title: Temperature induced morphological transitions from native to unfolded aggregated States of human serum albumin.
abstract: The circulatory protein, human serum albumin (HSA), is known to have two melting point temperatures, 56 and 62 °C. In this present manuscript, we investigate the interaction of HSA with a synthesized bioactive molecule 3-pyrazolyl 2-pyrazoline (PZ). The sole tryptophan amino acid residue (Trp214) of HSA and PZ forms an excellent FRET pair and has been used to monitor the conformational dynamics in HSA as a function of temperature. Molecular docking studies reveal that the PZ binds to a site which is in the immediate vicinity of Trp214, and such data are also supported by time-resolved FRET studies. Steady-state and time-resolved anisotropy of PZ conclusively proved that the structural and morphological changes in HSA mainly occur beyond its first melting temperature. Although the protein undergoes thermal denaturation at elevated temperatures, the Trp214 gets buried inside the protein scaffolds; this fact has been substantiated by acrylamide quenching studies. Finally, we have used atomic force microscopy to establish that at around 70 °C, HSA undergoes self-assembly to form fibrillar structures. Such an observation may be attributed to the loss of α-helical content of the protein and a subsequent rise in β-sheet structure.
authors.affiliation: Department of Chemistry, Indian Institute of Science Education and Research Bhopal Indore By-Pass Road, Bhauri, Bhopal 462 066, Madhya Pradesh, India.
authors.forename: Nirmal Kumar
authors.initials: NK
authors.lastname: Das
authors.forename: Narayani
authors.initials: N
authors.lastname: Ghosh
authors.forename: Ajit Prabhakar
authors.initials: AP
authors.lastname: Kale
authors.forename: Ramakanta
authors.initials: R
authors.lastname: Mondal
authors.forename: Uttam
authors.initials: U
authors.lastname: Anand
authors.forename: Subhadip
authors.initials: S
authors.lastname: Ghosh
authors.forename: Virendra Kumar
authors.initials: VK
authors.lastname: Tiwari
authors.forename: Manmohan
authors.initials: M
authors.lastname: Kapur
authors.forename: Saptarshi
authors.initials: S
authors.lastname: Mukherjee
mesh_terms: D001665:Binding Sites; D031541:Fluorescence Resonance Energy Transfer; D006801:Humans; D018625:Microscopy, Atomic Force; D062105:Molecular Docking Simulation; D011489:Protein Denaturation; D017434:Protein Structure, Tertiary; D011720:Pyrazoles / Q000737:chemistry / Q000378:metabolism; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism; D044366:Transition Temperature
chemical_list: C544223:3-pyrazolyl 2-pyrazoline; D011720:Pyrazoles; D012709:Serum Albumin