Team:Aalto-Helsinki/Modeling micelle

Introduction

--Picture of the pathway here, CAR, ADO and butyraldehyde highlighted to clarify what we are talking about.--

The product of second to last enzyme of our pathway, butyraldehyde, is toxic to the cell. Because of that and about 15 naturally occurring butyraldehyde-eating enzymes in the cell it is essential for the propane production that Butyraldehyde goes swiftly to the enzyme we want it to go, ADO. As the solution to this our team wanted to put CAR and ADO close together in a micelle so that butyraldehyde would go with more probability to ADO than to any other enzyme.

--Basic picture of micelle to explain what is micelle here? Or is it essential since we explain it at the next part?--

We have made a model of effectiveness of having enzymes close together, but our team also wanted to know if the micelle structure was possible at the first place. We know (references as links for this statement!) that it is possible to form the micelle without any proteins at the end and with green fluorecent protein, but could CAR and ADO be part of this kind of structure?

Geometrical approach

Micelle structure

The micelle is formed by amphiphilic proteins that have both hydrophilic and hydrophobic parts. At the end of hydrophilic part there is short protein, a linker that attaches CAR or ADO to the amphiphilic part.

--picture of micelle somewhere near!--

Amphiphilic proteins are 10 nm long, 5 nm for both hydrophilic and hydrophobic parts. (Here where we got amphiphilic proteins sizes.) The linker (here link for more info about this. Structure and such, does lab have that somewhere?) consists of eight amino acids, for which the maximum lengths are 3,8Å. From this we can calculate that at most the length of one linker is 2,8 nm. If the linker would form $\alpha$-helical structure, then the length for one peptide would be about 1,5 Å so the one linker would be 1,2 nm long. (we need some source for the Å-lengths) However, we can estimate that the linkers are straight, since when running the structure in peptide structure prediction software doesn't yield strong folding or helical structure.

The mass of CAR is 127 797 DA and the mass of ADO is 27 569.15 Da. Based on this information and this paper we can calculate that if the enzymes were spheres, their radiuses would be 3,5 nm for CAR and 2 nm for ADO. (do we need more info about these calculations here?)

--picture of two amphiphilic proteins with ADO and CAR where all the above numbers are marked as well as total lengths--

Calculations

We can estimate how many amphiphilic proteins we can theoretically fit in one micelle by calculating how big solid angles they take with attached enzymes. The easiest way to estimate the solid angles is to think the amphiphilic proteins linked with enzymes as cones. We can calculate the solid angle $\Omega$ for these by \[ \Omega = 2\pi \left( 1-\cos(\theta) \right), \] where $\theta$ is half of the apex angle. So for CAR we get \[ \Omega_{CAR} = 2\pi \left( 1-\cos\left( \arctan\left(\frac{3.5}{14.1}\right)\right) \right) \approx 0.185 \text{ rad} \] and for ADO \[ \Omega_{ADO} = 2\pi \left( 1-\cos\left( \arctan\left(\frac{2}{9.8}\right)\right) \right) \approx 0.127 \text{ rad}.\]

--picture of this cone-like structure--

Discussion

Here text about how the results obtained show normal micelle sizes so the formation should be ok geometrically.

Here text about how we didn't take into account any forces and how this model could be improved.