Amyloid Fibres: Understanding Elasticity & Bending Angles

[tribaggili]

Hello,

I`m studying amyloid fibres, which are filamentous proteins that intertwine between them (from 2 to 4 and more) and form fibres (2-20nm thick). I see that when that below a threshold length, the fibre is linear, beyond the threshold length, the fibre bend always with the same, constant angle. My questions are:

-why does this happen?

-can I calculate the elastic modulus from the bending angle?

I`m not a physicist, trying to become a biophysicist, so any help will be very welcomed!

Thank you,
Andrea

 

[Nidum]

Please post a picture or clear drawing for us to understand this problem properly .

 

[tribaggili]

Here is a picture...on the right part there is a long fibre, with that constant bending, on the left part few small fibres, straight.

Thank you,
Andrea

 

[tribaggili]

since the radius of curvature is small, it is possible that the bending can be appreciated only on long fibres, so maybe no different behaviour between short and long fibres...these fibres (short and long) are probably composed of 2-or more entwined filaments...my question is why they bend? and could I obtain physical properties from this bending? such as stiffness?

Andrea

 

[Nidum]

http://arxiv.org/pdf/1410.6780.pdf

http://doc.utwente.nl/80311/1/thesis_K_Sweers.pdf

I read the above documents with interest and they appear to explain a great deal but I do not have the technical background needed to make any meaningful comments .

 

[Andy Resnick]

Hello,

I`m studying amyloid fibres, which are filamentous proteins that intertwine between them (from 2 to 4 and more) and form fibres (2-20nm thick). I see that when that below a threshold length, the fibre is linear, beyond the threshold length, the fibre bend always with the same, constant angle. My questions are:

If I understand your question correctly, you are asking about the 'persistence length' of a polymer:

https://en.wikipedia.org/wiki/Persistence_length

For amyloids in paerticular:

http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.96.238301
http://pubs.acs.org/doi/abs/10.1021/ja206513r

 

[tribaggili]

Well, Nidum and Andy, I`m surprised how much you helped me, with your links I think I got all the theoretical and experimental information to properly interpret my fibres and understand their behaviour...I even found a freeware app, FiberApp, that runs with Matlab and should predict all the properties of amyloid fibrils...currently I`m trying to install it and hopefully it will works...so a big thank you for your work and very relevant contributions!

Andrea