Photoisomerizable monolayer

I. Willner, R. Blonder, and A. Dagan, Application of photoisomerizable antigenic monolayer electrodes as reversible amperometric immunosensors. J. Am. Chem. Soc. 116, 9365-9366 (1994). 

I. Willner and B. Willner, Electronic transduction of photostimulated binding interactions at photoisomerizable monolayer electrodes novel approaches for optobioelectronic systems and reversible immunosensor devices. Biotechnol. Prog. 15, 991-1002 (1999). 

An interesting example of a system whose components become mechanically bound upon surface immobilization is rotaxane trans-21 (Fig. 13.24), consisting of a ferrocene-functionalized /3-cyclodextrin (fi-CD) macrocycle threaded on a molecule containing a photoisomerizable azobenzene unity and a long alkyl chain.33 A monolayer of trans-21 was self-assembled on a gold electrode. Therefore, the ring... 

Monolayers representing two-dimensional arrays of membrane-mimetic assemblies, consisting of azobenzene (poly-L-lysine) with 43 % loading of the photoisomerizable units, were prepared.1441 The compressed trans-azobenzene polymer mono-layer exhibited a surface pressure of 7 mN m 1, whereas photoisomerization of the monolayer to the cis-azobenzene state by UV light decreased the surface pressure to... 

Scheme 8 Assembly of a photoisomerizable glucose oxidase monolayer electrode and the reversible photoswitchable activa-tion/deactivation of the bioelectrocatalytic functions of the enzyme electrode.

Fig. 10 Photoswitchable bioelectrocatalyzed oxidation of glucose (5 x 1(T2 M) by a photoisomerizable FAD-reconstituted GOx assembled as a monolayer on an Au electrode and using ferrocenecarboxylic acid (23)...

A further approach to controlling electrical communication between redox proteins and their electrode support through a photo-command interface includes photo stimulated electrostatic control over the electrical contact between the redox enzyme and the electrode in the presence of a diffusional electron mediator (Scheme 12).[58] A mixed monolayer, consisting of the photoisomerizable thiolated nitrospiropyran units 30 and the semi-synthetic FAD cofactor 25, was assembled on an Au electrode. Apo-glucose oxidase was reconstituted onto the surface FAD sites to yield an aligned enzyme-layered electrode. The surface-reconstituted enzyme (2 x 10-12 mole cm-2) by itself lacked electrical communication with the electrode. In the presence of the positively charged, protonated diffusional electron mediator l-[l-(dimethylamino)ethyl]ferrocene 29, however, the bioelectrocatalytic functions of the enzyme-layered electrode could be activated and controlled by the photoisomerizable component co-immobilized in the monolayer assembly (Figure 12). In the... 

Scheme 15 Preparation of a photoisomerizable dinitrospiro-pyran monolayer on a transducer and the reversible sensing of anti-DNP-Ab.

Scheme 18 Photochemical patterning of a photoisomerizable dinitrospiropyran monolayer associated with a glass support with agarose beads functionalized with DNP-Ab.

Figure 12.3 Coupling of photoinduced electrical interaction of cytochrome c (cyt c) with the photoisomerizable monolayer modified Au electrode to the biocatalyzed reduction of 02 by cytochrome oxidase (COX) [33]...

Figure 12.4 Photoinduced bioelectrocatalyzed oxidation of glucose to gluconic acid by glucose oxidase (COD) reconstituted with a nitrospiropyran-modified FAD cofactor (Sp-FAD) assembled as a monolayer on the Au electrode. Fhe Sp-FAD reveals reversible photoisomeriz-able properties yielding nitromerocyanine-FAD isomer (MRH+-FAD) [34]...

In the example shown in Fig. 4.39, a photoisomerizable command mono-layer was immobilized on a sohd surface and hquid crystalline layers were then deposited on the monolayer. Photoisomerization of the command monolayer can then change the orientation of the thick hquid crystalhne layer. Molecular... 

In addition to crown-ethers, calix[4]resorcinarenes 19 have also been used as head groups to obtain azobenzene amphipbiles with sufficient photo-isomerization in LBK films. For this purpose, azobenzene moieties have been tethered to the lower rim of the crown conformer of the calixarene. O-octacarboxymethoxylated calix[4]resorcinarenes 19 (X = CH2-COOH) display efficient trans to cis photoisomerizability in densely packed mono-layers on a water surface, in LBK films, and in surface-adsorbed monolayers, whereas the noncarboxymetylated 19 (X = H) derivative gives films that are too densely packed. However, the aggregation is already suppressed efficiently compared to the azobenzene derivative without calixaren. ... 

Fujimaki, M., Matsuzawa, Y., Flayashi, Y., and Ichimura, K. Monolayers of Calixl4 resor-cinarenes with Azobenzene Residues Exhibiting Efficient Photoisomerizability. Chem. Lett., 165 99S). 

FIG. 7.7 (A) Schematic representation of a photoisomerizable azobenzene-TCNQ Langmuir-Blodgett monolayer. (B) Changes in (a) absorbance at 356 nm, and (b) conductivity of the monolayer upon photoisomerization. 

---