17 research outputs found
Helix compactness and stability: Electron structure calculations of conformer dependent thermodynamic functions
Structure, stability, cooperativity and molecular packing of two major backbone forms: 310-helix and β-strand are investigated. Long models HCO-(Xxx)n-NH2 Xxx = Gly and (l-)Ala, n ⩽ 34, are studied at two levels of theory including the effect of dispersion forces. Structure and folding preferences are established, the length modulated cooperativity and side-chain determined fold compactness is quantified. By monitoring ΔG°β→α rather than the electronic energy, ΔEβ→α, it appears that Ala is a much better helix forming residue than Gly. The achiral Gly forms a more compact 310-helix than any chiral amino acid residue probed here for l-Ala
Kinetics of 1,6-hydrogen migration in alkyl radical reaction class
The kinetics of the 1,6-intramolecular hydrogen migration in the alkyl
radical reaction class has been studied using the reaction class transition state theory
(RC-TST) combined with the linear energy relationship (LER) and the barrier height
grouping (BHG) approach. The RC-TST/LER, where only reaction energy is needed,
and RC-TST/BHG, where no other information is needed, are found to be promising
methods for predicting rate constants for any reaction in the 1,6-intramolecular H
migration in alkyl radicals reaction class. Direct comparison with available experimental
data indicates that the RC-TST/LER, where only reaction energy is needed, can
predict rate constants for any reaction in this reaction class with satisfactory accuracy