Noncontact dipole effects on channel permeation. III. Anomalous proton conductance effects in gramicidin

Proton transport on water wires, of interest for many problems in membrane biology, is analyzed in side-chain analogs of gramicidin A channels. In symmetrical 0.1 N HCl solutions, fluorination of channel Trp(11), Trp-(13), or Trp(15) side chains is found to inhibit proton transport, and replacement of one or more Trps with Phe enhances proton transport, the opposite of the effects on K(+) transport in lecithin bilayers. The current-voltage relations are superlinear, indicating that some membrane field-dependent process is rate limiting. The interfacial dipole effects are usually assumed to affect the rate of cation translocation across the channel. For proton conductance, however, water reorientation after proton translocation is anticipated to be rate limiting. We propose that the findings reported here are most readily interpreted as the result of dipole-dipole interactions between channel waters and polar side chains or lipid headgroups. In particular, if reorientation of the water column begins with the water nearest the channel exit, this hypothesis explains the negative impact of fluorination and the positive impact of headgroup dipole on proton conductance.     

MiR‐29 coordinates age‐dependent plasticity brakes in the adult visual cortex

The authors regret having omitted grant attributions in the original publication. The funding section is herewith updated to reflect the change. “Funding attributed to Tommaso Pizzorusso was provided by EPIGEN Flagship project and PRIN2017HM8FA, funding attributed to Alessandro Cellerino was provided by Fondazione Pisa ETHERNA project, funding attributed to Pierre Baldi was provided by NIH (grant NIH {"type":"entrez-nucleotide","attrs":{"text":"GM123558","term_id":"221306858","term_text":"GM123558"}}GM123558), funding attributed to Jessica Kwok was provided by the Leverhulme Trust project grant (RPG‐2018‐100).”     

Characterization of Peanut Mottle Virus in Cote d'Ivoire

A virus, hitherto unreported in Cote d'Ivoire, was detected in groundnut plant ( Arachis hypogaea ) from the northern parts of the country. Infected plants showed mottling, interveinal depression, and very prominent light and dark green patches on leaves. The causal agent was characterized as a strain of peanut mottle virus, a member of the potyvirus group, on the basis of its host range, mode of transmission, physical properties, particle morphology and on the basis of its serological properties studied in comparison with these of other groundnut viruses.