title: Conformational properties of the isolated 1-23 fragment of human hemoglobin alpha-chain.
abstract: With the purpose of establishing whether, as a general rule, regions of a protein chain that are helical in the native structure maintain, at least partially, the same helical structure when isolated in solution, we have prepared the 1-23 fragment of human hemoglobin alpha-chain, and studied its conformational properties in aqueous solution by CD and 1H-NMR. From the analysis of CD and NMR spectral changes with temperature, salt and addition of trifluoroethanol (TFE) it can be concluded that the 1-23 peptide forms a measurable population (18% at 22 degrees C (pH 5.6) TFE/H2O, 30:70 (v/v)) of an alpha-helix structure that spans the same residues that are helical in the native protein (namely, 6 to 17). These results, taken together with similar ones obtained previously in the 1-19, 21-42 and 50-61 RNAase fragments, support the idea that no helices other than the native ones are actually formed in solution by protein fragments. This implies that the final helical structure of a protein is present from the very beginning of the folding process, and also that such elements of secondary structure can act as primary nucleation centers.
authors.affiliation: Institute of Structure of Matter, CSIC, Madrid, Spain.
authors.forename: M C
authors.initials: MC
authors.lastname: Peña
authors.forename: M
authors.initials: M
authors.lastname: Rico
authors.forename: M A
authors.initials: MA
authors.lastname: Jiménez
authors.forename: J
authors.initials: J
authors.lastname: Herranz
authors.forename: J
authors.initials: J
authors.lastname: Santoro
authors.forename: J L
authors.initials: JL
authors.lastname: Nieto
mesh_terms: D002942:Circular Dichroism; D005914:Globins; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D010446:Peptide Fragments; D011487:Protein Conformation / Q000187:drug effects; D013696:Temperature; D014270:Trifluoroethanol / Q000494:pharmacology
chemical_list: D010446:Peptide Fragments; D014270:Trifluoroethanol; D005914:Globins