Polyamines compaction

Polymeric polyamines are also strongly adsorbed in the compact region of the electric double layer as a combination of multisite electrostatic and hydrophobic interactions. The adsorption results in masking the silanol groups and the other adsorption active sites on the capillary wall and in altering the EOF, which is lowered and in most cases reversed from cathodic to anodic. One of the most widely employed polyamine coating agents is polybrene (or hexadimetrine bromide), a linear hydrophobic polyquaternary amine polymer of the ionene type [129]. 

This polyamine-induced compaction and aggregation of DNA (PICA effect Gos-ule and Schellman 1976) leads to a protection of DNA against OH-attack much beyond that expected on account of the OH-scavenging capacity of the polyamines (k( OH + putrescine) = 7 x 109 dm3 mol-1 s 1, k( OH + spermine) = 1.2 X 109 dm3 mol-1 s-1 Newton et al. 1996 Douki et al. 2000). Putrescine with only two positive charges cannot compact DNA and thus does not provide radiation protection beyond its OH scavenging capacity (Spotheim-Maurizot et al. 1995a Newton et al. 1996 Fig. 12.15). 

Newton GL, Aguilera JA, Ward JF, Fahey RC (1996) Polyamine-induced compaction and aggregation of DNA - a major factor in radioprotection of chromatin under physiological conditions. Radiat Res 145 776-780... 

Polymeric polyamines are also strongly adsorbed in the compact region of the electric double layer as a combination of multisite electrostatic and hydrophobic interactions. The adsorption results in masking the silanol groups and the other adsorption active sites on... 

The results of the calculations were compared with experimental data on the compactization of DNA in a solution of polyethylene glycol and in solutions of polyamine of different valences. A rather good correspondence between theoretical results and experimental data was found [34,35]. 

No. As mentioned, each nucleosome is associated with approximately 200 base pairs of DNA. If this DNA were coiled into a sphere with a diameter of approximately 100 A, it would be condensed from 200 base pairs x 3.4 A per base pair = 680 A of linear DNA to 100 A, which is a packing ratio of about 7. The chromatin fiber, which is composed a helical array of nucleosomes, must be formed, and the resulting 360-A coils must themselves be looped and folded. Scaffolding proteins, topoisomerases, and small basic molecules, such as the polyamines, also contribute to the ultimate compaction of lO that is observed in metaphase chromosomes. 

Nucleic acids are polyanions, and the compact structure is stabilized by the interaction of negatively charged phosphate groups with cations such as Na, K, Ca and cationic polyamines. The stabilization of DNA and RNA with Na and Mg is often not specific, although in some cases a specific interaction has been found. stabilizes the DNA telomere structure at the end of a double helix of chromosomes by interaction with eight guanine bases as shown in Fig. 2-3. The relative stability depends on the cellular concentration of Na"" and K ". 

Gene delivery vehicles The DNA chain is collapsed into a compact globule through neutralization of its negative charge by cationic polymers such as polyamines and multivalent cations such as spermidine and cobalt hexamine... 

Higashibata H, Fujiwara S, Ezaki S, Takagi M, Fukui K, Imanaka T (2000) Effect of polyamines on histone-induced DNA compaction of hyperthermophilic Archaea. J Biosci Bioeng 89 103-106 Hou MH, Lin SB, Yuann JM, Lin WC, Wang AH, Kan Ls L (2001) Effects of polyamines on the thermal stability and formation kinetics of DNA duplexes with abnormal structure. Nucleic Acids Res 29 5121-5128... 

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