How to get certain biochemical data?

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Zhen Zhang

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Aug 22, 2014, 8:55:03 AM8/22/14
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For example, I use λ pl promoter to start the downstream transcription, and I use cI as the upstream signal, or a repressor protein, which would inhibit the transcription of pl promoter.

So I suppose that I should use Hill Kinetics to model this regulation process.

So I need three parameter to describe the regulated transcription rate

1. Hill coefficient or the cooperativity constant n.
In the Wikipedia, it give two conditions with n = 2 and n = 3.
2. Dissociation constant Kd which I don't know
3. The Maximum Transcriptional Rate Vm which I also have no idea of.

Where should I go to find the later two parameters on web?
Is there any database that you always use for such condition?

I am not a professional biology researcher, so I have searched so much but ended up with nothing. Thank you a lot if you can help me! 

Matt Lawes

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Aug 22, 2014, 9:22:50 AM8/22/14
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Hmm seems like theory getting in the way of practical. Cooperativity refers to number of cI binding sites, either 2 or 3. But you should find that repressor is temperature sensitive dimer (cI857 allele) and falls apart above a certain temperature. In which case, heat pulse causes transcription. If wild type repressor, repressor will be under IPTG induction (ptac or plac)  remove IPTG and the repressor levels will begin to drop and expression from pI will begin.
>matt

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Zhen Zhang <izg...@gmail.com> wrote:

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Nathan McCorkle

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Aug 22, 2014, 10:54:57 AM8/22/14
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Josiah Zayner

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Aug 30, 2014, 8:31:38 PM8/30/14
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Is there a reason you are using Hill Kinetics?

The max transcription rate should be related to the number of ribosomes bound. Which is related to the number of repressors proteins bound.

Things you need to answer this question:
Concentration of Ribosomes
Concentration of DNA
Concentration of Repressor Protein
Kd of Ribosome for DNA
Kd of Repressor for DNA
Transcription Rate of Single Ribosome

You should be able to use Michaelis Menten Kinetics to solve then


Is this a homework question?

zhen zhang

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Aug 31, 2014, 2:53:56 AM8/31/14
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Thank you! It is not a homework, since I am just researching into this topic out of curiosity.

Why I use Hill Kinetics: As I know through a book, the Hill equation can be derived from MM equations, or as a special form of MM. In my opinion, the main difference between these two is the how many binding sites are there. In hill kinetics, there might be multiple binding sites. 

So in your answer, concentration of ribosome, two K_d value and transcription rate can be seen as constant in a particular cell. And I thought they are not  equivalent to K_d, Vm and n.

As far as I know, when repressor binds to the promoter, transcription won't happen. But there might be multiple repressors binding to the promoter to take effect.

However, this problem still annoys me a lot.

Thank you :) 

Josiah Zayner

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Aug 31, 2014, 2:53:59 PM8/31/14
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Hill kinetics is used to calculate cooperativity of binding.

What do you mean they are constant? Do you mean you assume they don't change? 

The number of molecules bound depends on the number of molecules present so you need some number. Are you looking for a simplifying case?

These numbers are not equivalent to Vm and n but you can use these numbers to calculate the Vm and n using Michaelis Menten kinetics.

Also, sorry I meant RNA polymerase not ribosome.



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