A full conformational space analysis of bilirubin

ESTEBAN GABRIEL VEGA HISSI; JUAN CEFERINO GARRO MARTÍNEZ; GRACIELA NILDA ZAMARBIDE; MARIO RINALDO ESTRADA; SVEND J. KNAK JENSEN; FRANCISCO TOMÁS-VERT; IMRE G. CSIZMADIA

JOURNAL OF MOLECULAR STRUCTURE THEOCHEM

Año: 2009 vol. 911 p. 24 - 29

0166-1280

Ab initio methods were utilized in a gas-phase systematic conformational search of bilirubin conformers. The whole molecule was divided into four fragments. Most stable conformers of them were employed to build 196 conformers of the complete bilirubin molecule. Initial geometries were optimized using HF/3- 21G level of theory and the minimum energy conformers were then reoptimized at B3LYP/6-31G(d) level. Ridge-tile conformer was the most stable one, in perfect agreement with X-ray data. We found that while tetrapyrrole backbone shows some .exibility, propionic acid side chains have a greater in.uence in bilirubin conformation because they can interact through different hydrogen bond patterns with the backbone and between them. The whole molecule was divided into four fragments. Most stable conformers of them were employed to build 196 conformers of the complete bilirubin molecule. Initial geometries were optimized using HF/3- 21G level of theory and the minimum energy conformers were then reoptimized at B3LYP/6-31G(d) level. Ridge-tile conformer was the most stable one, in perfect agreement with X-ray data. We found that while tetrapyrrole backbone shows some .exibility, propionic acid side chains have a greater in.uence in bilirubin conformation because they can interact through different hydrogen bond patterns with the backbone and between them. The whole molecule was divided into four fragments. Most stable conformers of them were employed to build 196 conformers of the complete bilirubin molecule. Initial geometries were optimized using HF/3- 21G level of theory and the minimum energy conformers were then reoptimized at B3LYP/6-31G(d) level. Ridge-tile conformer was the most stable one, in perfect agreement with X-ray data. We found that while tetrapyrrole backbone shows some .exibility, propionic acid side chains have a greater in.uence in bilirubin conformation because they can interact through different hydrogen bond patterns with the backbone and between them.