56-89-3

Basic information

• Product Name: L-Cystine
• Synonyms: (r-(r*,r*))-3,3’-dithiobis(2-aminopropanoicacid);1-cystine;3,3’-dithiobis(2-amino-,(r-(r*,r*))-propanoicaci;3,3’-dithiobis(2-aminopropanoicacid);3,3’-dithiobis-l-alanin;3,3'-Dithiobis(2-aminopropanoic acid);3,3'-Dithiodialanine;Alanine, 3,3'-dithiobis-
• CAS NO: 56-89-3
• Molecular Formula: C₆H₁₂N₂O₄S₂
• Molecular Weight: 240.3
• EINECS: 200-296-3
• Product Categories: Food and Feed Additive;Amino Acids;Amino Acid Derivatives;Cysteine [Cys, C];Nutritional Supplements;L-Amino Acids;Amino Acids;amino
• Mol File: 56-89-3.mol

Chemical Properties

• Melting Point: >240 °C (dec.)(lit.)
• Boiling Point: 468.2 °C at 760 mmHg
• Flash Point: 237 °C
• Appearance: White/Powder/Solid
• Density: 1.68
• Refractive Index: -222.5 ° (C=1, 1mol/L HCl)
• Storage Temp.: Store at RT.
• Solubility: 1 M HCl: 100 mg/mL
• PKA: 1.0, 2.1, 8.02, 8.71(at 25℃)
• Water Solubility: 0.112 g/L (25 ºC)
• Stability: Stable. Incompatible with strong oxidizing agents.
• Merck: 14,2782
• BRN: 1728094
• CAS DataBase Reference: L-Cystine(CAS DataBase Reference)
• NIST Chemistry Reference: L-Cystine(56-89-3)
• EPA Substance Registry System: L-Cystine(56-89-3)

Safety Data

• Hazard Codes: Xi,Xn
• Statements: 36/37/38-22
• Safety Statements: 26-36-24/25
• RIDADR: 2811
• WGK Germany: 3
• RTECS: HA2690000
• TSCA: Yes
• PackingGroup: III
• Hazardous Substances Data: 56-89-3(Hazardous Substances Data)

Usage

Uses

Used in Human Development:
L-Cystine is a non-essential amino acid for human development, formed by the dimerization of two cysteines through the sulfur.
Used in Antioxidant Applications:
L-Cystine is used as an antioxidant, protecting tissues against radiation and pollution.
Used in Protein Synthesis:
L-Cystine finds application in protein synthesis, being a crucial component for the formation of proteins.
Used in Vitamin B6 Utilization:
It is required for the utilization of vitamin B6, playing a vital role in the body's metabolic processes.
Used in Healing Burns and Wounds:
L-Cystine is useful in healing burns and wounds due to its role in wound healing and formation of epithelial tissue.
Used in Cell Culture Media:
It is required by certain malignant cell lines in the culture medium, as well as for the growth of certain micro-organisms.
Used in Hematopoietic System Stimulation:
L-Cystine stimulates the hematopoietic system and promotes the formation of white and red blood cells.
Used in Medications for Dermatitis Treatment:
L-Cystine is an active ingredient in medications used to treat dermatitis.
Used in In Vitro Cystine Solubility Assay:
L-Cystine has been used in in vitro cystine solubility assay to identify potential drugs that influence cystine solubility.
Used in Phosphate-Buffered Saline Supplement:
L-Cystine is used as a supplement of phosphate-buffered saline to slice and wash periprosthetic tissues.
Used in Pharmaceutical and Nutritional Applications:
L-Cystine can be used as a component of parenteral and enteral nutrition, as well as for the treatment of dermatitis and protection of liver function.
Used in Microchemical Procedures Validation:
L-Cystine is used in validating microchemical procedures for the determination of carbon, hydrogen, nitrogen, and sulfur in organic matter, as demonstrated by the Standard Reference Material (SRM) 143d.

References

http://www.ajiaminoscience.com/products/manufactured_products/l-amino_acids/L-Cystine.aspx https://pubchem.ncbi.nlm.nih.gov/compound/L-cystine#section=Pharmacology https://en.wikipedia.org/wiki/Cystine

Biochem/physiol Actions

Cysteine is the source of disulfide linkages in proteins and has a role in sulfur transport. It undergoes rapid oxidation to form cystine at physiological pH. L-cystine is crucial for oxygen production and low density lipoprotein modification by arterial smooth muscle cells. It also has a role in the synthesis of glutathione.

Safety Profile

Low toxicity by ingestion. When heated to decomposition it emits toxic fumes of PO, and SOx

Purification Methods

Cystine disulfoxide impurity is removed by treating an aqueous suspension with H2S. The cystine is filtered off, washed with distilled water and dried at 100o under a vacuum over P2O5. Crystallise it by dissolving in 1.5M HCl, then adjusting to neutral pH with ammonia. Likely impurities are D-cystine, meso-cystine and tyrosine. Also purify it by dissolving it in 10% NH3 and adding gradually dilute AcOH until the point of precipitation and cooling slowly [Dughton & Harrison Acta Cryst 12 396, 402 1959.] Alternatively dissolve it in 6N NH4OH and evaporate it at room temperature for crystallisation to occur. [Chaney & Steinrauf Acta Cryst 30 711 1974, Beilstein 4 IV 3155.]

InChI:InChI=1/C3H6NO2S3/c5-3(6)2(4-7)1-9-8/h2H,1,4H2,(H,5,6)

Synthetic route

L-Cysteine (52-90-4) → L-cystine (56-89-3)

Conditions	Yield
With 3-bromo-2-(1-hydroxycyclohexyl)[1,2]selenazolo[2,3-a]pyridinium chloride; dihydrogen peroxide In methanol; water at 20℃; for 0.166667h;	100%
With dihydrogen peroxide; sodium iodide In water at 25℃; for 1h; Cooling with ice;	100%
With bis(4-methoxyphenyl)telluride; rose bengal In water; isopropyl alcohol at 0℃; for 0.833333h; Irradiation;	99%

L-Cysteine (52-90-4) + (R)-2-Amino-3-(4-methoxy-phenylmethanesulfinyl)-propionic acid (73243-09-1) → L-cystine (56-89-3)

Conditions	Yield
With dimethylsulfide; trifluorormethanesulfonic acid In trifluoroacetic acid at 0℃; for 1h;	100%

(R)-9H-fluorenyl-9-methyl-L-cysteine (84888-38-0) → L-cystine (56-89-3)

Conditions	Yield
With piperidine In N,N-dimethyl-formamide for 2h;	100%

S-nitroso-L-cysteine (134469-02-6, 51209-75-7) → L-cystine (56-89-3) + NO

Conditions	Yield
With copper(II) ion In water at 25℃; Rate constant; var. conc. of Cu2+;	A 100% B n/a

(R)-S-tert-butylcysteine (2481-10-9) → L-cystine (56-89-3)

Conditions	Yield
With Methyltrichlorosilane; 1,1'-sulfinylbisbenzene at 4℃; for 0.166667h;	99%

L-Cysteine (52-90-4) + H-Cys(Acm)(O)-OH (75893-05-9) → L-cystine (56-89-3)

Conditions	Yield
With dimethylsulfide In trifluoroacetic acid at 0℃; for 1h;	97.9%

Reaxys ID: 11465027 → L-cystine (56-89-3)

Conditions	Yield
With sodium hydroxide In water at 20 - 60℃; for 2h; pH=~ 4.0;	97%
With ammonia In water at 20 - 60℃; for 0.666667 - 2h; pH=~ 3.0;	97%
With ammonia In water at 20 - 80℃; for 2h; pH=~ 2.3 - ~ 3.0;	95%

L-Cysteine (52-90-4) + N-(benzoylsulfide)benzamide (134861-13-5) → L-cystine (56-89-3) + benzamide (55-21-0) + D-N-benzoylcysteine

Conditions	Yield
In methanol; aq. phosphate buffer at 20℃; pH=7.4;	A 95% B 96% C 80%

S-(4-methoxybenzyl)-L-cysteine (2544-31-2) → L-cystine (56-89-3)

Conditions	Yield
With Methyltrichlorosilane; 1,1'-sulfinylbisbenzene at 4℃; for 0.166667h;	95%
With methoxybenzene; thallium(III) trifluoroacetate In trifluoroacetic acid at 0℃; for 1h;	86.7%
With methoxybenzene; thallium(III) trifluoroacetate In trifluoroacetic acid at 0℃; for 1h; Product distribution; cleavage various S-protecting groups of cystein;	86.7%

S-acetamidomethyl-L-cysteine (19647-70-2) → L-cystine (56-89-3)

Conditions	Yield
With Methyltrichlorosilane; 1,1'-sulfinylbisbenzene at 4℃; for 0.5h;	93%
With Methyltrichlorosilane; 1,1'-sulfinylbisbenzene at 4℃; for 0.5h; Product distribution; other S-protected cysteines;	93%

(R)-2-Amino-3-(4-methoxy-phenylmethanesulfinyl)-propionic acid (73243-09-1) + H-Cys(Ad)-OH (59709-71-6) → L-cystine (56-89-3)

Conditions	Yield
With dimethylsulfide; trifluorormethanesulfonic acid In trifluoroacetic acid at 0℃; for 1h;	92.4%

S-(4-methoxybenzyl)-L-cysteine (2544-31-2) + (R)-2-Amino-3-(4-methoxy-phenylmethanesulfinyl)-propionic acid (73243-09-1) → L-cystine (56-89-3)

Conditions	Yield
With dimethylsulfide; trifluorormethanesulfonic acid In trifluoroacetic acid at 0℃; for 1h;	92.2%

S-(diphenyl-4-pyridylmethyl)-L-cysteine (62982-12-1) → L-cystine (56-89-3)

Conditions	Yield
In hydrogenchloride; acetic acid at 0℃; for 0.75h; electrolysis (mercury cathode, 250 mA);	91%

S-benzyloxymethylcysteine (123043-33-4) → L-cystine (56-89-3)

Conditions	Yield
With methoxybenzene; thallium(III) trifluoroacetate In trifluoroacetic acid	88.8%
With methoxybenzene; thallium(III) trifluoroacetate In trifluoroacetic acid Product distribution; other reagent;	88.8%

S-Trimethylacetamidomethyl-L-cysteine (H-Cys(Tacm)OH) (125700-47-2) → L-cystine (56-89-3)

Conditions	Yield
With Methyltrichlorosilane; 1,1'-sulfinylbisbenzene at 4℃; for 0.5h;	88%
With iodine In acetic acid at 25℃; for 1h;	83%
With iodine In acetic acid at 25℃; for 1h; stability of protecting group under various conditions, various reagents, other substrates;	83%

H-Cys(Ad)-OH (59709-71-6) + H-Cys(Acm)(O)-OH (75893-05-9) → L-cystine (56-89-3)

Conditions	Yield
With dimethylsulfide; trimethylsilyl trifluoromethanesulfonate In trifluoroacetic acid at 0℃; for 1h;	86.3%

S-(4-methoxybenzyl)-L-cysteine (2544-31-2) + H-Cys(Acm)(O)-OH (75893-05-9) → L-cystine (56-89-3)

Conditions	Yield
With dimethylsulfide In trifluoroacetic acid at 25℃; for 1h;	85.3%

N-t-butoxycarbonyl-S-acetamidomethyl-L-cysteine (19746-37-3) → L-cystine (56-89-3) + S-acetamidomethyl-L-cysteine (19647-70-2)

Conditions	Yield
With Methyltrichlorosilane; 1,1'-sulfinylbisbenzene; trifluoroacetic acid at 4℃; for 0.166667h; Product distribution; Mechanism; var. reaction times, silyl chlorides and sulfoxides; other S-protected cystine-peptides;	A 79% B 15%

S-Benzamidomethyl-L-cystein (57357-62-7) → L-cystine (56-89-3)

Conditions	Yield
With Methyltrichlorosilane; 1,1'-sulfinylbisbenzene at 4℃; for 0.5h;	76%

S-<(4-methylphenyl)methyl>-L-cysteine (42294-52-0) → L-cystine (56-89-3)

Conditions	Yield
With Methyltrichlorosilane; 1,1'-sulfinylbisbenzene at 4℃; for 0.166667h;	49%
With dimethyl sulfoxide; methoxybenzene; trifluoroacetic acid Ambient temperature;

(+)-D-glucosamine hydrochloride (1078691-95-8) → L-cystine (56-89-3) + 2-(D-arabino-1',2',3',4'-tetrahydroxybutyl)-5-(D-erythro-2",3",4"-trihydroxybutyl)piperazine (17460-13-8)

Conditions	Yield
With pyridine; l-cysteine hydrochloride In methanol; water for 32h; Heating;	A n/a B 45%

Boc-Cys(Acm)(O)-OH (75893-04-8) + phenol (108-95-2) → L-cystine (56-89-3) + S-(4-hydroxyphenyl)-L-cysteine (73243-10-4)

Conditions	Yield
With hydrogenchloride at 110℃; for 24h;	A 16% B 41%

H-Cys(Acm)(O)-OH (75893-05-9) → L-Cysteine (52-90-4) + L-Cysteic acid (498-40-8) + L-cystine (56-89-3) + S-acetamidomethyl-L-cysteine (19647-70-2)

Conditions	Yield
With ammonia; sodium for 0.00277778h; Product distribution;	A n/a B 19% C 10% D 21%

L-Cysteine (52-90-4) + (R)-3-(Adamantane-1-sulfinyl)-2-amino-propionic acid → L-cystine (56-89-3)

Conditions	Yield
With dimethylsulfide; trifluorormethanesulfonic acid In trifluoroacetic acid at 0℃; for 1h;	20.8%

S-(4-methoxybenzyl)-L-cysteine (2544-31-2) + (R)-3-(Adamantane-1-sulfinyl)-2-amino-propionic acid → L-cystine (56-89-3)

Conditions	Yield
With dimethylsulfide; trifluorormethanesulfonic acid In trifluoroacetic acid at 0℃; for 1h;	15.5%

H-Cys(Ad)-OH (59709-71-6) + (R)-3-(Adamantane-1-sulfinyl)-2-amino-propionic acid → L-cystine (56-89-3)

Conditions	Yield
With dimethylsulfide; trifluorormethanesulfonic acid In trifluoroacetic acid at 0℃; for 1h;	10.5%

L-serin (56-45-1) → L-cystine (56-89-3)

Conditions	Yield
im Organismus der Ratte;

L-cystine (56-89-3) + methyl chloroformate (79-22-1) → (R,R)-N,N'-dimethoxycarbonyl-3,3'-dithiobis(2-aminopropionic acid) (78589-87-4)

Conditions	Yield
With sodium hydroxide; sodium carbonate at 20℃; for 2h; pH=8 - 9;	100%
With sodium carbonate In tetrahydrofuran; water at 20℃; for 16h;	65%

L-cystine (56-89-3) + di-tert-butyl dicarbonate (24424-99-5) → di-t-butoxycarbonyl-L-cystine (10389-65-8)

Conditions	Yield
With sodium carbonate In 1,4-dioxane; water at 20℃;	100%
With triethylamine In water Cooling with ice;	96%
With triethylamine In water at 20℃; for 2h;	95%

L-cystine (56-89-3) + toluene-4-sulfonic acid (104-15-4) + allyl alcohol (107-18-6) → L-cystine-bis-allyl ester bis-(toluene-4-sulfonate)

Conditions	Yield
In benzene at 90℃; for 16h;	100%
In benzene for 12h; Esterification; Heating;	95%

methanol (67-56-1) + L-cystine (56-89-3) → L-cystine dimethyl ester dihydrochloride (32854-09-4)

Conditions	Yield
With chloro-trimethyl-silane	100%
With thionyl chloride at 25℃; for 24h; Schlenk technique; Inert atmosphere;	99%
With thionyl chloride for 20h; Reflux;	98%

L-cystine (56-89-3) + benzyl chloroformate (501-53-1) → N,N'-bis(benzyloxycarbonyl)-L-cystine (6968-11-2)

Conditions	Yield
With sodium hydrogencarbonate In water at 20℃;	99%
Stage #1: L-cystine; benzyl chloroformate With sodium hydroxide In tetrahydrofuran; water at 20℃; for 3.25h; pH=10; Cooling with ice; Inert atmosphere; Stage #2: With hydrogenchloride In water pH=2; Inert atmosphere;	98%
With sodium hydroxide at 0℃; for 4h;	72%

L-cystine (56-89-3) → L-Cysteine (52-90-4)

Conditions	Yield
With ethandithiol at 40℃; for 5h; pH=7.5 adjusted with 5 percent NH4OH;	98.5%
With ammonia; sodium Reduction;	90%
With hydrogenchloride; tin man verduennt die Loesung, befreit sie mit H2S vom Zinn, verdunstet zur Trockne, loest den Rueckstand in Alkohol und faellt vorsichtig mit Ammoniak;

methanol (67-56-1) + L-cystine (56-89-3) → L-cystine dimethyl ester (1069-29-0)

Conditions	Yield
With thionyl chloride for 12.5h; Cooling with ice;	98%
With hydrogenchloride man zersetzt das Hydrochlorid mit Natriummethylat;
With thionyl chloride
With thionyl chloride at 0℃; for 12h; Inert atmosphere; Reflux;
With thionyl chloride at 0℃; for 12h; Reflux;	12.4 g

L-cystine (56-89-3) + chloroformic acid ethyl ester (541-41-3) → (R,R)-N,N'-diethoxycarbonyl-3,3'-dithiobis(2-aminopropionic acid) (19887-39-9)

Conditions	Yield
With sodium hydroxide; sodium carbonate at 20℃; for 1.5h; pH=8 - 9;	98%
With sodium hydroxide	98%

L-cystine (56-89-3) + (fluorenylmethoxy)carbonyl chloride (28920-43-6) → N,N'-bis[(9H-fluoren-9-ylmethoxy)carbonyl]-L-cystine (135273-01-7)

Conditions	Yield
With sodium carbonate In 1,4-dioxane; water at 10 - 20℃; for 2h;	98%
Stage #1: L-cystine With sodium hydroxide In tetrahydrofuran; water pH=10; Stage #2: (fluorenylmethoxy)carbonyl chloride In tetrahydrofuran; water at 0℃; for 3h; pH=10;

L-cystine (56-89-3) + nickel(II) → Ni(L-cystinate) * H2O

Conditions	Yield
With sodium hydroxide In perchloric acid mixing stoich. amts. of metal (in H2O) and ligand (in 0.2 M HClO4), pH adjustment to 7-8 with NaOH (boiling, pptn.); filtration, washing (H2O, EtOH, ether); elem. anal.;	97.7%

L-cystine (56-89-3) + zinc(II) cation → Zn(L-cystinate) * H2O

Conditions	Yield
With sodium hydroxide In perchloric acid mixing stoich. amts. of metal (in H2O) and ligand (in 0.2 M HClO4), pH adjustment to 7-8 with NaOH (room temp., pptn.); filtration, washing (H2O, EtOH, ether); elem. anal.;	96%

L-cystine (56-89-3) + copper(II) ion → Cu(L-cystinate) * 1/2 H2O

Conditions	Yield
With sodium hydroxide In perchloric acid mixing stoich. amts. of metal (in H2O) and ligand (in 0.2 M HClO4), pH adjustment to 7-8 with NaOH (room temp., pptn.); filtration, washing (H2O, EtOH, ether); elem. anal.;	95.2%

L-cystine (56-89-3) + benzyl pyridin-2-yl carbonate (96452-48-1) → N,N'-bis(benzyloxycarbonyl)-L-cystine (6968-11-2)

Conditions	Yield
With triethylamine In water; N,N-dimethyl-formamide for 1h; Ambient temperature;	95%

L-cystine (56-89-3) + Allyl chloroformate (2937-50-0) → N,N-Bis-allyloxycarbonyl-L-cystine (80349-71-9)

Conditions	Yield
With potassium hydroxide; water; sodium carbonate at 20℃; for 48h; Acylation;	95%

L-cystine (56-89-3) + lead(2+) cation → Pb(L-cystinate)

Conditions	Yield
With sodium hydroxide In perchloric acid mixing stoich. amts. of metal (in H2O) and ligand (in 0.2 M HClO4), pH adjustment to 7-8 with NaOH (room temp., pptn.); filtration, washing (H2O, EtOH, ether); elem. anal.;	95%
With NaHCO3 In water treatment of aq. soln. of L-cystine with NaHCO3 soln., heating with Pb(II) salts at 50-60°C in water bath for about 1/2 h; cooling, crystn. at room temp., filtration, washing with cold H2O, drying over silica gel in a desiccator; elem. anal.;

L-cystine (56-89-3) → L-Cysteine (52-90-4) + L-Cysteic acid (498-40-8)

Conditions	Yield
With hydrogenchloride; sulfuric acid; hydrogen bromide In water at 45℃; electrolysis (graphite sheets, i = 0.5 A/cm2);	A 94% B n/a
With hydrogenchloride; sulfuric acid; hydrogen bromide In water at 45℃; Product distribution; Mechanism; paired electrosynthesis (graphite sheets, i = 0.5 A/cm2);	A n/a B 94%
With hydrogenchloride at 40℃; Electrolysis;

L-cystine (56-89-3) + copper(II) ion → Cu(L-cystinate) * H2O

Conditions	Yield
With sodium hydroxide In perchloric acid mixing stoich. amts. of metal (in H2O) and ligand (in 0.2 M HClO4), pH adjustment to 7-8 with NaOH (boiling, pptn.); filtration, washing (H2O, EtOH, ether); elem. anal.;	94%

L-cystine (56-89-3) + N-(9H-fluoren-2-ylmethoxycarbonyloxy)succinimide (82911-69-1) → N,N'-bis[(9H-fluoren-9-ylmethoxy)carbonyl]-L-cystine (135273-01-7)

Conditions	Yield
With sodium carbonate In water; acetone at 50℃;	94%
With sodium carbonate In tetrahydrofuran; water at 20℃; Cooling with ice;

Upstream product

• 921-01-7 rac-cysteine 
• 52-90-4 L-Cysteine 
• 505-73-7 disulfanediyldiacetic acid 
• 69-78-3 5,5'-dithiobis-(2-nitrobenzoic acid) 
• 16136-29-1 2-Amino-2-carboxy-ethanethiol anion 
• 90792-25-9 anthraquinone-2,6-disulfonate 
• 51209-75-7 S-nitroso-cysteine 
• 7647-01-0 hydrogenchloride 
• 861021-29-6 bis-(5-methyl-3,6-dioxo-piperazin-2-ylmethyl)-disulfide 
• 23052-19-9 di-γ-glutamyl-cystine 
• 7664-93-9 sulfuric acid 
• 7732-18-5 water 
• 7664-41-7 ammonia 
• 7722-84-1 dihydrogen peroxide 

Downstream Products

• 2150-55-2 2-amino-⁽²⁾-thiazoline-4-carboxylic acid 
• 74-93-1 methylthiol 
• 352-93-2 diethyl sulphide 
• 921-01-7 rac-cysteine 
• 52-90-4 L-Cysteine 
• 13100-82-8 cysteic acid 
• 349-46-2 S,S-cystine 
• 51-85-4 2,2'-dithio-bis[ethylamine] 
• 75-07-0 acetaldehyde 
• 5545-17-5 N,N'-diacetyl-DL-cystine 
• 302-72-7 rac-Ala-OH 
• 107-96-0 3-mercaptopropionic acid 
• 29581-98-4 N,N'-diformyl-DL-cystine 
• 879878-64-5 NSC₁₁₄₅₃₂ 

Relevant articles and documents

A REINVESTIGATION OF THE OXIDATION OF CYSTEINE BY Br2(1-)(.) AND I2(1-)(.). EVIDENCE FOR CySBr(1-) AND CySI(1-).

The existence of the species CySBr(1-) and CySI(1-), which may be regarded as complexes between the thiyl radical from cysteine and bromide or iodide ions, is reported, and their properties discussed in relation to other sulphur- and halogen- containing species which also, have a three-electron half-order bond.The oxidation of cysteine by I2(1-)(.) is shown to be much more complex than hitherto reported, and pH-dependent equilibria involving iodine atoms, iodide ions, cysteine, and cysteinyl radicals are described.The first measured rate constant for the reaction of iodine (as I3(1-)) with a thiol is also reported.

Mechanism of oxidation of L-Cysteine by Tetraoxoiodate(VII) in aqueous acid medium

The kinetics and mechanism of the oxidation of L-cysteine by tetraoxoiodate(VII) ion in aqueous acid medium has been studied at 0.03 δ[H+] δ0.1 mol dm-3- under pseudo-first order conditions of an excess of tetraoxoiodate(VII) concentration at 1 = 0.11 mol dm-3- (NaClO4). The reaction obeys the rate expression:-d [IO4-]/dt = {k3K1K2 [H+] + k5} [RSH][IO4 -] Addition of AcO- and NO3 - had no effect on the reaction but the rate of reaction decreased with increase in ionic strength of the medium. Increase in dielectric constant decreased the rate of reaction. The rates are consistent with a mechanism which involves the formation of free radicals which subsequently dimerized into disulfides. The reaction has been rationalized on the basis of the inner-sphere electron transfer mechanism.

Hierarchical cystine flower based electrochemical genosensor for detection of Escherichia coli O157:H7

This work reports on a facile and reproducible approach to synthesize novel organic flowers of cystine (CysFls) with high uniformity. These 3D flower-like structures have a purely hierarchical arrangement, wherein each petal is composed of several cystine molecules with an average size of 50 μM, as determined by transmission electron microscopy. The CysFls were self-assembled onto a gold electrode and were utilized as matrices for the covalent immobilization of an Escherichia coli O157:H7 (E. coli) specific probe oligonucleotide that was identified from the 16s rRNA coding region of the E. coli genome. This fabricated CysFl platform sought to provide improved fundamental characteristics to electrode interface in terms of electro-active surface area and diffusion coefficient. Electrochemical impedance spectroscopy revealed that this genosensor exhibits a linear response to complementary DNA in the concentration range of 10-6 to 10-15 M with a detection limit of 1 × 10-15 M. Under optimal conditions, this genosensor was found to retain about 88% of its initial activity after being used for 6 times. This journal is the Partner Organisations 2014.

Electrocatalytic oxidation of cysteine on a nafion-ruthenium oxide pyrochlore chemically modified electrode

The electrocatalytic oxidation of cysteine (CySH) to cystine (CyS-SCy) was noticed on the Nafion-ruthenium oxide pyrochlore chemically modified electrode. The electrocatalytic oxidation was mediated by the RuVI/IV redox sites in the oxide pyrochlore network in terms of the Michaelis-Menten kinetics. The obtained heterogeneous catalytic rate constant (kc) and transfer coefficient (α) are 6.33 s-1 and 0.99, respectively.

Simple and facile preparation of silver-polydopamine (Ag-PDA) core-shell nanoparticles for selective electrochemical detection of cysteine

Selective and sensitive non-enzymatic electrochemical detection of cysteine (CySH) is achieved in the present work using a polydopamine capped silver nanoparticles (Ag-PDA) modified indium tin oxide (ITO) electrode. Efficient redox properties, synergistic effects and the specific steric hindrance associated with the Ag-PDA core-shell nanoparticles provide higher selectivity and larger sensitivity for CySH detection over other competitive bio-thiols namely, homo-cysteine and glutathione. A simple one-step method is used for the preparation of Ag-PDA core-shell nanoparticles. The structure, morphology and composition of Ag-PDA nanoparticles are characterized by using field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible (UV-vis) and Fourier transform infra red (FTIR) spectroscopic techniques. Electrochemical characteristics are investigated by using cyclic voltammetry (CV) and linear sweep voltammetry (LSV). These studies clearly reveal the formation of Ag-PDA nanocomposite on the ITO electrodes and their corresponding redox properties. Non-enzymatic electrochemical detection of CySH is carried out using Ag-PDA modified ITO electrodes in 0.1 M PBS (pH = 5.0) aqueous solution. Under the optimized conditions, this particular electrochemical biosensor exhibits a perfect linear calibration plot in the concentration range between 0.05 μM and 300 μM. Further, a sensitivity value of 0.023 μA μM-1 and a lower detection limit of 0.02 μM are determined for CySH detection. Moreover this Ag-PDA modified ITO electrode is applied further for the determination of CySH in human blood serum samples and the results are promising and satisfactory, suggesting the possible analytical application of this biosensor for the determination of CySH in biological samples.

Kinetic Studies on the Role of Dioxygen in the Cooper-Catalyzed Autoxidation of Cysteine

Kinetic studies on a role of dioxygen in the copper-catalyzed autoxidation of cysteine in glycylglycine-phosphate buffers have been carried out.The rate of autoxidation was obtained by measuring the consumption of cysteine.It has been revealed that cysteine is oxidized by a "sequential mechanism".The reaction pathway can be shown by Eqs. 1, 2, 3, and 4; cysteine is oxidized not only by copper(II) species, but also by copper(I)-O2 adducts: Cu(II)-L + CyS- = L-Cu(II)-CyS- (1) L-Cu(II)-CyS- -> Cu(I)-L + CySradical (2) Cu(I)-L + O2 = L-Cu(I)-O2 (3) L-Cu(I)-O2 + Cy S- + 2H+ -> Cu(II)-L + CySradical + H2O2 (4) Here, L represents ligands including cysteine.The oxidation step (4) catalyzed by the Cu(I)-O2 species was proposed to be rate-determining.

An unusual electrochemical oxidation of phenothiazine dye to phenothiazine-bi-1,4-quinone derivative (a donor-acceptor type molecular hybrid) on MWCNT surface and its cysteine electrocatalytic oxidation function

Phenothiazine (PTZ), a thiazine class heterocyclic compound, is a well-known electron donating system and has been widely used as a starting compound to prepare various phenothiazine dyes and pharmaceutically important compounds. Quinones and its derivatives are constituents of biologically active molecules serve as excellent electron-acceptor systems. Oxidation of PTZ by chemical and electrochemical methods often resulted into monohydroxylation of benzene ring moiety, S-oxidized and polymerized compounds as end products. Electrochemical oxidation of PTZ on a multiwalled carbon nanotube (MWCNT) modified glassy carbon electrode in pH 7 phosphate buffers solution (PBS) has been investigated in this work. A highly redox active surface confined PTZ-bi-1,4-quinone derivative (PTZ-biQ) on MWCNT modified glassy carbon electrode, designated as GCE/MWCNT@PTZ-biQ, as a product was unusually observed. The GCE/MWCNT@PTZ-biQ showed well-defined redox peaks at E1/2 = -0.07 and +0.29 V vs Ag/AgCl corresponding to surface confined electron-transfer behavior of the bi-quinone (acceptor) and PTZ-cationic radical species (donor) respectively. No such electrochemical characteristics were noticed when unmodified GCE was subjected to the electrochemical oxidation of PTZ. Existence of PTZ-biQ was confirmed by XRD, Raman spectroscopy, FT-IR and GC-MS (methanolic extract of the active layer) analyses. Position of biQ in PTZ-biQ as 1,4-quinone isomer was confirmed by observation of absence of copper-complexation with 1,4-quinone and H2O2 electrochemical reduction reactions at -0.1 V vs Ag/AgCl unlike to the specific copper-complexation and H2O2 reduction with 1,2-quinone isomer in pH 7. Cysteine (CySH) oxidation was studied as a model system to understand the electron-transfer function of the MWCNT@PTZ-biQ. A highly selective electrocatalytic oxidation and sensing by amperometric i-t and flow injection analysis of CySH at low oxidation potential, 0.3 V vs Ag/AgCl in pH 7 PBS with detection limit values (signal-to-noise ratio = 3) of 11.10 μM and 110 nM respectively, without any interference from other biochemicals like uric acid, dopamine, nitrite, citric acid and H2O2, unlike the conventional chemically modified electrodes with serious interference's, have been demonstrated.

Selective detection of cysteine/cystine using silver nanoparticles

The selective detection of cysteine and cystine amino acids over other standard amino acids was possible with the naked eye using silver nanoparticles (AgNPs) in a simple procedure at room temperature. The change in color and the aggregation of NPs were studied using UV-vis spectroscopy and transmission electron microscopy, respectively. It was observed that when the derivative and substructures of cysteine were employed as analytes the detection was possible only when there is free SH or S-S group present in the analytes. The method was extended to a dipeptide 'cys-gly' as a model peptide where the detection was successful due to the presence of SH moiety.

Cysteine oxidation reactions catalyzed by a mononuclear non-heme iron enzyme (OvoA) in ovothiol biosynthesis

OvoA in ovothiol biosynthesis is a mononuclear non-heme iron enzyme catalyzing the oxidative coupling between histidine and cysteine. It can also catalyze the oxidative coupling between hercynine and cysteine, yet with a different regio-selectivity. Due to the potential application of this reaction for industrial ergothioneine production, in this study, we systematically characterized OvoA by a combination of three different assays. Our studies revealed that OvoA can also catalyze the oxidation of cysteine to either cysteine sulfinic acid or cystine. Remarkably, these OvoA-catalyzed reactions can be systematically modulated by a slight modification of one of its substrates, histidine.

A cytotoxic tantalum(v) half-sandwich complex: A new challenge for metal-based anticancer agents

Despite the biological relevance of complexes of various transition metals, tantalum complexes have long been neglected by bioinorganic chemists. Herein, we demonstrate potential chemotherapeutic applicability of the [Ta(η5-Cp?)Cl2(salaph)] (1) complex, containing deprotonated Schiff base 2-{(E)-[(2-hydroxyphenyl)imino]methyl}phenol (H2salaph), which shows strong cytotoxicity in cancer cells, related to the induction of apoptosis and apoptosis-related processes, but shows low cytotoxicity in healthy cells.