An FTIR study of the complex melting behavior of α-lactalbumin

Hui Zhong, Rudolf Gilmanshin, Robert Callender

Research output: Contribution to journalArticle

12 Scopus citations

Abstract

We have studied the thermal denaturation of holo α-lactalbumin (α-LA) using FTIR spectroscopy by monitoring the absorbance of protein bands in the secondary structure sensitive amide I region. In agreement with results obtained by other techniques, a major cooperative melting transition is observed between 60 and 80°C. This main transition is found to involve predominantly the unfolding of helical structures. Addition of excess Ca2+ ions raises the Tm of the cooperative melting transition but does not change the protein substructures involved in the transition. In addition to the main transition, there are at least two other distinct melting processes. One of them is gradual, is independent of excess Ca2+, and occurs throughout the measured temperature range below the major cooperative transition. This melting process involves denaturation of α-LA's β-hairpin. The other melting process is affected by the addition of excess Ca2+ and involves the denaturation of helical structures. In the absence of excess calcium, this transition, occurring between 45 and 60°C, strongly overlaps with the major cooperative melting. Our results indicate that the β-hairpin of α-LA is not directly stabilized by the bound calcium ion present in the holo protein and melts independently from the rest of the protein.

Original languageEnglish (US)
Pages (from-to)3947-3953
Number of pages7
JournalJournal of Physical Chemistry B
Volume103
Issue number19
DOIs
StatePublished - May 13 1999

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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