Titration of poly(dA-dT).poly(dA-dT) in solution at variable NaCl concentration

Marta Airoldi, Giuseppe Gennaro, Fabio Cadoni, C. Andrea Boicelli, Marcello Giomini, Mauro Giustini

Risultato della ricerca: Article

9 Citazioni (Scopus)

Abstract

CD and uv absorption data showed that high molecular weight poly(dA-dT) poly(dA-dT),at 298 K, undergoes an acid-induced transition from B-double helix to random coil in NaCl solutions ofdifferent concentrations, ranging from 0.005 to 0.600M. Similarly, titration of the polynucleotide with astrong base causes duplex-to-single strands transition. The base- and acid-induced transitions were bothreversible by back-titration (with an acid or, respectively, with a base): the apparent pKa were the samein both directions. However, the number of protons per titratable site (adenine N1) required to reachhalf-denaturation was in great excess over the stoichiometric value; to a much larger extent, the sameeffect was observed also for the deprotonation of the N3H sites of thymine. Moreover, in the basicdenaturation experiments, at low salt concentrations ([NaCl] 0.300M) less acid than calculated wasneeded to back-titrate the base excess to half-denaturation. Both effects could be qualitatively justifiedon the basis of the counterion condensation theory of polyelectrolytes and considering the energy barriercreated by the negatively charged phosphodiester groups to the penetration of the OH ions inside thedouble helix and the screening effect of the Na ions on such charges, in the deprotonation experiments.
Lingua originaleEnglish
pagine (da-a)118-127
Numero di pagine10
RivistaBiopolymers
Volume75
Stato di pubblicazionePublished - 2004

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Poly dA-dT
Titration
Deprotonation
Denaturation
Acids
Ions
Polynucleotides
Thymine
Adenine
Polyelectrolytes
Protons
Condensation
Screening
Salts
Molecular Weight
Experiments
Molecular weight

All Science Journal Classification (ASJC) codes

  • Biophysics
  • Biochemistry
  • Biomaterials
  • Organic Chemistry

Cita questo

Airoldi, M., Gennaro, G., Cadoni, F., Boicelli, C. A., Giomini, M., & Giustini, M. (2004). Titration of poly(dA-dT).poly(dA-dT) in solution at variable NaCl concentration. Biopolymers, 75, 118-127.

Titration of poly(dA-dT).poly(dA-dT) in solution at variable NaCl concentration. / Airoldi, Marta; Gennaro, Giuseppe; Cadoni, Fabio; Boicelli, C. Andrea; Giomini, Marcello; Giustini, Mauro.

In: Biopolymers, Vol. 75, 2004, pag. 118-127.

Risultato della ricerca: Article

Airoldi, M, Gennaro, G, Cadoni, F, Boicelli, CA, Giomini, M & Giustini, M 2004, 'Titration of poly(dA-dT).poly(dA-dT) in solution at variable NaCl concentration', Biopolymers, vol. 75, pagg. 118-127.
Airoldi, Marta ; Gennaro, Giuseppe ; Cadoni, Fabio ; Boicelli, C. Andrea ; Giomini, Marcello ; Giustini, Mauro. / Titration of poly(dA-dT).poly(dA-dT) in solution at variable NaCl concentration. In: Biopolymers. 2004 ; Vol. 75. pagg. 118-127.
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abstract = "CD and uv absorption data showed that high molecular weight poly(dA-dT) poly(dA-dT),at 298 K, undergoes an acid-induced transition from B-double helix to random coil in NaCl solutions ofdifferent concentrations, ranging from 0.005 to 0.600M. Similarly, titration of the polynucleotide with astrong base causes duplex-to-single strands transition. The base- and acid-induced transitions were bothreversible by back-titration (with an acid or, respectively, with a base): the apparent pKa were the samein both directions. However, the number of protons per titratable site (adenine N1) required to reachhalf-denaturation was in great excess over the stoichiometric value; to a much larger extent, the sameeffect was observed also for the deprotonation of the N3H sites of thymine. Moreover, in the basicdenaturation experiments, at low salt concentrations ([NaCl] 0.300M) less acid than calculated wasneeded to back-titrate the base excess to half-denaturation. Both effects could be qualitatively justifiedon the basis of the counterion condensation theory of polyelectrolytes and considering the energy barriercreated by the negatively charged phosphodiester groups to the penetration of the OH ions inside thedouble helix and the screening effect of the Na ions on such charges, in the deprotonation experiments.",
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AU - Airoldi, Marta

AU - Gennaro, Giuseppe

AU - Cadoni, Fabio

AU - Boicelli, C. Andrea

AU - Giomini, Marcello

AU - Giustini, Mauro

PY - 2004

Y1 - 2004

N2 - CD and uv absorption data showed that high molecular weight poly(dA-dT) poly(dA-dT),at 298 K, undergoes an acid-induced transition from B-double helix to random coil in NaCl solutions ofdifferent concentrations, ranging from 0.005 to 0.600M. Similarly, titration of the polynucleotide with astrong base causes duplex-to-single strands transition. The base- and acid-induced transitions were bothreversible by back-titration (with an acid or, respectively, with a base): the apparent pKa were the samein both directions. However, the number of protons per titratable site (adenine N1) required to reachhalf-denaturation was in great excess over the stoichiometric value; to a much larger extent, the sameeffect was observed also for the deprotonation of the N3H sites of thymine. Moreover, in the basicdenaturation experiments, at low salt concentrations ([NaCl] 0.300M) less acid than calculated wasneeded to back-titrate the base excess to half-denaturation. Both effects could be qualitatively justifiedon the basis of the counterion condensation theory of polyelectrolytes and considering the energy barriercreated by the negatively charged phosphodiester groups to the penetration of the OH ions inside thedouble helix and the screening effect of the Na ions on such charges, in the deprotonation experiments.

AB - CD and uv absorption data showed that high molecular weight poly(dA-dT) poly(dA-dT),at 298 K, undergoes an acid-induced transition from B-double helix to random coil in NaCl solutions ofdifferent concentrations, ranging from 0.005 to 0.600M. Similarly, titration of the polynucleotide with astrong base causes duplex-to-single strands transition. The base- and acid-induced transitions were bothreversible by back-titration (with an acid or, respectively, with a base): the apparent pKa were the samein both directions. However, the number of protons per titratable site (adenine N1) required to reachhalf-denaturation was in great excess over the stoichiometric value; to a much larger extent, the sameeffect was observed also for the deprotonation of the N3H sites of thymine. Moreover, in the basicdenaturation experiments, at low salt concentrations ([NaCl] 0.300M) less acid than calculated wasneeded to back-titrate the base excess to half-denaturation. Both effects could be qualitatively justifiedon the basis of the counterion condensation theory of polyelectrolytes and considering the energy barriercreated by the negatively charged phosphodiester groups to the penetration of the OH ions inside thedouble helix and the screening effect of the Na ions on such charges, in the deprotonation experiments.

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