INTRACTION OF SODIUM , CALCIUM AND MAGNESIUM IONS WITH DEOXYRIBONUCLEIC ACID
INTRACTION OF SODIUM , CALCIUM AND MAGNESIUM IONS WITH DEOXYRIBONUCLEIC ACID
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Date
1971-03
Authors
OlAYEMI, JULIUS YINKA
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Abstract
The i n t e r a c t i o n of sodium ( i ) , polonium (ii) and magnesium ( I I)
with Ribonucleic acid (DNA) of oaf thymus has been studied
by d i a l y s i s equilibrium, conductance measurements, u l t r a v i o l et
l i g h t absorption and l i g h t s c a t t e r i n g methods. The r e s u l t s have
been summarized as follows:
( i ) DNA i n t e r a c t s with sodium, calcium and magnesium ions
and more strongly with the two divalent c a t i o n s.
( i i ) Magnesium and calcium ions bind q u a n t i t a t i v e l y to DNA
to form complexes of the following optometrists:
0.125:; 0.30:1 and 0.50:1 moles of divalent cation to one mole of
nucleate phosphorus. In a l k a l i n e medium, a 1:1 mole complex was formed.
( i i i ) The s t a b i l i t y of the complexes formed between the divalent
cations and DNA depends on (a) the concentration of sodium chloride
supporting e l e c t r o l y t e , and ( b ) , the pH of the s o l u t i o n . The s t a ability
decreases with increasing s a l t concentration and with increasing
a c i d i t y f o r each DNA-M2+ system. The s t a b i l i t y constants for the
DNA-Mg complexes are comparable with those of DNA-Ca2+ complexes.
( i v ) At room temperature, DNA r e t a i n s i t s n a t i v e s t r u c t u r e when
prepared in s o l u t i o n of sodium chloride of at l e a s t 1 0 - 4 a n d in
both caloric and magnesium chloride of about one hundredth of t h is
concentration.
The molar absorptivity e(P) of DNA becomes a function of the
concentration of NaCl2 CaCl2 and HgClp only when the acid is
denatured, but is completely independent of salt concentration when
in i t s native form. DNA naturalization temperature (Tm) is increased
in the presence of increasing concentrations of NaCl, CaCl2 and MgC2.
Calcium and magnesium ions are more effective than the sodium ions in
causing this increase in (Tm), showing a stronger interaction of the
divalent orations than of the covalent sodium ions with DNA.
Low concentration of calcium and magnesium ions (of the order of
and below) have no destructive influence on the secondary
structure of DNA. However, high concentrations of these divalent
orations (of the order of 0.05H and above) have been suspected to
produce a naturalization followed by a precipitation and/or aggregation
of a system of DNA-M on heating beyond the naturalization temperature (Tm).
(v) The method of light scattering has shown that the molecular
weight of DNA depends on the concentrations of calcium and magnesium
ions up to a certain maximum concentration of these orations, when the
molecular weight of the DNA is doubled. This suggests that calcium
and magnesium ions are engaged in an intermolecular bonding to DNA.
The molecular weight of DNA was found to be independent of the
concentration of sodium ions
Description
Dissertation
presented to
The Ahmadu Bello University
for the degree of
DOCTOR OF PHILOSOPHY
i n the
Faculty of Science
BY
JULIUS YINKA OlAYEMI, B.Sc.
Department of Chemistry
Ahmadu Bello University
Zaria
March, 1971
Keywords
INTRACTION,, SODIUM,, CALCIUM,, MAGNESIUM IONS., DEOXYRIBONUCLEIC,, ACID