Abstract
The thionucleoside 2-thiocytidine (C2S) occurs in nature in transfer RNAs; it receives attention in diverse fields like drug research and nanotechnology. By potentiometric pH titrations we measured the acidity constants of H(C2S)+ and the stability constants of the M(C2S)2+ and M(C2S−H)+ complexes (M2+ = Zn2+, Cd2+), and we compared these results with those obtained previously for its parent nucleoside, cytidine (Cyd). Replacement of the (C2)=O unit by (C2)=S facilitates the release of the proton from (N3)H+ in H(C2S)+ (pK a = 3.44) somewhat, compared with H(Cyd)+ (pK a = 4.24). This moderate effect of about 0.8 pK units contrasts with the strong acidification of about 4 pK units of the (C4)NH2 group in C2S (pK a = 12.65) compared with Cyd (pK a ≈ 16.7); the reason for this result is that the amino–thione tautomer, which dominates for the neutral C2S molecule, is transformed upon deprotonation into the imino–thioate form with the negative charge largely located on the sulfur. In the M(C2S)2+ complexes the (C2)S group is the primary binding site rather than N3 as is the case in the M(Cyd)2+ complexes, though owing to chelate formation N3 is to some extent still involved in metal ion binding. Similarly, in the Zn(C2S−H)+ and Cd(C2S−H)+ complexes the main metal ion binding site is the (C2)S− unit (formation degree above 99.99% compared with that of N3). However, again a large degree of chelate formation with N3 must be surmised for the M(C2S−H)+ species in accord with previous solid-state studies of related ligands. Upon metal ion binding, the deprotonation of the (C4)NH2 group (pK a = 12.65) is dramatically acidified (pK a ≈ 3), confirming the very high stability of the M(C2S−H)+ complexes. To conclude, the hydrogen-bonding and metal ion complex forming capabilities of C2S differ strongly from those of its parent Cyd; this must have consequences for the properties of those RNAs which contain this thionucleoside.
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References
Dubler E (1996) Met Ions Biol Syst 32:301–338
Iranzo O, Khalili H, Epstein DM, Morrow JR (2004) J Biol Inorg Chem 9:462–470
Odani A, Kozlowski H, Swiatek-Kozlowska J, Brasún J, Operschall BP, Sigel H (2007) J Inorg Biochem 101:727–735
Raj CR, Behera S (2005) Biosens Bioelectron 21:949–956
Van Rompay AR, Norda A, Lindén K, Johansson M, Karlsson A (2001) Mol Pharmacol 59:1181–1186
Leipuviene R, Qian Q, Björk GR (2004) J Bacteriol 186:758–766
Lukovits I, Kalman E, Zucchi F (2001) Corrosion 57:3–8
Zhang X-H, Wang S-F (2005) Sens Actuators B 104:29–34
Zhang X-H, Wang S-F, Sun N-J (2004) Bioelectrochem 65:41–46
Shigeta S, Mori S, Watanabe F, Takahashi K, Nagata T, Koike N, Wakayama T, Saneyoshi M (2002) Antivir Chem Chemother 13:67–82
Kawaguchi T, Ichikawa T, Hasegawa T, Saneyoshi M, Wakayama T, Kato H, Yukita A, Nagata T (2000) Chem Pharm Bull 48:454–457
Van Rompay AR, Johansson M, Karlsson A (1999) Mol Pharmacol 56:562–569
Sigel H (2004) Chem Soc Rev 33:191–200
Sigel H (1999) Pure Appl Chem 71:1727–1740
Sigel H, Griesser R (2005) Chem Soc Rev 34:875–900
Civcir PÜ (2001) J Phys Org Chem 14:171–179
Davies DB, Rajani P, Sadikot H (1985) J Chem Soc Perkin Trans 2:279–285
Aoki K (1996) Met Ions Biol Syst 32:91–134
Lauhon CT, Skovran E, Urbina HD, Downs DM, Vickery LE (2004) J Biol Chem 279:19551–19558
Lauhon CT (2002) J Bacteriol 184:6820–6829
Lundgren HK, Björk GR (2006) J Bacteriol 188:3052–3062
Pettit LD, Powell HKJ (2001) IUPAC stability constants database, release 5, version 5.16. Academic Software, Timble, Otley, West Yorkshire, UK
Smith RM, Martell AE (2003) NIST critically selected stability constants of metal complexes, reference database 46; version 7.0. US Department of Commerce, National Institute of Standards and Technology, Gaithersburg, MD, USA
Murray K, May PM (2001) Joint expert speciations system (JESS), version 6.4. Division of Water Technology, CSIR, Pretoria, South Africa, and School of Mathematical and Physical Sciences, Murdoch University, Murdoch, Western Australia
Knobloch B, Sigel H (2004) J Biol Inorg Chem 9:365–373
Kinjo Y, Ji L-n, Corfù NA, Sigel H (1992) Inorg Chem 31:5588–5596
Gans P, Sabatini A, Vacca A (1985) J Chem Soc Dalton Trans:1195–1200
Aragoni MC, Arca M, Crisponi G, Nurchi VM (1995) Anal Chim Acta 316:195–204
Yamauchi O, Odani A, Masuda H, Sigel H (1996) Met Ions Biol Syst 32:207–270
Scheller KH, Hofstetter F, Mitchell PR, Prijs B, Sigel H (1981) J Am Chem Soc 103:247–260
Kowalik-Jankowska T, Varnagy K, Swiatek-Kozlowska J, Jon A, Sóvágó I, Sochacka E, Malkiewicz A, Spychala J, Kozlowski H (1997) J Inorg Biochem 65:257–262
Swiatek-Kozlowska J, Brasuń J, Dobosz A, Sochacka E, Glowacka A (2003) J Inorg Biochem 93:119–124
Pogorelyi VK, Barvinchenko VN, Lobanov VV (1979) Teor Eksp Khim 15:547–552
Song B, Sigel RKO, Sigel H (1997) Chem Eur J 3:29–33
Da Costa CP, Krajewska D, Okruszek A, Stec WJ, Sigel H (2002) J Biol Inorg Chem 7:405–415
Sigel H, Martin RB (1994) Chem Soc Rev 23:83–91
Lippert B (2005) Prog Inorg Chem 54:385–447
Sigel RKO, Sigel H (2007) Met Ions Life Sci 2:109–180
Stewart R, Harris MG (1977) Can J Chem 55:3807–3814
Housecroft CE, Sharpe AG (2001) Inorganic Chemistry. Pearson Education Ltd, Harlow, UK, p 37
Podolyan Y, Gorb L, Blue A, Leszczynski J (2001) J Mol Struct (Theochem) 549:101–109
Bereket G, Öğretir C, Yaman M, Hür E (2003) J Mol Struct (Theochem) 625:31–38
Steger E, Martin K (1963) Z Anorg Allg Chem 323:108–113
Steger E, Martin K (1961) Z Anorg Allg Chem 308:330–336
Frey PA, Reimschüssel W, Paneth P (1986) J Am Chem Soc 108:1720–1722
Frey PA, Sammons RD (1985) Science 228:541–545
Sigel H (2004) Pure Appl Chem 76:1869–1886
Griesser R, Kampf G, Kapinos LE, Komeda S, Lippert B, Reedijk J, Sigel H (2003) Inorg Chem 42:32–41
Garijo Añorbe M, Lüth MS, Roitzsch M, Morell Cerdà M, Lax P, Kampf G, Sigel H, Lippert B (2004) Chem Eur J 10:1046–1057
Kapinos LE, Sigel H (2002) Inorg Chim Acta 337:131–142
Martin RB, Sigel H (1988) Commun Inorg Chem 6:285–314
Sigel RKO, Song B, Sigel H (1997) J Am Chem Soc 119:744–755
Da Costa CP, Okruszek A, Sigel H (2003) Chembiochem 4:593–602
Sánchez-Moreno MJ, Fernández-Botello A, Gómez-Coca RB, Griesser R, Ochocki J, Kotyński A, Niclós-Gutierrez J, Moreno V, Sigel H (2004) Inorg Chem 43:1311–1322
Sigel H, Massoud SS, Song B, Griesser R, Knobloch B, Operschall BP (2006) Chem Eur J 12:8106–8122
Aoki K, Saenger W (1984) J Inorg Biochem 20:225–245
Aoki K (1976) Biochim Biophys Acta 447:379–381
Knobloch B, Linert W, Sigel H (2005) Proc Natl Acad Sci USA 102:7459–7464
Wilton-Ely JDET, Schier A, Mitzel NW, Nogai S, Schmidbaur H (2002) J Organomet Chem 643–644:313–323
Ma C-L, Shi Y, Zhang Q-F, Jang Q (2005) Polyhedron 24:1109–1116
Yamanari K, Fukuda I, Yamamoto S, Kushi Y, Fuyuhiro A, Kubota N, Fukuo T, Arakawa R (2000) J Chem Soc Dalton Trans: 2131–2136
Hu X, Li H, Zhang L, Han S (2007) J Phys Chem B 111:9347–9354
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The competent technical assistance of Astrid Sigel in the preparation of the manuscript and the support by the Universities of Basel and Wroclaw are gratefully acknowledged.
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Species written without a charge either do not carry one or represent the species in general (i.e., independent of their protonation degree); which of the two possibilities applies is always clear from the context. A formula like (C2S−H)+ means that the ligand has lost a proton and it is to be read as C2S minus H+.
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Brasuń, J., Matera, A., Sochacka, E. et al. Acid–base and metal ion binding properties of 2-thiocytidine in aqueous solution. J Biol Inorg Chem 13, 663–674 (2008). https://doi.org/10.1007/s00775-008-0351-1
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DOI: https://doi.org/10.1007/s00775-008-0351-1