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The chemical reaction of ozone with decanethiol monolayers on Au(111) was characterized using X-ray photoelectron spectroscopy and scanning tunneling microscopy. Our results show that exposure to ozone results in oxidation of the thiol terminus. The reaction initiates at the domain boundary network of the alkanethiol monolayer and propagates into the domains. Above a threshold surface oxygen content, the monolayer converts to a two-dimensional fluid that can subsequently recrystallize to a commensurate monolayer of partially oxidized thiol. Further exposure to ozone results in conversion of the monolayer to a fluid phase and a 10% to 30% expansion of the Au lattice at the Au−thiol interface with concomitant formation of Au islands. Our results demonstrate that crystallographic defects in monolayer films can play an important role in their chemical reactions.

Scent marks are important mediators of territorial behaviour and sexual selection, especially among mammals. The evolution of compounds used in scent marks has the potential to inform our understanding of signal evolution in relation to social and sexual selection. A major challenge in studies of chemical communication is that the link between semiochemical compounds and genetic changes is often unclear. The major urinary proteins (MUPs) of house mice provide information on sex, status and individual identity. Importantly, MUPs are a direct protein product of genes, providing a clear link between genotype and phenotype. Here, we examine the evolution of urinary protein signals among house mice and relatives by examining the sequences and patterns of mRNA expression of Mup genes related to urinary scent marks. MUP patterns have evolved among mouse species both by gene duplication and variation in expression. Notably, protein scent signals that are male specific in well‐studied inbred laboratory strains vary in sex‐specificity among species. Our data reveal that individual identity signals in MUPs evolved prior to 0.35 million years ago and have rapidly diversified through recombining a modest number of amino acid variants. Amino acid variants are much more common on the exterior of the protein where they could interact with vomeronasal receptors, suggesting that chemosensory perception may have played a major role in shaping MUP diversity. These data highlight diverse processes and pressures shaping scent signals, and suggest new avenues for using wild mice to probe the evolution of signals and signal processing.

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The high resolution IR spectrum of cyclobutane in a supersonic molecular beam was obtained for the region of 2981 to 2991 cm-1. The spectrum reveals four overlapping bands suggestive of vibrational mode coupling in the C-H stretching region. Ground -state combination differences demonstrate that these bands__ Ac_:e io For originate from 2 different ground states, the symmetric and INT IS CF-., asymmetric ring puckering states. Evidence of vibrational mode, ' coupling is present in all four bands. The coupling depends on' J both J and the symmetry of the puckering state. A model:. coupling scheme involving two qualitatively different types of y couplings is developed to explain the observed spectrum.. -----------Symmetry restrictions and the Interaction between molecular" rotation and ring puckering qualitatively accounts for the[ dramatically different coupling behavior between the two ring/ puckering states.