Biology subjects

Sharifian, F.

Publications and source records attributed to Sharifian, F..

3 recordsLinked to original sources

bioRxiv2025

Effect of membrane composition on interaction and permeation of a mycobacterial siderophore

1Iron acquisition is a crucial determinant of Mycobacterium tuberculosis (Mtb) survival and pathogenesis, as the bacterium must scavenge iron from the host environment during infection. To achieve this, Mtb synthesizes two structurally distinct siderophores, mycobactin (MBT) and carboxymycobactin (cMBT), efficiently chelate iron and facilitate its uptake. While MBT remains embedded in the membrane due to its hydrophobicity, cMBT is secreted to scavenge extracellular iron. Despite their biological importance, the dynamics of siderophore-membrane interactions remain poorly understood. In this study, we employ coarse-grained molecular dynamics simulations to investigate the spontaneous flip-flop of iron-bound MBT (Fe-MBT) across the mycobacterial membrane. Our results reveal that Fe-MBT flip-flop occurs on a significantly slower timescale compared to generic bacterial lipids, with rates nearly an order of magnitude lower. The lipid composition of the membrane plays a critical role in modulating this process, with mycobacterial membranes exhibiting a higher degree of lipid order and reduced Fe-MBT mobility compared to generic bacterial membranes. Furthermore, we show that flip-flop transitions are relatively fast, occurring within 100 ns and, in some cases, on the order of a few nanoseconds. Our findings contribute to a mechanistic understanding of siderophore dynamics in Mtb membranes and provide a foundation for future studies on iron acquisition and potential drug targeting strategies.

biophysics↗

bioRxiv2018

Cross-task perceptual learning of object recognition in simulated retinal implant perception

The perception gained by retina implants (RI) is limited, which asks for a learning regime to improve patients visual perception. Here we simulated RI vision and investigated if object recognition in RI patients can be improved and maintained through training. Importantly, we asked if the trained object recognition can be generalized to a new task context, and to new viewpoints of the trained objects. For this purpose, we adopted two training tasks, a naming task where participants had to choose the correct label out of other distracting labels for the presented object, and a discrimination task where participants had to choose the correct object out of other distracting objects to match the presented label. Our results showed that, despite of the task order, recognition performance was improved in both tasks and lasted at least for a week. The improved object recognition, however, can be transferred only from the naming task to the discrimination task but not vice versa. Additionally, the trained object recognition can be transferred to new viewpoints of the trained objects only in the naming task but not in the discrimination task. Training with the naming task is therefore recommended for RI patients to achieve persistent and flexible visual perception.

neuroscience↗

bioRxiv2018

Not scene learning, but attentional processing is superior in team sport athletes and action video game players

We tested if high-level athletes or action video game players have superior context learning skills. Incidental context learning was tested in a spatial contextual cueing paradigm. We found comparable contextual cueing of visual search in repeated displays in high-level amateur handball players, dedicated action video game players and normal controls. In contrast, both handball players and action video game players showed faster search than controls, measured as search time per display item, independent of display repetition. Thus, our data do not indicate superior context learning skills in athletes or action video game players. Rather, both groups showed more efficient visual search in abstract displays that were not related to sport-specific situations.

neuroscience↗