Raman study of the effects of polyamines on DNA:spermine and histamine J. Ruiz-Chica a, * , M.A. Medina b , F. Sa ´nchez-Jime ´nez b , F.J. Ramı ´rez a,1 a Departamento de Quı ´mica Fı ´sica, Universidad de Ma ´laga, Campus de Teatinos, 29071-Ma ´laga, Spain. b Departamento de Biologı ´a Molecular y Bioquı ´mica Facultad de Ciencias, Universidad de Ma ´laga, Campus de Teatinos, 29071-Ma ´laga, Spain. Received 25 August 1998; received in revised form 13 November 1998; accepted 13 November 1998 Abstract Fourier transform Raman spectroscopy was used to investigate the interaction of spermine and histamine with calf-thymus DNA. Polyamine–DNA solutions at different polyamine concentrations ranging from 5 mM to 75 mM were prepared. For spermine, solutions no higher than 15 mM were prepared because this molecule induces condensation and aggregation on DNA at upper concentrations. Possible sites of bindings for polyamine–DNA complexes were discussed on the basis of the spectral changes observed with respect to the Raman spectra of DNA. The results seem to indicate that one spermine molecule induces on DNA a similar effect to two or more histamine molecules.  1999 Elsevier Science B.V. All rights reserved. Keywords: Raman; Spermine; Histamine; DNA; Polyamines 1. Introduction Raman spectroscopy is a suitable technique for studying specific interactions between biological molecules [1] because of its high sensitivity and the possibility of recording spectra of water solutions. Fourier transform Raman (FT-Raman) spectroscopy improves the performance of this tool allowing a fast recording of a great number of spectra. The exci- tation radiation (a near infrared laser) prevents fluor- escence signals. For example, Raman spectroscopy has been applied to investigate structural changes in drug-interacting nucleic acids [2–5]. Among the great variety of drugs which can interact with DNA, polyamines have an important biological significance. They have been found at significant concentrations in all cells, where they play fundamental roles in cellular proliferation and growth [6,7]. Interactions between polyamines and nucleic acids, involving complexa- tion, precipitation and structural changes have been proposed to understand the polyamine biological function [8,9]. In a series of theoretical studies, Feuerstein et al. [10,11] have built models for the interaction of sper- mine and DNA, in which evidences of preferential binding of spermine to specific sites in DNA have been found. The present work is aimed to get experi- mental proofs concerning this interaction, using FT- Raman spectroscopy The analyses were extended to histamine molecule. The chemical structures of these two molecules are shown in Fig. 1. Two close nitrogen–nitrogen interatomic distances were obtained from molecular mechanics optimizations; Journal of Molecular Structure 480–481 (1999) 455–458 0022-2860/99/$ - see front matter  1999 Elsevier Science B.V. All rights reserved. PII: S0022-2860(98)00819-9 * Corresponding author. Tel.: + 34-5-2132-258; fax: + 34-5- 132-000. 1 E-mail address: ramirez@uma.es (F.J. Ramı ´rez)