ramachandran plot

[farmacista]

so we put two peptidic bond on the same plane, in an extended conformation with all substituent in trans position, and we assign 180 degrees to the angle between C(alpha)/N and C(alpha)/C=O. Then one book said the angles increase by rotate the bond's axis to the right watching from carbon alpha, but the picture in wikipedia and one picture in another book says the angle C(aplha)/N increase when rotate to the left watching from carbon aplha.

the angle phi rotate the other way in the book. Which is right?

 

[serotonin2A]

so we put two peptidic bond on the same plane, in an extended conformation with all substituent in trans position, and we assign 180 degrees to the angle between C(alpha)/N and C(alpha)/C=O. Then one book said the angles increase by rotate the bond's axis to the right watching from carbon alpha, but the picture in wikipedia and one picture in another book says the angle C(aplha)/N increase when rotate to the left watching from carbon aplha.

the angle phi rotate the other way in the book. Which is right?

It looks like the angle would be less than 180 degrees -- wouldn't that mean the bonds were alligned in a straight line?

 

[farmacista]

i'm not talking about bond angles but the phi and psi angles that can be measured by comparison with this reference structure that has the two amides and the alpha carbon on the same plane...so in this ideal plane structure the angles are of 180 degrees, and increase or decrease rotating the bond from the reference structure

 

[farmacista]

basically wikipedia says the phi angle increase when rotate the bond to the left watching from carbon alpha, while the book said the opposite, that increase when rotate to the right, so i wonder who's right

 

[sekio]

it depends which direction you're looking at the peptide

 

[serotonin2A]

i'm not talking about bond angles but the phi and psi angles that can be measured by comparison with this reference structure that has the two amides and the alpha carbon on the same plane...so in this ideal plane structure the angles are of 180 degrees, and increase or decrease rotating the bond from the reference structure

I know that you are talking about bond angles. But you wrote "we assign 180 degrees to the angle between C(alpha)/N and C(alpha)/C=O." That would make the bond linear, which is impossible.

 

[farmacista]

sorry i meant the dihedral angles generate by rotation of those bonds, and i'm looking the peptide from carbon alpha to nitrogen when rotate this bond, and from carbon alpha to carbonyl when rotate that (so the opposite direction). the book says angles always increase when rotate to the right watching from C(alpha) while picture shows the opposite for phi

 

[serotonin2A]

sorry i meant the dihedral angles generate by rotation of those bonds, and i'm looking the peptide from carbon alpha to nitrogen when rotate this bond, and from carbon alpha to carbonyl when rotate that (so the opposite direction). the book says angles always increase when rotate to the right watching from C(alpha) while picture shows the opposite for phi

The following link shows how torsional angles are defined:

http://goldbook.iupac.org/T06406.html