In this method, A and B are two proteins whose interaction is to be studied. Two-step site-specific cell surface protein labeling protocol. A lipoic acid ligase polypeptide as described herein is fused to protein A, and an acceptor polypeptide e. Hydrazine hydrate mg, 8. For imaging, HEK cells were plated as a monolayer on glass coverslips, while A cells were plated directly onto well plates. June 24, Presented by:

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The reaction proceeded for 12 hours at ambient temperature. In some embodiments, when R 1 is C 5 alkyl, R does not comprise a diaziridine.

Cells were then washed three times with DPBS with 0. Ligated alkynes are then derivatized with a picolyl azide-probe conjugate via chelation-assisted CuAAC. The goal was to extend and optimize this concept for aqueous CuAAC reactions, under conditions relevant for biomolecular labeling.

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We started with a preliminary screen of nineteen W37 point mutants and fourteen E20 point mutants, against four probe structures. SlideBook was used to calculate bostiv mean intensities in both channels. To measure noise, 10 cells with no obvious surface fluorescence by eye at the sec.

The flask was wrapped in foil and the reaction was stirred for 18 h at room temperature. Upon reaction between the functional group handle in the first protein conjugate and the functional group in the compound, the detectable label is linked to the protein of interest. Most of this nonspecific signal can be washed away after cells are fixed, suggesting that it arises from non-specific binding to cellular structures.


The present disclosure also embraces so-called expression kits, which allow the artisan to prepare a desired expression vector or vectors. Other homologs of E. Azides and aryl phosphines generally have no cellular counterparts. Such labels would be particularly useful for X-ray crystallographic study of the target protein. As a result, the reaction is quite specific. Lipoic acid ligase is an enzyme that catalyzes the ATP-dependent ligation of the small molecule lipoic acid to a specific lysine sidechain within one of three natural acceptor proteins E2p, E2o, and H-protein.

US20150125904A1 – Probe incorporation mediated by enzymes – Google Patents

In some embodiments, the labeled compound used in the second step contains a phosphine group and a lipoic acid analog e. A negative control with EU omitted is shown third column. The identity of the LAP-azide 9 product peak was confirmed by mass spectrometry. Consequently, lipoic acid conjugation to an acceptor peptide would be lower in the presence of a lipoic acid analog. Alternatively, fluorogenic cyclooctynes Jewett, et al.

Both Tz1 and Tz2 were conjugated to fluorescein. The flask was wrapped in foil and the reaction was allowed to stir for 22 h at room temperature. In the second step, the first protein conjugate is in contact with a compound comprising a functional group that is reactive to the functional group handle in the first protein conjugate and a detectable directly detectable or indirectly detectable label.


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Neuron j2b was performed at 5 days in vitro, using Lipofectamineusing half the amount of the manufacturer’s recommended reagent quantity. Coumarin fluorescence was visualized on an Alpha Innotech Chemilmager instrument. The natural reaction of LplA has now been redirected such that unnatural structures, dissimilar to lipoic acid, can be ligated to either the natural protein substrates or engineered peptide substrates.

To a vostic of 5-azidomethylnicotinic acid succinimidyl ester 15 mg, 0. Guided by the LplA crystal structure, we were able to create a small and focused library of single and double LplA mutants to screen for the desired PB ligation activity.

In some embodiments, only conservative mutations are introduced into positions corresponding to these 36 residues within the tolerable range.

Cells were imaged live. For the red trace, the reaction was performed for 30 min with 1 mM ATP. See Jewett et al. For instance, X-rhodamine is a bright and photostable fluorophore commonly used for speckle imaging of actin Lim, et al.