Characterization of the surface geometry of acetyl-[Leu 28,31 ]-NPY(24- 36), a selective Y 2 receptor agonist, onto the Ag and Au surfaces Helena Domin a , Dominika  Swie ˛ch b , Natalia Piergies c , Ewa Pie ˛ta d , Younkyoo Kim e , Edyta Proniewicz b, * a Department of Neurobiology, Institute of Pharmacology, Polish Academy of Sciences, Sme ˛tna 12, 31-343 Kraków, Poland b Faculty of Foundry Engineering, AGH University of Science and Technology, ul. Reymonta 23, 30-059 Kraków, Poland c Institute of Nuclear Physics, Polish Academy of Science, 31-342 Krakow, Poland d Faculty of Chemistry, Jagiellonian University, ul. Ingardena 3, 30-060 Kraków, Poland e Department of Chemistry, Hankuk University of Foreign Studies, Yongin, Kyunggi-Do, 449-791, South Korea A R T I C L E I N F O Article history: Received 30 October 2015 Received in revised form 21 March 2016 Accepted 22 March 2016 Available online 22 March 2016 Keywords: Surface-enhanced Raman spectroscopy SERS Ag and Au surfaces Mutated C-terminal analogue of NPY Y 2 receptor agonist A B S T R A C T In this study, we present adsorption geometry of the mutated C-terminal analogue of neuropeptide Y (NPY), acetyl-[Leu 28,31 ]-NPY(24-36), immobilized onto different SERS-active substrates (colloidal and specifically prepared in oxidation-reduction cycles Ag and Au substrates). Some changes in the adsorption geometry of the investigated peptide immobilized onto these SERS-active substrates are observed. The obtained SERS results demonstrated that the Tyr and Arg residues are mainly responsible for the molecule/metal interaction onto the Ag and Au surfaces. ã 2016 Elsevier B.V. All rights reserved. 1. Introduction Neuropeptide Y or neuropeptide tyrosine (NPY; Tyr 1 -Pro-Ser- Lys-Pro-Asp-Asn-Pro-Gly-Glu-Asp-Ala-Pro-Ala-Glu-Asp-Leu-Ala- Arg 19 - Tyr 20 -Tyr 21 -Ser 22 -Ala-Leu 24 -Arg-His 26 - Tyr 27 -IIe-Asn-Leu 30 - IIe-Thr-Arg 33 -Gln-Arg 35 -Tyr 36 -NH 2 ), structurally and functionally related to 36-amino acids pancreatic peptide (PYY) and pancreatic polypeptide (PP), is one of the most abundant neuropeptides in the mammalian brain [1–4]. NPY has a compact tertiary structure, consisting of a harpin-like conformation, that is characterized by the extensive hydrophobic interactions between the N-terminal polyproline helix, and the more C-terminally located a-helix. These helices, joined by a b-turn, interact via hydrophobic contacts to produce a compact and stable tertiary fold [5,6]. NPY has been associated with a number of physiological and pathological functions, such as: feeding behavior, memory process, pain, anxiety, cell proliferation, and many other processes in the central and peripheral nervous systems [7,8]. These actions are exerted via the NPY interaction with a family of specific membrane bound G protein coupled receptors (GPCRs), characterized by seven a-helical fragments (7TM) that span the cellular membrane, named Y 1 , Y 2 , Y 3 , Y 4 , Y 5 , and y 6 [9,10]. All these receptor subtypes mediate the NPY’s biological responses via the Ga i signaling pathway [4,11]. The Y 2 receptors (Y 2 R) are the most abundant Y subtype receptors in the central nervous system (CNS) and are widely expressed in the brain, including: hippocampus, thalamus, hypothalamus, and cortex [12–14]. In the peripheral nervous system, Y 2 R are found in parasympathetic, sympathetic, and sensory neurons as well as in intestine and certain blood vessels [15–17]. The Y 2 receptors primarily act as presynaptic autorecep- tors, modulating endogenous NPY release and as heteroreceptors, regulating the release of other neurotransmitters, such as: g-amino butyric acid (GABA) and glutamate [18,19]. The significant role of the Y 2 receptors in the various physiological and pathological processes and the potential therapeutic use of the Y 2 R modulators have been postulated [20]. The Y 2 receptors are implicated in food intake regulation, alcohol and drugs abuse, bone formation, affective disorders, epilepsy, in mechanism of pain induction, and cancer [21,22]. There are also several reports indicating that Y 2 R may be attractive targets for neuroprotective therapy [23–26]. Our earlier study has shown that the NPY(13-36) Y 2 receptor agonist (the 13-36 fragment of NPY) induces neuro- protective effects against kainate-induced excitotoxicity both in * Corresponding author. E-mail address: proniewi@agh.edu.pl (E. Proniewicz). http://dx.doi.org/10.1016/j.vibspec.2016.03.018 0924-2031/ ã 2016 Elsevier B.V. All rights reserved. Vibrational Spectroscopy 85 (2016) 1–6 Contents lists available at ScienceDirect Vibrational Spectroscopy journa l homepage: www.e lsevier.com/locate/vibspec