### Abstract

An exhaustive ab initio and DFT search for energetically stable conformers from the topologically possible set was undertaken on the N-acetyl-phenylalanyl-N-methylamide and N-acetyl-tyrosyl-N-methylamide systems. The geometries of all 81 phenylalanyl and 162 tyrosyl possible rotamers, described under the rules outlined by Multi-Dimensional Conformational Analysis (MDCA), were attempted at each of the RHF/3-21G, RHF/6-31G(d) and B3LYP/6-31G(d) levels of theory. A total of 32 and 66 stable conformational minima were found for the phenylalanyl and tyrosyl amino acid diamides, respectively, at the B3LYP/6-31G(d) level. From the tyrosyl set, 33 unique conformers emerge when the orientation of the A_{i}^{3} dihedral angle (p-OH orientation) is disregarded. A total of 31 conformers were common to both sets and showed nearly identical geometries. The comparison of the optimized DFT geometries of the two systems showed near by perfect linear fits with R^{2} values of 0.9997, 0.9994, 0.9997, and 0.9996 for the φ_{i}, ψ_{i}, A_{i}^{1}, and A_{i}^{2} dihedral angles, respectively. Relative energies of the matching 31 conformers also fitted to a linear plot with an R^{2} value of 0.9985. The geometric centroid of the aromatic ring in the sidechain of both systems was found to be within 4.1 Å of the H and O atoms of the peptide groups, in 21 and 2 of the conformers, respectively. None of the non-matching conformers showed any such interaction distance ≤4.1 Å.

Original language | English |
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Pages (from-to) | 481-497 |

Number of pages | 17 |

Journal | European Physical Journal D |

Volume | 20 |

Issue number | 3 |

DOIs | |

Publication status | Published - Sep 2002 |

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### ASJC Scopus subject areas

- Physics and Astronomy(all)
- Atomic and Molecular Physics, and Optics

### Cite this

*European Physical Journal D*,

*20*(3), 481-497. https://doi.org/10.1140/epjd/e2002-00155-6

**The role of enhanced aromatic π-electron donating aptitude of the tyrosyl sidechain with respect to that of phenylalanyl in intramolecular interactions.** / Chass, G. A.; Lovas, S.; Murphy, R. F.; Csizmadia, I.

Research output: Contribution to journal › Article

*European Physical Journal D*, vol. 20, no. 3, pp. 481-497. https://doi.org/10.1140/epjd/e2002-00155-6

}

TY - JOUR

T1 - The role of enhanced aromatic π-electron donating aptitude of the tyrosyl sidechain with respect to that of phenylalanyl in intramolecular interactions

AU - Chass, G. A.

AU - Lovas, S.

AU - Murphy, R. F.

AU - Csizmadia, I.

PY - 2002/9

Y1 - 2002/9

N2 - An exhaustive ab initio and DFT search for energetically stable conformers from the topologically possible set was undertaken on the N-acetyl-phenylalanyl-N-methylamide and N-acetyl-tyrosyl-N-methylamide systems. The geometries of all 81 phenylalanyl and 162 tyrosyl possible rotamers, described under the rules outlined by Multi-Dimensional Conformational Analysis (MDCA), were attempted at each of the RHF/3-21G, RHF/6-31G(d) and B3LYP/6-31G(d) levels of theory. A total of 32 and 66 stable conformational minima were found for the phenylalanyl and tyrosyl amino acid diamides, respectively, at the B3LYP/6-31G(d) level. From the tyrosyl set, 33 unique conformers emerge when the orientation of the Ai3 dihedral angle (p-OH orientation) is disregarded. A total of 31 conformers were common to both sets and showed nearly identical geometries. The comparison of the optimized DFT geometries of the two systems showed near by perfect linear fits with R2 values of 0.9997, 0.9994, 0.9997, and 0.9996 for the φi, ψi, Ai1, and Ai2 dihedral angles, respectively. Relative energies of the matching 31 conformers also fitted to a linear plot with an R2 value of 0.9985. The geometric centroid of the aromatic ring in the sidechain of both systems was found to be within 4.1 Å of the H and O atoms of the peptide groups, in 21 and 2 of the conformers, respectively. None of the non-matching conformers showed any such interaction distance ≤4.1 Å.

AB - An exhaustive ab initio and DFT search for energetically stable conformers from the topologically possible set was undertaken on the N-acetyl-phenylalanyl-N-methylamide and N-acetyl-tyrosyl-N-methylamide systems. The geometries of all 81 phenylalanyl and 162 tyrosyl possible rotamers, described under the rules outlined by Multi-Dimensional Conformational Analysis (MDCA), were attempted at each of the RHF/3-21G, RHF/6-31G(d) and B3LYP/6-31G(d) levels of theory. A total of 32 and 66 stable conformational minima were found for the phenylalanyl and tyrosyl amino acid diamides, respectively, at the B3LYP/6-31G(d) level. From the tyrosyl set, 33 unique conformers emerge when the orientation of the Ai3 dihedral angle (p-OH orientation) is disregarded. A total of 31 conformers were common to both sets and showed nearly identical geometries. The comparison of the optimized DFT geometries of the two systems showed near by perfect linear fits with R2 values of 0.9997, 0.9994, 0.9997, and 0.9996 for the φi, ψi, Ai1, and Ai2 dihedral angles, respectively. Relative energies of the matching 31 conformers also fitted to a linear plot with an R2 value of 0.9985. The geometric centroid of the aromatic ring in the sidechain of both systems was found to be within 4.1 Å of the H and O atoms of the peptide groups, in 21 and 2 of the conformers, respectively. None of the non-matching conformers showed any such interaction distance ≤4.1 Å.

UR - http://www.scopus.com/inward/record.url?scp=0036770062&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0036770062&partnerID=8YFLogxK

U2 - 10.1140/epjd/e2002-00155-6

DO - 10.1140/epjd/e2002-00155-6

M3 - Article

VL - 20

SP - 481

EP - 497

JO - Zeitschrift fur Physik D-Atoms Molecules and Clusters

JF - Zeitschrift fur Physik D-Atoms Molecules and Clusters

SN - 1434-6060

IS - 3

ER -