Abstract
The effect of divalent ions on the thermal stability of the double-stranded polynucleotide polyinosinic:polycytidylic acid (poly(I:C)) in a buffer solution (pH 7) was studied by UV absorption spectroscopy and thermal denaturation by measuring the absorbance at 260 nm. The concentration dependence of the polynucleotide melting temperature (Tm) in the presence of metal ions (2.5 × 10−6–10−2 M) was obtained. It was found that the duplex thermal stability grew gradually upon an increase of Ca2+ and Mn2+ concentration. The thermal stability of the duplex in the presence of Cd2+, Ni2+, and Zn2+ rises up to an ion concentration of about 10−4 M and further falls. In contrast to these ions, the addition of Cu2+ to the solution leads to a sharp decline in Тm of the duplex at a concentration above 10−5 M. The observed difference in the influence of metal ions on the poly(I:C) thermal stability is explained by the different affinity of these ions to both the phosphate groups and the nitrogenous bases of the polynucleotides. Based on the analysis of the Tm concentration dependence, the dominant binding of each ion to the specific polynucleotide components was proposed.
Highlights
Interest in studying the conformational state and the stability of polynucleotides of RNA family is caused by their biological functionality, their use in human disease treatments, and the possibility of using them as biomarkers, drug targets, and promising elements for nanoelectronics and nanobiosensors [1, 2]
It is known that the double-stranded biopolymer polyinosinic:polycytidylic acid (poly(I:C)) (Figure 1) is used for the treatment of certain viral diseases as a potent agent that induces the interferon formation [3]. is duplex is characterized by the substitution of guanine-cytosine for inosine-cytosine pairs during replication or transcription without significant changes in the structural parameters of the helix [4]. e random substitution can lead to point mutations. e application of the targeted one allows using oligo- and polynucleotides containing inosine monophosphate (IMP) for solving problems of genetic engineering [4]
Divalent metal ions play an important role in the functionality and the conformation stability of biopolymers [6]. e numerous data on metal complexes of the natural DNA and double-stranded homopolynucleotides containing pairs of canonical nitrogenous bases are already available [1, 7,8,9,10,11,12,13,14,15,16]
Summary
Interest in studying the conformational state and the stability of polynucleotides of RNA family is caused by their biological functionality, their use in human disease treatments, and the possibility of using them as biomarkers, drug targets, and promising elements for nanoelectronics and nanobiosensors [1, 2]. It is known that the double-stranded (ds) biopolymer polyinosinic:polycytidylic acid (poly(I:C)) (Figure 1) is used for the treatment of certain viral diseases as a potent agent that induces the interferon formation [3]. It is known that the main binding sites of metal ions to polynucleotides are oxygen atoms of phosphate groups, as well as nitrogen or oxygen atoms of nitrogenous bases [10, 12,13,14]. It is shown that alkali and alkaline earth metal ions interact predominantly with phosphate groups resulting in stabilization of the structure of nucleic acids. E ions of transition metals interact with both phosphate groups and nucleic acid bases inducing the destabilization of the nucleic acid structure [10, 12,13,14] It is shown that alkali and alkaline earth metal ions interact predominantly with phosphate groups resulting in stabilization of the structure of nucleic acids. e ions of transition metals interact with both phosphate groups and nucleic acid bases inducing the destabilization of the nucleic acid structure [10, 12,13,14]
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