Fmoc-Cys(Acm)-OH

Fmoc-Cys(Acm)-OH

A 'conovenomic' analysis of the milked venom from the mollusk-hunting cone snail Conus textile--the pharmacological importance of post-translational modifications.[Pubmed:24055806]

Peptides. 2013 Nov;49:145-58.

Cone snail venoms provide a largely untapped source of novel peptide drug leads. To enhance the discovery phase, a detailed comparative proteomic analysis was undertaken on milked venom from the mollusk-hunting cone snail, Conus textile, from three different geographic locations (Hawai'i, American Samoa and Australia's Great Barrier Reef). A novel milked venom conopeptide rich in post-translational modifications was discovered, characterized and named alpha-conotoxin TxIC. We assign this conopeptide to the 4/7 alpha-conotoxin family based on the peptide's sequence homology and cDNA pre-propeptide alignment. Pharmacologically, alpha-conotoxin TxIC demonstrates minimal activity on human acetylcholine receptor models (100 muM, <5% inhibition), compared to its high paralytic potency in invertebrates, PD50 = 34.2 nMol kg(-1). The non-post-translationally modified form, [Pro](2,8)[Glu](16)alpha-conotoxin TxIC, demonstrates differential selectivity for the alpha3beta2 isoform of the nicotinic acetylcholine receptor with maximal inhibition of 96% and an observed IC50 of 5.4 +/- 0.5 muM. Interestingly its comparative PD50 (3.6 muMol kg(-1)) in invertebrates was ~100 fold more than that of the native peptide. Differentiating alpha-conotoxin TxIC from other alpha-conotoxins is the high degree of post-translational modification (44% of residues). This includes the incorporation of gamma-carboxyglutamic acid, two moieties of 4-trans hydroxyproline, two disulfide bond linkages, and C-terminal amidation. These findings expand upon the known chemical diversity of alpha-conotoxins and illustrate a potential driver of toxin phyla-selectivity within Conus.

The investigation of Fmoc-cysteine derivatives in solid phase peptide synthesis.[Pubmed:2577698]

Pept Res. 1989 Jan-Feb;2(1):147-52.

Fmoc-Cys(t-Bu)-OH, Fmoc-Cys(Acm)-OH, and Fmoc-Cys(Trt)-OH exhibit excellent synthesis characteristics when used in Fmoc solid phase peptide synthesis on the Applied Biosystems Model 431A peptide synthesizer. The actual 5% scavenger mixture will vary according to the particular amino acid residues present. As was previously mentioned, an anisole/ethanedithiol/ethylmethylsulfide mixture (3:1:1) works well as a general scavenger solution for TFA cleavage of Fmoc synthesized peptide resins. It also may be possible to use lower acid (TFA) concentrations. The syntheses and workups of the peptide Somatostatin utilizing these derivatives demonstrate the ease of using these cysteine derivatives with the Fmoc chemistry approach. The use of either the t-Bu or the Acm moiety produces a peptide containing protected thiol groups after cleavage with 95% TFA. The Fmoc-Cys(Trt)-OH derivative is efficiently deprotected using 95% TFA. This investigation should provide further insight into synthesis options and cleavage protocols when working with cysteine-containing peptides.