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A dynamic, physics-based model is presented for ionic polymer-metal composite (IPMC) sensors. The model is an infinite-dimensional transfer function relating the short-circuit sensing current to the applied deformation. It is obtained by deriving the exact solution to the governing partial differential equation (PDE) for the sensing dynamics, where the effect of distributed surface resistance is incorporated. The PDE is solved in the Laplace domain, subject to the condition that the charge density at the boundary is proportional to the applied stress. The physical model is expressed in terms of fundamental material parameters and sensor dimensions and is thus scalable. It can be easily reduced to low-order models for real-time conditioning of sensor signals in targeted applications of IPMC sensors. Experimental results are provided to validate the proposed model.

Translation initiation of most mRNAs involves mG-cap binding, ribosomal scanning and AUG selection. Initiation from a mG-cap-proximal AUG can be bypassed resulting in leaky-scanning, except for mRNAs bearing the ranslationnitiator of hort 5'UTR (TISU) element. mG-cap-binding is mediated by eIF4E-eIF4G1 complex. eIF4G1 also associates with eIF1 and both promote scanning and AUG selection. Understanding the dynamics and significance of these interactions is lacking. We report that eIF4G1 exists in two complexes, either with eIF4E or with eIF1. Using an eIF1 mutant impaired in eIF4G1 binding, we demonstrate that eIF1-eIF4G1 interaction is important for leaky scanning and for avoiding mG-cap-proximal initiation. Intriguingly, eIF4E-eIF4G1 antagonizes the scanning promoted by eIF1-eIF4G1 and is required for TISU. Mapping eIF1-binding site on eIF4G1 we unexpectedly found that eIF4E also binds it indirectly. These findings uncover the RNA features underlying regulation by eIF4E-eIF4G1 and eIF1-eIF4G1 and suggest that 43S ribosome transition from the mG-cap to scanning involves relocation of eIF4G1 from eIF4E to eIF1.

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