Photocleavable Groups

On many occasions, and this is certainly correct for 2-nitrobenzyl derivatives, photocleavable groups can be eliminated under mild conditions (aqueous media, neutral pH, and low temperature). Frequently, at a sufficiently long wavelength, only the bond designated for cleavage is affected by irradiation, so that, whenever the irradiation itself and the photoproducts formed are not harmful to the biological system (such as cells,... 

Avidin technology can also be applied to the isolation of proteins and other materials from cells. Because the irreversibility of the binding of biotin may be a problem, photocleavable biotin derivatives have been developed. In the following structure, the biotin derivative has been joined to a protein (as in the first equation in this box) and is ready for separation, perhaps on a column containing immobilized avidin or streptavidin. After separation the biotin together with the linker and photocleavable group are cut off by a short irradiation with ultra-... 

Physiological conditions the photocleavable group can be eliminated under mild conditions (aqueous medium, neutral pH and low temperatures). 

Several applications of nitrobenzenyl derivatives have recently been reported. Figure 4.20 presents a photodegradable dendron with a hydrophilic and a lipophilic unit connected by the photocleavable group. ° Micelles of this dendron have been used for encapsulating and light-mediated delivering of Nile red. 

The previously described N3-modified thymidine (35) has been used for photochemical control for the regulation of NFkB driven transcription of alkaline phosphatase.A related N3-photocleavable group attached to a C5-modified fluorescent nucleotide was used to image cell hybridisation... 

Fernandes MJG, Gonfalves MST, Costa SPG (2008) Comparative study of polyaromatic and polyheteroaromatic fluorescent photocleavable protecting groups. Tetrahedron 64 ... 

Example 28 a caged compound includes a photocleavable-protecting group that masks an essential functionality upon removal by photolysis [58]. Imperiali and associates have developed an interassembly approach for the synthesis of peptides containing l-(2-nitrophenyl)ethyl-caged phos-phamino acids [59]. The peptides described in that paper are based on phosphorylation sites of kinases involved in cell movements. 

The 9-phenylthioxanthyl (S-pixyl) group is a photocleavable 5 -OH protecting group for deoxyribonucleosides <99TL7911>. 

The development of light-sensitive protective groups began in the early 1960s [129-131] and led to the identification of several functionalities that could be selectively cleaved under UV irradiation (for a review, see [132]). Some of these protective groups, such as 2-nitrobenzyl esters, carbonates, or carbamates [131,133-135], benzoin [136-139], and other phenacyl esters [140] were also found to be useful as photocleavable linkers. 

The virtual wall created can also be employed to carry out gas-liquid reactions. For instance, acetic acid vapor was allowed to react with a pH indicator solution at the virtual wall, allowing kinetic studies to be carried out (see Figure 3.21) [433], Moreover, using photocleavable SAM (with the 2-nitrobenzyl photosensitive group), the SAM can be patterned through a UV photomask, giving rise to complex flow patterns [433,434],... 

Figure 18 UV photopatterning method. The molecular structure of a photocleavable SAM formed on glass surfaces. UV irradiation through masks placed on top of SAM-modified microchannels leads to the production of hydrophilic carboxylate groups in the irradiated regions (Zhao et al, 2001).

Misetic, A. and Boyd, M.K. (1998) The pixyl (Px) group a novel photocleavable protecting group for primary alcohols. Tetrahedron Letters, 39, 1653-1656. 

Coleman, M.P. and Boyd, M.K. (2002) S-Pixyl analogues as photocleavable protecting groups for nucleosides. Journal of Organic Chemistry, 67, 7641-7648. 

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