Activity-based probes reactive groups

Activity-based protein profiling (ABPP) is a chemical proteomic strategy in which active-site-directed covalent probes are used to profile the functional states of enzymes in complex proteomes. Activity-based probes (ABPs) can distinguish active enzymes from their inactive zymogens or inhibitor-bound forms. They contain a reactive group intended to modify enzyme active sites covalently and a reporter group (typically rhodamine or biotin) that assists in detection and identification of protein targets. 

In their most basic form, activity-based probes consist of three distinct functional elements (Figure 2.1) a reactive group for covalent attachment to the enzyme, a linker region that can modulate reactivity and specificity of the reactive group, and a tag for identification and purification of modified... 

Figure 21 Haloacetamide-derived probes as potent tools for the labeling of arginine deaminase PAD4. The probe design is based on arginine as a natural substrate that is converted into a F/CI reactive group. Active site labeling occurs via a nucleophilic substitution of the halogene by the catalytically active cysteine of PAD4.

An activity-based chemical probe consists of at least two general elements (a) a reactive group (RG) that binds and covalently modifies the active sites... 

Figure 16.9 Structures of chemical components of activity/affinity probes The activity/affinity-based probe consists of reactive group and tag connected by a linker (L indicates the points of connection to the linker). Specific examples of each of the chemical components are shown. Two types of tags are commonly employed. The affinity tag for isolation/purification and the flnorescent or radiolabel tags for identification. Taken from Jeffery and Bogyo (2003)...

Finally, another group of derivatives are the aldehyde-/ketone-reactive probes. This group is based on the activation of a sulfonyl hydrazine group of carbon number 5. They are based on Lissamine and Texas Red structures and used to label aldehyde-/ketone-containing molecules (with sugars). The most common aldehyde-/ ketone-reactive probes are Lissamine rhodamine B hydrazine and Texas Red hydrazine. 

The development of fluorescent probes for detection of reactive oxygen species (ROS) has become an active research field. Probe 30 is a BODIPY-based probe bearing the reaction site of o-phenylenediamine toward NO. It shows fluorescence at 500 nm with low quantum yield due to the PET mechanism. The conversion of o-phenylenediamine into a benzotriazole group upon reaction with NO elicits a remarkable fluorescence enhancement (Scheme 7.26). 

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