Photoreactive Crosslinker Chemistry

Crosslinking is the process of chemically joining two or more molecules by a covalent bond. Crosslinking reagents contain reactive ends to specific functional groups (primary amines, sulfhydryls, etc.) on proteins or other molecules.
The availability of several chemical groups in proteins and peptides make them targets for conjugation and for studyusing crosslinking methods. Crosslinkers also are commonly used to modify nucleic acids, drugs and solid surfaces.

Photoreactive Crosslinker Chemistry
用于标记和交联蛋白质和生物分子的试剂中可光活化的反应性化学基团包括芳基叠氮化物（苯基叠氮化物）和重氮基。本文介绍了这类试剂的反应化学和生物学研究应用。
Photo-activatable reactive chemical groups in reagents for labeling and crosslinking proteins and biomolecules include aryl azides (phenyl azides) and diazirines. This article describes the reaction chemistries and biology research applications of this class of reagents.

光反应性交联剂反应性基团
光活化（或光化学）交联反应需要光能来引发。光反应性基团是化学惰性的化合物，当暴露于紫外线或可见光时会发生反应。实际上，用于交联应用的试剂中使用的所有光反应性基团品种都需要暴露于紫外光（UV光）中以进行分子活化。下图提供了可光活化交联剂和UV交联应用中使用的仪器类型的示例。

Photoreactive crosslinker reactive groups
Photo-activatable (or photo-chemical) crosslinking reactions require energy from light to initiate. Photoreactive groups are chemically inert compounds that become reactive when exposed to ultraviolet or visible light. Practically all varieties of photoreactive groups used in reagents for crosslinking applications require exposure to ultraviolet light (UV light) for molecular activation. The following image provides an example of the type of instrument used with photoactivatable crosslinkers and UV-crosslinking applications.

代表紫外线灯。luyor-3410 高强度紫外线灯是紧凑的紫外灯，特别是用于与可光活化交联剂和UV交联方法中使用的365nm的拨号可选择波长的设置。
Representative ultraviolet lamp. LUYOR-3410 UV Lamps are compact,  ultraviolet lamps with 365 nm dial-selectable wavelength settings especially for use with photoactivatable crosslinkers and UV-crosslinking methods.

对于与生物样品和实验进行交联和标记应用，光化学反应基团比严格的热化学试剂具有某些优势。最重要的是，它们使在实验的早期步骤中添加试剂成为可能，然后在随后的某个步骤中引发交联（通过暴露于紫外线），从而与目标特定生物学条件相协调。另外，这些基团中的许多基团将与它们在激活后的短时间内遇到的蛋白质中几个常见功能基团中的任何一个缀合。此功能使它们在捕获蛋白质相互作用中特别有用（请参见下面的讨论）。已掺入用于生物共轭技术的交联和标记化合物的光反应性基团包括芳基叠氮化物，叠氮基甲基香豆素，二苯甲酮，蒽醌，某些重氮化合物，重氮基和补骨脂素衍生物。这些蛋白质生物学研究中最有用的是芳基叠氮化物和重氮。

蛋白质交联中使用的选定的光反应性化学基团。传统上，最广泛使用的是芳基叠氮化物（也称为苯基叠氮化物，前两行）。补骨脂素（右下图）几乎只与RNA或DNA反应，用于标记核酸或交联并研究蛋白质与核酸的相互作用。Diazirines（左下）是一类新的化合物，在蛋白质研究中越来越流行和实用。花键代表标记试剂或具有反应性基团的交联剂的一端。
Photochemical reactive groups have certain advantages over strictly thermochemical reagents for crosslinking and labeling applications with biological samples and experiments. Most importantly, they make it possible to add reagents at an early step in an experiment and then to initiate crosslinking (by exposure to UV light) at some later step that coordinates with the particular biological condition of interest. Additionally, many of these groups will conjugate to any one of several common functional groups in proteins that they encounter during the brief time when they are activated. This feature makes them particularly useful in capturing protein interactions (see discussion below).

Photoreactive groups that have been incorporated into crosslinking and labeling compound for use in bioconjugate techniques include aryl azides, azido-methyl-coumarins, benzophenones, anthraquinones, certain diazo compounds, diazirines, and psoralen derivatives. The most useful of these for protein biology research are aryl azides and diazirines.

Photocleavable Linker (PC Linker) often used in the design of multi-functional single-stranded nucleotide conjugates for the selection of novel DNA or RNA-based catalysts in vitro. Photocleavable PC linker modified oligonucleotide are demonstrated in Bruker Daltonik's genoSNIP, a MALDI-TOF MS based assay system for SNP detection.

 Photocleavable  PC linker contained a non-nucleosidic group that can be used to link two nucleotide sequences through a short, UV photo-cleavable C3 spacer arm. Upon irradiation by UV light, photo-cleavage released oligonucleotide contain a 5-phosphorylated group with greater hybridization affinity for a complementary DNA strand than PC spacer.

 Photocleavable PC linker can be incorporate at any position within an oligonucleotide. Contact Bio-Synthesis for service details.

Cleavage Protocol

 Cleavage occurs by irradiation with near-UV light (300-350 nm, complete cleavage occurs within 5 minutes. Try using a Black Ray LUYOR-3410 UV lamp  at a distance of 15 cm (emission peak 365 nm, 300 nm cut-off, 1.1 mW intensity at~31 cm).