I'm trying to model the hydrophobic regions of my protein; I used tissue paper last year, but it took forever and was extremely difficult to put on (at least in my opinion, but then again, I'm a paranoid perfectionist...). Is there a type of paint that I can use on my toober, that doesn't smear very much? I understand that it's difficult to find a paint that won't smear on the porous material (if you rub it while working with the toober after the paint has dried), but I just want one that does the job.
My friend suggested a thick oil-based paint, one used for model cars, etc.
Acrylic paint. Use a thin layer, and it will dry very quickly. It will not smear, although it could rub off somewhat with heavy handling – but in that case, you just retouch it before competition.
Would it be a good idea to include chain c as well in the model as one of the additions? I'm not really sure why we only had to do chains a and b, besides that's what they told us to do.
The reason we were told to only do chains A and B is that together, they represent one "asymmetrical unit" of caspase-3 – meaning that while chains A + B PLUS chains C + D is the way caspase-3 is found in the body (as a heterotetramer), A and C are identical and B and D are identical, so you can get a good idea of the functional shape of the protein by just looking at one heterodimer.
Like I said, the "biological unit" of caspase-3 – the way it's found in the body – does include all four chains A through D, so that could be one reason to show the other two chains as a creative addition (yes, the result would be huge, like Dragonshark suggested – even just the required part is already gigantic this year – but it could be useful).
Chains E and F are also identical to each other, and both represent XIAP. You could represent one, both, or neither as a creative addition; I mean, in order to totally inhibit the caspase-3 tetramer, you'd need two molecules of XIAP, but you can show how it binds on your model with only one, should you so desire.
Totally get what your saying. Last year I tried painting my protein... compelte fail. I then used tape... more of a fail. In the end I used pipe cleaners and tied them around. You can also use twisty-ties, or even yarn/string.
I used masking tape in my 2010 hemagglutinin prebuild (to show the fusion peptide, if anyone remembers that), and after a couple layers, it actually looked relatively neat. It was not easy, however. I've never actually painted my prebuild, but I've gotten acrylics on my Toober in the process of painting other things, and they seem to stick.
I use Sharpie to mark my protein fairly regularly, and it definitely rubs off – both over time and by scratching off with a nail/the edge of a piece of heavy paper/a blunt scissor. I tend to think of this as a feature rather than a bug, though: it lets me change things fairly easily between competitions if I change my mind about what to display.