Deoxyribonucleic acid linear form

Nucleic acids are linear polymers of nucleotides linked 3 to 5 by phosphodi-ester bridges (Figure 11.17). They are formed as 5 -nucleoside monophosphates are successively added to the 3 -OH group of the preceding nucleotide, a process that gives the polymer a directional sense. Polymers of ribonucleotides are named ribonucleic acid, or RNA. Deoxyribonucleotide polymers are called deoxyribonucleic acid, or DNA. Because C-1 and C-4 in deoxyribonucleotides are involved in furanose ring formation and because there is no 2 -OH, only... 

Microsomal reduction of chromium(VI) can also result in the formation of chromium(V), which involves a one-electron transfer from the microsomal electron-transport cytochrome P450 system in rats. The chromium(V) complexes are characterized as labile and reactive. These chromium(V) intermediates persist for 1 hour in vitro, making them likely to interact with deoxyribonucleic acid (DNA), which may eventually lead to cancer (Jennette 1982). Because chromium(V) complexes are labile and reactive, detection of chromium(V) after in vivo exposure to chromium(VI) was difficult in the past. More recently, Liu et al. (1994) have demonstrated that chromium(V) is formed in vivo by using low-frequency electron paramagnetic resonance (EPR) spectroscopy on whole mice. In mice injected with sodium dichromate(VI) intravenously into the tail vein, maximum levels of chromium(V) were detected within 10 minutes and declined slowly with a life time of about 37 minutes. The time to reach peak in vivo levels of chromium(V) decreased in a linear manner as the administered dose levels of sodium... 

Nucleic acids, both DNA (deoxyribonucleic acid) and RNA (ribonucleic acid), are linear polymers of four bases linked to a sugar-phosphate backbone as shown in Fig. 2.5a. The differences between DNA and RNA reside in the sugar moiety forming the backbone, and in one of the four bases whereas the sugar in RNA is ribose, it is deoxyribose in DNA both molecules contain bases adenine (A), guanine (G), and cytosine (C)... 

It is of interest to note that many natural forms of deoxyribonucleic acid (DNA) have been shown to be circular macromolecules [29]. Furthermore, a detailed knowledge of the properties and molecular conformations of cyclic polymers should lead to a better understanding of the behaviour of linear polymers, as well as giving new insights into the properties of rubbers, gels and other systems where closed loops are known to exist. 

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