A multi-component reaction (MCR) approach to the synthesis of highly diverse polymers with polypeptide-like features

A new strategy for the combinatorial synthesis of new materials has been developed through the consecutive application of an Ugi 4CC reaction and a ring-opening metathesis polymerization (ROMP) reaction. Norbornenyl aldehydes and carboxylic acids could be used in the Ugi MCR to give highly diverse monomers that were converted to the corresponding polymers by exposure to the second-generation Grubbs' catalyst. These polymers have structural features reminiscent of polypeptides and the process could be extended to the preparation of chiral materials.     

Proliferation assessment in breast cancer: a double-staining technique for AgNOR quantification in MIB-1 positive cells especially adapted for image cytometry

There are two ways of measuring the cell proliferation. The first one consists of quantifying the number of cycling cells with the help of antibodies directed against cells either in G1, S, G2 or M phase. The second way is to assess the cell cycle duration by the quantification of AgNOR proteins. Measuring both the features on the same slide represents an attractive way to tackle the proliferating activity of a cell culture or a tumor. Here, we propose a MIB-1 and AgNOR double staining method especially adapted to image cytometry measurement using MIB-1 antibody coupled to FITC in order to avoid the thresholding problems encountered with such a multilabeling technique. We have applied this new method on a series of 39 breast cancer cases, with at least 4 years follow-up, in order to determine the prognosis significance of this measurement. MIB-1 alone is not linked to prognosis, while the global mean AgNOR area is significantly linked to prognosis in terms of development of visceral metastasis or death. However, the global mean AgNOR area is insufficient to determine the time limit of appearance of metastasis or relapse. Our results clearly demonstrate that a high mean AgNOR area within a cell population having a high MIB-1 index can discern tumors with a high metastatic potential. By multiplying AgNOR area by the percentage of MIB-1 positive cells we calculate the proliferative activity, P, which brings very important information concerning the time limit of relapse.     

Ultra fine carbon nitride nanocrystals synthesized by laser ablation in liquid solution

Crystalline carbon nitride nanopowders and nanorods have been successfully synthesized at room temperature and pressure using the novel technique of pulsed laser ablation of a graphite target in liquid ammonia solution. High-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), and Fourier transform infrared spectroscopy (FTIR) were used to systematically study the morphology, nanostructure and chemical bonding. The experimental composition and structure of the nanoparticles are consistent with the theoretical calculations for α-C₃N₄. After 2 h ablation the particles had a size distribution ∼8–12 nm, whereas after 5 h ablation the particles had grown into nanorod-like structures with a crystalline C₃N₄ tip. A formation mechanism for these nanorods is proposed whereby nanoparticles are first synthesized via rapid formation of an embryonic particle, followed by a slow growth, eventually leading to a one-dimensional nanorod structure.     

The contribution of high frequencies to human brain activity underlying horizontal localization of natural spatial sounds

Background  

In the field of auditory neuroscience, much research has focused on the neural processes underlying human sound localization. A recent magnetoencephalography (MEG) study investigated localization-related brain activity by measuring the N1m event-related response originating in the auditory cortex. It was found that the dynamic range of the right-hemispheric N1m response, defined as the mean difference in response magnitude between contralateral and ipsilateral stimulation, reflects cortical activity related to the discrimination of horizontal sound direction. Interestingly, the results also suggested that the presence of realistic spectral information within horizontally located spatial sounds resulted in a larger right-hemispheric N1m dynamic range. Spectral cues being predominant at high frequencies, the present study further investigated the issue by removing frequencies from the spatial stimuli with low-pass filtering. This resulted in a stepwise elimination of direction-specific spectral information. Interaural time and level differences were kept constant. The original, unfiltered stimuli were broadband noise signals presented from five frontal horizontal directions and binaurally recorded for eight human subjects with miniature microphones placed in each subject's ear canals. Stimuli were presented to the subjects during MEG registration and in a behavioral listening experiment.     

Infrared and Mössbauer studies of some diamine complexes with trimethyltin halides and dimethyltin dihalides

To obtain more structural information on complexes formed between alkyltin halides and bidentate ligands, the solid-state IR and Mössbauer spectra of the 1,2-ethanediamine and 1,4-butanediamine complexes of trimethyltin halides and dimethyltin dihalides were examined. The structures of the trimethyltin halide complexes were found to be trigonal bipyramidal with coplnar methyl groups. The dimethyltin dihalide complexes were octahedral with the methyl groups in the cis-positions and the halides trans to each other. However, there were no differences in the structures of the chloro and bromo complexes of either type.     

A convenient MnIII starting material for the synthesis of homo- and heterometallic manganese carboxylate clusters: Mn9 and Mn10−xFex complexes

The use of a convenient source of Mn^III ions, namely the [Mn(OR)(O₂CR′)₂]_n (R = H, Me, and R′ = Me, Bu^t) family of 1-D coordination polymers, afforded two new enneanuclear and decanuclear molecular clusters, homometallic [Mn₉O₇(O₂CBu^t)₁₃(MeCN)₂] (3) and heterometallic [Mn_10?xFe_x(OMe)₂₀(O₂CMe)₁₀] (x < 10) (4), respectively. Compound 3 was synthesized by a solvent-induced structural transformation, whereas complex 4 resulted from the reaction of [Mn(OH)(O₂CMe)₂]_n with an Fe^III source. The core of 3 comprises two [Mn₄O₂]⁸⁺ butterfly units and a [Mn₃O]⁷⁺ triangular unit fused together by sharing one Mn atom. Magnetic susceptibility measurements of 3 revealed dominant antiferromagnetic interactions within the molecule, and a ground state of S = 1 with many low-lying excited states. Complex 4 is a mixed Fe^III/Mn^III single-strand molecular wheel, which forms 3D nanotubular stacks arranged in a zig–zag fashion. The described work suggests that the [Mn(OR)(O₂CR′)₂]_n compounds represent excellent starting materials for Mn^III carboxylate cluster chemistry.