00:01
Let us try to solve problem number two from chapter 4.
00:04
There are two sub -questions in this question.
00:07
We will try to solve part a first.
00:10
Coming to part a, alpha -carotin are successive turns of helix, which are spaced at an interval of 5 .4 angstrom.
00:21
This is, this keratin is a supercoiled structure, or at least a coiled structure like you see on the screen.
00:28
And these helices, the helix that you see, are spaced at 5 .4 angstrom.
00:34
The interval or the spacing between these helixis or helices is 5 .4 angstrom.
00:43
So these two alpha keratin strands twisted into a coiled coil, they produce 5 .2 angstrom spacing.
00:54
The spacing between them, in fact, the whole structure of protein or whole structure of this alpha keratin is spaced like.
01:02
This and the distance between these two is formed by the hydrogen bonds and in fact the stability as well is because of the h bonds or the hydrogen bonds between them the whole fiber is thus formed like this because of the hydrogen bonds and the spacing of 5 .4 angstrom now coming to the steaming and stretching of the fiber as they have asked in the question you can also refer to the figure for the elaborate explanation or i can or you can refer to the screen that i will be drawing the figures out there steaming and stretching the fiber is an extended polypeptide chain with the beta confirmation all this while we were talking about alpha keratin but this leads to some this leads to a beta confirmation the extending and stretching of this polypeptide alpha keratin is a polypeptide chain in which the distance from the distance between the adjacent r groups is about 7 .5 angstrom.
02:10
Now we are talking about the beta confirmation of this.
02:13
And here the spacing or the interval comes around 7 angstrom for this beta confirmation.
02:21
This is the spacing between the adjacent all groups in the alpha keratin.
02:26
So upon re -steaming the structure, the polypeptide chains again assume the less extended alpha helix conformation.
02:34
They again go back to this structure upon re -steaming...