Please cite this article in press as: S.K. Chaturvedi, et al., Int. J. Biol. Macromol. (2015), http://dx.doi.org/10.1016/j.ijbiomac.2015.06.035 ARTICLE IN PRESS G Model BIOMAC 5181 1–10 International Journal of Biological Macromolecules xxx (2015) xxx–xxx Contents lists available at ScienceDirect International Journal of Biological Macromolecules j ourna l h o mepa ge: www.elsevier.com/locate/ijbiomac Biophysical insight into the anti-amyloidogenic behavior of taurine Sumit Kumar Chaturvedi a Q1 , Parvez Alam a , Javed Masood Khan a , Mohd. Khursheed Siddiqi a , Ponnusamy Kalaiarasan b , Naidu Subbarao c , Zeeshan Ahmad a , Rizwan Hasan Khan a,∗ a Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh 202002, India b National Centre of Applied Human Genetics, School of Life Sciences, Jawaharlal Nehru University, New Delhi 110067, India c School of Computational and Integrative Sciences, Jawaharlal Nehru University, New Delhi, India a r t i c l e i n f o Article history: Received 5 February 2015 Received in revised form 15 June 2015 Accepted 16 June 2015 Available online xxx Keywords: HSA Taurine Amyloid fibril Q2 Aggregation a b s t r a c t In this work, we investigated the inhibitory ability of taurine on the aggregation of Human serum albu- min (HSA) and also examined how it controls the kinetic parameters of the aggregation process. We demonstrated the structural alterations in the HSA after binding to the taurine at 65 ◦ C by exploiting various biophysical techniques. UV–vis spectroscopy was used to check the turbidometric changes in the protein. Thioflavin T fluorescence kinetics was subjected to explore kinetic parameters comparing the amyloid formation in the presence of varying concentration of taurine. Further, Congo red binding and ANS binding assays were performed to determine the inhibitory effect of taurine on HSA fibrillation process and surface hydrophobicity modifications occurring before and after the addition of taurine with protein, respectively. Far UV CD and Dynamic Light Scattering (DLS) confirmed that taurine stabilized the protein -helical structure and formed complex with HSA which is further supported by differential scanning calorimetry (DSC). Moreover, microscopic imaging techniques were also done to analyze the morphology of aggregation formed. Taurine is also capable of altering the cytotoxicity of the protein- aceous aggregates. Molecular docking study also deciphered the possible residues involved in protein and drug interaction. © 2015 Published by Elsevier B.V. 1. Introduction Q3 Protein misfolding and aggregation is most interesting and chal- lenging topic in industry and human health [1,2]. Amyloids are well defined protein aggregates which are responsible for more than 20 diseases in humans such as Alzheimer, Parkinson, diabetes II and Huntington, etc. [2–5]. Soluble protein aggregates possess cell cytotoxic effect and insoluble aggregates may be undesirable for drug products therefore prevention or retardation is an essen- tial task [6,7]. In addition to protein associated with diseases other proteins such as lysozyme, serum albumins, insulin, etc. also form amyloids under suitable conditions like high temperature, low pH, in presence of surfactants, oxidation, ionic strength and crowding agents [8–10]. Number of evidences are available that proves that morphological and histochemical properties of disease associated ∗ Corresponding author. Tel.: +91 571 2720388; fax: +91 571 2721776. E-mail addresses: rizwanhkhan1@gmail.com, rizwanhkhan1@yahoo.com (R.H. Khan). or disease unrelated proteins are very similar which suggests that fibril formation is the intrinsic property of all polypeptide [11]. Currently, the research is being done that provoke aggregation inhibition of proteins in vitro and in vivo. Small molecules such as polyphenols, metal ions, vitamins, nucleotides and synthetic pep- tides have been reported as anti-aggregation agents [12–14]. Human serum albumin is a globular protein composed of 585 amino acid residues and 17 disulphide bonds. It is the most abun- dant plasma protein and serves as a carrier protein for the large number of small molecules, fatty acids and drugs [15]. Interaction of HSA with large number of molecules is widely studied because of its role as a carrier molecule. Although HSA is very stable protein but possesses propensity to aggregate provided suitable conditions in vitro [9]. Recently, a lot of work has been reported dealing with aggregation inhibition of serum albumin in vitro which can serve as a model for designing anti amyloidogenic drugs [16]. Here, we are reporting first time inhibitory effect of taurine on thermally induced aggregation of human serum albumin. Taurine (2-amino-ethanesulfonic acid) is a ubiquitous small sul- phur containing amino acid found in almost all mammals [17]. It can be obtained from egg, meat and seafood or alternatively can be http://dx.doi.org/10.1016/j.ijbiomac.2015.06.035 0141-8130/© 2015 Published by Elsevier B.V. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57