The Difference between Rare Earth Ions and Alkaline Earth Metal Ions in DNA Condensation Process

The structural transition of DNA double-stranded induced by Ce3+ or Mg2+ ions was investigated in this paper. By atomic force microscopy, different types of condensed DNA structures were observed at the presence of Ce3+ or Mg2+ ions. The results show that there are some differences between rare earth ions and alkaline earth metal ions in the DNA condensation process.

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Specific Adsorption of Cations

Chemistry of Variable Charge Soils ◽

10.1093/oso/9780195097450.003.0008 ◽

1997 ◽

Author(s):

T. R. Yu ◽

H. Y. Sun

Keyword(s):

Heavy Metals ◽

Alkali Metal ◽

Metal Ions ◽

Alkaline Earth ◽

Earth Metal ◽

Specific Adsorption ◽

Alkaline Earth Metal ◽

Electrostatic Adsorption ◽

Alkaline Earth Metal Ions ◽

The Difference

In the adsorption of cations by soils, except for the electrostatic force discussed in Chapter 3, specific forces between the surface of soil particles and the cations may sometimes be involved. The adsorption caused by these specific forces is called specific adsorption. Apparently, this adsorption would be related to both the nature of the cations and the surface properties of the soil. Generally speaking, various oxides are the principal materials responsible for specific adsorption of cations in soils. Variable charge soils contain large amounts of iron and aluminum oxides. At the same time, their negative surface charge sites that can attract cations electrostatically are small in quantity. It can be expected that, compared to constant charge soils, their specific adsorption for cations would have more significance. Most of the cation species that can be adsorbed specifically by soils, such as copper, zinc, cobalt, and cadmium, belong to heavy metals. A large part of these heavy metals are transition elements in the periodic table. Alkali metal and alkaline earth metal ions can also be adsorbed specifically to some extent by soils under certain circumstances. However, this kind of adsorption is of less importance when compared to electrostatic adsorption, and the mechanism involved may be different from that for heavy metals. Among heavy metals, zinc occupies a special position in soil science because it is one important nutrient element for plants. In this chapter, after treatment on the principles of specific adsorption of heavy metal ions, detailed discussions will be presented for both the relative importance of specific adsorption and electrostatic adsorption of these ions and the consequences of specific adsorption, using the adsorption of zinc ions as an example. The cause of the difference in properties between the transition metal ions and the alkali metal and alkaline earth metal ions with respect to adsorption lies primarily in the difference in their atomic structure. Alkali metal and alkaline earth metal ions are characterized by a small amount of electric charge in the atomic nucleus, large ionic size, and weak polarizability. Therefore, the atom is difficult to deform.

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