Biological properties of water-soluble phosphorhydrazone dendrimers

1984-8250Dendrimers are hyperbranched and perfectly defined macromolecules, constituted of branches emanating from a central core in an iterative fashion. Phosphorhydrazone dendrimers constitute a special family of dendrimers, possessing one phosphorus atom at each branching point. The internal structure of these dendrimers is hydrophobic, but hydrophilic terminal groups can induce the solubility of the whole structure in water. Indeed, the properties of these compounds are mainly driven by the type of terminal groups their bear; this is especially true for the biological properties. For instance, positively charged terminal groups are efficient for transfection experiments, as drug carriers, as anti-prion agents, and as inhibitor of the aggregation of Alzheimer's peptides, whereas negatively charged dendrimers have anti-HIV properties and can influence the human immune system, leading to anti-inflammatory properties usable against rheumatoid arthritis. This review will give the most representative examples of the biological properties of water-soluble phosphorhydrazone dendrimers, organized depending on the type of terminal groups they bear

Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET

The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR

Does Charge Carrier Dimensionality Increase in Mixed-Valence Salts of Tetrathiafulvalene-Terminated Dendrimers?

In four new dendrimers terminated by 12 electroactive tetrathiafulvalenyl substituents, the tridimensional character of the inter- and intradendrimeric charge and electron transfer, and hence of the electroconductivity, is evidenced by examination of the electronic spectra of their corresponding neutral state and cation radical, dication, and mixed-valence salts, including a closed-shell anion

Relationship of edge localized mode burst times with divertor flux loop signal phase in JET

A phase relationship is identified between sequential edge localized modes (ELMs) occurrence times in a set of H-mode tokamak plasmas to the voltage measured in full flux azimuthal loops in the divertor region. We focus on plasmas in the Joint European Torus where a steady H-mode is sustained over several seconds, during which ELMs are observed in the Be II emission at the divertor. The ELMs analysed arise from intrinsic ELMing, in that there is no deliberate intent to control the ELMing process by external means. We use ELM timings derived from the Be II signal to perform direct time domain analysis of the full flux loop VLD2 and VLD3 signals, which provide a high cadence global measurement proportional to the voltage induced by changes in poloidal magnetic flux. Specifically, we examine how the time interval between pairs of successive ELMs is linked to the time-evolving phase of the full flux loop signals. Each ELM produces a clear early pulse in the full flux loop signals, whose peak time is used to condition our analysis. The arrival time of the following ELM, relative to this pulse, is found to fall into one of two categories: (i) prompt ELMs, which are directly paced by the initial response seen in the flux loop signals; and (ii) all other ELMs, which occur after the initial response of the full flux loop signals has decayed in amplitude. The times at which ELMs in category (ii) occur, relative to the first ELM of the pair, are clustered at times when the instantaneous phase of the full flux loop signal is close to its value at the time of the first ELM

Vibrational spectra and DFT studies of conjugation in poly(phosphorhydrazone) dendrimers

International audienceThe FTIR and FT Raman spectra of the 11 generations of poly(phosphorhydrazone) dendrimers built from thiophosphoryl core with P−Cl (Gi) and oxybenzaldehyde (G'i) terminal groups have been studied. Spectral pattern of dendrimers depends on the ratio of the number of end groups and repeating units. This ratio tends to r–1 (r– functionality of the repeating unit) and becomes constant when the generation number exceeds 3. The experimental IR and Raman spectra of the different generations of dendrimers are very similar to each other in the agreement with the theory. Optimization of the structure and the analysis of normal vibrations was made for G'0 and G1 using the density functional theory (DFT). Calculations showed that the molecules of the first generation dendrimer have the form of a propeller with three blades and flat repeating units. Bond lengths and angles in the optimized geometry obtained by DFT show good agreement with experiment. Consideration of the molecular orbitals shows that in the repeating units and oxybenzaldehyde end groups of poly(phosphorhydrazone) dendrimers conjugation is realized. The oxybenzaldehyde terminal groups are characterized by a band 1702 cm−1 in the experimental IR spectra of G’i. The line in the Raman spectra of Gi and G’i at 1576 cm−1 refers to the vibrations of the repeating units

Spectroscopic and molecular structure investigation of the phosphorus-containing G′2 dendrimer with terminal aldehyde groups using DFT method

International audienceThe FTIR and FT Raman spectra of the second generation dendrimer G′2 built from thiophosphoryl core with terminal aldehyde groups have been recorded. The structural optimization and normal mode analysis were performed for model compound C, consisting of thiophosphoryl core, one branch with three repeated units, and four 4-oxybenzaldehyde terminal groups on the basis of the density functional theory (DFT) at the PBE/TZ2P level. The vibrational frequencies, infrared and Raman intensities for the t,g,g- and t,-g,g-conformers of the terminal groups were calculated. The t,g,g-conformer is 2.0 kcal/mol less stable compared to t,-g,g-conformer. A reliable assignment of the fundamental bands observed in the experimental IR and Raman spectra of dendrimer was achieved. For the low generations (G′1 to G′3) the disk form of studied dendrimer molecules is the most probable. For higher generations, the shape of dendrimer molecules will be that of a cauliflower

Structure, IR and Raman spectra of phosphotrihydrazide studied by DFT

International audienceThe FTIR and FT Raman measurements of the phosphotrihydrazide (S)P[N(Me)-NH2](3) have been performed. This compound is a zero generation dendrimer G(0) with terminal amine groups. Structural optimization and normal mode analysis were obtained for G(0) by the density functional theory (DFT). Optimized geometric bond length and angles obtained by DFT show good agreement with experiment. The amine terminal groups are characterized by the well-defined bands at 3321, 3238, 1614 cm(-1) in the experimental IR spectrum and by bands at 3327, 3241 cm(-1) in the Raman spectrum of G(0). The experimental frequencies of asymmetric and symmetric NH2 stretching vibrations of amine group are lower than theoretical values due to intramolecular N-H center dot center dot center dot S hydrogen bond. This hydrogen bond is also responsible for higher experimental infrared intensity of these bands as compared with theoretical values. Relying on OFT calculations a complete vibrational assignment is proposed for the studied dendrimer