Diazirines, photoaffinity labelling

Bergmann, K. E., Carlson, K. E., and Katzenellenbogen, J. A. (1994) Hexestrol diazirine photoaffinity labeling reagent for the estrogen receptor. Bioconjugate Chem. 5,141—150. 

Keywords Signal transduction, Photoaffinity labeling, G-Protein coupled receptors, Protein kinase, Tyrosine kinase, Aryl azide, Benzophenone, Diazirine... 

Smith and Knowles (1973) made several 3-H-3-aryldiazirines and suggested that they had several advantages as photoaffinity labeling reagents over the aryl azides and diazo compounds that were then current. These diazirines did not become popular, however, because they are inconvenient to prepare. The situation today is unchanged. 

Fig. 9 Structures of compounds used to compare the photoaffinity labeling of different photoreactive groups, (a) Photoreactive dUTP analogs 84a-d reported by Tate et al. [87]. (b) Photoreactive SAH analogs 85a,b reported by Dalhoff et al. [88]. The insert shows the transfer of the activated methyl group from SAM to nucleophilic positions (Nu) in various substrates by methyltransferases (MTase). A adenosine, (c) Photoreactive metalloprotease probes 86a,b reported by Yao et al. [65]. (d) Diazirine-containing analog of clicked compound 79-80 for labeling of y-secretase, reported by Fuwa et al. [82], (e) Photoreactive peptide vinyl sulfones 88a-c used to probe the 20S proteasome cavity, reported by Geurink et al. [89]...

The photolysis of diazo compounds and the isomeric diazirines continues to attract a great deal of interest, ranging from fundamental theoretical studies to applications such as photoaffinity labelling. 

To study the relation between structure and photoaffinity labeling of sugar-binding proteins, a number of diazirine acyclo C-nucleosides (40-42) have been synthesized using a similar sequence to that shown in Scheme 5 (93MI5). 

Derivatives of Cgo for photoaffinity labelling studies have been synthesized, including the cis and treats diazirine compounds (21a). The photochemical properties of these are currently being studied in various applications. An... 

The carbene-generating biotinylated 2-acetamido-2-deoxy-D-glucopyranosyl-amide diazirine derivative 54 and the lactoside 55 have been synthesized for photoaffinity labelling of P-(l ->4)-galactosyl transferase and GMj synthase. ... 

Diazirines are simply cyclic isomers of diazo compounds (Eq. 16.74). In fact, the two forms can sometimes be interconverted photochemically. The photochemistry of a diazirine mirrors that of the analogous diazo compound—that is, loss of N2 to produce a carbene. In some circumstances the diazirine form is more desirable, especially in photoaffinity labeling applications. 

Hatanaka, Y, Nakayama, H. Kanaoka, Y. (1996). Diazirine-based photoaffinity labeling chemical approach to biological interfaces. Reviews on Heteroatom Chemistry, 14,213-243. 

The C5 position of dU has been used to attach a variety of labels or reporter groups, in particular fluorophores ° (see section 3.5). The pyrene-modified analogue (39) has been used to detect RNA bulge conformations in the HIV-TAR RNA sequence where the fluorescence is greatly enhanced,and as a donor for the red emitter nile red (40) when the two dyes are adjacent in duplex DNA the result is white light that is emitted upon excitation of (39). A zinc-porphyrin complex has been added to C5 of dU for use in electron transfer. Norbornene has been attached via an alkyne linker for post-synthetic modification with nitrile oxides in a copper-free Click reaction, " and various dienes have been attached for Diels-Alder tagging of DNA. The photoaffinity tag (41) has been incorporated into DNA adjacent to a damaged DNA base (8-oxo-dG or thymine dimer) such that when exposed to repair systems, the repair enzyme is trapped by the diazirine for mass spectroscopic characterisation. ... 

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