Localized interaction of the polyamine methylspermidine with double-helical DNA as monitored by 1H NMR self-diffusion measurements.
The 1H NMR pulsed field gradient self-diffusion method has been used to measure the diffusion coefficient of the polyamine analogue methylspermidine (completely N-methylated spermidine) in DNA solution, as a function of the concentration ratio of methylspermidine to DNA phosphate. Three different DNA's have been investigated: d(GC)4 (8 base pairs), core length calf thymus DNA (approximately 120 base pairs), and sonicated high molecular weight calf thymus DNA (average 7500 base pairs). For a constant ratio of methylspermidine to DNA phosphate, the diffusion coefficient decreases with increasing DNA length. Moreover, at low concentration ratios the diffusion coefficient of methylspermidine approaches a limiting value that is close to that of the DNA molecule. The experimental data are well reproduced by a two-state diffusion model. In this model the diffusion coefficient of the polyamine is a population-weighted average of polyamine associated with DNA (with a diffusion coefficient given by that of the DNA molecule) and polyamine free in solution.
Andreasson
B
B
Division of Physical Chemistry, University of Stockholm, Sweden.
Nordenskiöld
L
L
Braunlin
W H
WH
Schultz
J
J
Stilbs
P
P
D000818:Animals; D002417:Cattle; D004247:DNA / Q000737:chemistry / Q000378:metabolism*; D004058:Diffusion; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D009690:Nucleic Acid Conformation; D013095:Spermidine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism; D013950:Thymus Gland / Q000737:chemistry
C079396:N-octamethylspermidine; D004247:DNA; D013095:Spermidine