Cu²⁺and AMP complexation of enlarged tripodal polyamines

Abstract

The synthesis, characterization, Cu2+ coordination and interaction with AMP of three tripodal polyamines are reported. The polyamines are based on the structure of the tetraamine (tren) which has been enlarged with three propylamino functionalities (), with a further anthrylmethyl fragment at one of its terminal primary nitrogens () or with naphthylmethyl fragments at its three ends (). The protonation constants of all three polyamines show that at pH 6, all six primary and secondary nitrogen atoms in the arms are protonated. The interaction with Cu2+ and AMP (adenosine-5'-monophosphate) has been studied by potentiometric, UV-Vis, ESI-MS spectroscopy and NMR techniques. pH-Metric, NMR and ESI/MS techniques indicate that and form with AMP adducts of 1:1, 2:1 and 3:1 AMP:L stoichiometries in water. This is one of the first examples for the formation of such complexes in aqueous solution. Formation of ternary complexes between , , , Cu2+ and AMP is observed. Paramagnetic NMR techniques have been used to obtain structural information on the binding mode of AMP to the Cu2+- binuclear complexes.

Acid–base properties of functionalised tripodal polyamines and their interaction with nucleotides and nucleic acids

“…23 AMP and CMP bear a protonation of the nitrogen N1 in the aromatic ring. By examining the different values of binding constants, it is interesting to notice that all tripodal receptors are able to form 15 mononuclear complexes of significant stability with the studied nucleotides. Figure S2 (ESI †) includes distribution diagrams for the studied systems and shows that the adduct species clearly predominate in a wide pH range.…”

“…10 The obtained IC 50 = 1.2 -0.15 suggest that affinities of L 4 -L 7 toward ct-DNA and poly A-poly U are comparable to the affinity of EB. Since the structures of L 4 -L 7 do not support intercalation into ds-DNA/RNA as a binding mode but more likely an electrostatic interactions, the obtained IC 50 values 15 cannot be used for accurate calculation of binding constants but only as a measure of high affinity (logKs > 5). Figures 4 and 5), respectively, allowed in the most cases for an accurate assignation of thermal transitions to corresponding polynucleotides.…”

“…10 In order to get insight into the changes of polynucleotide secondary structure induced by small molecule binding, we have chosen Circular Dichroism (CD) spectroscopy. 30 In addition, achiral small molecules can eventually acquire induced CD spectrum (ICD) upon binding to polynucleotides, 15 which could give useful information about modes of interaction. 30 It should be noted that the studied compounds are achiral and therefore do not possess intrinsic CD spectrum.…”

“…Current challenges in diagnostics and emerging therapies for treating genetic diseases call for novel, improved technologies 15 for in vitro and in vivo targeting of nucleic acids. The rational design of new molecules able to interact selectively with nucleic acids has an immense practical application in several fields ranging from construction of nanomaterials to drug design and delivery.…”

“…15 Figure 1 gives an example of distribution diagram for the species existing in equilibrium for the protonation of receptor L 5 . Figure S1 (ESI † ) includes the distribution diagram for the species existing in equilibrium for all receptors L 4 -L 7 .…”