The complexes’ emission in the NIR domain and the excitation spectrum, extending down to ca. 600 nm, also showed that they are promising for use in in vivo studies.     

Integrable boundary conditions and modified Lax equations

We consider integrable boundary conditions for both discrete and continuum classical integrable models. Local integrals of motion generated by the corresponding “transfer” matrices give rise to time evolution equations for the initial Lax operator. We systematically identify the modified Lax pairs for both discrete and continuum boundary integrable models, depending on the classical r-matrix and the boundary matrix.     

Impedimetric DNA Sensor Based on Poly(proflavine) for Determination of Anthracycline Drugs

Electropolymerization is often used as a tool for immobilization of charged biopolymers and their electric wiring in the biosensor assembly. In this work, electropolymerization of proflavine has been for the first time used for the physical adsorption of DNA and measurement of anthracycline drugs (doxorubicin and daunorubicin) able to intercalate DNA. Redox properties of the proflavine polymers on the glassy carbon electrode and DNA deposition were characterized with cyclic voltammetry, scanning electron microscopy and electrochemical impedance spectroscopy. It was shown that DNA decreased the peak currents on voltammogram but increased the charge transfer resistance. The latter effect is pronounced with the following drug application. The impedimetric response regularly increased with the drugs concentration in the range 1 nM to 0.1 μM for doxorubicin and 1 pM–10 nM for daunorubicin (limit of detections 0.3 and 0.001 nM, respectively). The biosensor was tested on pharmaceutical preparations and spiked solution simulating the plasma electrolytes and possible interference of serum proteins.     

Modulation of the singlet-singlet through-space energy transfer rates in cofacial bisporphyrin and porphyrin-corrole dyads

A new series of relatively flexible cofacial donor-acceptor dyads for singlet-singlet energy transfer with the corrole or etio-porphyrin free base and zinc porphyrin as the acceptor and donor, respectively, were synthesized and characterized (represented as (PMes2COx)ZnH3 (13), (PMes2CO)ZnH3 (14), and (PMes2CX)ZnH3 (15)) where (PMes2COx = [2-[5-(5,15-dimesitylcorrol-10-yl)-diphenylether-2'-yl]-13,17-diethyl-2,3,7,8,12,18-hexamethylporphyrin]), (PMes2CO = [5-[5-(5,15-dimesitylcorrol-10-yl)-dibenzofuran-4-yl]-13,17-diethyl-2,3,7,8,12,18-hexamethylporphyrin]), and (PMes2CX = [5-[5-(5,15-dimesitylcorrol-10-yl)-9,9-dimethylxanthen-4-yl)]-13,17-diethyl-2,3,7,8,12,18-hexamethylporphyrin]), respectively) along with the homobismacrocycles (DPOx)ZnH2 (17) and (DPOx)Zn2 (18) (where (DPOx = 2,2'-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]diphenylether) as comparison standards. The rate for energy transfer (kET) extracted by the measurements of fluorescence lifetimes are of the same order of magnitude as those recently reported for the rigidly held face-to-face dyads ((DPB)ZnH2 (1), (DPX)ZnH2 (2), (DPA)ZnH2 (3), (DPO)ZnH2 (4), and (DPS)ZnH2 (5) where (DPB = 1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]biphenylene), (DPX = 4,5-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]-9,9-dimethylxanthene), (DPA = 1,8-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]anthracene), (DPO = 4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenzofuran), and (DPS = 4,6-bis[5-(2,8,13,17-tetraethyl-3,7,12,18-tetramethylporphyrinyl)]dibenzothiophene), respectively), but for the first time, it is shown that the presence of a bulky group located between the acceptor and the donor moiety influences the transfer rate. The presence of perpendicular mesityl groups on the acceptor macrocycle prevents the two macrorings from interacting strongly; therefore, kET is slower. On the other hand, by rendering the rigid spacer flexible (i.e., changing the dibenzofuran rigid spacer to the flexible diphenylether assembling fragment), kET increases due to stronger intermacrocycle interactions. This study is complemented by DFT computations (B3LYP/3-21G*) as a molecular modeling tool where subtle structural features explain the changes in kET. During the course of this study, X-ray structures of 17 and 18 were investigated and exhibit a linear stacking of the bismacrocycles where intermolecular porphyrin-porphyrin interactions are observed (dinter(Zn...Zn) = 4.66 and 4.57 A, for 17 and 18, respectively).     

Constrained numerical optimization methods for blind deconvolution

This paper describes a nonlinear least squares framework to solve a separable nonlinear ill-posed inverse problem that arises in blind deconvolution. It is shown that with proper constraints and well chosen regularization parameters, it is possible to obtain an objective function that is fairly well behaved and the nonlinear minimization problem can be effectively solved by a Gauss–Newton method. Although uncertainties in the data and inaccuracies of linear solvers make it unlikely to obtain a smooth and convex objective function, it is shown that implicit filtering optimization methods can be used to avoid becoming trapped in local minima. Computational considerations, such as computing the Jacobian, are discussed, and numerical experiments are used to illustrate the behavior of the algorithms. Although the focus of the paper is on blind deconvolution, the general mathematical model addressed in this paper, and the approaches discussed to solve it, arise in many other applications.     

The Effect of a Horseshoe Crab Citizen Science Program on Middle School Student Science Performance and STEM Career Motivation

The purpose of the present quasi‐experimental study was to examine the impact of a horseshoe crab citizen science program on student achievement and science, technology, engineering, and mathematics (STEM) career motivation with 86 (n = 86) eighth‐grade students. The treatment group conducted fieldwork with naturalists and collected data for a professional biologist studying horseshoe crab speciation and a mock survey. The comparison group studied curriculum related to horseshoe crabs in the science classroom. A series of measures related to self‐efficacy, interest, outcome expectations, choice goals, and content knowledge were given to participants before and after the intervention. It was hypothesized that students would report higher motivational beliefs regarding science and show higher levels of achievement following the intervention than the comparison group. Support was shown for most of the hypotheses. In addition, path analyses indicated that students' motivational beliefs influence content knowledge and outcome expectations, which in turn affect their career goals. These results have implications for incorporating authentic fieldwork within a formal school structure as an effective method for promoting student achievement and STEM career motivation.     

Smoothness characterization and stability of nonlinear and non-separable multiscale representations

The aim of the paper is the construction and the analysis of nonlinear and non-separable multiscale representations for multivariate functions defined using a non-diagonal dilation matrix M. We show that a function in L^p or Besov spaces can be characterized by means of its multiscale representation. We also study the stability of these representations, a key issue to design adaptive algorithms.     

Synthetic studies toward A-74528

A potentially biomimetic approach toward the complex polyketide A-74528 is described. It is based on highly substituted biaryl compounds, synthesized using advanced cross-coupling and condensation methodologies.