Helix, of DNA

Figure 3.10 Stniciural details of the bridging units between pairs of bases in separate strands of the double helix of DNA (a) the thymine-adenine pair (b) the cytosine-guanine pair.

The curvature effect of the double helix of DNA, caused by the binding of dimers of active receptors to the HRE sequences, has been obtained by means of experiments of transfection of lineal DNA structures to cells that previously did not express the gene under study. The reality of the cells in vivo must be... 

The Beato group has studied in depth the influence of the nucleosome structure in response to glucocorticoids (Beato 1989). Nucleosomes are formed by segments of 120 nucleotides of the double helix of DNA that make two twists around an octamer of histone. There are 200 nucleotides between two consecutive nucleosomes, so that a gene normally has tens of nucleosomes. 

Intercalation the insertion of a molecule between adjacent base pairs in the double helix of DNA. 

For quantitative structure-activity relationship (QSAR) studies a three-dimensional model of a DNA-quinoIone complex was built using molecular modeling techniques. It was based on the intercalation of quinolone into the double helix of DNA. It was concluded that the intercalation model is consistent with most available data on the structure of the quinolone complex. This predicted... 

If the sequence of one chain of a double helix of DNA is ATTACGTCAT, what is the sequence of the adjacent chain ... 

Many if not most furanocoumarln derivatives possess potent photoactive properties. It is generally accepted that the biological actions of furanocoumarins are attributable to the fact that these compounds easily intercalate into the double helix of DNA, where they produce cyclobutane adducts with... 

DNA, short for deoxyribonucleic acid, is the coding machinery of life. The beauty of DNA is in its simplicity that results in the complexity of life. The double helix of DNA is made of the chemicals adenine (A), guanine (G), thymine (T), and cytosine (C). These chemical are bound in long stretches as AT and CG pairs,... 

In the medium scale are various substructures of a molecule such as delocalized bonds, rings and fused rings, and their conformations—whether they are planar or shaped like a boat or a chair. Large biological molecules have secondary and tertiary structures, such as the a helix and p sheets of proteins, and the double helix of DNA molecules. 

The replication of DNA Double helix of DNA unwinds. Each single strand serves as a template for the formation of a new DNA strand containing the complementary sequence. Two daughter double helices are formed, each containing one of the parent strands. 

Like proteins, nucleic acids can undergo denatur-ation. The strands of the double helix of DNA are separated and the double-stranded regions of RNA molecules "melt." Denaturation can be accomplished by addition of acids, bases, and alcohols or by removal of stabilizing counter ions such as Mg2+. The product is a random coil and denaturation can be described as a helix —> coil transition. Denaturation of nucleic acids by heat, like that of proteins, is cooperative (Chapter 7, Section A,3) and can be described by a characteristic melting temperature. 

In Figure 16.15 we show a schematic representation of the duplex formed from d(GAATTC). Bases from one monomer pair with those from a second to form the duplex. G forms base-pairs with C, and A with T through hydrogen bonding. These base-pairs are referred to as Watson-Crick base-pairs, and they make up the rungs of the ladder associated with the familiar double helix of DNA. 

This section deals exclusively with protein targets enzymes and receptors. Is not the structure of oligonucleotides also important It certainly is. The difference between proteins and oligonucleotides, especially DNA, is that proteins are far less predictable in terms of structure. An essentially universal structure like the double helix of DNA has no parallel in the world of proteins. Considerable research effort is expended on determining the three-dimensional structure of target proteins. 

Described in 1953 by James Watson and Francis Crick, the double helix of DNA (deoxyribonucleic acid) is the cellular storehouse of genetic information. This biopolymer consists of a pair of complementary chains approximately 2.4 nanometers (9.5XlO-8 inches) in diameter and composed of... 

Watson and Crick also found that the two complementary strands of DNA are coiled into a helical conformation about 20 A in diameter, with both chains coiled around the same axis. The helix makes a complete turn for every ten residues, or about one turn in every 34 A of length. Figure 23-27 shows the double helix of DNA. In this drawing, the two sugar-phosphate backbones form the vertical double helix with the heterocyclic bases stacked horizontally in the center. Attractive stacking forces between the pi clouds of the aromatic pyrimidine and purine bases are substantial, further helping to stabilize the helical arrangement. 

Double helix of DNA. Two complementary strands are joined by hydrogen bonds between the base pairs. This double strand coils into a helical arrangement. 

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