Team:Oxford/progress

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<h1>Modelling Progress</h1>
 
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<h2>Week 3 Day 2 </h2>
 
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<h2>Oliver says:</h2>
 
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<p>Matched up the growth curves. This allows us to use the growth rate (the red dotted line) to find the exact values of the gradient and therefore the exact value of the maximum growth rate in the various concentrations of DCM. This is very useful for the biochemists. The graph of this is shown below.</p>
 
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<p>In the afternoon I began work on building a very large and complex model that Jack conceptualized that brings in lots of different areas of the project to model how the DCM is degraded over time. The model depends on many variables and includes factors like intracellular pH change and how this will affect growth rate of the bacteria and therefore the rate of DCM degradation.</p>
 
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[[File:Oxford model 12.png|930px|left]]
 
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<h2>Week 3 Day 1 </h2>
 
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<h2>Leroy says:</h2>
 
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<p>Getting up to speed with everything that has been done in the past few weeks particularly with regards to the repressor and activator modelling. Have been put on the modelling of the pdu micro-compartments (a.k.a. protein prisons as they shall henceforth be known). Shifted focus initially from trying to predict micro-compartment geometry from ratios of protein components to modelling the number of molecules that could fit in the protein prison (PP). Enzyme dimensions obtained from Jack. They are being modelled as spheroids and I am currently investigating the packing density of spheroids according to a number of characterizing variables e.g. sphericity and aspect ratio.</p>
 
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[[File:Formaldehyde_dehydrogenase_crystal_4_subunits.png|450px|thumb|left|Formaldehyde Dehydrogenase crystal structure (monomer of tetramer highlighted) dimensions estimation]]
 
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[[File:DcmA_predicted_structure.png|350px|thumb|right|DcmA predicted structure (monomer of hexamer shown) dimensions estimation.]]
 
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<h2>Matt says:</h2>
 
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<p>Spent today researching suitable LEDs for absorption of light for GFP, and suitable photodiodes for picking up the emission from it. On consulting Ciaran and the plate reader, i realised that SFGFP had significantly different peaks for absorption/emission than regular GFP. We diluted "pure" GFP up to 100 000 and tested its luminosity in the plate reader, only diluting it by 10 gave off too much light for the reader to measure and up to 100 000 there was still a readable difference.</p>
 
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<h2>Oliver says:</h2>
 
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<p>Cracking on with more modelling. I've had a chat with Andy about the growth curves that he obtained from the bacteria in different concentrations of DCM and plotted them on Matlab. This will allow me to manipulate them much more easily. I have also written a script for the solving of the first order ODE that describes general bacteria growth (it's just a combination of two delayed exponentials). It describes an initial stationary phase, then a growth phase and then a stationary phase. Having plotted this on similar scales, my plan is to match the modelled curve and the real curve to allow me to calculate the constants that describe the growth of the two types of bacteria. This will allow me to predict the growth behaviour of the bacteria for future experiments with varying concentrations of DCM without actually doing the experiment in real life. INCLUDE THIS EQUATION IN FINAL WRITE UP.</p>
 
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[[File:Oxford model 11.png|930px|thumb|left|Real life growth]]
 
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[[File:Oxford model 10.png|930px|thumb|left|I will fit this graph to the above data. The growth line is just the gradient of the purple line]]
 
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<h2>Week 2 Day 5 </h2>
 
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<h2>Oliver says:</h2>
 
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<p>Had the meeting this morning, very helpful and I think it should ensure we stay on track for the next week or so. Spent the day working with Jack modelling the rate of degradation of DCM by the beads, dependent on the 5 different variables that we can change by changing how we make the beads. He's not completely happy with how robust the model is though so won't let me upload the graphs yet. Something for regular followers of 'Oliver says' to look forwards to! </p>
 
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<h2>Week 2 Day 4 </h2>
 
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<h2>Matt says:</h2>
 
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<p>Spent this morning learning how to produce 2D/3D graphs on matlab.
 
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In the afternoon, we thought about some ideas for having a digital (and continuous) test for when the DCM had been used up to a defined level, using comparators and light dependent resistors.</p>
 
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<p>Below is a basic design for a circuit which will have a glowing (Green) LED when the fluorescent bacteria reach a certain light level (level to be found later). Once the light level is found, i will record the value of the LDR's resistance at this level, i will set R1 to this value so that the comparator will switch at this point. Depending on the design for the container this could then possibly be linked to a digital dispencer of DCM/Nutrients for bacteria.</p>
 
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[[File:Matt circuit.png|930px|left]]
 
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<h2>Oliver says:</h2>
 
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<p>The effect of changing the activation and degradation rate of the sfGFP protein on the response of the system. This is brilliant and is exactly what synthetic biology is about. These graphs will be very useful to the biochemists as they allow them to choose a degradation and activation coefficient before they begin the experiment, thus saving them lots of time and many experiments. Therefore, they will be relying completely on this modelling, especially as this competition is so short in duration. </p>
 
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<p>We are aiming for a step response in the GFP glowing, this will allow a very effective reporter system for when the bacteria have run out of DCM. Therefore, based on this model, we are going to start with a high activation coefficient because this doesn't affect the speed of response but increases the amplitude of the response. Choosing the degradation coefficient is more difficult as you have to choose between a fast response and a high amplitude of response </p>
 
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<p> Therefore we're going to start off with a high activation coefficient and a low degradation coefficient; if the response of this is bright enough we'll steadily increase the degradation coefficient until we get a satisfactory speed of response of the green glow turning 'off'.</p>
 
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[[File:Oxford model 8.png|930px|left]]
 
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[[File:Oxford model 7.png|930px|left]]
 
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<h2>Week 2 Day 3 </h2>
 
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<h2>Oliver says:</h2>
 
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<p>Had a long chat with Fran, George, Ciaran and Glen this morning about the surface plot, we established that if the system behaves as the model predicts it will be very beneficial. This is because it provides a sharp cut off when the amount of DCM gets low, this is exactly what is needed as we're designing an on/off biosensor.</p>
 
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<p>We established that as long as the concentration of TCY stays above a certain threshold (this threshold will remain unknown until we get lab data), the response of the system isn't affected by the concentration of TCY. Therefore, in experiments and models from now on, we will be holding TCY constant while changing the concentration of DCM. In some experiments it will be a step up and a ramp down (to simulate real life as the DCM gets degraded) and in other experiments we will be using a step up and a step down in concentration of DCM to check that our biosensor is responding correctly and robustly. </p>
 
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<p> I think that the model will help to cut down the number of experiments necessary by quite a lot.</p>
 
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<p>I will now plot graphs of how the GFP expression will change in response to a step up and step down in DCM concentration depending on varying expression rate and degradation rate of GFP. The biochemists assure me that these two parameters are the only two that we can realistically play around with.</p>
 
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<p>Also had a chat with Jack about doing surface plots that displayed the expected output of the variation in diffusivity of DCM and H2O through the polymer that he's making, depending on the thickness of the polymer and the AcCl stoichoimetry in synthesis. This polymer will coat the agarose beads that will contain the bacteria. It will be important to maintain the correct concentration of DCM inside the beads so obtaining the correct surface plot will be important.</p>
 
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<p>Plated up some bacteria cultures with Phil in the evening!</p>
 
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<h2>Week 2 Day 2 </h2>
 
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<h2>Matt says:</h2>
 
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<p>I spent today reading up on lecture notes for modelling biochemical systems and catching up with Ollie's progress. Also qualitatively described the effect of GFP's ( or DCMA) degradation rate on its production over time as it uses up the DCM.</p>
 
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<h2>Oliver says:</h2>
 
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<p>Today I pretty much nailed the time varying 3D surface plot. It allows the user to see the variation in fluorescence over time when varying amounts of DCM and tetracycline are added. It has shown how important varying time will be when taking measurements of GFP to allow the characterization of this system.</p>
 
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[[File:Oxford model 5.png|900px|thumb|left|A sneak preview of the upcoming movie]]
 
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<h2>Week 2 Day 1 </h2>
 
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<h2>Oliver says:</h2>
 
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<p>Today was spent sat at the computer writing code. Last Thursday George introduced me to a few extra levels that were involved in the real system and so would require these extra levels to be built into the model. I have been thinking about these complications over the weekend and I'm pretty sure that I was able to work out how to modify the relevant equations accordingly. </p>
 
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<p>The new model that I built in the morning took into account not only the addition of Tetracycline, but also the addition of DCM to the system. This means that the model responds much more robustly and accurately to extreme circumstances, such as when either TCY or DCM is set to zero.</p>
 
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<p>In the afternoon I successfully plotted the variation in the value of steady state GFP after addition of varying amounts of DCM and TCY. Next goal is to combine these to get a surface plot!</p>
 
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[[File:Oxford model 2.png|900px|thumb|left|An example of the model's output]]
 
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[[File:Oxford model 3.png|400px|thumb|left|An example of the model's output]]
 
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[[File:Oxford model 4.png|400px|thumb|right|An example of the model's output]]
 
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<h2>Week 1 Day 5 </h2>
 
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<h2>Jack says:</h2>
 
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<p>(Part D): A very productive day designing the bacterial containment system and overall chemical/mechanical logistics;</p>
 
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<p>5mm diameter agarose-bacteria 'beads' will be coated with a DCM-diffusion-limiting modified cellulose-based polymer, such that the DCM influx is less than or equal to the rate of DCM breakdown. The aim is maintaining an internal capsule [DCM] within our bacterial tolerance limits, while enabling direct capsule exposure to high [DCM]. In our physical system, the manufactured beads will have lower than water density, lying at the aqueous surface of a biphasic mixture of DCM and water, giving our bacteria access to both components by exploiting the DCM-water solubility of up to 206mM (25oC).</p>
 
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<p>The DCM-polymer permeability will be controlled by the stoichiometry of acetylation of the cellulose substrate - hence its hydrophobicity, and coating thickness, while overall capsule density may be modified if necessary by introducing a permeable second coating of low density.</p>
 
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<p>Minimal user-intervention - How the currently proposed system will work from a user perspective:
 
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<li>To a PTFE container, add in order, the ratios:
 
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          <center>W mL DCM : X mL water : Y g 'powder mix'* : Z g capsules</center>
 
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(volume measurements aided by container graduation and masses by 'scoops' etc. provided)
 
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*containing buffer to minimize solution pH drop on HCl production, and {biochemically necessary compounds for the bacteria}.
 
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<li>When system response** to complete dcm degradation is seen, the solution is safe to dispose of down the sink.
 
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**dcm detection will be directly achieved by a gfp response from our bacteria, activating a green LED on the container lid via a photodiode circuit.
 
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<p>The strengths of this setup are minimal user intervention and the direct, quick, low-cost measurement of [dcm], possible using synthetic biology.
 
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As HCl has greater solubility in water than in DCM, the greater the H2O/DCM vol. ratio, the lower the rate of pH drop with HCl production. This is something we can model and optimise.
 
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<p>Next, for me, is to experiment producing agarose etc. beads by various methods, identify candidate coating materials, do kinetic calculations based on permeability data, and identify coating methods that the bacteria will survive.
 
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<h2>Oliver says:</h2>
 
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<p>Sheffield meet up!</p>
 
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<h2>Week 1 Day 4 </h2>
 
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<h2>Oliver says:</h2>
 
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<p>Spent the morning with Jack looking at where the parameters come in. Played with the model and after speaking with George discovered that I hadn't modelled quite what the system is.</p>
 
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<h2>Week 1 Day 3</h2>
 
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<h2>Jack says:</h2>
 
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<p>(Part A): Modelled the <a href="https://2014.igem.org/Team:Oxford/modellingA">thermodynamics of solution-vapour equilibration</a>, justifying our [DCM] approximation by calculating its deviation due to this effect.</p>
 
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<h2>Oliver says:  - Major Breakthrough</h2>
 
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<p>Finished the first draft of the model, will leave it until we have real data to feed back into the system. The model is very robust and allows any user to input a large variety of parameters and scenarios that could be realistically expected in the laboratory results. The output of the model is the colour that you can expect over time (the outputs of the real system will be from a combination of mCherry and GFP).</p>
 
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<p>The model reveals surprising results, including how even a small basal rate of gene expression (due to leakage of the promoters) can really change the results.</p>
 
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<p>The way that I finally got the model to work was by returning to the ODE15s function in Matlab and not bothering with Laplace transforms. Information on how to use Matlab to model repressor and activator networks very easily, accurately and quickly will be uploaded to this wiki soon! If you want more details please don't hesitate to contact us.</p>
 
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[[File:OxiGEM_Model_1.png|900px|thumb|left|An example of the model's output]]
 
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<h2>Week 1 Day 2 </h2>
 
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<h2>Oliver says:</h2>
 
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<p>Today was difficult. It was spent trying to write Matlab code to solve the differential equations. Having already written the code successfully for an autorepressor and an autoactivator using the built in function ode15s, I thought it would be relatively easy to use similar code to model a network. However, I ran into quite a lot of problems with transferring all of the required values back and forth between the function script and the data entry script.</p>
 
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<p> In the afternoon, I tried to get the model to work using Laplace transforms and more specifically Matlab's incredible computing ability at calculating the inverse laplace transform of complex functions to allow solutions to be obtained. However, this presented more problems than the ode15s function due to vector sizes and things that quite quickly got quite messy.</p>
 
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<p>Help with the autorepressor/autoactivator code will be up on the wiki shortly, please don't hesitate to contact us in the meantime for more info though.</p>
 
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<h2>Week 1 Day 1 - Conceptualizing part B</h2>
 
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<h2>Jack says:</h2>
 
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<p>(Part B): day 1 modelling was spent setting up a kinetic 'map' of the tetR system as a biological repressor analogue to uncharacterised dcmR. Stochastic kinetic data was found <font style="vertical-align: super; font-size: 70%;"><a href="https://2014.igem.org/Team:Oxford/references">2</a></font> and required coefficients approximated (relative orders of magnitude) from these data sets will be fed into Ollie's ODE Model. </p>
 
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<h2>Oliver says:</h2>
 
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<p>The morning was spent with Glen and Fran (who are working on part B) discussing exactly what network of activation and repression we were trying to categorize and turning it from Snapgene files (that the Biochemists understand) into a series of possible repression and activation scenarios.</p>
 
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<p>Then, it was a matter of condensing the network of seemingly complex interactions into a set of differential equations with the relevant constants. This allows the response of the system to an external known input be accurately modeled.</p>
 
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[[File:Repress and activate network.jpg.png|930px|left]]
 
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Latest revision as of 01:01, 18 October 2014

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