On the role of chirality in structure-odor relationships

The influence of chirality on odors was studied on 16 enantiomericpairs according to the dispersion/hydrogen bonding theory ofreceptor-odorant interaction. Comparisons of molecular structures were made by superimpositionof optimized conformations, using the Alchemy II package. Thequality of fit was assessed using the RMS parameter includedin Alchemy II and a new index for hydrogen bonding: the anglebetween H-bonds in the two molecules. In the case of camphoraceous odorants where an interaction modelwas already known superimposition according to the model ledto correct predictions of the high similarity of odors observedin enantiomeric pairs. For several urinous odorants comparisons were made using d-androstenoneas a reference compound for the urinous odor. Correct predictionswere obtained for l-androstenone, both enantiomers of androsta-4,16-dienone, and (+)-2-methyl-4-(5,5,6-exo-trimethy1-2-exonorbornyl)-cyclobexane.The (–) enantiomer of the latter compound was correctlypredicted only if it was assumed that its weak intensity isdue to a partial interaction with the hydrophobic zone of thereceptor. For ambergris odorants which have a complex odor (–)-Ambroxwas selected as the reference compound. The odors of (+)-Ambroxand enantiomers of four other compounds (ambergris or woody)were correctly predicted by superimposition. For nootkatone and three derivatives which have a grapefruitnote for one enantiomer and a woody note for the other no modelsor reference compounds were available. The superimpositionswere made between grapefruit enantiomers, on the one hand, andwoody enantiomers on the other hand. Woody and grapefruit characterswere correctly predicted in all cases. The limits of this approach based on molecular modelling arediscussed.     

Odor intensity of binary mixtures of odorous compounds

This paper presents the MBO model for the perceived intensity of odour mixtures. This model is based on an equation previously reported by our team, intended to model the whole stimulus-response intensity curve of pure odorous compounds. The MBO model was applied to a set of published data, and compared to other published models. The results show a high modelling efficiency of the MBO model compared to other proposed equations, especially for binary mixtures exhibiting significant asymmetry of intensity for different ratios of the two components. Furthermore, the MBO model includes parameters specific to the respective effects of each component in the mixture, which may help to clarify the masking and synergy effects that are often sought in odour mixtures.     

A multidimensional statistical study of similarities between 74 notes used in perfumery

From a data bank of 2467 odoriferous products, the similaritiesbetween 74 notes used in perfumery were calculated. The similaritymatrix (74,74) contains – 63% of zero values and showsthat only a few pairs of notes present high similarity coefficients.A fine analysis using ascending hierarchical taxonomy with thecomplete linkage procedure shows that 14 notes are isolatedwhile 60 notes are regrouped in 27 groups containing two tofour notes. The isolated notes correspond to well-defined structuralparticularities. Some pairs of notes or groups present similaritiesin their chemical structures but some groups are built on thebasis of semantic processes. This study shows that the notesare generally independent, with no strict hierarchy among them,and rules out the existence of primary odors.     

A Comparative Mechanical Analysis of Plant and Animal Cells Reveals Convergence across Kingdoms

Plant and animals have evolved different strategies for their development. Whether this is linked to major differences in their cell mechanics remains unclear, mainly because measurements on plant and animal cells relied on independent experiments and setups, thus hindering any direct comparison. In this study we used the same micro-rheometer to compare animal and plant single cell rheology. We found that wall-less plant cells exhibit the same weak power law rheology as animal cells, with comparable values of elastic and loss moduli. Remarkably, microtubules primarily contributed to the rheological behavior of wall-less plant cells whereas rheology of animal cells was mainly dependent on the actin network. Thus, plant and animal cells evolved different molecular strategies to reach a comparable cytoplasmic mechanical core, suggesting that evolutionary convergence could include the internal biophysical properties of cells.     

Differential pulse voltammetry: focus on the measurement of 5-hydroxyindole compounds and uric acid in the brain

The electrochemical signal obtained at the +300 mV potential (peak 3) in rats implanted for more than one week could be dependent upon extracellular fraction of 5-hydroxyindolacetic acid (5-HIAA) since a single injection of Pargyline is sufficient to suppress it in caudate and raphe dorsalis nuclei. In contrast, in rats implanted for less than one week, this signal could be dependent upon extracellular fractions of 5-HIAA and uric acid since consecutive injections of Pargyline and Allopurinol are necessary to suppress it.     

Hypnogenic effects of des-acetyl-alpha-MSH and CLIP (ACTH 18-39) in the rat

In the rat, the intraventricular administration of ACTH (adrenocorticotropic hormone) has no effect upon the sleep-waking cycle. However, administration of two ACTH-derived peptides is followed by a selective and significant increase of each sleep state: Des-alpha-MSH (Des-acetyl-alpha-melanocyte stimulating hormone) administration induces an increase of slow wave sleep, while CLIP (corticotropin-like intermediate lobe peptide) is followed by an increase of paradoxical sleep.     

Opposite variations of extracellular concentrations of 5-hydroxyindoleacetic acid (5-HIAA) measured by voltammetry of axonal terminals and cell bodies of the dorsal raphe nucleus through the sleep-wake cycle

Differential pulse voltammetry was used for 5-hydroxyindoleacetic acid (5-HIAA) detection in the rat caudate (n. Cd) and Raphe Dorsalis (n. RD) nuclei, in chronic experimental conditions. In the anterior and ventral part of n. RD, large increases in the extracellular concentrations of 5-HIAA were reported during slow wave sleep (SWS) and paradoxical sleep (PS) whereas a decrease occurred during waking. These variations could reflect the dendritic release of serotonin. In n. Cd, opposite variations of the extracellular concentrations of 5-HIAA were observed i.e. increase during waking state and decrease during SWS and PS.