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[en] Cysteines possess a unique property among the 20 naturally occurring amino acids: it can be present in proteins in either the reduced or oxidized form, and can regulate the activity of some proteins. Consequently, to augment our previous treatment of the other types of residues, the 13Cα and 13Cβ chemical shifts of 837 cysteines in disulfide-bonded cystine from a set of seven non-redundant proteins, determined by X-ray crystallography and NMR spectroscopy, were computed at the DFT level of theory. Our results indicate that the errors between observed and computed 13Cα chemical shifts of such oxidized cysteines can be attributed to several effects such as: (a) the quality of the NMR-determined models, as evaluated by the conformational-average (ca) rmsd value; (b) the existence of high B-factor or crystal-packing effects for the X-ray-determined structures; (c) the dynamics of the disulfide bonds in solution; and (d) the differences in the experimental conditions under which the observed 13Cα chemical shifts and the protein models were determined by either X-ray crystallography or NMR-spectroscopy. These quantum-chemical-based calculations indicate the existence of two, almost non-overlapped, basins for the oxidized and reduced -SH 13Cβ, but not for the 13Cα, chemical shifts, in good agreement with the observation of 375 13Cα and 337 13Cβ resonances from 132 proteins by Sharma and Rajarathnam (2000). Overall, our results indicate that explicit consideration of the disulfide bonds is a necessary condition for an accurate prediction of 13Cα and 13Cβ chemical shifts of cysteines in cystines.
[en] Microcystins (MCs) are hepato toxins with a potent inhibitor activity of protein phosphatases P P1 and PP2A. These non-ribosomal peptides are getting more and more attention due to their acute toxicity and potent tumor-promoting activity. These toxins are produced by freshwater cyanobacteria. we report a toxicological study conducted on aquatic animal models such as the medaka fish. to date, the detailed mechanisms underlying the toxicity of microcystins are unknown. MC-leucine-arginine (MC-LR) is the most toxic and the most commonly encountered variant of MCs in aquatic environment. it has been used for toxicological investigations on the liver of intoxicated medeka. We performed differential proteome analyses of MC-LR - treated and untreated medaka fish in order to investigate the mechanisms of establishment of early responses to the toxin. The identification of proteins involved in these early responses might constitute candidates as bio markers of MC-LR exposure. Cytosolic proteins from livers of exposed or non-exposed medaka were resolved by 2D electrophoresis and detected using stains specific for phosphoproteins and for whole proteinaceous content. Overall, phosphoproteomic 2D maps. Of these 15 proteins, only two could not be identified by mass spectrometry. Among the other identified proteins, phenylalanine hydroxylase and keratin 18 (type I) showed variations in phosphoryl content in agreement with inhibition of PP2A activity after exposure of the fish to MC-LR. The other identified proteins exhibited variations in their expression level. The identified proteins appear to be involved in cytoskeleton assembly, cell signalling, oxidative w tress and apoptosis. The functional implications of responses to MC-LR exposure of these proteins are discussed. The methodology described in this report should be widely generalizable to a number of tissues and organisms, thus helping in the search for bio markers of MC-LR contamination
[en] The ph of the water associated with toxic blooms of cyanobacteria is typically in the alkaline range; however, previously only microcystin-degrading bacteria growing in neutral ph conditions have been isolated. Therefore, we sought to isolate and characterize an alkali-tolerant microcystin-degrading bacterium from a water bloom using microcystin-LR. Analysis of the 16 S rRNA gene sequence revealed that the isolated bacterium belonged to the genus Sphingopyxis, and the strain was named C-1. Sphingopyxis sp. C-1 can grow; at ph 11.0; however, the optimum ph for growth was ph 7.0. The microcystin degradation activity of the bacterium was the greatest between ph 6.52 and ph 8.45 but was also detected at ph 10.0. The m/rA homolog encoding the microcystin-degrading enzyme in the C-1 strain was conserved. We concluded that alkali-tolerant microcystin-degrading bacterium played a key role in triggering the rapid degradation of microcystin, leading to the disappearance of toxic water blooms in aquatic environments.
[en] The disulphide chromophore of the amino acid L-cystine absorbs radiation at 250 nm. The optical reflectance spectrum of crystalline L-cystine following irradiation with UVC at 254 nm shown in the figure exhibits two absorption bands near 600 and 420 nm. The figure also shows that a similar spectrum is obtained following UVC irradiation of dry Merino wool keratin, which contains high concentrations (35 mol% half cystine) of cystine residues near the fibre surface. In previous work on gamma-irradiated single crystals of L-cystine dihydrochloride, Akasaka observed two absorption peaks in the optical spectrum at 550 and 400 nm. He found that the primary radiolytic event is removal of an electron from cystine to give the radical cation (the 550 nm absorber), followed by capture of the electron by another disulphide group to give the radical anion (the 400 nm absorber). The similarity of the positions of the absorption bands suggest that the same process occurs when L-cystine is exposed to UVC. It is interesting that cystine appears to undergo a similar ionisation process when exposed to radiation over a wide range of wavelengths which includes UVC, X- and gamma-rays. The radioprotective ability of disulphides and thiols against ionising radiation in biological systems is well known, and it appears that protection against UVC occurs via a similar mechanism
[en] Cystinosis and cystinuria, both recessive genetic disorders, are fundamentally different in their pathophysiologic mechanisms. Cystinosis is a disease of cystine storage in which the kidney is the initial, but not the sole target organ. Cystinuria is a disease of renal tubular cystine transport in which excessive loss of this insoluble amino acid causes precipitation at physiologic urine pH and concentration. The former disorder uniformly results in the need for renal allograft despite recent advances in medical therapy. Cystinuria has a variable severity of expression and may be amenable to long-term medical treatment in some patients. Others may have frequent stone recurrence and infection and progress to chronic renal failure in long term. It is purpose of this review to provide the reader with an understanding of the respective diseases and the reasons for the differences in their prognoses and long-term outcomes. (author)
[en] Multiple shapes of nano- and micro-structured cystine aggregates, including spheres, rods, spindles, dendrites, and multipods, were easily synthesized just by adjusting the concentrations and pH values of L-Cysteine solutions under ultrasonic irritation. Importantly, highly monodispersed nanospheres of cystine aggregates 225 nm in diameter without any other shapes were easily obtained for the system of 0.1 M L-Cysteine with pH 8. This will provide a very simple and effective approach to produce monodispersed cystine microspheres, which could promote new possibilities for future applications in biosensor, drug delivery, medicine, and the production of nanomaterials
[en] Since Pasteur discovered in 1848 that biological molecules possess a rotatory power, the origin of the chiral purity in living organisms has been a constant preoccupation in biology, but the problem is not solved yet. In particular, the appeal to weak interactions, a fundamental physical process which is known to violate parity, has not permitted so far to establish any firm relation between parity nonconservation and the complete dissymmetry between mirror image biological molecules. The main difficulty resides in the weakness of the physical forces, and can be overcome only when some amplification process can be proved to be at work. Recently such a mechanism was proposed, which does not seem to ask for any ad hoc new concept: due to the attractive character of the parity violating force in electro-weak interactions, a phase transition leading eventually to enantiometric purity is predicted. Phase transitions at low temperature have already been detected in biological materials, but no signature concerning the parity aspect was obtained. We undertook this year in Lyon a series of experiments to measure the rotatory power of solutions containing organic dissymmetric molecules, in order to observe if it varies with temperature. Our first measures involved cystine, which possesses a high rotatory power. No variation of this quantity was observed down to .6K. Lower temperatures will be attained in a next step. (author). 4 refs