DNA noncovalent

Lim YB, Kim T, Lee JW et al (2002) Self-assembled ternary complex of cationic dendrimer, cucurbituril, and DNA noncovalent strategy in developing a gene delivery carrier. Bioconjug Chem 13 1181-1185... 

Researchers have also studied DNA-mediated electron transfer by using donor-acceptor pairs that bind DNA noncovalently (27-30). Early work in our laboratory used cationic tris(phenanthroline) metal complexes as donor-acceptor pairs (29, 30). These complexes, shown in Figure 1, associate with DNA through two modes, (i) intercalation and... 

To distinguish DHBV CCC DNA from other viral replicative intermediates, a modified salt extraction of the extracts must be performed, which enriches for viral DNAs noncovalently bound to protein (5). 

Some metal complexes that bind DNA noncovalently primarily through intercalation (top) or binding in the minor groove (bottom). Some metalloporphyrins also primarily associate via intercalation. 

Very recently, the Shipman group have made a further step towards a comprehensive structure/activity profile for noncovalent interactions between azinomycin B and DNA [152]. They synthesized simplified azinomycin analogues 69 and 96-98 (Scheme 11.13), retaining both the epoxide and aziridine alkylating functionalities, with systematically altered substitution on the naphthoate fragment, and analyzed their DNA crosslinking by gel electrophoresis. They found that cross-... 

Chromatin is a noncovalent complex consisting of DNA and dedicated packing proteins, the histones. The name chromatin is derived from the Greek word chroma... 

The DNA double heUx illustrates the contribution of multiple forces to the structure of biomolecules. While each individual DNA strand is held together by covalent bonds, the two strands of the helix are held together exclusively by noncovalent interactions. These noncovalent interactions include hydrogen bonds between nucleotide bases (Watson-Crick base pairing) and van der Waals interactions between the stacked purine and pyrimidine bases. The hehx presents the charged phosphate groups and polar ribose sugars of... 

Noncovalent Association of the Alkylating Agent can Direct Reaction to Selected Atoms and Selected Sequences in DNA... 

Many compounds that damage DNA via radical intermediates have been identified. Some of the agents, such as bleomycin and the enediynes, damage DNA primarily through abstraction of hydrogen atoms. ° In these cases, chemical reactions are directed to certain positions on the DNA backbone by noncovalent binding that places the reactive intermediates in close proximity to particular deoxyribose sugar residues. Similar to the reactions of HO described above, small radicals, such as... 

The nature of the target to be attacked by any drug obviously depends on the specific application. Many cytotoxic metal complexes target DNA because of its importance in replication and cell viability. Coordination compounds offer many binding modes to polynucleotides, including outer-sphere noncovalent binding, metal coordination to nucleobase and phosphate backbone... 

A different pH-triggered deshielding concept with hydrophilic polymers is based on reversing noncovalent electrostatic bonds [78, 195, 197]. For example, a pH-responsive sulfonamide/PEl system was developed for tumor-specific pDNA delivery [195]. At pH 7.4, the pH-sensitive diblock copolymer, poly(methacryloyl sulfadimethoxine) (PSD)-hZocA -PEG (PSD-b-PEG), binds to DNA/PEI polyplexes and shields against cell interaction. At pH 6.6 (such as in a hypoxic extracellular tumor environment or in endosomes), PSD-b-PEG becomes uncharged due to sulfonamide protonation and detaches from the nanoparticles, permitting PEI to interact with cells. In this fashion PSD-b-PEG is able to discern the small difference in pH between normal and tumor tissues. 

In addition to small organic molecules or metal ions, proteins may have other components tightly associated with them. Nucleoproteins, for instance, contain noncovalently bound DNA or RNA, as in some of the structural proteins of viruses. Lipoproteins contain associated lipids or fatty acids and may also carry cholesterol, as in the high-density and low-density lipoproteins in serum. 

Y. Belosludtsev, B. Iverson, S. Lemeshko, R. Eggers, R. Wiese, S. Lee, T. Powdrill, and M. Hogan, DNA microarrays based on noncovalent oligonucleotide attachment and hybridization in two dimensions. Anal. Biochem. 292, 250—256 (2001). 

An alternative efficient approach to disperse CNTs relies on the use of synthetic peptides. Peptides were designed to coat and solubilise the CNTs by exploiting a noncovalent interaction between the hydrophobic face of amphiphilic helical peptides and the graphitic surface of CNTs (Dieckmann et al., 2003 Zoibas et al., 2004 Dalton et al., 2004 Arnold et al., 2005). Peptides showed also selective affinity for CNTs and therefore may provide them with specifically labelled chemical handles (Wang et al., 2003). Other biomolecules, such as Gum Arabic (GA) (Bandyopadhyaya et al., 2002), salmon sperm DNA, chondroitin sulphate sodium salt and chitosan (Zhang et al., 2004 Moulton et al., 2005), were selected as surfactants to disperse CNTs (Scheme 2.1). 

Liu Y, Wu DC, Zhang WD, Jiang X, He CB, Chung TS, Goh SH, Leong KW (2005) Polyethylenimine-grafted multiwalled carbon nanotubes for secure noncovalent immobilization and efficient delivery of DNA. Angew. Chem. Int. Ed. 44 4782 4785. 

The alternative noncovalent functionalization does not rely on chemical bonds but on weaker Coulomb, van der Waals or n-n interactions to connect CNTs to surface-active molecules such as surfactants, aromatics, biomolecules (e.g. DNA), polyelectrolytes and polymers. In most cases, this approach is used to improve the dispersion properties of CNTs [116], for example via charge repulsion between micelles of sodium dodecylsulfate [65] adsorbed on the CNT surface or a large solvation shell formed by neutral molecule (e.g. polyvinylpyrrolidone) [117] around the CNTs. 

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