Time-Dependent pH Scanning of the Acid-Induced Unfolding of Human Serum Albumin Reveals Stabilization of the Native Form by Palmitic Acid Binding

Research output: Contribution to journalArticle


The most abundant plasma protein, human serum albumin (HSA), is known to undergo several conformational transitions in an acidic environment. To avoid buffer effects and correlate global and local structural changes, we developed a continuous acidification method and simultaneously monitored the protein changes by both small-angle scattering (SAXS) and fluorescence. The progressive acidification, based on the hydrolysis of glucono-δ-lactone from pH 7 to pH 2.5, highlighted a multistep unfolding involving the putative F form (pH 4) and an extended and flexible conformation (pH < 3.5). The scattering profile of the F form was extracted by component analysis and further 3D modeled. The effect of acid unfolding at this intermediate stage was assigned to the rearrangement of the three albumin domains drifting apart toward a more elongated conformation, with a partial unfolding of one of the outer domains. To test the stabilizing effect of fatty acids, here palmitic acid, we compared the acid unfolding process of albumin with and without ligand. We found that when binding the ligand, the native conformation was favored up to lower pH values. Our approach solved the problem of realizing a continuous, homogeneous, and tunable acidification with simultaneous characterization applicable to study processes triggered by a pH decrease.


  • Alessandra Del Giudice
  • Cedric Dicko
  • Luciano Galantini
  • Nicolae V. Pavel
External organisations
  • Sapienza University of Rome
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Biophysics
Original languageEnglish
Pages (from-to)4388-4399
Number of pages12
JournalJournal of Physical Chemistry B
Issue number17
Publication statusPublished - 2017 May 4
Publication categoryResearch