In molecular biology, Quadruplex structures is a nucleic acid sequence rich G-quadruplex (also known as G4-DNA or G-four minutes) guanine, it is possible to form four-stranded structures. In order to form a flat structure of a square, called guanine 4 may, four molecules guanine 2 or more, to form a G-quadruplex even when connected via Hoogsteen hydrogen bonding four guanine bases are stacked. Located in the central channel between each pair of the four molecules are further stabilized by the presence of potassium cations, particularly in the quadruple structure. Be prepared Quadruplex structures DNA, RNA, LNA, PNA and a can and can be, they may be intermolecular or intramolecular tetramolecular. It is possible that depending on the direction of the fibers or portions of the strands forming the four molecular structure described as a parallel or antiparallel.
A specialized region of DNA called telomeres at the ends of linear chromosomes, there. To enable the Quadruplex structures cell to reproduce the chromosome, usually, the main features of these regions, the enzyme telomerase, such as enzymes to be copied can be used to replicate the 3 ‘end final chromosome DNA You end up using, the. Stop system recovery of DNA in cells by treating them also chromosomal cap these special protects the ends of the DNA, so as to correct the damage. In human cells, telomere length is a single-stranded DNA comprising a simple sequence repeat thousands of TTAGGG, usually.
Quadruplex DNA formed by the telomere repeat. Curved shape of the DNA backbone, are very different from the DNA helix typical. By not the main unit 4, to form the structure of the group ordered base pairs usually it is found in DNA molecules other sequences of guanine rich These may stabilize the ends of chromosomes possible. Here, stacked on top of each other to form a stable G-quadruplex structure is then formed on a flat plate, guanine bases of four basic units flat these four. The end of the base, these structures are stabilized by hydrogen bonds between the chelate metal ions in the center of the base of all four. Other structures can be folded around the parallel strand several different base or formation or set in the center of the base of the four is coming from the thread, each of which contributes to the base of the one in the center structure.
In addition to the layered structure of these, large loop Quadruplex structures and form telomere is called a T-loop or telomere loop,. Here, single-stranded DNA is bent around the average longer stabilized by telomere-binding proteins. At the end the T-loop, single-stranded telomeric DNA is performed in the region of double-stranded DNA from the chaos of the telomere loop of base pairs to one of the two chains and the double helix DNA. The triple helical structure, which is known as D-loop or displacement loop.
The length of the nucleic acid sequence involved in the formation of four sets of fold which quadrupole. The short sequence consisting of a series of one or more bases guanine these three, it is necessary to form four heavy strands four separate. For example, to reflect the request of the thread of four separate, it is described as a quadruplex tetramolecular. Long sequence containing a field for two adjacent guanine bases or more, guanine region, in order to provide sufficient guanine base to form a quadruple or three, separated by a base of one or more It requires only such sequences of two. It is formed by the fiber G-rich two separate, these structures are referred to as two molecular quadruplex. Finally, the sequence of configuring the execution of four separate guanine bases can form a quadruple and quadruple itself a stable structure which is formed entirely from a single thread, but in the molecule It is called a quadruple.
That depending on how the execution of individual guanine bases are arranged in four weight molecule or two molecules, four heavy, take one of several topologies line and different settings. The direction of the thread – ‘3’ all is the same as the quadruple is called parallel, i.e. to all of the DNA strands running in the same direction when 5. For four heavy chain molecule, it means that it must be present in the vane-type, edge or each loop region is disposed in the wall of the quadruple. The opposed to the other track guanine base state quadruple execution of one or more guanine bases have adopted the anti-parallel topology, in the case of the 5′-3 ‘direction. Loop that connects the run of guanine bases in the molecule anti-parallel quadruplex during participating chain to run the two edge type guanine adjacent (or participate in the two diagonal run the guanine base) or diagonal.
To form these structures in vitro telomeric repeats in various organisms have been shown, they also may be formed in vivo in some cases has been shown. I a repeat of the quadruplex and (GGTTAG) the sequence d, is studied by X-ray crystal structure analysis and NMR as well (which is the same in all vertebrates) human telomeric repeat, formed by this structure. The formation of four heavy chains of these telomeres, that is responsible for the maintenance of telomere length, thereby decreasing the activity of the enzyme telomerase, which is involved in approximately 85% of all cancers have been shown. This is the purpose of the active drug discovery