ISSN:
0006-3525
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
Notizen:
By means of carbon-13 nmr (at 25 MHz) the trans/cis conformer ratio in glycyl-L-proline has been measured in aqueous (D2O) solution over the temperature range 33-96°C. It is found that ΔH0 = -4.2 kJ/mole and ΔS0 = -9.7 J/mole/K.Measurements of the T1 values for the proline ring carbons yielded values consistent with a fast puckering process involving both the β- and γ-carbons.Measurements of the rate of cis-trans conformational interconversion in glycyl-L-proline, using complete line-shape analysis for the glycyl α-carbon resonance, gave values for the trans → cis isomerization as follows: ΔH≠ = 83.5 ± 0.2 kJ/mole; ΔS≠ = 0.0 ± 10 J/mole/K. A more approximate determination from coalescence temperature observations gave a value of ΔG≠ of 82.0 ± 0.4 kJ/mole for this process in acetyl-L-proline in aqueous solution. The presence of 12M NaSCN lowered this barrier by ca. 2.6 kJ/mole.Such measurements are relevant to present theoretical models of the denaturation-renaturation processes in proteins, in which proline residues may play a key role.
Zusätzliches Material:
2 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/bip.1977.360160707
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