In this paper, we present spectroscopic studies of neuropeptide Y (NPY) and its native NPY3-36, NPY13-36, and NPY22-36 and mutated acetyl-(Leu(28,31))-NPY24-36 C-terminal fragments acting on Y-2 receptor. Since there is some evidence for the correlation between the SERS patterns and the receptor binding ability, we performed a detailed analysis for these compounds at the metal/water interface using Raman spectroscopy (RS) and surface-enhanced Raman spectroscopy (SERS) methods. Many studies have suggested that interactions of this kind are crucial for a variety of biomedical and biochemical phenomena. The identification of amino acids in these peptide sequences by SERS allowed us to determine which molecular fragments were responsible for the interaction with the silver nanoparticle surface. Our findings demonstrated that in all of the investigated compounds, the NPY32-36 C-terminal fragment (Thr(32)-Arg(33)-Gln(34)-Arg(36)-Tyr(36)NH(2)) was involved in the adsorption process onto metal substrate. The results of the present study suggest that the same molecular fragment interacts with the Y-2 receptor, what proved the usefulness of the SERS method in the study of these biologically active compounds. The search for analogs acting on Y-2 receptor may be important from the viewpoint of possible future clinical applications. (c) 2014 Elsevier Inc. All rights reserved.