RESUMO
In a clinical trial registry, one determines whether a trial is registered prospectively or retrospectively by comparing the date of registration with the date on which enrollment started. However, in Clinical Trials Registry – India (CTRI), in addition, the top of each record is labelled with the phrase “Trial Registered Prospectively” or “Trial Registered Retrospectively”. In examining CTRI records, we have found that (a) although retrospective registration has been disallowed from April 1, 2018, some trials were registered retrospectively; (b) in some cases, enrollment started after registration, even though they were labelled “Trial Registered Retrospectively”, which is misleading; and (c) in some cases, the date of first enrollment was modified, changing a retrospective registration to a prospective one, although the label “Trial Registered Retrospectively” persisted. This, too, is misleading. The CTRI administration should take suitable steps to prevent late registration and mislabelling of trials regarding their registration status.
RESUMO
The linear gramicidins are peptide antibiotics that form cation-selective channels in lipid bilayers. Gramicidin channels have very well-defined functional characteristics, and the structure of membrane-spanning gramicidin A channels is known at atomic resolution. These features make the gramicidins well suited to study how the amino acid sequence encodes the structure and function of a membrane-spanning channel. We show how one can use electrophysiological measurements to obtain structural information about conducting channels and to quantify the conformational preferences of sequence-substituted gramicidin mutants.