Predicting olfactory receptor neuron responses from odorant structure

Background  

Olfactory receptors work at the interface between the chemical world of volatile molecules and the perception of scent in the brain. Their main purpose is to translate chemical space into information that can be processed by neural circuits. Assuming that these receptors have evolved to cope with this task, the analysis of their coding strategy promises to yield valuable insight in how to encode chemical information in an efficient way.     

CdS plume composition and dynamics of neutral species upon ablation with 532 nm laser light

The neutral species present in CdS ablation plumes upon nanosecond 532 nm laser irradiation at a moderate fluence of 0.5–0.75 J cm⁻² have been studied. Neutral Cd _n S _m clusters have been identified, some as large as (CdS)₃₃₋₃₄ (1–2 nm in diameter). The analysis of the dynamics of neutral species shows an expansion with two components that differ both in composition and dynamics. A fast, high kinetic energy component, dominated by S₂ which acquires free-flow conditions at short distances from the target, is followed by a slower component characterized by similar speeds for all species. This slower component shows dynamic features that are expected to favor aggregation processes leading to effective cluster formation.     

Secondary ion mass spectrometry of some promazines and photochemistry of chlorpromazine in glycerol

SIMS using 6 keV Cs⁺ ions has been performed on glycerol solutions of various promazines. Fragmentation patterns are compared to those obtained by other ionization methods. The photochemical degradation of chlorpromazine has been observed directly in the glycerol droplet, showing the potentiality of SIMS for the direct study of photochemical reactions in solution.     

Formation of amorphous Al1−x Au x films as a consequence of low-temperature Al/Au-interface reactions in a multilayered system

Al/Au multilayers (average composition Al₂Au, individual layer thicknesses 1 nm Al and 0.71 nm Au) are prepared at 90 K by ion beam sputtering. The electrical resistance of the growing films is monitored in situ. From the results obtained in this way it can be concluded that interface reactions occur transforming the ultrathin layers into an amorphous phase, which is stable up to 255 K.For larger individual layer thicknesses (2.1 nm Au and 3 nm Al), the interface reaction into the amorphous state is incomplete. Based on a simple parallel-resistor model, one finds that the interface reaction into the amorphous phase is restricted to a thickness of less than 3.5 nm. The temperature dependence of the resistance of such thicker multilayers indicates the onset of interdiffusion of the yet unreacted material at T=200 K resulting in the crystalline Al₂Au-phase.     

Metal‐Free Cyclization of ortho‐Nitroaryl Ynamides and Ynamines towards Spiropseudoindoxyls

An efficient metal‐free cascade reaction between 1‐dibromovinyl‐2‐nitro‐substituted arenes and secondary amines results in the formation of polycyclic pseudoindoxyls in a single step. The reaction mechanism leading to these fused ring systems was investigated, and is believed to involve the initial formation of nitroarylated ynamines/ynamides. These intermediates cycloisomerize towards N‐alkenyl‐tethered 2‐aminoisatogens via a carbene intermediate as demonstrated by QTAIM (quantum theory of atoms in molecules) and ELF (electron localization function) analysis. A subsequent intramolecular dipolar cycloaddition afforded the title compounds.     

Design of multiplex calibrant plasmids, their use in GMO detection and the limit of their applicability for quantitative purposes owing to competition effects

Five double-target multiplex plasmids to be used as calibrants for GMO quantification were constructed. They were composed of two modified targets associated in tandem in the same plasmid : (1) a part of the soybean lectin gene and (2) a part of the transgenic construction of the GTS40-3-2 event. Modifications were performed in such a way that each target could be amplified with the same primers as those for the original target from which they were derived but such that each was specifically detected with an appropriate probe. Sequence modifications were done to keep the parameters of the new target as similar as possible to those of its original sequence. The plasmids were designed to be used either in separate reactions or in multiplex reactions. Evidence is given that with each of the five different plasmids used in separate wells as a calibrant for a different copy number, a calibration curve can be built. When the targets were amplified together (in multiplex) and at different concentrations inside the same well, the calibration curves showed that there was a competition effect between the targets and this limits the range of copy numbers for calibration over a maximum of 2 orders of magnitude. Another possible application of multiplex plasmids is discussed.     

KINETIC STUDY OF THE REACTIONS OF TRIARYLPHOSPHINES WITH α-HALO SULFONES

Abstract

Reaction of a series of triarylphosphines with α-halo-m-cyanobenzyl phenyl sulfones gives the following Hammett ρ values: (CI) ρ = ?1.84; (Br) ρ = ?3.03; (I) ρ = ?3.36.