OSMOTIC EFFECTORS AND DNA-STRUCTURE - EFFECT OF GLYCINE ON PRECIPITATION OF DNA BY MULTIVALENT CATIONS

We have investigated the effect of glycine (an organic osmolyte) on DNA precipitation induced by spermine(4+), spermidine(3+) and Tb3+ addition, using circular dichroism (CD), UV spectroscopy (UV), and electric linear dichroism (ELD) techniques. DNA precipitation by the three compounds is perturbed by glycine: more spermine(4+), spermidine(3+) and Tb3+ must be added to obtain the same extent of precipitation as compared to the behaviour in absence of this organic osmolyte. It seems that glycine has a general effect on the DNA environment. Calculations based on experimental results and Manning's counterion condensation theory show that glycine could modify the electrostatic environment of DNA as a consequence of a change in dielectric constant.