I am reading an article on developmental biology and cannot understand (even after searching the internet) what is meant by "out-titration". For example, in this phrase:

We have previously shown that Drf1, together with Cut5, Treslin and Recq4, are out-titrated on chromatin by increasing N/C ratios in vitro.

From this article: Chk1 Inhibition of the Replication Factor Drf1 Guarantees Cell-Cycle Elongation at the Xenopus laevis Mid-blastula Transition

Thank you!!


1 Answer 1


It does seem oddly phrased, but is still understandable. The paper explains how the combination of low zygotic transcription and increasing amount of DNA due to rapid cell division can function as a switch to trigger the mid-blastula transition. Before this event, most factors in the cell are of maternal origin (ie they are not being expressed in the zygote) and are thus in limited supply. As cell division progresses, the stoichiometric ratio between these factors and DNA decreases until, eventually, there is more DNA than these replication factors. At this point, you could say that the DNA has titrated the replication factors in that there is no unbound form left. This is analogous to the equivalence point of acid-base titrations commonly encountered in first-year chemistry courses.

  • $\begingroup$ Thank you for your input! I had correctly understood the general sense of the expression, but was wandering if it was a specific process. $\endgroup$ Jul 15, 2017 at 12:17
  • $\begingroup$ @BeatriceBaldi No, it's just part of the description of the process described in the paper. I often say something is "titrated into/out of solution", which I believe is a more standard phrasing. $\endgroup$
    – canadianer
    Jul 26, 2017 at 5:32

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