Biomolecules, intercalation

The biochemical activity and accessibility of biomolecule-intercalated AMP clays to small molecules was retained in the hybrid nanocomposites. For example, the absorption spectrum of the intercalated Mb-AMP nanocomposite showed a characteristic soret band at 408 nm associated with the intact prosthetic heme group of the oxidised protein (Fe(III), met-myoglobin) (Figure 8.9). Treatment of Mb with sodium dithionite solution resulted in a red shift of the soret band from 408 to 427 nm, consistent with the formation of intercalated deoxy-Mb. Reversible binding of CO under argon to the deoxy-Mb-AMP lamellar nanocomposite was demonstrated by a shift in the soret band from 427 to 422 nm. Subsequent dissociation of CO from the heme centre due to competitive 02 binding shifted the soret band to 416nm on formation of intercalated oxy-Mb. 

Intercalation of Biomolecules within Organically Modified Magnesium Phyllosilicates... 

Fig. 8.8 CD spectra of native or intercalated biomolecules in solution or within re-assembled AMP, respectively. (A) Native myoglobin and myoglobin-AMP, (B) native glucose oxidase and glucose oxidase-AMP.

Fig. 8.9 UV—Vis spectra of intercalated biomolecules assembled AMP. Soret band absorptions for (A) oxidized myoglobin (met-Mb) and after dithionite reduction (deoxy-Mb), and (B) after CO (CO-Mb) and 02 bindingto intercalated deoxy-Mb.

Nanohybrids can be prepared in the form of intercalated layered nanocomposites produced by co-assembly of guest biomolecules in the presence of exfoliated organoclay sheets (Section 8.4), or by wrapping single biomolecules in ultrathin layers of condensed organoclay oligomers (Section 8.5). Such approaches should provide new general routes towards the development of functional biomaterials with numerous applications. 

A colloidal suspension of conductive vanadium pentoxide [130] can be used to perform intercalation, adsorption or encapsulation of electroactive molecules or biomolecules for electrodes or biosensor realization [131]. Encapsulation of glucose oxidase in nanocomposite films made with polyvinyl alcohol and V205 sol-gel matrix or in ferrocene intercalated V2Os sol-gel [132] were envisaged to prepare glucose biosensors. 

Fullerene showed antibacterial activity, which can be attributed to different interactions of C60 with biomolecules (Da Ros et al., 1996). In fact, there is a possibility to induce cell membrane disruption. The fullerene sphere seems not really adaptable to planar cellular surface, but for sure the hydrophobic surface can easily interact with membrane lipids and intercalate into them. However, it has been demonstrated that fullerene derivatives can inhibit bacterial growth by unpairing the respiratory chain. There is, first, a decrease of oxygen uptake at low fullerene derivative concentration, and then an increase of oxygen uptake, which is followed by an enhancement of hydrogen peroxide production. The higher concentration of C60 seems to produce an electron leak from the bacterial respiratory chain (Mashino et al., 2003). 

Choy et al. have also intercalated biological macromolecules such as DNA, ATP and nucleosides into Mg/Al-NOs LDHs [189,190,194,195], where the host lattice may protect relatively delicate biomolecules from degradation and also aid their transport to specific targets within the body, and hence the intercalation reactions lead to the formation of novel bioinorganic nanohybrids with potential practical significance, such as new DNA reservoirs or carriers for the delivery of genetic material to cells [189]. 

Examples of biochemical processes successfully studied by spectroscopic monitoring and multivariate resolution techniques include protonation and complexation of nucleic acids and other events linked to these biomolecules, such as drug intercalation processes and salt, solvent, or temperature-induced conformational transitions [90-97], In general, any change (thermodynamic or structural) that these biomolecules undergo is manifested through a distinct variation in an instrumental signal (usually spectroscopic) and can be potentially analyzed by multivariate resolution techniques. 

For example, the relative inerease in the viscosity of a DNA solution with K4 (cdna = 5 x 10 mol r ) reaehed 5.7% at the dye/DNA concentration ratio of 0.5 (an increase in the viscosity was also observed for other meso-substituted thiaearboeyanines). The increase in the DNA solution viseosity is explained in this ease by the faet that some unwinding of coils of the DNA double helix oeeurs upon dye intercalation, which leads to elongation of the biomolecule [12]. The possibility of formation of interealation eomplexes K4-DNA were also made by Biver et al. [13]. 

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