cysteine

Carbocisteine (Mucodyne) is commonly used as an anti-infective nasal spray with mucolytic and expectorant effects.

Z-Nle-Lys-Arg-AMC is a fluorescent peptide substrate used specifically to monitor the activity of cathepsin B within a wide pH range.

Z-Arg-Arg-4MβNA triacetate serves as a specific substrate for cathepsin B, producing the fluorescent product 4MβNA, which has an excitation wavelength (λ ex) of 355 nm and an emission wavelength (λ em) of 430 nm [1] [2].

Bz-FVR-AMC is a fluorogenic substrate utilized for procathepsin, demonstrating a catalytic efficiency (k_cat/K_m) of 1070 mM^-1 s^-1. Notably, elevated levels of Bz-FVR-AMC can inhibit the substrate [1][2]. For storage, it is essential to protect this compound from light exposure.

Z-Gly-Pro-Arg-AMC hydrochloride is a synthetic peptide that is often used as a trypsin and histone K fluorescent substrate to measure enzyme activity, which fluoresces when the enzyme is cleaved from the peptide.

5-IAF is a fluorescein derivative of indoleacetamide, a fluorescent probe that can be used to label proteins and others containing free thiols (cysteine side chains). 5-IAF can label the catalytic (alpha) subunit of dog kidney Na,K-ATPase.

Tetramethylrhodamine-5-iodoacetamide (5-TMRIA) is a thiol-selective reactive dye used to non-specifically label proteins through cysteine residues and to covalently label DNA fragments [1].

AF 488 maleimide, a thiol-reactive dye, efficiently labels protein SH groups and facilitates the attachment of the AF 488 fluorophore to proteins and peptides with cysteine residues or other thiolated molecules. It features an emission wavelength (λ em) of 520 nm and an excitation wavelength (λ ex) of 470 nm.

ZNL0325 is a covalent probe based on pyrazolo[1,2-a]pyrimidine that demonstrates an alternative binding mode for kinases, where the C3 position is reversed facing the ribose-binding pocket. ZNL0325 and its analogs feature an acrylamide side chain at the C3 position, capable of forming covalent bonds with various kinases possessing cysteine at the αD-1 position, including BTK, EGFR, BLK, and JAK3.

Cy3B maleimide is a mono-reactive dye containing a maleimide group, designed to selectively and efficiently attach the Cyanine3 fluorophore (an analog of Cy3) to proteins and peptides with cysteine residues, as well as other thiolated molecules, such as thiol-containing oligonucleotides. Cy3B is an enhanced version of the Cy3 dye, offering significantly improved fluorescence quantum yield and photostability.

EN219-alkyne is an alkyne-functionalized EN219 probe. EN219 is a synthetic covalent ligand with moderate specificity for the N-terminal cysteine (C8) of RNF114, exhibiting an IC50 of 470 nM. It inhibits RNF114-mediated autoubiquitination and p21 ubiquitination. EN219-alkyne acts as a click chemistry reagent, containing an alkyne group that can undergo a copper-catalyzed azide-alkyne cycloaddition reaction (CuAAc) with molecules containing azide groups.

Z-IETD-R110 is a fluorescent substrate for cysteine proteases (caspases). Specifically, it serves as a substrate for caspase-8, which, upon activation, recognizes and cleaves Z-IETD-R110, releasing a fluorophore. This process results in enhanced fluorescence signals that can be detected through fluorescence microscopy. Z-IETD-R110 is employed in studies of oxidative stress-induced apoptosis, particularly in pancreatic acinar cells.

Ac-VEID-AMC is a fluorescent substrate used for assessing the activity of caspase-6 and related cysteine proteases (Ex=340-360 nm, Em=440-460 nm).

TPA-NAC is a non-fluorescent prodrug created by incorporating N-acetyl-L-cysteine (NAC) into a conjugated receptor framework. It allows for selective fluorescent labeling of human serum albumin (HSA).

Suc-YVAD-AMC is utilized to assess the cysteine protease activity of the proteasome. When cleaved by the cysteine protease activity of the proteasome, Suc-YVAD-AMC releases fluorescent AMC, which allows for the evaluation of the proteasome's enzymatic activity.

Biotin-benzoboroxole (Bio-ben) is a functional probe utilized for detecting cysteine sulfinic acid (Cys-SOOH).

Alexa Fluor 680 C2-Maleimide is a maleimide-functionalized derivative of Alexa Fluor 680, emitting near-infrared fluorescence with excitation/emission maxima around 680/705 nm. The maleimide group efficiently forms covalent bonds with thiol (-SH) groups in proteins or peptides, enabling specific labeling and tracking of cysteine residues. It is commonly used as a functional near-infrared fluorescent probe in life science research.

Alexa Fluor 647 C2-Maleimide 6C is a maleimide-functionalized derivative of Alexa Fluor 647, emitting far-red fluorescence with excitation/emission maxima around 651/670 nm. Its maleimide group specifically reacts with thiol (-SH) groups in proteins or peptides, enabling efficient labeling of cysteine residues and other thiol-containing molecules. This dye is widely used in cell biology, neuroscience, and disease research as a functional far-red fluorescent probe.

FlAsH-EDT2 is a membrane-permeable fluorescent reagent that can label proteins. FlAsH-EDT2 can bind to CCXXCC motifs and nonspecific endogenous cysteine-rich proteins. FlAsH-EDT2 can only be used to label recombinant proteins that are expressed at very high levels.

Suc-Leu-Tyr-AMC is a fluorescent substrate for calpain I and II, papain (another cysteine protease), and is used to measure the chymotrypsin-like peptidase activity of the 20S proteasome (excitation max: 360 nm; emission max: 460 nm). Suc-Leu-Tyr-AMC can also be cleaved by the Ti protease from E. coli.

7-Fluoro-2,1,3-benzoxadiazole-4-sulfonate (SBD-F) is a thiol-reactive fluorogenic probe.1It has been used to quantify the levels of homocysteine, cysteine, and cysteamine in human plasma.2SBD-F displays excitation/emission maxima of 380/515 nm, respectively.1 1.Imai, K., Toyo'oka, T., and Watanabe, Y.A novel fluorogenic reagent for thiols: Ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonateAnal. Biochem.128(2)471-473(1983) 2.Ichinose, S., Nakamura, M., Maeda, M., et al.A validated HPLC-fluorescence method with a semi-micro column for routine determination of homocysteine, cysteine and cysteamine, and the relation between the thiol derivatives in normal human plasmaBiomed. Chromatogr.23(9)935-939(2009)

Mu-6S-Palm-β-Glc is a fluorogenic substrate specifically designed for palmitoyl-protein thioesterase (PPT). It is enzymatically cleaved by PPT1 to release the fluorescent 4-methylumbelliferone (MU) moiety, enabling sensitive quantification of enzyme activity. This substrate is a critical tool in the study of infantile neuronal ceroid lipofuscinosis (INCL), a lysosomal storage disorder. It is utilized for both prenatal and postnatal diagnostic assays, as well as in the evaluation of bi-functional IgG-lysosomal enzyme fusion proteins for brain-targeted drug delivery.

The rapid, selective, and sensitive sensing of thiols is important in diverse areas of research. This thiofluor 623 responds upon exposure to thiols with an increase in fluorescence intensity of up to 120-fold. The response is selective for thiols and occurs in aqueous media. In the absence of thiols, the probe is essentially non-fluorescent; thiols cause cleavage of the probe, generating a fluorophore with an absorption maximum of 563 nm and emission at 623 nm. The fluorescence quantum yield of the cleaved product, generated in response to thiols, increases in more viscous media, suggesting ideal performance in biological systems and applicability to single-molecule or 2-photon sensing schemes. The thiofluor 623 is cell-permeable and reacts selectively with intracellular thiols. The pseudo-first order rate constant (kobs) depends on substrate (e.g., 2.1 x 10-3 s-1 for cysteine, 2.0 x 10-5 s-1 for human serum albumin).

CAY10731 is a fluorescent probe for hydrogen sulfide (H2S).[1] Upon reaction with H2S, fluorescein (FITC) is released and its fluorescence can be used to detect H2S. FITC displays excitation/emission maxima of 485/535 nm, respectively. CAY10731 is selective for H2S over glutathione (GSH), cysteine, H2O3-, SO3-, and H2O2 as well as tBuO and OH radicals. It has been used to detect H2S in rat hippocampal slices and nematodes.