Copper/H2O2-mediated oxidation of 2'-deoxyguanosine in the presence of 2-naphthol leads to the formation of two distinct isomeric adducts

Exposure of cells to phenolic compounds through exogenous and endogenous sources can lead to deleterious effects via nucleobase modifications of DNA occurring under oxidative conditions. 2'-Deoxyguanosine (dG) is the most electron rich of the four canonical bases and includes many nucleophilic sites; it is also susceptible to oxidation with numerous reactive oxygen species. In these studies, dG was allowed to react with 2-naphthol in the presence of copper or iron salts yielding two principal isomeric products. Spectroscopic analysis and reactions with alkylated nucleosides support the assignment of compound 1a/1b as a pair of atropisomer N(2) adducts and compound 2a/2b as a diastereomeric mixture of tricyclic [4.3.3.0] adducts. Both products are the result of an overall four-electron oxidation process and consequently have the same masses, though drastically different structures, providing mechanistic insight into their formation. Thus, dG alkylation by 2-naphthol under oxidative conditions yields products whose structural properties are altered, leading to potentially mutagenic effects in genomic DNA.     

Efficient generation of Bessel beam arrays by means of an SLM

We use a Spatial Light Modulator (SLM) to produce arrays of Bessel beams by using multiple axicon phase-masks on the SLM. This approach utilises the whole of the SLM, rather than just a thin annular region (which is the case if the SLM is in the far-field of the generated Bessel beams). Using the whole SLM rather than just an annular region means that the required intensity on the SLM is an order of magnitude lower for a given power in the Bessel beams. Spreading the power over the whole SLM is important for high-power applications such as laser micromachining. We allow the axicons to overlap and interfere in the hologram, so the axial length of the Bessel beam core is maintained as we add more beams to the array.     

Formation of guided Cherenkov radiation in silicon-based nanocomposites

We use a monochromated 200 keV electron beam as a nanometer-resolution probe of the photonic density of states in bulk and nanoparticle Si/SiO(2) systems, observing infrared to ultraviolet waveguided Cherenkov modes in Si slabs, but none in SiO2. While isolated Si nanoparticles are too small to support Cherenkov radiation, we find high densities of Si nanoparticles in SiO2 support a damped form of the radiation, with the modes determined by the effective medium of the Si/SiO(2) mixture. The guided nature of the radiation is confirmed by the presence of a thickness-dependent cutoff.     

Laser applications and system considerations in ocular imaging

We review laser applications for primarily in‐vivo ocular imaging techniques, describing their constraints based on biological tissue properties, safety, and the performance of the imaging system. We discuss the need for cost‐effective sources with practical wavelength‐tuning capabilities for spectral studies. Techniques to probe the pathological changes of layers beneath the highly scattering retina and diagnose the onset of various eye diseases are described. The recent development of several optical‐coherence‐tomography‐based systems for functional ocular imaging is reviewed, as well as linear and nonlinear ocular‐imaging techniques performed with ultrafast lasers, emphasizing recent source developments and methods to enhance imaging contrast.     

Protection and Labelling of Thymidine by a Fluorescent Photolabile Group

A fluorescent photolabile group including coumarin and MeNPOC moieties was synthesized to protect 5′‐OH terminal function of thymidine (T). Its photochemical and photophysical properties were studied, in particular the photocleavage (photodeprotection under a 365‐nm irradiation) is only lowered by a factor of two by addition of the fluorophore. Fluorescence properties of the coumarin probe are not changed upon irradiation, which is satisfactory for the application required, i.e., in situ synthesis of DNA microarrays.     

Interface,morphology, and the rheological properties of polymethylmethacrylate/impact modifier blends

Impact modifiers with grafted PMMA shell are used to modify polymethylmethacrylate matrix. The composition of the shell is chosen to enhance the interactions at the modifier/matrix interface and to obtain good dispersion of the impact modifier in order to optimize impact strength of the blend. The degree of interactions at the interface is characterized by the interfacial region where the chains of the matrix mix with those of the shell of the modifier. The deviation of the measured viscoelastic behavior of these blends from that predicted by the emulsion models has been attributed to the formation of the network structure due to the association of matrix chains with the shell of the modifier. It is expected that the network structure will decrease with increasing frequency and, as such, the effective volume of the particle is frequency dependent. This study uses the emulsion models to estimate the larger effective volume of the particle and, therefore, the extent of interaction at the interface. In the blends of this study it can be shown that at low modifier levels the solvent swelling of the modifier shell results in stronger interactions with the matrix; this effect is negated by the aggregation of particles at higher modifier loadings. The interaction of core modifier with the PMMA matrix seems to be similar to that of the core-shell modifier. This would not be expected from the calculated interfacial thickness of approximately 4 nm. It is, therefore, proposed that during melt-processing the core modifier surface was altered due to grafting of the matrix PMMA chains during melt-blending to (BA/St) copolymer of the core modifier thus reducing the interfacial tension. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. B Polym. Phys. 36: 2623–2634, 1998     

3‐[2,6‐Bis­(diethyl­carbamoyl)­pyridin‐4‐yl]‐N‐(tert‐butoxy­carbonyl)­alanine methyl ester: a chiral tridentate ligand that causes a diastereomeric excess of its lanthanide complexes in solution

L⁴, or 3‐[2,6‐bis­(diethyl­carbamoyl)­pyridin‐4‐yl]‐N‐(tert‐but­oxy­car­bonyl)­alanine methyl ester, C₂₄H₃₈N₄O₆, crystallizes in neat [010] laths stabilized by abundant intra‐ and intermolecular hydrogen bonds. The strongest of these form [010] chains of mol­ecules, thus rationalizing the fastest growth direction, while the slowest direction coincides with the normal to the (110) layers, which are linked by very weak hydrogen bonds. There exist two independent mol­ecules, the distances and bond angles of which differ in a random manner only. The torsion and dihedral angles, however, differ so as to achieve optimal packing. The influence of the chiral group in the 4‐position of the pyridine ring on the helical wrapping and on the ensuing diastereomeric induction is briefly discussed.     

Properties of GeSi Nanocrystals Embedded in Hexagonal SiC

In this paper high‐resolution electron microscopy investigations and molecular dynamics simulations of GeSi nanocrystals buried in 4H‐SiC are performed, showing that the experimentally observed shapes of the GeSi nanocrystals are strongly correlated with their orientational relationships. Measurements of the lattice spacing suggest that the nanocrystals are strained. Quantum confinement in selected nanocrystals has been detected using spatially‐resolved electron energy loss spectroscopy performed in conjunction with atomic resolution annular dark‐field scanning TEM.     

Catalytic Synthesis of β-(Hetero)arylethylamines: Modern Strategies and Advances

β-(Hetero)arylethylamines appear in a myriad of pharmaceuticals due to their broad spectrum of biological properties, making them prime candidates for drug discovery. Conventional methods for their preparation often require engineered substrates that limit the flexibility of the synthetic routes and the diversity of compounds that can be accessed. Consequently, methods that provide rapid and versatile access to those scaffolds remain limited. To overcome these challenges, synthetic chemists have designed innovative and modular strategies to access the β-(hetero)arylethylamine motif, paving the way for their more extensive use in future pharmaceuticals. This review outlines recent progresses in the synthesis of (hetero)arylethylamines and emphasizes how these innovations have enabled new levels of molecular complexity, selectivity, and practicality.