Biology subjects

Kambara, T.

Publications and source records attributed to Kambara, T..

3 recordsLinked to original sources

bioRxiv2026

Kinetic design of reversible probe exchange enables continuous single-molecule tracking beyond the photobleaching limit

Single-molecule fluorescence imaging enables direct tracking of molecular dynamics. Prolonged observation, however, is limited by photobleaching, restricting access to rare events and slow transitions. Exchangeable fluorogenic labeling has been developed to overcome this limitation, yet continuous single-molecule tracking has not been achieved. We define two quantitative kinetic conditions for continuous tracking: pre-bleach dissociation and within-frame rebinding. Mapping reported systems onto a kinetic landscape delineates the regime required for continuous tracking. To reach this regime, we turned to odorant-binding proteins, whose biological role favors rapid ligand capture and release. We paired this scaffold with high-contrast fluorogenic probes to maximize rebinding capacity while preserving rapid dissociation. The resulting system, EverGreen, sustains uninterrupted single-molecule observation for over 24 hours and establishes a general kinetic design framework beyond the photobleaching limit.

biophysics↗

bioRxiv2025

Enhanced axonal transport in large vertebrates: KIF5A adaptations in giraffes and pythons

Efficient axonal transport is essential for neuronal function, particularly in species with exceptionally long axons. The Kinesin-1 motor protein KIF5A plays a key role in this process, but whether and how it adapts to the transport demands of large vertebrates remains unclear. Here, we show that KIF5A from giraffes (GcKIF5A) and pythons (PbKIF5A), moves 25% faster than its mouse counterpart (MmKIF5A) on neuronal microtubules in vitro and within axons of cultured mouse hippocampal neurons. This enhanced velocity, driven by three unique amino acid substitutions (R114Q, S155A and Y309F), facilitates long-distance transport in these species and represents a case of convergent evolution. Our structural analysis reveals that accelerated ADP release underlies the increased speed of GcKIF5A. Despite exhibiting a reduced force generation, GcKIF5A maintains efficient cargo transport under load. Furthermore, GcKIF5A exerts less drag in mixed-motor environments, an adaptation particularly beneficial for multiple motor-driven long-distance axonal transport. These findings reveal that KIF5A has evolved specific adaptations to facilitate efficient axonal transport in large vertebrates, highlighting the evolutionary plasticity of kinesin motors.

biophysics↗

bioRxiv2025

Visualization of functional and effective connectivity underlying auditory descriptive naming

ObjectiveWe visualized functional and effective connectivity within specific white matter networks in response to auditory descriptive questions. MethodsWe investigated 40 Japanese-speaking patients with focal epilepsy and estimated connectivity measures using cortical high-gamma dynamics and MRI tractography. ResultsHearing a wh-interrogative at question onset enhanced inter-hemispheric functional connectivity, with left-to-right callosal facilitatory flows between the superior-temporal gyri, contrasted by functional connectivity diminution with right-to-left callosal suppressive flows between dorsolateral prefrontal regions. Processing verbs associated with concrete objects or adverbs increased left intra-hemispheric connectivity, with bidirectional facilitatory flows through extensive white matter pathways. Questions beginning with what, compared to where, induced greater neural engagement in the left posterior inferior-frontal gyrus at question offset, linked to enhanced functional connectivity and bidirectional facilitatory flows to the temporal lobe neocortex via the arcuate fasciculus. During overt responses, inter-hemispheric functional connectivity was enhanced, with bidirectional callosal flows between Rolandic areas, and individuals with higher IQ scores exhibited less prolonged neural engagement in the left posterior middle frontal gyrus. ConclusionsVisualization of directional neural interactions within white matter networks during overt naming is feasible. SignificancePhrase order may influence network dynamics in listeners, even when presented with auditory descriptive questions conveying similar meanings.

neuroscience↗