Vibrational spectra and dynamics of conformation and hydrogen bonding of n-methylacetamide. I. Conformational dynamics of the CH3CONHCH3 molecule and NH out of plane band splitting

The infrared spectra of CH₃CONHCH₃ and CH₃CONDCH₃ have been investigated as low temperature crystals, pure liquids and solutions in various solvents in the 400-800 cm^?1 range. A new assignment of the bands associated with the NH group is given. Multiplets of γ NH and γ ND fundamentals have generally been observed and have been interpreted in terms of a double minimum potential function of the γ NH mode with a tunnelling between two minima. The potential functions of γ NH and τ CN modes are similar and can be combined to give a potential surface with four minima corresponding to four molecular conformations. The influence of the hydrogen bonding on the γ NH splitting and barrier height is discussed.     

Surface-mediated nucleation in the solid-state polymorph transformation of terephthalic acid

A molecular mechanism for nucleation for the solid-state polymorph transformation of terephthalic acid is presented. New methods recently developed in our group, aimless shooting and likelihood maximization, are employed to construct a model for the reaction coordinate for the two system sizes studied. The reaction coordinate approximation is validated using the committor probability analysis. The transformation proceeds via a localized, elongated nucleus along the crystal edge formed by fluctuations in the supramolecular synthons, suggesting a nucleation and growth mechanism in the macroscopic system.     

Design and synthesis by click triazole formation of paclitaxel mimics with simplified core and side-chain structures

A library of paclitaxel (taxol) mimics was obtained by a straightforward strategy involving rational design and an efficient synthesis of a simplified taxane core substitute, together with a click-chemistry combinatorial search for phenylisoserine side-chain surrogates.     

Photodynamic therapy with Pc 4 induces apoptosis of Candida albicans

The high prevalence of drug resistance necessitates the development of novel antifungal agents against infections caused by opportunistic fungal pathogens, such as Candida albicans. Elucidation of apoptosis in yeast-like fungi may provide a basis for future therapies. In mammalian cells, photodynamic therapy (PDT) has been demonstrated to generate reactive oxygen species, leading to immediate oxidative modifications of biological molecules and resulting in apoptotic cell death. In this report, we assess the in vitro cytotoxicity and mechanism of PDT, using the photosensitizer Pc 4, in planktonic C. albicans. Confocal image analysis confirmed that Pc 4 localizes to cytosolic organelles, including mitochondria. A colony formation assay showed that 1.0 μM Pc 4 followed by light at 2.0 J cm(-2) reduced cell survival by 4 logs. XTT (2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxyanilide) assay revealed that Pc 4-PDT impaired fungal metabolic activity, which was confirmed using the FUN-1 (2-chloro-4-[2,3-dihydro-3-methyl-(benzo-1,3-thiazol-2-yl)-methylidene]-1-phenylquinolinium iodide) fluorescence probe. Furthermore, we observed changes in nuclear morphology characteristic of apoptosis, which were substantiated by increased externalization of phosphatidylserine and DNA fragmentation following Pc 4-PDT. These data indicate that Pc 4-PDT can induce apoptosis in C. albicans. Therefore, a better understanding of the process will be helpful, as PDT may become a useful treatment option for candidiasis.     

Dopant profiling in silicon nanowires measured by scanning capacitance microscopy

Silicon nanowires (SiNWs) with axial doping junctions were synthesized via the Au‐catalyzed vapor–liquid–solid growth method with the use of HCl. In this work, dopant profiling from three axially doped SiNWs with p–i, p–n and n–i–p junctions were investigated using both scanning electron microscopy (SEM) and scanning capacitance microscopy (SCM). It turns out that observed doping contrasts in SEM are also affected by the surface roughness and sample charging. In contrast, SCM allows us to delineate with sub‐10 nm resolution the electrical junctions and provides a relative value of the doping concentration in each segment of the NW. SCM clearly evidences the expected doping regions within these SiNWs thanks to the addition of HCl during the growth that strongly prevents shell overgrowth. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)