Opposite effect of polyamines on <i>In vitro</i> gene expression: Enhancement at low concentrations but inhibition at high concentrations - Fig 1

Chemical formulas of (A) spermidine, [SPD(3+)] and (B) spermine, [SP(4+)].</p

AFM images of DNA conformations at different concentrations of SPD(3+).

SPD(3+) concentration is (A) 0.004 mM (control), (B) 0.1 mM, (C) 0.3 mM, and (D) 2 mM.</p

Gene expression efficiency depending on the DNA concentration at a fixed concentration of SPD(3+), 1.5 mM.

<p>Gene expression efficiency depending on the DNA concentration at a fixed concentration of SPD(3+), 1.5 mM.</p

Schematic representation of the nature of the interaction of polyamine with DNA and also with RNA polymerase depending on the polyamine concentration.

(A): elongated DNA without polyamine, (B): parallel alignment of DNA segments with the inset of the AFM image of Fig 5(C), (C): compact DNA with the inset of AFM of Fig 5(D).</p

AFM images of DNA conformations at different concentrations of SP(4+).

<p>SP(4+) concentration is (A) 0.004 mM (control), (B) 0.007 mM, (C) 0.06 mM, and (D) 0.6 mM.</p

Gene expression efficiency depending on the concentrations of polyamines, SPD(3+) and SP(4+).

The longitudinal axis shows the relative emission intensity of luciferin-luciferase reaction, which corresponds to the efficiency of gene expression. DNA concentration was fixed at 0.3 μM.</p

Specific Conformational Change in Giant DNA Caused by Anticancer Tetrazolato-Bridged Dinuclear Platinum(II) Complexes: Middle-Length Alkyl Substituents Exhibit Minimum Effect

Derivatives of the highly antitumor-active compound [{<i>cis</i>-Pt­(NH₃)₂}₂­(μ-OH)­(μ-tetrazolato-<i>N2</i>,<i>N3</i>)]²⁺ (<b>5-H-Y</b>), which is a tetrazolato-bridged dinuclear platinum­(II) complex, were prepared by substituting a linear alkyl chain moiety at C5 of the tetrazolate ring. The general formula for the derivatives is [{<i>cis</i>-Pt­(NH₃)₂}₂(μ-OH)­(μ-5-R-tetrazolato-<i>N2</i>,<i>N3</i>)]²⁺, where R is (CH₂)_<i>n</i>CH₃ and <i>n</i> = 0 to 8 (complexes <b>1</b>–<b>9</b>). The cytotoxicity of complexes <b>1</b>–<b>4</b> in NCI-H460 human non-small-cell lung cancer cells decreased with increasing alkyl chain length, and those of complexes <b>5</b>–<b>9</b> increased with increasing alkyl chain length. That is, the <i>in vitro</i> cytotoxicity of complexes <b>1</b>–<b>9</b> was found to have a U-shaped association with alkyl chain length. This U-shaped association is attributable to the degree of intracellular accumulation. Although circular dichroism spectroscopic measurement indicated that complexes <b>1</b>–<b>9</b> induced comparable conformational changes in the secondary structure of DNA, the tetrazolato-bridged complexes induced different degrees of DNA compaction as revealed by a single DNA measurement with fluorescence microsopy, which also had a U-shaped association with alkyl chain length that matched the association observed for cytotoxicity. Complexes <b>7</b>–<b>9</b>, which had alkyl chains long enough to confer surfactant-like properties to the complex, induced DNA compaction 20 or 1000 times more efficiently than <b>5-H-Y</b> or spermidine. A single DNA measurement with transmission electron microscopy revealed that complex <b>8</b> formed large spherical self-assembled structures that induced DNA compaction with extremely high efficiency. This result suggests that these structures may play a role in the DNA compaction that was induced by the complexes with the longer alkyl chains. The derivatization with a linear alkyl chain produced a series of complexes with unique cellular accumulation and DNA conformational change profiles and a potentially useful means of developing next-generation platinum-based anticancer drugs. In addition, the markedly high ability of these complexes to induce DNA compaction and their high intracellular accumulation emphasized the difference in mechanism of action from platinum-based anticancer drugs