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Table 5 Secondary structure matrix. The occurrence of the secondary structure types of proline in the cis and trans conformation is shown. For the five defined secondary structure elements (bend, coil, helix, strand and turn) we analyzed the surrounding of the fixed proline in the mid-position. Rows indicate the secondary structure type with fixed secondary structure of the proline. Columns show the relative occurrences of the secondary structure at the 4 positions around proline. Bold face highlights the most probable secondary structure. For the cis peptide bond conformation of the central proline in helix and strand not enough entries could be collected from the PDB to reach significance.

From: Statistically significant dependence of the Xaa-Pro peptide bond conformation on secondary structure and amino acid sequence

secondary structure structure of trans Pro structure of cis Pro
  position position
  i-2 i-1 bend i+1 i+2 i-2 i-1 bend i+1 i+2
bend: 257 0.21 317 0.26 1211 684 0.56 229 0.19 176 0.24 467 0.63 742 143 0.19 105 0.14
coil: 462 0.38 813 0.67 1211 334 0.28 545 0.45 329 0.44 180 0.24 742 433 0.58 321 0.43
helix: 77 0.06 2 0.00 1211 22 0.02 107 0.09 31 0.04 0 0.00 742 28 0.04 70 0.09
strand: 254 0.21 74 0.06 1211 135 0.11 228 0.19 164 0.22 95 0.13 742 104 0.14 174 0.23
turn: 161 0.13 5 0.00 1211 36 0.03 102 0.08 42 0.06 0 0.00 742 34 0.05 72 0.10
  i-2 i-1 coil i+1 i+2 i-2 i-1 coil i+1 i+2
bend: 1401 0.22 1614 0.25 6505 952 0.15 901 0.14 41 0.18 80 0.35 231 29 0.13 37 0.16
coil: 2966 0.46 4430 0.68 6505 3749 0.58 2656 0.41 112 0.48 137 0.59 231 127 0.55 81 0.35
helix: 377 0.06 8 0.00 6505 532 0.08 862 0.13 9 0.04 0 0.00 231 9 0.04 14 0.06
strand: 934 0.14 360 0.06 6505 788 0.12 1312 0.20 41 0.18 13 0.06 231 62 0.27 91 0.39
turn: 827 0.13 93 0.01 6505 484 0.07 774 0.12 28 0.12 1 0.00 231 4 0.02 8 0.03
  i-2 i-1 helix i+1 i+2 i-2 i-1 helix i+1 i+2
bend: 361 0.14 193 0.07 2603 1 0.00 12 0.00 0 0.00 0 0.00 8 0 0.00 1 0.13
coil: 752 0.29 913 0.35 2603 1 0.00 38 0.01 0 0.00 0 0.00 8 0 0.00 2 0.25
helix: 722 0.28 935 0.36 2603 2597 1.00 2489 0.96 8 1.00 8 1.00 8 8 1.00 0 0.00
strand: 165 0.06 43 0.02 2603 0 0.00 6 0.00 0 0.00 0 0.00 8 0 0.00 0 0.00
turn: 603 0.23 519 0.20 2603 4 0.00 58 0.02 0 0.00 0 0.00 8 0 0.00 5 0.63
  i-2 i-1 strand i+1 i+2 i-2 i-1 strand i+1 i+2
bend: 124 0.09 98 0.07 1352 123 0.09 202 0.15 0 0.00 2 0.22 9 1 0.11 1 0.11
coil: 268 0.20 157 0.12 1352 391 0.29 322 0.24 4 0.44 2 0.22 9 2 0.22 2 0.22
helix: 10 0.01 0 0.00 1352 80 0.06 115 0.09 0 0.00 0 0.00 9 0 0.00 0 0.00
strand: 788 0.58 1096 0.81 1352 703 0.52 603 0.45 3 0.33 4 0.44 9 6 0.67 4 0.44
turn: 162 0.12 1 0.00 1352 55 0.04 110 0.08 2 0.22 1 0.11 9 0 0.00 2 0.22
  i-2 i-1 turn i+1 i+2 i-2 i-1 turn i+1 i+2
bend: 334 0.12 247 0.09 2717 12 0.00 450 0.17 57 0.14 0 0.00 400 54 0.14 39 0.10
coil: 777 0.29 1266 0.47 2717 26 0.01 835 0.31 142 0.36 9 0.02 400 88 0.22 138 0.35
helix: 534 0.20 127 0.05 2717 239 0.09 414 0.15 34 0.09 0 0.00 400 57 0.14 74 0.19
strand: 447 0.16 155 0.06 2717 20 0.01 192 0.07 38 0.10 13 0.03 400 20 0.05 69 0.17
turn: 625 0.23 922 0.34 2717 2420 0.89 826 0.30 129 0.32 378 0.95 400 181 0.45 80 0.20