Abstract
We studied the effect of branched-chain polyamines on the folding transition of genome-sized DNA molecules in aqueous solution by the use of single-molecule observation with fluorescence microcopy. Detailed morphological features of polyamine/DNA complexes were characterized by atomic force microscopy (AFM). The AFM observations indicated that branched-chain polyamines tend to induce a characteristic change in the higher-order structure of DNA by forming bridges or crosslinks between the segments of a DNA molecule. In contrast, natural linear-chain polyamines cause a parallel alignment between DNA segments. Circular dichroism measurements revealed that branched-chain polyamines induce the A-form in the secondary structure of DNA, while linear-chain polyamines have only a minimum effect. This large difference in the effects of branched- and linear-chain polyamines is discussed in relation to the difference in the manner of binding of these polyamines to negatively charged double-stranded DNA.
Highlights
Polyamines, small cationic compounds with two or more amino groups, are found in all living cells and play roles in cell growth, proliferation, and many other important cellular functions.1 The most common natural polyamines are putrescine [2+], spermidine [3+], and spermine [4+], all of which have a linear skeleton
It has been reported that spermine [4+] is much more potent at promoting DNA compaction than putrescine [2+] and spermidine [3+], which indicates that the valence strongly influences the degree of DNA compaction
We investigated the effects of these polyamines on the secondary structure of DNA by circular dichroism (CD)
Summary
Polyamines, small cationic compounds with two or more amino groups, are found in all living cells and play roles in cell growth, proliferation, and many other important cellular functions. The most common natural polyamines are putrescine [2+], spermidine [3+], and spermine [4+], all of which have a linear skeleton. The most common natural polyamines are putrescine [2+], spermidine [3+], and spermine [4+], all of which have a linear skeleton. It is known that these polyamines affect the induction of DNA condensation/compaction.. It has been reported that spermine [4+] is much more potent at promoting DNA compaction than putrescine [2+] and spermidine [3+], which indicates that the valence strongly influences the degree of DNA compaction.. In addition to the number of positive charges, structural differences affect their interactions with DNA. Several systematic studies have shown that their influence on DNA compaction is dependent on the geometrical arrangement of positively charged amino groups.. It has been reported that the potential for DNA compaction exhibits an even-odd effect with respect to the number of methylene groups that separate neighboring amino groups.. Several systematic studies have shown that their influence on DNA compaction is dependent on the geometrical arrangement of positively charged amino groups. It has been reported that the potential for DNA compaction exhibits an even-odd effect with respect to the number of methylene groups that separate neighboring amino groups. Chiral effects on DNA compaction have been reported.
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