A conformational comparison of N- and C-protected methionine and N- and C-protected homocysteine

• Published in: Journal of molecular structure. Theochem Vol. 666; pp. 219 - 241
• Main Authors: Láng, András, György, Krisztina, Csizmadia, Imre G., Perczel, András
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 29-12-2003
• Subjects: Ab initio computations; Amino acid; Molecular conformation; Multidimensional conformation analysis (MDCA); Peptide model; Ramachandran potential energy surface (PES); GRP, glucose regulated protein; HepG2, human hepatocarcinoma cell; HDL, high density lipoprotein; Wnt, Wingless-type murine mammary tumour virus i ntegration site; cAMP, cyclic adenosine monophosphate; Ab initio computations; Hcy, homocysteine; Amino acid; SAH, S-adenosylhomocysteine; HERP, HES (hairy and enhancer of split)-related repressor protein; SAM, S-adenosylmethionine; UPR, unfolded protein response; Ramachandran potential energy surface (PES); PEC/PEHS, potential energy curve/potential energy hypersurface; Met, methionine; Multidimensional conformation analysis (MDCA); HUVEC, human umbilical vascular endothelial cell; PDB, Protein Data Bank; NOS, nitric oxide synthase; APC, adenomatous polyposis of the colon; MDCA, multidimensional conformation analysis; Molecular conformation; BiP, immunoglobulin heavy chain-binding protein; CHOP/GADD153, C/EBP (CCAAT/enhancer-binding protein) homologous protein or growth arrest- and DNA damage-inducible gene; HASMC, human aortic smooth muscle cells; Peptide model; cGMP, cyclic guanosine monophosphate; SREBP-1, sterol regulatory element-binding protein-1; MTHFR, methylenetetrahydrofolate reductase; TCF/LEF, T cell factor/lymphoid enhancer factor; ER, endoplasmic reticulum
• ISSN: 0166-1280; 1872-7999
• DOI: 10.1016/j.theochem.2003.08.029

The conformational space for the five
l type backbone forms of
N-formyl-
l-methioninamide has been explored by ab initio computation. Initially, we expected 135 conformers associated with the five
l type backbone forms (right-handed α-helix or α
l
, β-pleated sheet or β
l
, inverse γ-turn or γ
l
, δ
l
and poly-Proline II or ε
l
). Using computation of RHF/3-21G level of theory, we describe 77 conformers by their five independent variables:
ϕ,
ψ,
χ
1,
χ
2,
χ
3. The β
l
conformers of
N-formyl-
l-methioninamide were compared with
N-acetyl-
l-homocysteine-methylamide and the different backbone forms of
N-formyl-
l-methioninamide were also compared. Calculation of stabilization energies of the conformers was completed.