Selectivity of spermine homologs on triplex DNA stabilization.
We synthesized seven homologs of spermine (H2N(CH2)3NH(CH2)nNH(CH2)3NH2, where n = 2-9; n = 4 for spermine) and studied their effects on melting temperature (Tm), conformation, and precipitation of poly(dA).2poly(dT). The triplex DNA melting temperature, Tm1 was 34.4 degrees C in the presence of 150 mM KCl. Addition of spermine homologs increased Tm1 in a concentration-dependent and structure-dependent manner, with 3-6-3 (n = 6) exerting optimal stabilization. The dTm1/dlog[polyamine] values were 9-24 for these compounds. The duplex melting temperature, Tm2 was insensitive to homolog concentration and structure, suggesting their ability to stabilize triplex DNA without altering the stability of the underlying duplex. Circular dichroism spectral studies revealed psi-DNA formation in a concentration-dependent and structure-dependent manner. Phase diagrams were constructed showing the critical ionic/polyamine concentrations stabilizing different structures. These compounds also exerted structural specificity effects on precipitating triplex DNA. These data provide new insights into the ionic/structural determinants affecting triplex DNA stability and indicate that 3-6-3 is an excellent ligand to stabilize poly(dA).2poly(dT) triplex DNA under physiologic ionic conditions for antigene therapeutics.
Antony
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T
Department of Environmental and Community Medicine, University of Medicine and Dentistry of New Jersey-Robert Wood Johnson Medical School, New Brunswick 08903, USA.
Thomas
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T
Shirahata
A
A
Sigal
L H
LH
Thomas
T J
TJ
D002942:Circular Dichroism; D004247:DNA / Q000187:drug effects*; D007477:Ions; D009690:Nucleic Acid Conformation / Q000187:drug effects*; D009691:Nucleic Acid Denaturation / Q000187:drug effects; D011089:Polydeoxyribonucleotides; D011189:Potassium Chloride / Q000494:pharmacology; D013096:Spermine / Q000031:analogs & derivatives*; D055672:Static Electricity; D013329:Structure-Activity Relationship
D007477:Ions; D011089:Polydeoxyribonucleotides; C098037:poly(dA)(poly(dT))2; C051802:triplex DNA; D013096:Spermine; D011189:Potassium Chloride; D004247:DNA