Activity-Based Probes Linked with Laser-Cleavable Mass Tags for Signal Amplification in Imaging Mass Spectrometry: Analysis of Serine Hydrolase Enzymes in Mammalian Tissue

Department of Biochemistry, Vanderbilt University, Nashville, Tennessee, United States.
Analytical Chemistry (Impact Factor: 5.64). 03/2012; 84(8):3689-95. DOI: 10.1021/ac300203v
Source: PubMed


A novel functional imaging mass spectrometry technology is described that utilizes activity-based probes for imaging enzyme active sites in tissue sections. We demonstrate this technology using an activity-based probe (fluorophosphate) that is specific for serine hydrolases. A dendrimer containing multiple mass tags that is attached to the activity-based probe is used to analyze the binding sites of the probe through release and measurement of the mass tags on laser irradiation. A generation 8 poly(amido amine) dendrimer with 1024 amino groups was labeled with an azide group, and then, more than 900 mass tags were attached in order to achieve signal amplification of nearly 3 orders of magnitude. The experimental protocol first involves binding of the activity-based probe containing an alkyne group to serine hydrolases in the tissue section followed by attachment of the dendrimer labeled with mass tags to the bound probe by Click chemistry. On irradiation of the labeled tissue by the laser beam in a raster pattern, the mass tags are liberated and recorded by the mass analyzer; consequently, the ion image of the mass tag reveals the distribution of serine hydrolases in the tissue. This process was shown using rat brain and mouse embryo sections. Targeted imaging has the advantage of providing high spatial resolution and high sensitivity through the use of signal amplification chemistry with high target specificity through the use of an enzyme activity probe.

Download full-text


Available from: Junhai Yang
  • Source
    • "In fact, Tag-Mass can be used to track low-abundance proteins or to investigate some proteins involved in biological processes or mechanisms. Moreover, Tag-Mass technology presents the ability to perform highly multiplexed studies due to its ability to incorporate a variety of tag-like peptides or inorganic compounds (e.g., an 8 poly (amidoamine) dendrimer with 1024 amino groups (Yang et al., 2012)). Conversely, TAM- SIM multiplexing is limited to the rare monoatomic elements that are available. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Since its introduction during the last decade, MALDI mass spectrometry imaging (MSI) is now a routine technique in biology. Nevertheless, a missing link exists in MALDI MSI. Lipids, peptides/proteins, metabolites and drugs can easily be mapped using MALDI-MSI, but this technique has not yet been used to map the transcriptome, which includes microRNA, siRNA and other components. This latter field of research is now one of the major fields in clinical research and needs to be explored using MALDI-MSI. To investigate the transcriptome, a novel imaging technique has been developed called Tag-Mass imaging mass spectrometry. The aim of this review is to discuss this technique from its history to its place in the future of mass spectrometric imaging.
    Full-text · Article · Sep 2012 · Progress in Histochemistry and Cytochemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: Matrix-assisted laser desorption/ionization (MALDI) imaging mass spectrometry (IMS) is a relatively new imaging modality that allows mapping of a wide range of biomolecules within a thin tissue section. The technology uses a laser beam to directly desorb and ionize molecules from discrete locations on the tissue that are subsequently recorded in a mass spectrometer. IMS is distinguished by the capability to directly measure molecules in situ ranging from small metabolites to proteins, reporting hundreds to thousands of expression patterns from a single imaging experiment. This article reviews recent advances in IMS technology, applications, and experimental strategies that allow it to significantly aid in the discovery and understanding of molecular processes in biological and clinical samples.
    No preview · Article · Dec 2012 · Biochemistry
  • [Show abstract] [Hide abstract]
    ABSTRACT: Covalent chemical probes enable investigation of a desired fraction of the proteome. It is possible to adjust the selectivity of these probes, so they either react with a certain amino acid in all proteins, a class of proteins or only a single protein species. A combination of specific reactive groups with additional recognition elements can fine tune probes to hit the desired proteins, even in the presence of related family members. Using probes of lower or higher selectivity, screening experiments for inhibitor discovery and imaging experiments for localization studies can be performed, showing only a fraction of the power of covalent small molecule probes.
    No preview · Article · Dec 2012 · Current opinion in chemical biology
Show more