The 129 local minima of the alanine tetrapeptide with relative energy < 10 kcal/mol were identified at the ωB97X-D/6-311++G(d,p) level of theory from initial structures generated by combining nine local minima of each residue. The CCSD(T), MP2, and dispersion-corrected DFT levels of theory with various basis sets were assessed for relative energies of the 24 representative conformations. The best performance was obtained at the double-hybrid DSD-PBEP86-D3BJ/def2-QZVP level of theory with RMSD = 0.12 kcal/mol against the CCSD(T)/CBS-limit energies. The ωB97X-D/def2-QZVP and CAM-B3LYP-D3BJ/def2-QZVP levels of theory can be an alternative level of theory with marginal deviations for conformational study of peptides.

相对能量<10丙氨酸四肽的129局部最小值千卡/摩尔在鉴定ω B97X-d从生成的初始结构理论/ 6-311 ++ G（d，p）水平通过组合每九个局部最小值残留物。针对24种代表性构象的相对能量，对CCSD（T），MP2和色散校正的DFT理论水平（具有各种基础集）进行了评估。在双混合DSD-PBEP86-D3BJ / def2-QZVP理论水平上，相对于CCSD（T）/ CBS极限能量，RMSD = 0.12 kcal / mol，可获得最佳性能。所述ω B97X-d / DEF2-QZVP和CAM-B3LYP-D3BJ /理论的DEF2-QZVP水平可以与肽的构象研究边际偏差理论的选择项层次。