Vibrational and electronic heating in nanoscale junctions

Understanding and controlling the flow of heat is a major challenge in nanoelectronics. When a junction is driven out of equilibrium by light or the flow of electric charge, the vibrational and electronic degrees of freedom are, in general, no longer described by a single temperature[1-6]. Moreover, characterizing the steady-state vibrational and electronic distributions {\it in situ} is extremely challenging. Here we show that surface-enhanced Raman emission may be used to determine the effective temperatures for both the vibrational modes and the flowing electrons in a biased metallic nanoscale junction decorated with molecules[7]. Molecular vibrations show mode-specific pumping by both optical excitation[8] and dc current[9], with effective temperatures exceeding several hundred Kelvin. AntiStokes electronic Raman emission\cite[10,11] indicates electronic effective temperature also increases to as much as three times its no-current values at bias voltages of a few hundred mV. While the precise effective temperatures are model-dependent, the trends as a function of bias conditions are robust, and allow direct comparisons with theories of nanoscale heating.Comment: 28 pages, including 4 main figures and 10 supplemental figure

Insights into Hox Protein Function from a Large Scale Combinatorial Analysis of Protein Domains

Protein function is encoded within protein sequence and protein domains. However, how protein domains cooperate within a protein to modulate overall activity and how this impacts functional diversification at the molecular and organism levels remains largely unaddressed. Focusing on three domains of the central class Drosophila Hox transcription factor AbdominalA (AbdA), we used combinatorial domain mutations and most known AbdA developmental functions as biological readouts to investigate how protein domains collectively shape protein activity. The results uncover redundancy, interactivity, and multifunctionality of protein domains as salient features underlying overall AbdA protein activity, providing means to apprehend functional diversity and accounting for the robustness of Hox-controlled developmental programs. Importantly, the results highlight context-dependency in protein domain usage and interaction, allowing major modifications in domains to be tolerated without general functional loss. The non-pleoitropic effect of domain mutation suggests that protein modification may contribute more broadly to molecular changes underlying morphological diversification during evolution, so far thought to rely largely on modification in gene cis-regulatory sequences