Abstract
Human serum albumin (HSA) is a protein that transports neutral and acid ligands in the organism. Depending on the environment’s pH conditions, HSA can take one of the five isomeric forms that change its conformation. HSA can form aggregates resembling those in vitro formed from amyloid at physiological pH (neutral and acidic). Not surprisingly, the main goal of the research was aggregation/fibrillation of HSA, the study of the physicochemical properties of formed amyloid fibrils using thioflavin T (ThT) and the analysis of ligand binding to aggregated/fibrillated albumin in the presence of dansyl-l-glutamine (dGlu), dansyl-l-proline (dPro), phenylbutazone (Phb) and ketoprofen (Ket). Solutions of human serum albumin, both non-modified and modified, were examined with the use of fluorescence, absorption and circular dichroism (CD) spectroscopy. The experiments conducted allowed observation of changes in the structure of incubated HSA (HSAINC) in relation to nonmodified HSA (HSAFR). The formed aggregates/fibrillation differed in structure from HSA monomers and dimers. Based on CD spectroscopy, previously absent β-structural constructs have been registered. Whereas, using fluorescence spectroscopy, the association constants differing for fresh and incubated HSA solutions in the presence of dansyl-amino acids and markers for binding sites were calculated and allowed observation of the conformational changes in HSA molecule.
Highlights
Human serum albumin (HSA) is the most common protein in the human body
Amyloid fibril plaques can be found in brain tissue of Alzheimer patients so they are associated with neurodegenerative diseases belonging to amyloidosis [15]
Amyloid fibrils are peptide or protein aggregates formed under certain conditions in vitro or in vivo
Summary
Human serum albumin (HSA) is the most common protein in the human body. HSA is present in plasma (60% of protein mass), lymph, saliva, cerebrospinal and interstitial fluid [1,2]. It is soluble in salt solutions in the pH range of 4.0 to 8.5, and in an aqueous environment [3]. The secondary structure of HSA is constituted by 67% α-helix, 23% stretched chain, 10% β-sheets and bends. The structure of albumin has been divided into three domains (I, II and III) [4], and each of domains has been divided into two subdomains, A and B, defining the ability to bind individual substrates by respective domains.
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