TRPA1, a member of the transient receptor potential (TRP) family of ion channels, is expressed by dorsal root ganglion neurons and by cells of the inner ear, where it has proposed roles in sensing sound, painful cold, and irritating chemicals. To test the in vivo roles of TRPA1, we generated a mouse in which the essential exons required for proper function of the Trpa1 gene were deleted. Knockout mice display behavioral deficits in response to mustard oil, to cold ( approximately 0 degrees C), and to punctate mechanical stimuli. These mice have a normal startle reflex to loud noise, a normal sense of balance, a normal auditory brainstem response, and normal transduction currents in vestibular hair cells. TRPA1 is apparently not essential for hair-cell transduction but contributes to the transduction of mechanical, cold, and chemical stimuli in nociceptor sensory neurons.

Ion channels of the transient receptor potential (TRP) superfamily are involved in a wide variety of neural signalling processes, most prominently in sensory receptor cells. They are essential for mechanosensation in systems ranging from fruitfly hearing, to nematode touch, to mouse mechanical pain. However, it is unclear in many instances whether a TRP channel directly transduces the mechanical stimulus or is part of a downstream signalling pathway. Here, we propose criteria for establishing direct mechanical activation of ion channels and review these criteria in a number of mechanosensory systems in which TRP channels are involved.

The role of heterogeneous reactions on particulate matter present in the Earth's atmosphere remains an important question in tropospheric chemistry. It has been proposed in several modeling studies that mineral dust may provide reactive surfaces for trace atmospheric gases. Laboratory studies can provide some answers concerning the kinetics of these reactions, so that heterogeneous chemistry can be quantitatively assessed in atmospheric chemistry models. In this study, the heterogeneous uptake kinetics of several volatile organic compounds (VOCs) on oxide surfaces have been measured with a Knudsen cell reactor at 295 K. In particular, the heterogeneous uptake of acetic acid, methanol, and formaldehyde on α-Fe2O3, α-Al2O2, and SiO2 has been investigated. These VOCs are representative of some of the different types of oxygenated organics found in the atmosphere. The oxide particles used in this study are models for mineral dust found in the Earth's atmosphere. Initial uptake coefficients, γ0, have been extracted from the Knudsen cell data. The uptake kinetics have been measured as a function of sample surface area to ensure that realistic surface areas are used in the calculation of the uptake coefficient. Heterogeneous reaction rates are then compared to homogeneous reactions rates for gas-phase reactions involving acetic acid, methanol, and formaldehyde. From this comparison, the possible atmospheric implications of heterogeneous reactions involving these oxygenated organics are discussed.

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