Biology subjects

Mayhew, E. J.

Publications and source records attributed to Mayhew, E. J..

3 recordsLinked to original sources

bioRxiv2026

Odors Smell Like Their Components: A Linear Framework for Predicting Olfactory Mixture Perception

Most smells, whether in food, perfume, or the environment, are complex mixtures of many odor molecules. A principled framework for modeling natural mixtures has been considered intractable because mixtures are widely assumed to generate nonlinear perceptual interactions that mirror nonlinear responses at the receptor and neural levels. We quantified perceptual interactions across 432 mixtures composed of 144 component odorants using a trained human panel, and nearly all mixtures were explained by a linear average of their component quality profiles. Within this linear modeling framework, averaging component profiles predicted mixture perception significantly better than the previous state-of-the-art and approached the ceiling set by measurement noise. Even mixtures previously reported to exhibit emergence were equally well predicted. These results suggest that the main challenge in modeling odor perception is characterizing individual components, rather than exhaustively mapping odor-odor interactions. Just as additive color mixing enabled colorimetry, linear mixing in olfaction opens the door to quantitative odorimetry, allowing mixtures to be predicted, reconstructed, and optimized computationally.

neuroscience↗

bioRxiv2023

Apple and banana fruits produce anteiso- and iso-branched-chain esters from newly synthesized precursors

Inhibitors of acetohydroxyacid synthase, the common enzyme of branched-chain amino acid biosynthesis, were applied to ripening apple (Malus xdomestica Borkh.), banana (Musa spp.), and flowering quince (Chaenomeles xsuperba) fruits to discern the contribution of newly synthesized precursors to branched-chain ester formation. After treatment, anteiso- and iso-branched-chain volatiles (i.e., those related to isoleucine, and valine and leucine, respectively) were observed to universally decrease in content. Fruits recovered production following exogenous feeding of branched-chain -ketoacids. Furthermore, apple and banana fruits were capable of metabolizing all three branched-chain -ketoacids to esters. Among free amino acids, only the branched-chain amino acids with correspondingly reduced branched-chain esters had a lesser concentration following treatment with inhibitor. Our results ultimately reject the hypothesis that anteiso- and iso-branched-chain esters are derived from preexisting amino acids and instead support the hypothesis that these esters are the product of de novo precursor biosynthesis. The novel use of these inhibitors also allowed for further investigation of branched-chain volatile biosynthesis, the citramalate synthase pathway, and the importance of precursor availability in fruits. Notably, in Valery banana fruit, ethyl acetate and butyl acetate were found to be dependent on acetohydroxyacid synthase activity for production whereas 1-methylbutyl acetate and 1-methylbutyl butanoate (sec-branched-chain esters) were not. Inhibitor usage on apples also allowed for a sensory study that found that humans can discern the absence of 2-methylbutyl and 2-methylbutanoate esters in apple fruit. Additionally, a population genetics analysis found that there is selection pressure against apples that lack these esters.

biochemistry↗

bioRxiv2020

Drawing the Borders of Olfactory Space

In studies of vision and audition, stimuli can be chosen to span the visible or audible spectrum; in olfaction, the axes and boundaries defining the analogous odorous space are unknown. As a result, the population of olfactory space is likewise unknown, and anecdotal estimates of 10,000 odorants have endured. The journey a molecule must take to reach olfactory receptors (OR) and produce an odor percept suggests some chemical criteria for odorants: a molecule must be 1) volatile enough to enter the air phase, 2) non-volatile and hydrophilic enough to sorb into the mucous layer coating the olfactory epithelium, 3) hydrophobic enough to enter an OR binding pocket, and 4) activate at least one OR. Here, we developed a simple and interpretable quantitative model that reliably predicts if a molecule is odorous or odorless based solely on the first three criteria. Applying our model to a database of all possible small organic molecules, we estimate that over 30 billion possible compounds are odorous, 6 orders of magnitude larger than current estimates of 10,000. With this model in hand, we can define the boundaries of olfactory space in terms of molecular volatility and hydrophobicity, enabling representative sampling of olfactory stimulus space.

neuroscience↗