G. Pietramellara et al., Effect of molecular characteristics of DNA on its adsorption and binding on homoionic montmorillonite and kaolinite, BIOL FERT S, 33(5), 2001, pp. 402-409
Adsorption or binding of DNA by montmorillonite or kaolinite, homoionic to
Ca2+, was not affected by base composition, blunt or cohesive ends. Fitting
data to both Freundlich and Langmuir adsorption isotherms showed that the
amount of lower molecular mass DNA adsorbed and bound by both clay minerals
was higher than that of the higher molecular mass DNA. The relevance of ph
osphate groups for the adsorption of DNA by clay minerals was investigated
by adding sodium metaphosphate before and after the addition of DNA to clay
minerals: DNA was partially not adsorbed even at low concentrations of sod
ium metaphosphate. The fact that the observed DNA was partially desorbed by
washing with double-distilled H2O indicated that bonds with different degr
ees of strength were formed between DNA molecules and clay minerals. The hi
gher molecular mass DNA could interact with a larger number of binding site
s on the external surface of clay mineral than the lower molecular mass DNA
. The number of external surface binding sites was higher on kaolinite than
on montmorillonite.