Temperature- and length-dependent energetics of formation for polyalanine helices in water: assignment of w(Ala)(n,T) and temperature-dependent CD ellipticity standards
- PMID: 16787087
- PMCID: PMC1560101
- DOI: 10.1021/ja060094y
Temperature- and length-dependent energetics of formation for polyalanine helices in water: assignment of w(Ala)(n,T) and temperature-dependent CD ellipticity standards
Abstract
Length-dependent helical propensities w(Ala)(n,T) at T = 10, 25, and 60 degrees C are assigned from t/c values and NMR 13C chemical shifts for series 1 peptides TrpLys(m)Inp2(t)Leu-Ala(n)(t)LeuInp2Lys(m)NH2, n = 15, 19, and 25, m = 5, in water. Van't Hoff analysis of w(Ala)(n,T) show that alpha-helix formation is primarily enthalpy-driven. For series 2 peptides Ac-Trp Lys5Inp2(t)Leu-(beta)AspHel-Ala(n)-beta-(t)LeuInp2Lys5NH2, n = 12 and 22, which contain exceptionally helical Ala(n) cores, protection factor-derived fractional helicities FH are assigned in the range 10-30 degrees C in water and used to calibrate temperature-dependent CD ellipticities [theta](lambda,H,n,T). These are applied to CD data for series 1 peptides, 12 < or = n < or = 45, to confirm the w(Ala)(n,T) assignments at T = 25 and 60 degrees C. The [theta](lambda,H,n,T) are temperature dependent within the wavelength region, 222 +/- 12 nm, and yield a temperature correction for calculation of FH from experimental values of [theta](222,n,T,Exp).
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References
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- The fractional helicity FH of a potentially helical peptide is the atom fraction of its backbone α-carbons that belong to helical conformations under particular experimental conditions. The site helicity FHi is the corresponding atom fraction of the α-carbons at a particular residue site i. The average of all FHi over a particular helical region equals the overall FH for that region.
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- Kallenbach NR, Spek EJ. Methods Enzymol. 1998;285:26–41. For a review through 1997 see: - PubMed
-
- For example: (a) Scheraga, H. A. The Intrinsic Tendency Toward α-Helix Formation. In Perspectives in Structural Biology; Vijayan, M., Yathindra, N., Kolaskar, A. S., Eds.; Indian Academy of Sciences: Bangalore, 1999; pp 275–282.
- Creamer TP, Rose GD. Proteins: Struct, Funct, Genet. 1994;19:85–97. (b) - PubMed
- Myers JK, Pace CN, Scholtz JM. Biochemistry. 1997;36:10923–10929. (c) - PubMed
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- Moreau, R. J.; Nasr, K. A.; Török, M.; Miller, J. S.; Schubert, C.; Kennedy, R. J.; Kemp, D. S. In preparation
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