International Journal of Biological Macromolecules 70 (2014) 312–319 Contents lists available at ScienceDirect International Journal of Biological Macromolecules j ourna l ho me pa g e: www.elsevier.com/locate/ijbiomac Effect of (-)-epigallocatechin gallate on the fibrillation of human serum albumin Susmita Bhattacharya a , Nitin K. Pandey b , Anushree Roy a,∗∗ , Swagata Dasgupta b,∗ a Department of Physics, Indian Institute of Technology, Kharagpur 721302, India b Department of Chemistry, Indian Institute of Technology, Kharagpur 721302, India a r t i c l e i n f o Article history: Received 3 March 2014 Received in revised form 2 July 2014 Accepted 4 July 2014 Available online 10 July 2014 Keywords: Human serum albumin Fibrillation (-)-Epigallocatechin gallate Spectroscopy a b s t r a c t Human serum albumin (HSA), the most abundant plasma protein in the human body is known to form fibrils under partial denaturing conditions. Natural polyphenols are known to interact with HSA and some polyphenols have been shown to be potent inhibitors of amyloid fibrillation. (-)-Epigallocatechin gallate (EGCG), the major component of green tea is known to inhibit amyloid fibrillation. In this report, we have investigated the effect of EGCG on native HSA as well as on the fibrillation process of HSA from amide III band analysis of their respective visible Raman spectra. The differential role of the tryptophan (Trp214) residue present in domain II of HSA in the absence and presence of EGCG has been pointed out using fluorescence anisotropy and visible Raman spectroscopy. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Polyphenols are natural substances, obtained from plants, fruits, and vegetables. Many of their biological effects including anti- cancer activity is under investigation in clinical studies [1,2]. Several natural polyphenols with potent inhibitory effects on amy- loid fibril formation have also been reported in the literature [3–5]. It has been suggested that polyphenols acquire a three- dimensional pharmacophore conformation during their binding to the -amyloid peptide, resisting amyloid formation [6]. The presence of vicinal dihydroxyphenyl moieties, irrespective of their position in the aromatic rings is believed to play a key role in their inhibition property [7]. Green tea contains catechins that are potent antioxidants, dominant among them is (-)-epigallocatechin gallate (EGCG) which is able to efficiently disaggregate pre-formed amy- loid fibrils of -synuclein and amyloid- fibrils [8]. The inhibitors are believed to affect the assembled conformation of the fibrillar species instead of the native state of the protein. This implies that the binding they exhibit to proteins is conformation dependent rather than sequence dependent [9]. It appears therefore that the effect of interfaces should be considered as it significantly affects the efficiency of inhibition by EGCG inhibitors [10]. In a recent ∗ Corresponding author. Tel.: +91 3222 283306; fax: +91 3222 255303. ∗∗ Corresponding author. Tel.: +91 3222 283856; fax: +91 3222 255303. E-mail addresses: anushree@phy.iitkgp.ernet.in (A. Roy), swagata@chem.iitkgp.ernet.in (S. Dasgupta). report, oxidized and un-oxidized EGCG was found to remodel mature amyloid fibrils of A 1–40 , IAPP 8–24 , Sup35NM 7–16 to amor- phous protein aggregates [11]. The oxidized EGCG molecule reacts with free amines, preventing dissociation as well as toxicity of the fibrils. Most of the drug molecules can only be transported to body organs through blood plasma. Human serum albumin (HSA) is the most abundant plasma protein in the human body. HSA consists of 585 amino acid residues, 17 disulfide (S–S) bridges and one free cysteine (Cys) [12,13]. The polypeptide chain folds form into three structurally similar -helical domains. These domains are char- acterized by a common motif of 10 -helices. Each domain can be divided into subdomains A and B, which contain six and four -helical region, respectively [12,13]. Domain II and III of HSA con- tain two primary drug binding sites, known as Sudlow’s site I and site II. Site II, reported to have higher affinity for small and neu- tral molecules is able to transport the reversibly bound drugs to their target [14–16]. HSA has a single tryptophan (Trp214) residue located in domain II. Binding of small molecules to proteins are the main processes involved in cellular biochemistry [17]. The usual concept is that ligand binding induces a change in the conformation of the target protein, which in turn, produces a given response. Incubation at high temperature and pH of the solution are the main parameters influencing the denaturation of protein monomers due to the disruption of non-covalent interactions such as electrostatic, van der Waal, hydrophobic forces which are responsible for the stability of the proteins [18,19]. Presence of alcohol as co-solvent has also been found to facilitate protein http://dx.doi.org/10.1016/j.ijbiomac.2014.07.003 0141-8130/© 2014 Elsevier B.V. All rights reserved.