Azobenzene photoregulation

In addition to proteins and polypeptides, nucleic acids such as DNA and RNA are other important biological macromolecules with optical activity. They form right-handed double and triple stranded helices, and the control of their formation and dissociation, which is closely related to the regulation of the gene expression, by external stimuli is currently one of the most important and attractive topics. Asanuma and Komiyama et al. prepared photoresponsive DNA bearing an azobenzene moiety in the side chain of a residue and successfully photoregulated the formation and dissociation of the DNA duplex and triplex [53-57]. 

An azobenzene-modified oligonucleotide 5 -AAAXAAAA-3 [15, X is the residue having an azobenzene moiety in the side chain (Fig. 4A)] was prepared and further separated into two diastereomers (15a and 15b) based on the chirality of the stereogenic carbon atom of 15 by re versed-phase HPLC [53]. The melting temperature (Tm) of the duplex of each diastereomer of 15 with its complementary oligonucleotide counterpart (5 -TTTTTTTT-3 ) was photoregulated by the trans-... 

Figure 4 Isomerization of the azobenzene moiety in the side chain of the residue upon photoirradiation of oligonucleotide 15 (A) and schematic illustration of photoregulation of the formation and dissociation of a DNA duplex (B).

K. Ichimura, Y. Hayashi, H. Akiyama, and N. Ishizuki, Photoregulation of in-plane reorientation of liquid crystals by azobenzenes laterally attached to substrate surfaces, Langmuir 9, 3298-3304 (1993). 

K. Ichimura, H. Akiyama, K. Kudo, N. Ishizuki, and S. Yamamura, Command surfaces 12. Factors affecting in-plane photoregulation of liquid crystal alignment by surface azobenzenes on a silica substrate, Liq. Cryst. 20, 423 435 (1996). 

T. Seki, M. Sakuragi, Y. Kawanishi, Y. Suzuki, T. Tamaki, R. Fukuda, and K. Ichimura, Command surface of Langmuir-Blodgett films. Photoregulation of liquid crystal alignment by molecularly tailored surface azobenzene layers, Langmuir 9, 211-218 (1993). 

H. Akiyama, K. Kudo, K. Ichimura, S. Yokoyama, M. Kakimoto, and Y. Imai, Azimuthal photoregulation of a liquid crystal with an azobenzene-modified polyimide Langmuir-Blodgett monolayer, Langmuir 11, 1033-1037 (1995). 

Photoisomerizable polymers have been well investigated and applied in various systems to allow physical properties to be reversibly controlled by irradiation.24-31 Accordingly, the encapsulation of proteins in photoisomerizable polymers could provide a general strategy for photoregulating enzymes by means of light-induced permeability of the substrate across the polymer membrane. Willner et a/.43 reported the photoregulation of the activity of a-chymotrypsin encapsulated in a photoisomerizable polymer. They chose azobenzene-, leuco-hydroxide-, and spiropyran-attached acrylamides 4-6 as photoisomerizable copo-... 

F. Ciardelli, O. Pieroni, A. Fissi, and J. L. Houben. Azobenzene-containing polypeptides Photoregulation of conformation in solution, Biopolymers 23, 1423-1437 (1984). 

Several approaches to the photoregulation of proteins have been employed, including photoisomerizable ligands and inhibitors, casting the protein inside a photoisomerizable polymer, and chemical modification of the protein itself [136], Several azobenzene protein effectors have been reported to act as photoregulators of enzymes and receptors. Photoregulation of cysteine and serine proteases was carried out using simple photoswitchable inhibitors which block the active site in their trans form only [137]. Conversely, the cis isomers of a-ketoester-based inhibitors were more potent inhibitors of a-chymotrypsin than the trans forms... 

Ferritto, M.S. and D.A. Tirrell, Photoregulation of the binding of an azobenzene-modified poly(methacrylic acid) to phosphatidylcholine bilayer membranes. Biomaterials, 1990, 11, 645-651. 

Liu N, et al. 2004. Photoregulation of mass transport through a photoresponsive azobenzene modified nanoporous membrane. Nano Lett 4(4) 551 554. 

Minoura N, et al. 2004. Preparation of azobenzene containing polymer membranes that function in photoregulated molecular recognition. Macromolecules 37(25) 9571 9576. 

Willner I, Rubin S, Zor T. 1991b. Photoregulation of alpha chymotrypsin by its immobi lization in a photochromic azobenzene copolymer. J Am Chem Soc 113(10) 4013 4014. 

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