Z-Cystine

Z-Cystine has been obtained by the hydrolysis of a large number of proteins. However, the keratins are the only common proteins rich enough in cystine to serve as a source for this amino acid. Many investigators have devised methods for its isolation from the hydrolytic products of human hair,3 wool,2 horn,3 nail,3 feathers,3 and horse hair.4 The method of Folin5 is the basis for most of the others. The present method does not claim to give as high a yield as some of those reported in the literature, but is convenient and gives consistent results. 

Assay Medium. Herrell el al. (16) recommend the use of fluid thioglycol-ate broth with the following composition yeast extract 5 g., Bacto-casitone 15 g., glucose 5 g., sodium chloride 2.5 g., Z-cystine 0.75 g., thioglycollic acid 0.3 ml., agar 0.75 g., resazurin (certified) 0.001 g., and distilled water 1 liter the final pH of this medium should be 7.1. 

J. Csapo, Z. Csapo Kiss, T.G. Martin, S. Folestad, O. Orwar, A. Tivesten, S. Nemethy, Age Estimation of Old Carpets Based on Cystine and Cy steic Acid Content Analytica Chimica Acta, 300,313 320(1995). 

Hu Z, Guan W, Wang W, Huang L, Xing H, Zhu Z (2007b) Protective effect of a novel cystine Cm derivative on hydrogen peroxide-induced apoptosis in rat pheochromocytoma PC12 cells. Chem. Biol. Interact. 167 135-144. 

Hu Z, Guan WC, Tang XY, Huang LZ, Xu H (2007) Synthesis of water-soluble cystine C derivative with catalyst and its active oxygen radical scavenging ability. Chin. Chem. Lett. 18 51-54. 

M. Tomi, T. Funaki, H. Abukawa, K. Katayama, T. Kondo, S. Ohtsuki, M. Ueda, M. Obinata, T. Terasaki, and K. Hosoya. Expression and regulation of L-cystine transporter, system Z(T, in the newly developed rat retinal Muller cell line (TR-MUL). Glia 43 208-217 (2003). 

Nur wenigc davon kdnncn im intaktcn Protein quantitativ erfaBt wer-den. So z.B, Tyiosin nnd Tiyptoplian durch Messung der Ultraviolett-Absorption, Trj ptophan durch spezifische koloriinetrische Methoden, Cystin und Cystein durch Titration oder durch photometrischc Methoden (siehc z.B. Block (9), Light und Smith 69)). 

A further approach for the synthesis of nonsymmetrically protected lanthionines is the conversion of thiosulfinates of symmetrically protected cystine derivatives into nonsymmetrically protected cystines via a reaction with a cysteine derivative and subsequently the conversion of the resulting unsymmetrically protected cystine into the nonsymmetrically protected lanthionines with a tris(dialkylamino)phosphineJ26l The oxidation of the symmetrically protected cystine, e.g. A,AT-bis(benzyloxycarbonyl)-L-cystine diethyl ester, of one stereochemical configuration to the thiosulfinate with m-chloroperoxybenzoic acid is essentially quantitative. The nonsymmetrical cystine is then formed in a subsequent step by the addition of the /V-/er/-butoxycarbonyl-L-cysteine tert-butyl ester derivative to give N-Z-N -Boc-L-cystine ethyl ferf-butyl diester. The desired 2f ,6f -lanthionine is then formed in the presence of P(NEt2)3 in yields of >50%. 

To a soln of /V-Z-TV -Boc-L-cystine tert-butyl ethyl diester (0.96 g, 1.74 mmol) in benzene (25 mL) was added P(NEt2)3 (0.47 g, 1.91 mmol) dropwise, with stirring under N2. After stirring at rt for 5h, the solvent was removed under reduced pressure and the oily residue purified by MPLC (hexane) to yield the title compound yield 0.47 g (52%) [a]D25 +2.3 (c 7.9, CHC13). 

The synthesis of four out of eight possible stereoisomers of 3-methyllanthionine [(25,35,67 ), (25,37 ,67 ), (25,35,65), (25,37 ,65)] has been achieved using the reaction of Z-protected 3-methyl-D-cysteine with d- or L-3-chloroalanine in yields of 35—53% J64 The methyl-D-cys-teine stereoisomers were obtained by two routes. Firstly from (25,35)-threonine via O-tosylation and subsequent inversion of configuration by nucleophilic attack with thiobenzoic acid. The resulting derivative was debenzoylated and oxidized to the respective cystine derivative prior to the reduction with Zn/HCl to give the eryt/u-o-3-methyl-D-cysteine... 

Ye Z. C., Rothstein J. D., and Sontheimer H. (1999). Compromised glutamate transport in human glioma cells reduction-mislocalization of sodium-dependent glutamate transporters and enhanced activity of cystine-glutamate exchange. J. Neurosci. 19 10767-10777. 

Kunert, J. and Stransky, Z. (1988). Thiosulfate production from cystine by the keratinolytic prokaryote Streptomyces fradiae. Arch. Microbiol. 150,600-601. 

In Eq. (10), E nt s(u) and Es(in) are the s=x,y,z components of the internal electric field and the field in the dielectric, respectively, and p u is the Boltzmann density matrix for the set of initial states m. The parameter tmn is a measure of the line-width. While small molecules, N<pure solid show well-defined lattice-vibrational spectra, arising from intermolecular vibrations in the crystal, overlap among the vastly larger number of normal modes for large, polymeric systems, produces broad bands, even in the crystalline state. When the polymeric molecule experiences the molecular interactions operative in aqueous solution, a second feature further broadens the vibrational bands, since the line-width parameters, xmn, Eq. (10), reflect the increased molecular collisional effects in solution, as compared to those in the solid. These general considerations are borne out by experiment. The low-frequency Raman spectrum of the amino acid cystine (94) shows a line at 8.7 cm- -, in the crystalline solid, with a half-width of several cm-- -. In contrast, a careful study of the low frequency Raman spectra of lysozyme (92) shows a broad band (half-width 10 cm- -) at 25 cm- -,... 

E. J. Mulders, Volatile components from the non-enzymic browning reaction of the cys-teine/cystine-ribose system, Z. Lebensm. Unters. Forsch, 1973, 152, 193-201. 

Fig. 44. Principle of sandwich complex formation of a cystin-bridged bicyclic peptide with a cation, Z.

Chemically, keratin is formed from polypeptide chains formed from 20 different amino acids. The relative proportion of which vary for different keratins. Some possess an acid side group (12 Z of which are glutamic acid) others a amine function (30 Z of which are lysine), others a hydroxyl (10 Z of which are serine). But the keratin is above all characterized by an important quantity of sulfur due to the presence of cystine units which form a disulfide bridge between two chains greatly contributing to the stability of the proteins. In conclusion, the chains are connected by a nuid>er of diverse interactions including hydrogen bonds, salt bonds and covalent bonds. 

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