The carbon–nitrogen peptide bond is rigid, but rotation can take place about the n−cα and the cα−c bonds in a protein (cα is the α carbon atom). these bond angles define the conformation of the peptide chain. consider the ramachandran plot to answer both questions. a ramachandran plot. the x axis is labeled the greek letter phi in degrees and has the values negative one hundred eighty, zero, and one hundred eighty. the y axis is labeled the greek letter psi in degrees and has values from negative one hundred eighty to positive one hundred eighty in intervals of sixty. the data plot regions are either light green, or dark green. light green regions include from negative 40 degrees psi to 100 degrees psi and from negative 180 degrees phi to to negative 40 degrees phi. there are two dark green regions. the first dark green region is 100 degrees phi to 180 degrees phi, and negative 140 degrees psi to negative 50 degrees psi. the second dark green region is negative 40 degrees phi to negative 60 degrees phi and negative 140 degrees psi to negative 40 degrees psi. which observation most likely describes part of an observed α helix? phi=+60°; =+40°; many gly residues phi=−140°; =+130°; many val residues phi=−59°; =+150°; many ser residues phi=−60°; =−47°; many ala residues phi=−57°; =−47°; many pro residues