Nucleic diameter

The neutral hydrophilic surface and the wide range of pore diameters available for SynChropak GPC allow many compounds from small peptides to nucleic acids and other polymers to be analyzed. Table 10.2 lists the approximate exclusion limits for both linear and globular solutes. Although this information... 

A wide variety of bases, nucleosides and nucleotides have been separated using porous layer bead ion exchangers. A representative chromatogram of the separation of ribonucleoside mono-phosphoric acids from the work of Smukler ( ) is shown in Figure 4. Recently, ion exchangers chemically bonded to small particle diameter (> 10 ym) silica have been successfully applied to the separation of nucleic acid constitutents (37). The rapid separations using such supports undoubtedly mean that they will find increasing use in the future. 

Nucleic acids, DNA and RNA, are attractive biopolymers that can be used for biomedical applications [175,176], nanostructure fabrication [177,178], computing [179,180], and materials for electron-conduction [181,182]. Immobilization of DNA and RNA in well-defined nanostructures would be one of the most unique subjects in current nanotechnology. Unfortunately, a silica surface cannot usually adsorb duplex DNA in aqueous solution due to the electrostatic repulsion between the silica surface and polyanionic DNA. However, Fujiwara et al. recently found that duplex DNA in protonated phosphoric acid form can adsorb on mesoporous silicates, even in low-salt aqueous solution [183]. The DNA adsorption behavior depended much on the pore size of the mesoporous silica. Plausible models of DNA accommodation in mesopore silica channels are depicted in Figure 4.20. Inclusion of duplex DNA in mesoporous silicates with larger pores, around 3.8 nm diameter, would be accompanied by the formation of four water monolayers on the silica surface of the mesoporous inner channel (Figure 4.20A), where sufficient quantities of Si—OH groups remained after solvent extraction of the template (not by calcination). 

Both approaches are simple and allow efficient encapsulation of nucleic acid-based molecules such as oligonucleotides (9,10) and pDNA (8,10,12) in liposomes that are small in size (about lOOnm diameter) and stable in circulation, protecting the cargo from degradation. In the sections to follow, we will provide a brief overview of these methods. 

The weakly immunogenic protamine sulfate USP (1) condenses DNA to form a toroid structure of super-coiled DNA about 50 nm in diameter (2). The DNA in this form or in the preformed LPDI complex cannot be displaced from the protamine by polycations such as spermidine and histones or by other nucleic acids like genomic DNA (2). DNA in this toroid structure is transcriptionally inactive and this conformation allows for protection of DNA from enzymatic degradation by nucleases and other environmental assaults such as mechanical stress (1,2). After the liposome surrounds the toroid, the resulting homogenous LPDI nanoparticles are slightly less than... 

Rybenkov, V.V., Vologodskii, A.V., and Cozzarelli, N.R. (1997) The effect of ionic conditions on DNA helical repeat, effective diameter and free energy of supercoiling. Nucleic Acids Res. 25, 1412-1418. 

Polymeric stationary phases have many advantages when polymerized in capillaries (diameter < 0.5 mm) as rods in the presence of porogens to yield channels for mobile phase transport. They are frequently used in the analysis of peptides, proteins, and nucleic acids when directly coupled to electro spray mass spectrometry. 

Amino Acids, Peptides, Proteins, Enzymes, and Nucleic Acids helix about 20 A in diameter. The arrangement is shown schematically in 12 ... 

The parameters of the double helix that is formed by DNA include a diameter of 20 A, a rise per nucleic acid residue of 3.4 A with ten residues per complete turn. The two chains that make up the molecule are antiparallel the chains grow by adding repeat units to the 3 group on ribose or the 5 group on ribose and therefore one chain is joined 3 to 5 by phos-phodiester bonds and in the other chain the riboses are joined by 5 to 3. The two polynucleotides are twisted around each other in such a way as to... 

A process was developed in Germany using the enzyme immobilized on 350 A pore diameter Eupergit C for production of 5 -ribonucleo-tides from crude nucleic acid mixtures containing both RNA and DNA (42). Apparently the larger DNA is excluded from the pore volume while the smaller RNA has access to the enzyme, thus eliminating the requirement for a difficult separation of RNA from DNA. Using a substrate stream of crude nucleic acid adjusted to 0.1 mM ZnSO at pH 5.0 and 60°C, a 10-inch x 25-inch fixed-bed bioreactor produced 10... 

In another study, 5 -amino-C6 modified nucleic acid was immobilized onto cyanogen bromide activated Sepharose beads (Fig. 4B) [15]. The 100 pm-diameter beads were then subsequently transferred at the PDMS/air interface (Fig. 3D). 

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