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Cheryl A. Slate Robert A. Binstead Thomas J. Meyer Bruce W. Erickson 《Letters in Peptide Science》1999,6(1):61-69
The kinetics of isomerization of the helical forms of three oligoprolines was determined by far-ultraviolet CD spectropolarimetry and kinetic analysis by singular value decomposition. ZRA (Pro3-X-Pro2-Y-Pro2-Z-Pro3) and ZRA2 (Pro7-X-Pro2-Y-Pro2-Z-Pro7) bear large redox-active substituents on proline residues X, Y, and Z, but P9 (Pro9) does not. All three peptides formed a stable proline-II helix in water. In acetonitrile, both ZRA2 and P9 were converted into a proline-I helical form but ZRA remained predominantly in the proline-II helical form. Evidently, in order to undergo substantial proline III isomerization, an oligoproline chain containing large substituents needs to have a segment of consecutive unsubstituted proline residues that is sufficiently long to form a stable proline helix. Biexponential kinetics (AB, k1 = 3.3 × 10-4 s-1; BC, k2 = 0.8 × 10-4 s-1) were observed for the proline III isomerization of ZRA2 and P9 in acetonitrile and for the proline III isomerization of ZRA2 in water, which provides evidence for the growth and decay of a major kinetic intermediate. 相似文献
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Slate Cheryl A. Binstead Robert A. Meyer Thomas J. Erickson Bruce W. 《International journal of peptide research and therapeutics》1999,6(1):61-69
Summary The kinetics of isomerization of the helical forms of three oligoprolines was determined by far-ultraviolet CD spectropolarimetry
and kinetic analysis by singular value decomposition. ZRA (Pro3-X-Pro2-Y-Pro2-Z-Pro3) and ZRA2 (Pro7-X-Pro2-Y-Pro2-Z-Pro7) bear large redox-active substituents on proline residues X, Y, and Z, but P9 (Pro9) does not. All three peptides formed a stable proline-II helix in water. In acetonitrile, both ZRA2 and P9 were converted
into a proline-I helical form but ZRA remained predominantly in the proline-II helical form. Evidently, in order to undergo
substantial proline II→I isomerization, an oligoproline chain containing large substituents needs to have a segment of consecutive
unsubstituted proline residues that is sufficiently long to form a stable proline helix. Biexponential kinetics (A→B, k1=∼3.3×10−4s−1; B→C, k2=∼0.8×10−4s−1) were observed for the proline II→I isomerization of ZRA2 and P9 in acetonitrile and for the proline I→II isomerization of
ZRA2 in water, which provides evidence for the growth and decay of a major kinetic intermediate. 相似文献
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