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PubMed1988

Synthesis and structural characterization of the dilactone derivative of GD1a ganglioside.

Treatment of GD1a [alpha-Neu5Ac-(2----3)-beta-GalNAc-(1----4)-[alpha- Neu5Ac-(2----3)]-beta-Gal-(1----4)-beta-Glc-(1----1)-Cer] with dicyclohexylcarbodi-imide in anhydrous methyl sulfoxide affords 94-98% of GD1a-dilactone. The involvement of the carboxyl groups of the two sialic acid residues in the lactone rings was proved by ammoniolysis and reduction experiments, which gave ganglioside derivatives containing the amide of sialic acid and N-acetylneuraminulose, respectively. 1H-N.m.r. spectroscopy showed that the lactone rings involved position 2 of each galactose residue in the ester linkages.

Chemical Phenomena↗
PubMed1989

Synthesis and reactions of O-acetylated benzyl alpha-glycosides of 6-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-N-acetylmuramoyl-L- alanyl-D-isoglutamine esters: the base-catalysed isoglutamine in equilibrium glutamine rearrangement in peptidoglycan-related structures.

Condensation of benzyl 2-acetamido-6-O-(2-acetamido-3,4,6-tri-O-acetyl-2- deoxy-3-O-[(R)-1-carboxyethyl]-alpha-D-glucopyranoside (2) and its 4-acetate (4) with L-alanyl-D-isoglutamine benzyl ester via the mixed anhydride method yielded N-(2-O-[benzyl 2-acetamido-6-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D- glucopyranosyl)-2,3-dideoxy-alpha-D-glucopyranosid-3-yl]-(R)-lacto yl)-L- alanyl-D-isoglutamine benzyl ester (5) and its 4-acetate (6), respectively. Condensation by the dicyclohexylcarbodi-imide-N-hydroxysuccinimide method converted 2 into benzyl 2-acetamido-6-O-(2-acetamido-3,4,6-tri-O-acetyl- 2-deoxy-beta-D-glucopyranosyl)-3-O-[(R)-1-carboxyethyl]-2-deoxy-alpha-D- glucopyranoside 1',4-lactone (7). In the presence of activating agents, 7 underwent aminolysis with the dipeptide ester to give 5. Zemplén O-deacetylation of 5 and 6 led to transesterification and alpha----gamma transamidation of the isoglutaminyl residue to give N-(2-O-[benzyl 2-acetamido-6-O-(2- acetamido-2-deoxy-beta-D-glucopyranosyl)-2,3-dideoxy-alpha-D-glucopyr anosid-3- yl]-(R)-lactoyl)-L-alanyl-D-isoglutamine methyl ester (8) and -glutamine methyl ester (9). Treatment of 6 with MgO-methanol caused deacetylation at the GlcNAc residue to give a mixture of N-(2-O-[benzyl 2-acetamido-6-O-(2-acetamido-2- deoxy-beta-D-glucopyranosyl)-4-O-acetyl-2,3-dideoxy-alpha-D-glucopyra nosid-3- yl]-(R)-lactoyl)-L-alanyl-D-isoglutamine methyl ester (11) and -glutamine methyl ester (12). Benzyl or methyl ester-protection of peptidoglycan-related structures is not compatible with any of the reactions requiring alkaline media. Condensation of 2 with L-alanyl-D-isoglutamine tert-butyl ester gave N-(2-O-[benzyl 2-acetamido- 6-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-beta-D-glucopyranosyl)-2,3-d ideoxy- alpha-D-glucopyranosid-3-yl]-(R)-lactoyl-L-alanyl-D-isoglutamine tert-butyl ester (16), deacetylation of which, under Zemplén conditions, proceeded without side-reactions to afford N-(2-O-[benzyl 2-acetamido-6-O-(2-acetamido-2-deoxy-beta-D- glucopyranosyl)-2,3-dideoxy-alpha-D-glucopyranosid-3-yl]-(R)-la cotyl)-L- alanyl-D-isoglutamine tert-butyl ester (17).

Acetylglucosamine↗
PubMed1989

A facile, regio- and stereo-selective synthesis of ganglioside GM3.

Gangliosides GM3, containing three different fatty acyl groups at the ceramide moiety, have been synthesized. Coupling of 2-(trimethylsilyl)ethyl O-(6-O-benzoyl-beta-D-galactopyranosyl)-(1----4)- 2,6-di-O-benzoyl-beta-D-glucopyranoside (4), prepared from 2-(trimethylsilyl)ethyl beta-lactoside (1) by selective 3'-O-benzylation, O-benzoylation, and subsequent removal of the benzyl group, with methyl (methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-2-thio-D-glycero-alpha-D- galacto - 2-nonulopyranosid)onate (5) using dimethyl(methylthio)sulfonium triflate as a glycosyl promoter, gave 2-(trimethylsilyl)ethyl O-(methyl 5-acetamido-4,7,8,9-tetra-O- acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto-2-nonulopyranosylonate++ +)-(2----3)- O-(6-O- benzoyl-beta-D-galactopyranosyl)-(1----4)-2,6-di-O-benzoyl-beta-D- glucopyranoside (6), which was converted, via O-acetylation, selective removal of the 2-(trimethylsilyl)-ethyl group, and subsequent imidate formation, into the alpha-N-acetylneuraminyl-(2----3')-lactose trichloroacetimidate 9. Glycosylation of (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol (10) with 9 afforded the beta-glycoside 11, which was converted, via selective reduction of the azide group, coupling with fatty acids, O-deacetylation, and de-esterification, into the title compounds.

Carbohydrate Conformation↗
PubMed1989

Synthesis, structure, and conformation of the dilactone derivative of GD1b ganglioside.

Treatment of DG1b, beta-Gal-(1----3)-beta-GalNAc-(1---- 4)-[alpha-Neu5Ac-(2----8)-alpha-Neu5Ac-(2---- 3)]-beta-Gal-(1----4)-beta-Glc-(1----1)-Cer, with dicyclohexylcarbodi-imide in anhydrous methyl sulfoxide affords 95-98% of GD1b-dilactone. The carboxyl groups of the two sialic acid units are involved in ester linkages, as proved by ammoniolysis and reduction which gave derivatives containing the amide of sialic acid and N-acetylneuraminulose, respectively. 1H-N.m.r. spectroscopy showed that the lactone rings involved position 9 of the inner sialic acid and position 2 of the inner galactose and that the disialosyl chain is extended toward the -beta-Gal-(1 ----4)-beta-Glc- portion of the ganglioside moiety.

Carbohydrate Conformation↗
PubMed1990

Synthesis of glycopeptides with the TN and T antigen structures, and their coupling to bovine serum albumin.

Glycopeptides with TN and T antigen structures that represent the N-terminal tripeptide of asialoglycophorin with blood-group M specificity have been synthesized using fluorenylmethoxycarbonyl (Fmoc) and 2-pyridylethoxycarbonyl (Pyoc) groups for amino protection and the benzyl ester as the carboxyl-blocking function. The Fmoc and the Pyoc groups could be removed by treatment with the weak base morpholine under conditions where the base-sensitive O-glycosyl-serine and -threonine linkages were stable. Ester groups were removed from the carbohydrate moieties with methanolic hydrazine, to give the TN and T antigen glycopeptides which were coupled to bovine serum albumin (BSA) via a carbodi-imide procedure and without any spacer groups. The resulting conjugates contained an average of greater than 20 glycopeptides per protein molecule. They are not microheterogeneous in the carbohydrate part as is commonly found for glycoproteins isolated from biological sources.

Antigens, Neoplasm↗
PubMed1990

[Synthesis of a highly branched nonasaccharide sequence of the "bisected"structure of N-glycoproteins].

A highly branched nonasaccharide, beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----2)-alpha-D-Manp-(1----3) -[beta-D- Glcp-NAc-(1----4)-[beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----2)-alpha-D- Manp- (1----6)]-beta-D-Manp-(1----4)-D-GlcNAc, that represents the carbohydrate chain of the "bisected" structure of lactosamine-type N-glycoproteins was synthesized by a block synthesis approach. The activated trisaccharide block beta-D-Galp-(1----4)-beta-D-GlcpNAc-(1----2)-D-Man was coupled first with the low reactive OH-3 group and, in a second step, with the reactive OH-6 group of the central beta-D-mannopyranosyl residue within the suitably protected trisaccharide block beta-D-GlcpNAc-(1----4)-beta-D-Manp-(1----4)-D-GlcNAc. During these coupling steps, the alpha-glycosidic linkages of D-mannopyranosyl residues were formed without neighboring-group participation, which is only successful by use of the imidate procedure.

Carbohydrate Conformation↗
PubMed1992

Synthesis of a series of ganglioside GM3 analogs containing a deoxy-N-acetylneuraminic acid residue.

Ganglioside GM3 analogs containing 4-, 7-, 8-, and 9-deoxy-N-acetylneuraminic acids in the place of N-acetylneuraminic acid (Neu5Ac) have been synthesized. Glycosylation of 2-(trimethylsilyl)ethyl O-(6-O-benzoyl-beta-D-galactopyranosyl)-(1----4)-2,6-di- O-benzoyl-beta-D-glucopyranoside with the methyl 2-thioglycoside derivatives of the respective deoxy-N-acetylneuraminic acids, using dimethyl(methylthio)sulfonium triflate as a promoter, gave the four required 2-(trimethylsilyl)ethyl alpha-sialosyl-(2----3b)-beta-lactosides. These were converted via O-acetylation, selective removal of the 2-(trimethylsilyl)ethyl group, and subsequent imidate formation, into the corresponding alpha-sialosyl-(2----3b)-alpha-lactose trichloroacetimidates 15, 17, 19, and 21. Glycosylation of (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol with 15, 17, 19, and 21 in the presence of boron trifluoride etherate afforded the expected beta glycosides, which were transformed in good yields, via selective reduction of the azido group, coupling with octadecanoic acid, O-deacylation, and de-esterification, into the target compounds.

Carbohydrate Conformation↗
PubMed1992

Synthesis of a position isomer of ganglioside GD3 having an alpha-Neu5Ac-(2----9)-alpha-Neu5Ac linkage.

A position isomer of ganglioside GD3 has been synthesized in which N-acetylneuraminic acid (Neu5Ac) is linked alpha-glycosidically at C-9 of the Neu5Ac residue of the ganglioside GM3, structure. The coupling of 2-(trimethylsilyl)ethyl O-(6-O-benzoyl-beta-D-galactopyranosyl)-(1----4)-2,6-di-O-benzoyl-beta-D -glucopyranoside with methyl O-(methyl 5-acetamido-4,7,8,9-tetra-O-acetyl-3,5-dideoxy-D-glycero-alpha-D-galacto -2-nonulopyranosylonate)-(2----9)-(methyl 5-acetamido-4,7,8-tri-O-acetyl-3,5-dideoxy-2-thio-D-glycero-D-galacto-2 -nonulopyranosid)onate, prepared from the corresponding 2-(trimethylsilyl)ethyl glycoside by selective removal of the 2-(trimethylsilyl)ethyl group, 1-O-acetylation, and introduction of the methylthio group with trimethyl(methylthio)silane, using N-iodosuccinimide-trifluoromethanesulfonic acid as a glycosylation catalyst, gave a tetrasaccharide (5). Compound 5 was converted, via O-acetylation, selective removal of the 2-(trimethylsilyl)ethyl group, and subsequent imidate formation, into a protected alpha-Neu5Ac-(2----9)-alpha-Neu5Ac-(2----3')-alpha-lactosyl trichloroacetimidate (8). Glycosylation of (2S,3R,4E)-2-azido-3-O-benzoyl-4-octadecene-1,3-diol with 8 afforded a ceramide precursor which was transformed, via selective reduction of the azido group, coupling with octadecanoic acid, O-deacylation, and hydrolysis of the methyl ester groups, into to the little ganglioside.

Carbohydrate Sequence↗
PubMed1991

[Synthesis of partial structure of complex types of N-glycoproteins].

Comparable syntheses of beta-D-GlcpNAc-(1----2)-[beta-D-GlcpNAc-(1----6)]-alpha-D-Manp-(1- ---6)-beta-D-ManpO(CH2)8CO2Me and beta-D-GlcpNAc-(1----2)-alpha-D-Manp-(1----3)-beta-D-ManpO(C H2)8CO2Me with the glycosyl halide and imidate methods were investigated. 3,4,6-Tri-O-acetyl-2-deoxy-(2,2,2-trichloroethoxycarbonylamino)-al pha-D-glucopyranosyl bromide or trichloroacetimidate are suitable glycosyl donors for beta-D-glycoside coupling with secondary hydroxyl groups.

Carbohydrate Sequence↗
PubMed1993

Synthesis of p-trifluoroacetamidophenyl 6-deoxy-2-O-(3-O-[2-O-methyl-3-O- (2-O-methyl-alpha-D-rhamnopyranosyl)-alpha-L-fucopyranosyl]-alpha-L- rhamnopyranosyl)-alpha-L-talopyranoside: a spacer armed tetrasaccharide glycopeptidolipid antigen of Mycobacterium avium serovar 20.

The synthesis of the title tetrasaccharide glycoside 38 is reported. p-Nitrophenyl endo-3,4-O-benzylidene-6-deoxy-alpha-L-talopyranoside (4), 3-O-acetyl-2,4-di-O-benzyl-alpha-L-rhamnopyranosyl trichloroacetimidate (7), methyl 3-O-acetyl-4-O-benzyl-2-O-methyl-1-thio-beta-L-fucopyranoside (15), 3-O-acetyl-4-O-benzyl-2-O-methyl-alpha-L-fucopyranosyl bromide (16), and ethyl 3-O-acetyl-4-O-benzyl-2-O-methyl-1-thio-alpha-D-rhamnopyranoside (33) were prepared as intermediates. Compound 4 was glycosylated with imidate 7 as well as with methyl 3-O-acetyl-2,4-di-O-benzyl-1-thio-alpha-L-rhamnopyranoside (9), affording the same disaccharide derivative 8. Deacetylation of 8 gave crystalline 17. Condensation of 17 with both fucosyl donors 15 and 16 yielded the same trisaccharide derivative 18 stereoselectively. Compound 18 was also prepared by the coupling of 4 with disaccharide glycosyl donor 20. After deacetylation of 18 (-->34), methyl triflate-promoted glycosylation with compound 33 resulted in tetrasaccharide 35. Conversion of the p-nitrophenyl group of 35 into the p-trifluoroacetamidophenyl group (-->36) and removal of the protecting groups gave the title tetrasaccharide glycoside 38.

Carbohydrate Conformation↗
PubMed1993

Synthesis and NMR spectroscopic investigation of oligosaccharides containing Kdo and L-glycero-D-manno-heptopyranosyl residues.

The disaccharides O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->8)-sodium (allyl 3-deoxy-beta-D-manno-2-octulopyranosid)onate (8), O-L-glycero-alpha-D-manno-heptopyranosyl-(1-->7)-sodium (allyl 3-deoxy-beta-D-manno-2-octulopyranosid)onate (12), and O-alpha-D-mannopyranosyl-(1-->7)-sodium (allyl 3-deoxy-beta-D-manno-2-octulopyranosid)onate (21) and the branched trisaccharides O-L-glycero-alpha-D-manno-heptopyranosyl-(1-->7)-[O-(sodium 3-deoxy-alpha- and -beta-D-manno-2-octulopyranosylonate)-(2-->8)]-sodium (allyl 3-deoxy-beta-D-manno-2-octulopyranosid)onate (15 and 16) and O-alpha-D-mannopyranosyl-(1-->7)-[O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->8)]-sodium (allyl 3-deoxy-beta-D-manno-2-octulopyranosid)onate (24) were prepared. Per-O-acetylated mannopyranosyl or Kdo bromide derivatives were employed for the glycosylation steps under Helferich conditions, whereas the imidate derivative 9 was used for the coupling of the L-glycero-D-manno-heptopyranosyl residues. The oligosaccharides were fully characterized by NMR spectroscopic data. Their structures correspond to an artificial linkage pattern providing a potential cross-reactive epitope for antibodies directed against the inner-core-region of enterobacterial as well as chlamydial lipopolysaccharides.

Carbohydrate Conformation↗
PubMed1994

Total synthesis of a modified ganglioside, de-N-acetyl GM2.

Regio- and stereo-selective glycosylation of a sialyl donor 6 that carries a N-phthaloyl protecting group at C-5 with a lactosyl acceptor 7 armed with a pivaloyl group at O-2a was performed to give the expected glycotrioside 5. Subsequent glycosylation of 5 with 2-azido galactosyl donor 4 gave glycotetraosyl derivatives 18 and 19. After conversion of 18 into imidates 25 and 26, coupling with (2S,3R,4E)-3-O-benzoyl-2-N-tetracosanoylsphingenine (2) was executed to afford completely protected ganglioside analogues 27 and 28. Selective cleavage of the methyl ester and N,O-deprotection gave the target de-N-acetyl GM2 (1).

Carbohydrate Conformation↗
PubMed1995

Synthesis of N-beta-D-glucopyranosyluronate derivatives of barbital, phenobarbital, metharbital, and mephobarbital.

The synthesis and characterization of barbital, phenobarbital, metharbital, and mephobarbital glucuronides is reported. The condensation of per(trimethylsilyl)-barbital and -phenobarbital with methyl 1,2,3,4-tetra-O-acetyl-beta-D-glucopyranuronate in the presence of trimethylsilyl trifluoromethanesulfonate gave moderate yields of the N1-(beta-D-glucopyranosyluronate) barbiturate derivatives. The diastereomers of the phenobarbital derivatives were resolved by use of C18 reversed-phase HPLC. The homologous N3-methyl barbiturate N1-glucuronates were prepared by reaction of the barbital and phenobarbital N1-glucuronate derivatives with diazomethane. The absolute configuration of the phenobarbital N1-beta-D-glucopyranuronate epimers was determined by oxidative removal of the glycon from the mephobarbital N1-beta-D-glucopyranuronate epimers to give the optical isomers of mephobarbital. The spectroscopic data for this series of compounds will facilitate the characterization of N-glycosylated imide xenobiotics that may be detected as mammalian metabolites in biodisposition studies.

Barbital↗
PubMed1994

Synthesis of allyl 3-deoxy- and 4-deoxy-beta-D-galactopyranoside and simultaneous preparations of Gal(1-->2)- and Gal(1-->3)-linked disaccharide glycosides.

Syntheses of galactose derivatives that are useful in probing the binding specificity of galactose-specific lectins are reported. These include allyl 3-deoxy- and 4-deoxy-beta-D-xylo-hexopyranoside and several disaccharide glycosides having Gal(1-->2) and Gal(1-->3) linkages. The beta-linked Gal disaccharide isomers were produced using 2,3,4,6-tetra-O-acetyl-alpha-D-galactopyranosyl bromide as glycosyl donor and the 4,6-O-benzylidene derivatives of allyl beta-D-galactopyranoside, alpha-D-glucopyranoside, alpha-D-mannopyranoside, and 2-acetamido-2-deoxy-alpha-D-galactopyranoside as acceptors. Only the Gal(1-->3)-linked disaccharide was obtained when the benzylidene derivatives of the mannopyranoside and 2-acetamido-2-deoxygalactopyranoside were used. Attempts at the preparation of Gal(alpha, 1-->2)Gal and Gal(alpha, 1-->3)Gal disaccharide glycosides were made using the same strategy, but employing the 1-trichloro-acetimidate or 1-N-methylacetimidate of 2,3,4,6-tetra-O-benzyl-D-galactopyranose as the glycosyl donor. The latter imidate produced a mixture of Gal(alpha, 1-->2)Gal and Gal(alpha, 1-->3)Gal derivatives as major products, but the former gave the Gal(beta, 1-->2)Gal isomer as the major product.

Carbohydrate Sequence↗
PubMed1996

Synthesis of eight glycosides of hexasaccharide fragments representing the terminus of the O-polysaccharide of Vibrio cholerae O:1, serotype Inaba and Ogawa, bearing aglycons suitable for linking to proteins.

The title substances were prepared from intermediate, fully acetylated alpha-trimethylsilylethyl (SE) glycosides. The latter were assembled in a blockwise manner, using as the glycosyl donor the alpha-glycosyl chloride of a disaccharide bearing two 4-azido-4-deoxy functions. Next, the azido groups in the assembled hexasaccharides were converted to the corresponding amines, and these were acylated with 4-O-benzyl-3-deoxy-L-glycero-tetronic acid in the presence of a water-soluble carbodiimide. The SE glycosides were then transformed to glycosyl imidates, and these were coupled with methyl 6-hydroxyhexanoate or methyl 2-(2-hydroxyethylthio) propionate. The aglycons in the glycosides thus obtained were then converted to the corresponding carboxylic acids or acyl hydrazides. Such compounds are suitable for linking to proteins to obtain neoglycoproteins.

Carbohydrate Sequence↗
PubMed1988

Reaction of trans-4-N-acetoxy-N-acetylaminostilbene with guanosine and deoxyguanosine in vitro: the primary reaction product at N2 of guanine yields different final adducts.

The model ultimate carcinogen, trans-4-N-acetoxy-N-acetylaminostilbene (N-acetoxy-AAS), was reacted with guanosine (Guo) and deoxyguanosine (d-Guo) and the resulting adducts were purified by Sephadex LH-20 chromatography and HPLC for structure identification. A number of new adducts was identified by mass and 1H-NMR spectroscopy. The generation of all known adducts can now be explained by a common mechanism. The electrophile formed from the hydroxamic acid ester at C-beta reacts in a first step predominantly with N2 of guanine (Gua). The resulting quinone-imide intermediate reacts in a second step with either one of three nucleophiles: (1) predominantly with N3 of Gua to yield the previously described angular cyclic adducts ((5R,6R)/(5S,6S)-9-oxo-5,6,7,9-tetrahydro-imidazo(2,1-b)purines); (2) with N1 of Gua to yield linear cyclic adducts ((6R,7R)/(6S,7S)-9-oxo-5,6,7,9-tetrahydro-imidazo(1,2-a)purines); (3) with water to yield the open ring (1R,2R)/(1S,2S)-2-(N2'-guanyl)-1-hydroxyethanes. To some minor extent (1:8-1:9) the electrophile reacts first with N1 or N3 of guanine which leads to the formation of two pairs of the corresponding regioisomeric cyclic adducts. This reaction mechanism may also explain the formation of cross-links between different bases.

Carcinogens↗
PubMed1989

Kinetic beta-deuterium isotope effects suggest a covalent mechanism for the protein folding enzyme peptidylprolyl cis/trans-isomerase.

The cis/trans interconversion of Glt-Ala-Ala-Pro-Phe-4-nitroanilide and Glt-Ala-Gly-Pro-Phe-4-nitroanilide was studied both enzymatically and nonenzymatically by measuring kinetic beta-deuterium isotope effects. The hydrogen atom at the alpha-carbon atom of the Xaa residue within the Xaa-Pro moiety was substituted by deuterium. In the nonenzymatic case the transition state of rotation is reflected by kH/kD greater than 1. When catalysed by 17 kDa PPIase the same bond rotation is characterized by kH/kD less than 1. This suggests a covalent mechanism of catalysis which involves an approximately tetravalent carbon of the prolyl imidic bond for the transition state of reaction.

Amino Acid Isomerases↗
PubMed1991

Assignment of the 15N NMR spectra of reduced and oxidized Escherichia coli thioredoxin.

As a necessary first step in the use of heteronuclear correlated spectra to obtain high resolution solution structures of the protein, assignment of the 15N NMR spectra of reduced and oxidized Escherichia coli thioredoxin (Mr 12,000) uniformly labeled with 15N has been performed. The 15N chemical shifts of backbone amide nitrogen atoms have been determined for both oxidation states of thioredoxin using 15N-1H correlated and two-dimensional heteronuclear single-quantum coherence (HSQC) TOCSY and NOESY spectra. The backbone assignments are complete, except for the proline imide nitrogen resonances and include Gly33, whose amide proton resonance is difficult to observe in homonuclear 1H spectra. The differences in the 15N chemical shift between oxidized and reduced thioredoxin, which occur mainly in the vicinity of the two active site cysteines, including residues distant in the amino acid sequence which form a hydrophobic surface close to the active site, are consistent with the differences observed for proton chemical shifts in earlier work on thioredoxin.

Amino Acid Sequence↗