JOURNAL OF RAMAN SPECTROSCOPY J. Raman Spectrosc. 2003; 34: 357–366 Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jrs.1001 Raman spectra of putrescine, spermidine and spermine polyamines and their N-deuterated and N-ionized derivatives A. M. Amorim da Costa, 1* M. P. M. Marques 1,2 and L. A. E. Batista de Carvalho 1 1 Unidade I&D ‘Qu´ ımica-F´ ısica Molecular,’ University of Coimbra, 3000 Coimbra, Portugal 2 Department of Biochemistry, Faculty of Sciences and Technology, University of Coimbra, 3000 Coimbra, Portugal Received 14 November 2002; Accepted 1 February 2003 The experimental and calculated Raman spectra of the N-hydrogenated and N-deuterated biogenic polyamines putrescine, spermidine and spermine and of their N-hydrogenated and N-deuterated hydrochloride salts in the 2000–3400 cm -1 spectral region (at distinct temperatures) are reported and analysed. A complete assignment of the N–H, C–H and N–D stretching modes is carried out, in the light of both steric and hydrogen-bonding interactions on the conformational behaviour of these systems. Copyright  2003 John Wiley & Sons, Ltd. KEYWORDS: putrescine; spermidine; spermine; conformational analysis; polyamines INTRODUCTION Putrescine [1,4-butanediamine, H 2 N(CH 2 ⊳ 4 NH 2 ], spermi- dine [N-(3-aminopropyl)-1,4-butanediamine, H 2 N(CH 2 ⊳ 4 - NH(CH 2 ⊳ 3 NH 2 ], formed from putrescine, and spermine [N,N 0 -bis(3-aminopropyl)-1,4-butanediamine, H 2 N(CH 2 ⊳ 3 NH(CH 2 ⊳ 4 NH(CH 2 ⊳ 3 NH 2 ] are biogenic polyamines present in all eukariotic organisms, which play an essential role in cell growth and differentiation and in the immunological system. Because of the basic nature of the amine groups, these compounds are prone to interact (mainly in their pro- tonated cationic forms) with the phosphonate groups of nucleic acids. 1–3 Although the exact nature of the biochemi- cal mechanism through which these aliphatic linear amines act in the living cell is still unknown, the relative importance of intra- and intermolecular interactions has proved to be one of the utmost importance in determining the confor- mational preferences of this kind of systems, either as pure compounds or in solution. 4–6 From a biosynthesis point of view, putrescine is the pre- cursor of the larger analogues spermidine and spermine, the comparative study of these three polyamines under similar conditions therefore being useful. A series of conforma- tional analyses using Raman vibrational spectroscopy and L Correspondence to: A. M. Amorim da Costa, Unidade I&D ‘Qu´ ımica-F´ ısica Molecular,’ University of Coimbra, 3000 Coimbra, Portugal. E-mail: acosta@ci.uc.pt Contract/grant sponsor: Portuguese Foundation for Science and Technology; Contract/grant number: POCTI/33199/QUI/2000. Contract/grant sponsor: European Community Fund FEDER. MO ab initio calculations, already carried out by the authors for 1,2-diaminoethane (H 2 N(CH 2 ⊳ 2 NH 2 ⊳, 4 and also for 1,4- butane diamine (H 2 N(CH 2 ⊳ 4 NH 2 ) 5,6 and 1,6-hexanediamine (H 2 N(CH 2 ⊳ 6 NH 2 ), 7 have yielded relevant information which will be used in the present study in order to achieve a better understanding of the structural behaviour of the tri- and tetraamines spermidine and spermine. Apart from a Raman and infrared (IR) study reported on spermidine and spermine interactions with hydrochloric and phosphoric acids, 1 a theoretical conformational analysis of putrescine 5 and a thorough vibrational study [by both Raman and inelastic neutron scattering (INS) spectroscopy] of the H 2 N(CH 2 ⊳ n NH 2 (n D 1–10 and 12), polyamines spermidine and spermine (in their unprotonated, protonated and N-deuterated forms) in the low-wavenumber region, 6 only a preliminary assignment of the Raman spectrum of putrescine, in aqueous solution, is to be found in the literature. 8 Actually, the assignment of the vibrational bands of polyamines and their hydrochloride salts, due to the stretching modes involving the hydrogen atoms, is uncertain and has been little discussed in the literature because of their complexity. The present work is a tentative approach in such a direction, dealing with the analysis of the Raman spectra of putrescine, spermidine and spermine in the 2000 – 3400 cm 1 region, in the light of steric and hydrogen-bonding effects on the corresponding molecular rearrangements. This paper is focused mainly on the interpretation and discussion of the N–H, C–H and N–D stretching vibrational modes, Copyright  2003 John Wiley & Sons, Ltd.