Selenocysteine is expected to have 9 x 9 = 81 conformations [3 x 3 = 9 backbone: ψ (g+,a,g-) x φ (g+,a,g-) and 3 x 3 = 9 side-chain: χ1 (g+,a,g-) x χ2(g+,a,g-)]. In the present study, all the torsional modes of the side-chain (χ1: rotation about the C(α)-C(β) and χ2: rotation about the C(β)-Se bonds) were investigated in the relaxed γ(L) backbone [(φ,ψ); (g-,g+)] conformation. Seven out of the nine expected minima were found at the RHF/3-21G level of theory for N-formyl-L-selenocysteinamide (For-L-Sec-NH2) and N-acetyl-L-selenocysteine-N-methylamide (Ac-L-Sec-NHMe). The stabilization energy exerted by the -CH2-SeH side-chain has been compared with that of -CH2-SH and -CH2-OH. Relative energies of the various conformers were also obtained via single point calculations at the B3LYP/6- 31G(d,p) level of theory. Topological analysis of the electron density has been performed by Bader's Atoms in Molecule (AIM) approach using the results. The structures were also optimized at the B3LYP/6-31+G(d,p) level of theory.
- Ab initio MO study
- Atoms in Molecules (AIM)
- Bader's electron density analysis
- Multidimensional Conformational Analysis (MDCA)
- Selenocysteine side-chain conformations
ASJC Scopus subject areas
- Organic Chemistry