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I'm looking at some data with substrate concentration on the $x$-axis and $k_\text{dep}$ on the $y$ axis. What does $k_\text{dep}$ mean? I understand that it must be a rate of some kind but what is the significance of the 'dep' part?

The data I'm looking at can be found in Fig. 9 in this paper (PDF):


enter image description here


Essentially this is a dose response curve for a substrate and enzyme. I suspect $k_\text{dep}$ is simply the rate but why $k_\text{dep}$ and not just $k$?

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  • $\begingroup$ Material deposition on a surface? I'm just guessing too! $\endgroup$ – Klaus-Dieter Warzecha Apr 9 '15 at 11:13
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    $\begingroup$ I looked at the paper. It uses a lowercase k with a subscript "dep" for the symbol you are asking about. You can use those symbols in your questions -- see here for more info. This time, I'll edit your question to give you an example of how to do this. $\endgroup$ – Curt F. Apr 9 '15 at 14:29
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    $\begingroup$ The "dep" probably stands for "depletion": read the paper you linked to for more context. Often times, subscripts on rate constants are used to refer to which reaction in a system of multiple reactions. You'll see $k_1$ and $k_2$ for rate constants of "reaction 1" and "reaction 2", etc. $\endgroup$ – Curt F. Apr 9 '15 at 14:32
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The "dep" probably stands for "depletion": read the paper you linked to for more context. Often times, subscripts on rate constants are used to refer to which reaction in a system of multiple reactions. You'll see $k_1$ and $k_2$ for rate constants of "reaction 1" and "reaction 2", etc.

I suspect in the paper, they were measuring the depletion of a substrate, and not what the substrate was converted to. So they wouldn't know if they were measuring the rate of a single reaction $\ce{A->B}$, or the combined rates of multiple reactions such as $\ce{A->B}$ and $\ce{A->C}$. Thus (probably) the desire to indicate $k_{depletion}$ instead of just $k$.

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    $\begingroup$ yes, the Fig. 9 caption reads "...The depletion of 4-oxo-atRA (A) and 18-OH-atRA (B) as a function of time was measured at six different concentrations of each substrate and the depletion rates were determined (insets in both panels). All depletion experiments were conducted in duplicate. The depletion constants as a function of substrate concentrations were used..." $\endgroup$ – DavePhD Apr 9 '15 at 18:12

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