The binding of polyamines and magnesium to DNA.
1. The binding of spermine and Mg2+ to DNA has been investigated using the dye arsenazo III to measure unbound cations. 2. The apparent dissociation constant, Kd, of DNA for spermine has been found to be 7.4 +/- 3.9 x 10(-8) M and that for Mg2+, 6.5 +/- 3.3 x 10(-7) M. 3. Binding of spermine in the presence of 1 mM Mg2+ has been shown to have a Kd of about 4 x 10(-6) M. 4. Magnesium ion (2 mM) halves the concentration of spermine needed to cause DNA aggregation. 5. Spermidine binds to DNA with a similar affinity to spermine but 3,3'-iminobispropylamine and 1,5,9,13-tetra-azatridecane bind with a lower affinity. The naturally occurring polyamines thus have a higher affinity for DNA than the related polyamines which do not occur naturally. 6. Binding of spermine or spermidine to DNA alters the spectrophotometric absorbance of DNA at 260 nm.
Rowatt
E
E
Department of Medical Microbiology, School of Pathology, University College and Middlesex School of Medicine, London, U.K.
Williams
R J
RJ
D000818:Animals; D001150:Arsenazo III; D002412:Cations; D002417:Cattle; D004247:DNA / Q000187:drug effects / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism* / Q000494:pharmacology; D011073:Polyamines / Q000378:metabolism*; D013053:Spectrophotometry; D013095:Spermidine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D013096:Spermine / Q000378:metabolism
D002412:Cations; D011073:Polyamines; D001150:Arsenazo III; D013096:Spermine; C006760:norspermidine; D004247:DNA; D008274:Magnesium; D013095:Spermidine