D/H amide isotope effect in model alpha-helical peptides |
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Authors: | Shi Zhengshuang Olson C Anders Kallenbach Neville R Sosnick Tobin R |
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Institution: | Department of Chemistry, New York University, 100 Washington Place, New York, NY 10003, USA. |
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Abstract: | The contribution of amide related hydrogen bonds to protein stability has recently been evaluated using the "Cm experiment", which measures the D/H amide isotope effect in proteins. We show here using isolated alpha-helical peptides that there is a significant effect of denaturant concentration on the measured D/H isotope effect, and that valid comparison of different proteins requires correcting for differences in denaturant (GdmHCl) concentration. Finally our results suggest that H-bonds in an isolated alpha-helix may contribute more to helix stability because of less strain compared to those in helical proteins and that the buried helical H-bonds in helical proteins are not necessarily energetically more favorable than solvent exposed H-bonds in isolated helices. |
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