0
$\begingroup$

When looking at this paragraph in Midorikawa's work for a fluorescence review I was confused, specifically around a time constant of ~4s being compared to ~300 ms.

  1. It is not explicitly mentioned so I assume the 300 ms is a time constant correct?
  2. How is the conclusion drawn that it is the step after tethering, priming, by the discrepancies in time constant? I am not hoping any readers know why biologically it is this way but rather how I can understand a 13x larger time constant can lead to conclusions that it is not rate-limiting? (emphasis mine)

By comparing the time course of fusion events and tethering events, it was suggested that tethering of new vesicles could refill the empty release sites with a time constant of ∼4 s. This is also surprising since the replenishment of the readily releasable vesicles (RRVs) at the calyx of Held terminal was estimated to be ∼300 ms by the electrophysiological experiments (Neher and Sakaba, 2008; Hallermann and Silver, 2013). Given that a depolarization elicit fusions of only a small fraction of already-tethered vesicles in TIRFM imaging, the discrepancy suggests that the replenishment time course was determined by the step after the tethering, i.e. priming.

Reference Midorikawa, M. (2018) Real-time imaging of synaptic vesicle exocytosis by total internal reflection fluorescence (TIRF) microscopy. Neuroscience Research, Volume 136, (2018), pp. 1-5, ISSN 0168-0102, https://doi.org/10.1016/j.neures.2018.01.008. (https://www.sciencedirect.com/science/article/pii/S0168010217307551)

Thank you for the help!

$\endgroup$
3
  • $\begingroup$ @Maurice I don't think you can talk for everyone on the site. Still, the question could be borderline off-topic... and somehow feels homeworky. Some links to provide context wouldn't hurt, not to mention title is pretty impressively unclear. $\endgroup$
    – Mithoron
    Apr 25, 2023 at 21:43
  • $\begingroup$ I linked the paper. I am writing a review of this total internal reflectance fluorescence microscopy paper which falls squarely into chemical biology and I was confused by the wording around results involving a time constant. Hope that provides enough context $\endgroup$
    – hoggywoggy
    Apr 25, 2023 at 22:44
  • $\begingroup$ (1) yes. (2) The extract suggest that they are in fact measuring different events as a way of explaining the discrepancy. Only you can know this as I'm not familiar with how good these techniques are. I presume time constant is the reciprocal of rate constant and not half-life. $\endgroup$
    – porphyrin
    Apr 26, 2023 at 7:28

0

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Browse other questions tagged or ask your own question.