Intercalation proton

Table III provides an overview of alkaloids that interfere with DNA, RNA, and associated proteins. Alkaloids with a planar and polycyclic structure are good candidates for DNA intercalation. Protonable ring nitrogens can stabilize the alkaloid-DNA complex by binding to the negatively charged DNA surface (19,20). Such properties are abundant in isoquinoline, quinoline, and indole alkaloids that are synthesized from the aromatic amino acids phenylalanine, tyrosine, and tryptophan (11,12,16).

This approach finds experimental support in FTIR measurements of the oxidation of PANI in organic solvents which indicate an anion intercalation mechanism for the second oxidation step. However, the IR findings may also be interpreted as support for the formation of a protonated imine structure... 

Bronsted acidity is the principal source of activity with the relative concentration of protonated and non-protonated reactants being dependent upon the nature of the exchangeable cation. Using FeCls - graphite intercalates - formed using a photochemical procedure and subsequently reduced using K/naphthalide - an efficient catalyst for the production of acetylene from syngas has been produced. 

This i>aper describes two broad types of intercalation conpomds which are based on graphite on the one hand and sheet aluminosilicate (clay) hosts on the other. Taken together these provide a rich veiriety of examples of heterogeneously catalysed reactions. Appropriately cation exchanged clays, for example, act as efficient catalysts for a number of commercially important proton catalysed reactions (10-13) (see Table I). Graphite intercalates, whilst also capable of... 

Thin self-supporting clay films (appropriate for IR measurement) readily take up organic amines such as cyclohexylamine with displacement of the major fraction of the intercalated water. For the Ua -exchanged sample the majority of the amine is present in the unprotonated form - there being insufficient Bronsted acidity generated by the interlayer cation. When Al + is the exchangeable cation, however, a major fraction of the intercalated amine becomes protonated (see Figure 2). 

For R = benzylamine (B) and R — cyclohexylamine (C) the amounts of BB and CC and of the BC cross product formed as the relative concentration of the reactants varies is shown in Figure 3. Clearly whilst for an approximately 50 50 reactant mixture the amount of CC formed has dropped to practically zero that of the cross product (BC) is still hi. The interpretation suggests that the less baisic atmine is more readily intercalated auid essentially remains urprotonated whilst the more basic amine, althou present in much smaller concentration, removes nearly all of the available protons. Hence the major reaction is between protonated B and non-protonated C, yielding BC (23,23). 

Detailed studies have been performed on pseudocapacitors with layers of hydrated ruthenium oxide, RuOj- HjO. Protons relatively readily undergo intercalation and deintercalation in this material ... 

Protons are not the sole species that can be incorporated into the lattices of different host materials. At the beginning of the 1960s, Boris N. Kabanov showed that during cathodic polarization of different metals in alkaline solutions, intercalation of atoms of the corresponding alkali metal is possible. As a result of such an electrochemical intercalation, either homogeneous alloys are formed (solid solutions) or heterogeneous polyphase systems, or even intermetallic compounds, are formed. 

Earlier studies using thermal denaturation analysis and spectrophotomet-ric titration with TxA T and CxC-C" containing DNA triplexes showed that coralyne binds strongly to these triplexes by intercalation and does not exhibit a significant sequence-selectivity [222]. In a later study by Morau Allen et al. [217], employing DNase footprinting, thermal denaturation analysis, UV-visible spectrophotometric titrations, circular dichroism and NMR spectroscopy, showed that coralyne is fully intercalated into TxA T triplex DNA whereas in C GxC triplex, it is partially intercalated due to electrostatic repulsion between the cationic alkaloid and the protonated cytosine [217]. Kepler et al. [223] demonstrated that coralyne intercalated to parallel triplex DNA but did not intercalate to antiparallel triplex DNA. Recently Hud and coworkers [219,224] demonstrated that duplex poly(dA) poly(dT) is trans-... 

Graphite nitrate stabilization co-intercalation exfoliation proton... 

On modifying graphite nitrate, as follows from the material balance of the reaction, a major part of nitric acid is replaced by the organic intercalant. The latter, if it is protonated by the rest of nitric acid in the interlayer space, is capable of the strong hydrogen bonding with two... 

The following theoretical and experimental data is presented to support the idea for activation of the BPDEs in an acid catalyzed Sjj2 reaction for trans addition (90) with some contribution to car-bonium ion formation in an Sjjl reaction for both trans and cis addition. The non-covalently bound BPDE adducts to DNA formed initially are intercalation complexes (H6,51-55) Meehan et al. (U6) and Geacintov et al. (5 0 reported that the BPDE intercalates into DNA on a millisecond time scale while the BPDE alkylates DNA on a time scale of minutes. Because the electrostatic potential is most negative in the grooves, positive ions are attracted to these regions (93,9, 95) Consequently, protonation of the BPDE l(+) to form the... 

The exceptional reactivity of DNA for protonated N-hydroxy arylamines can be rationalized by at least two mechanisms. First, intercalation of the electrophilic intermediate between DNA bases could sterically assist in desolvation and in directing the electrophilic center of the carcinogen over the nucleophilic region of the DNA base. This seems unlikely, however, as pretreatment of DNA with cis-Pt, which decreased the DNA contour length by 50%, failed to reduce the reactivity of N-hydroxy-1-naphthylamine for the DNA (137). A second possibility involves an electrostatic attraction between the electrophile and the phosphate backbone of the DNA (77). This seems more probable since eithe j +high ionic strength or stoichiometric (to DNA-P) amounts of Mg strongly inhibit DNA adduct formation (77,137). In addition, evidence has been presented that N-hydroxy arylamine-DNA/RNA phosphotriesters may be formed which induce strand breaks (137,138) and could serve as a catalyst for desolvation and subsequent adduct formation. 

The coordination chemistry of the trichalcogenophosphonates is very undeveloped when compared to the analogous metal organophosphonates (RP032), which have been extensively studied owing to their potential and practical applications as ion exchangers, sorbents, sensors, proton conductors, nonlinear optical materials, photochemically active materials, catalysts and hosts for the intercalation of a broad spectrum of guests.145... 

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