Publications by authors named "A B Hirshfeld"

Introduction: The population is ageing. This trend is expected to cause an increase in the number of driver licenses among the elderly, and in their mobility. The effect of medications on driving capability may be significant.

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Understanding the factors affecting the stability and function of proteins at the molecular level is of fundamental importance. In spite of their use in bioelectronics and optogenetics, factors influencing thermal stability of microbial rhodopsins, a class of photoreceptor protein ubiquitous in nature are not yet well-understood. Here we report on the molecular mechanism for thermal denaturation of microbial retinal proteins, including, a highly thermostable protein, thermophilic rhodopsin (TR).

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The development of tandem ion mobility spectroscopy (IMS) known as IMS-IMS has led to extensive research into isomerizations of isolated molecules. Many recent works have focused on the retinal chromophore which is the optical switch used in animal vision. Here, we study a shortened derivative of the chromophore, which exhibits a rich IM spectrum allowing for a detailed analysis of its isomerization pathways, and show that the longer the chromophore is, the lower the barrier energies for isomerization are.

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The barrier energies for isomerization and fragmentation were measured for a series of retinal chromophore derivatives using a tandem ion mobility spectrometry approach. These measurements allow us to quantify the effect of charge delocalization on the rigidity of chromophores. We find that the role of the methyl group on the C13 position is pivotal regarding the ground state dynamics of the chromophore.

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The 11-cis retinal chromophore is tightly packed within the interior of the visual receptor rhodopsin and isomerizes to the all-trans configuration following absorption of light. The mechanism by which this isomerization event drives the outward rotation of transmembrane helix H6, a hallmark of activated G protein-coupled receptors, is not well established. To address this question, we use solid-state NMR and FTIR spectroscopy to define the orientation and interactions of the retinal chromophore in the active metarhodopsin II intermediate.

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