You are right, NH1 and NH2 are distinct in a way that CD1 and
CD2 in Phenylalanine are not, since the torsion angle that exchanges
them is not freely rotatable (except perhaps in a highly acidic
solution).
The practical difference is that the convention for defining
labels in Phe and the oth
Hi Gerard,
Interesting - isn't it the case that for Arg, the the NH1 and NH2 atoms
are chemically distinguishable and the convention is unambiguous (NH1
cis to CD and NH2 trans, if I recall correctly).
The truly symmetric sidechains of Asp, Glu, Tyr, Phe, and the
pseudosymmetric sidechains o
Is there any convention to define the order of the two terminal nitrogens
(NH1 and NH2) of the arginine side chain. For example, should the name NH1 be
assigned to the nitrogen that is in trans position with respect to the CD
carbon, and NH2 to the nitrogen in cis (or viceversa)?
Yes there is
