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101.
Wenqin Ni Melanie Lin Paul Salinas Philip Savickas Shiaw-Lin Wu Barry L. Karger 《Journal of the American Society for Mass Spectrometry》2013,24(1):125-133
Cystine knots or nested disulfides are structurally difficult to characterize, despite current technological advances in peptide mapping with high-resolution liquid chromatography coupled with mass spectrometry (LC-MS). In the case of recombinant human arylsulfatase A (rhASA), there is one cystine knot at the C-terminal, a pair of nested disulfides at the middle, and two out of three unpaired cysteines in the N-terminal region. The statuses of these cysteines are critical structure attributes for rhASA function and stability that requires precise examination. We used a unique approach to determine the status and linkage of each cysteine in rhASA, which was comprised of multi-enzyme digestion strategies (from Lys-C, trypsin, Asp-N, pepsin, and PNGase F) and multi-fragmentation methods in mass spectrometry using electron transfer dissociation (ETD), collision induced dissociation (CID), and CID with MS3 (after ETD). In addition to generating desired lengths of enzymatic peptides for effective fragmentation, the digestion pH was optimized to minimize the disulfide scrambling. The disulfide linkages, including the cystine knot and a pair of nested cysteines, unpaired cysteines, and the post-translational modification of a cysteine to formylglycine, were all determined. In the assignment, the disulfide linkages were Cys138–Cys154, Cys143–Cys150, Cys282–Cys396, Cys470–Cys482, Cys471–Cys484, and Cys475–Cys481. For the unpaired cysteines, Cys20 and Cys276 were free cysteines, and Cys51 was largely converted to formylglycine (>70 %). A successful methodology has been developed, which can be routinely used to determine these difficult-to-resolve disulfide linkages, ensuring drug function and stability. 相似文献
102.
Cecilia Saiz Valerie Castillo Pablo Fontán Mariana Bonilla Gustavo Salinas Alejandra Rodríguez-Haralambides S. Graciela Mahler 《Molecular diversity》2014,18(1):1-12
In this study, we report a strategy using dynamic combinatorial chemistry for targeting the thioredoxin (Trx)-reductase catalytic site on Trx glutathione reductase (TGR), a pyridine nucleotide thiol-disulfide oxido-reductase. We chose Echinococcus granulosus TGR since it is a bottleneck enzyme of platyhelminth parasites and a validated pharmacological target. A dynamic combinatorial library (DCL) was constructed based on thiol-disulfide reversible exchange. We demonstrate the use of 5-thio-2-nitrobenzoic acid (TNB) as a non-covalent anchor fragment in a DCL templated by E. granulosus TGR. The heterodimer of TNB and bisthiazolidine (2af) was identified, upon library analysis by HPLC (IC $_{50}$ = 24 $\upmu $ M). Furthermore, 14 analogs were synthetically prepared and evaluated against TGR. This allowed the study of a structure–activity relationship and the identification of a disulfide TNB-tricyclic bisthiazolidine (2aj) as the best enzyme inhibitor in these series, with an IC $_{50}$ = 14 $\upmu $ M. Thus, our results validate the use of DCL for targeting thiol-disulfide oxido-reductases. 相似文献
103.
Lenart VM Gómez SL Bechtold IH Figueiredo Neto AM Salinas SR 《The European physical journal. E, Soft matter》2012,35(1):4
We use Z-scan technique to investigate the nonlinear optical response of the thermotropic liquid crystal E7 in the neighborhood of
the nematic-isotropic phase transition. The analysis of the data for the nonlinear optical birefringence is compatible with
an effective critical exponent of the order parameter, β = 0.28 ± 0.03, which is close to the classical value, β = 0.25 , for a tricritical point. The nonlinear optical absorption in the nematic range depends on the geometrical configuration
of the nematic director with respect to the polarization beam, and vanishes in the isotropic phase. 相似文献
104.
105.
106.
A compressible pseudo-spin Ising model hamiltonian is used to calculate the pressure-temperature phase diagram of quasi-one-dimensional hydrogen-bonded ferroelectric crystals such as CsD2PO4. We assume strong effective interactions, which are treated exactly, along chains, and weak volume dependent interactions, which are treated in the mean field approximation, between chains. In agreement with the experimental findings, the phase diagram exhibits a triple point and transition lines between ferroelectric, antiferroelectric, and paraelectric phases. However, the results suggest that the Ising model may be too simple to account for the detailed form of the phase diagram of CsD2PO4. 相似文献
107.
Summary
Determination of Magnesium by Spectrofluorimetry and Synchronous Scanning First and Second Derivative Spectrofluorimetry with 2-Quinizarinsulpbonate
An analytical method has been developed for the fluorimetric determination of microgram amounts of magnesium in solution. The method is based on the reaction of magnesium with 2-quinizarinsulphonate. Synchronous scanned first and second derivative fluorimetry has been employed to increase the sensitivity of the method. The influence of reaction variables as well as instrumental parameters and the composition of the complex is discussed. The interference of various foreign cations and anions has also been examined and in some cases eliminated or reduced by addition of cyanide. 相似文献
108.
109.
Munshi G Mustafa Sudhir Raniwala T Awes B Rai RS Bhalerao JG Contreras RV Gavai SK Ghosh P Jaikumar GC Mishra AP Mishra H Mishra B Mohanty J Nayak J-Y Ollitrault SC Phatak L Ramello R Ray PK Sahu AM Srivastava DK Srivastava VK Tiwari 《Pramana》2006,67(5):961-981
This is the report of Heavy Ion Physics and Quark-Gluon Plasma at WHEPP-09 which was part of Working Group-4. Discussion and
work on some aspects of quark-gluon plasma believed to have created in heavy-ion collisions and in early Universe are reported. 相似文献
110.
Biomimetic Apatite Deposition on Calcium Silicate Gel Glasses 总被引:5,自引:0,他引:5
A. J. Salinas M. Vallet-Regi I. Izquierdo-Barba 《Journal of Sol-Gel Science and Technology》2001,21(1-2):13-25
In order to understand the Biomimetic apatite formation mechanism on gel glasses, a glass (in mol-%) SiO2 80%—CaO 20% (80S20C) was prepared by the sol-gel method and its behaviour in a simulated body fluid (SBF) was studied. To study the role of phosphorous in the in vitro apatite formation, a gel glass (in mol-%) SiO2 80%—CaO 17%—P2O5 3% (80S17C3P) was prepared comparing its behaviour in SBF with that of 80S20C. In both studies, a protocol without renovation of SBF (static) was used. To mimic the conditions in the living organisms, an in vitro protocol with continuous renovation of solution (dynamic) was proposed. To check the feasibility of dynamic protocol, 80S20C and 80S17C3P were studied in dynamic and results compared with obtained in static. Static studies of 80S20C allowed us to verify that phosphorus is not essential for bioactivity because the apatite-like layer was formed from the phosphorous in SBF. However, a 3 mol-% of P2O5 in 80S17C3P gel glass favoured apatite crystallization. In dynamic, complete assays were performed with ionic concentrations and pH in solution almost equal to human plasma. After 7 days in dynamic, apatite crystals and crystalline aggregates were larger than in static. Besides, compositional variations were observed in the newly formed layer as a function of the protocol. In static, the layer formed in both glasses contained calcium and phosphorous, (Ca/P molar ratio = 1.6) and silicon. In dynamic, the layer did not contain silicon and the Ca/P molar ratio was 1.2. Differences in composition and pH of assay solution, 8 in static and 7.3 in dynamic could explain these variations. In static, an apatite close to stoichiometric could be formed. In dynamic, a mixture of calcium deficient apatite and other calcium phosphates could constitute the layer. 相似文献