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81.
[reaction: see text] Cycloartenol synthase cyclizes and rearranges oxidosqualene to the protosteryl cation and then specifically deprotonates from C-19. To identify mutants that deprotonate differently, randomly generated mutant cycloartenol synthases were selected in a yeast lanosterol synthase mutant. A novel His477Asn mutant was uncovered that produces 88% lanosterol and 12% parkeol. The His477Gln mutant produces 73% parkeol, 22% lanosterol, and 5% Delta(7)-lanosterol. These are the most accurate lanosterol synthase and parkeol synthase that have been generated by mutagenesis. 相似文献
82.
Yuko Ogata Pamela M. Quizon Nancy S. Nightlinger Pongkwan Sitasuwan Casey Snodgrass L. Andrew Lee Jeffrey D. Meyer Richard S. Rogers 《Rapid communications in mass spectrometry : RCM》2022,36(3):e9222
Rationale
The multi-attribute method (MAM) has become a valuable mass spectrometry (MS)-based tool that can identify and quantify the site-specific product attributes and purity information for biotherapeutics such as monoclonal antibodies (mAbs) and fusion molecules in recent years. As we expand the use of the MAM at various stages of drug development, it is critical to enhance the sample preparation throughput without additional chemical modifications and variability.Methods
In this study, a fully automated MAM sample preparation protocol is presented, where rapid desalting in less than 15 minutes is achieved using miniaturized size-exclusion chromatography columns in pipette tips on an automated liquid handler. The peptide samples were analyzed using an electrospray ionization (ESI) orbitrap mass spectrometer coupled to an ultra-high-performance liquid chromatography (UHPLC) system with a dual column switching system.Results
No significant change was observed in product attributes and their quantities compared with manual, low-artifact sample preparation. The sample recovery using the buffer exchange tips was greatly enhanced over the manual spin cartridges while still demonstrating excellent reproducibility for a wide variety of starting sample concentrations. Unlike a plate desalting system, the individual columns provide flexibility in the number of samples prepared at a time and sample locations within plates.Conclusions
This automated protocol enables the preparation of up to 96 samples with less “at-bench” time than the manual preparation of a smaller batch of samples, thereby greatly facilitating support of process development and the use of the MAM in quality control.83.
Bis(peroxo)vanadium(V) complexes are widely investigated as anticancer agents. They exert their antitumor and cyctotoxic effects through inhibition of tyrosine phosphatases and DNA cleavage, respectively. The latter process remains poorly understood. The mechanism of DNA cleavage by NH(4)[(phen)V(O)(eta(2)-O(2))(2)] (phen = 1,10-phenanthroline) was investigated. Kinetic studies on DNA cleavage revealed that the complex is a single-strand nicking agent with no specificity. EPR experiments using 2,2,6,6-tetramethyl-4-piperidone (TMP) and 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO) as spin-traps for singlet oxygen and hydroxyl radical, respectively, implicated hydroxyl radical production upon photodecomposition of bis(peroxo)vanadium(V). This was corroborated by benzoate inhibition of DNA strand scission and stoichiometric oxidation of 2-propanol to acetone upon irradiation of bis(peroxo)vanadium(V) phenanthroline. High-resolution polyacrylamide gel analysis of the vanadium cleavage reaction and [Fe(II)EDTA](2)(-)/H(2)O(2) resulted in comigration of "ladder" pattern bands, which superimposed when both reactions were run on the same lane. These findings identify hydroxyl radical produced from the photooxidation of the peroxo ligand on vanadium as the active species in DNA cleavage. 相似文献
84.
Liliana Cseh Carol Csunderlik Ingo Pantenburg Gerd Meyer Otilia Costisor 《无机化学与普通化学杂志》2003,629(6):985-988
The complex Co(C14H13NO)2Cl2 with the protonated N‐salicylidene‐p‐toluidine ligand was synthesized from an ethanolic solution of CoCl2·6H2O and N‐salicylidene‐p‐toluidine. The crystal structure was determined from X‐ray single crystal data (monoclinic, space group Cc, a = 1496.2(3) pm, b = 1257.4(4) pm, c = 1544.6(3) pm, β = 115.01(1)°, Z = 4). Co2+ adopts a distorted tetrahedral geometry. The UV‐Vis and IR spectra of the complex are discussed. 相似文献
85.
Contributions to the Investigation of Inorganic Non-stoichiometric Compounds. XIV. Oxidation Products of Orthorhombic Nb12O29, Electron Optical Investigation An electron optical investigation shows that the orthorhombic starting material Nb12O29(BII) is well ordered. The oxidation products Nb2O5(Ox1BII) and Nb2O5(Ox2BII) are different from each other in structures as well as in their reactions. Nb2O5(Ox1BII) is unstable in the electron beam and differs from BII by characteristic point-defects. The radiation load can lead to the reduction to BII or to a transition into a defect structure with R-type-tunnels. The not well ordered structure of Nb2O5(Ox2BII) is stable in the electron beam. Characteristic is the sequence of [2×5] and [3×4] blocks, the latter in two different orientations. The observed composition O/Nb = 2.500 can be described by the present structural modell assuming vacant niobium tetrahedral sites. The large structural differences between the oxidation products of the orthorhombic and the monoclinic Nb12O29 are remarkable. 相似文献
86.
S. Meyer und O. G Koch 《Fresenius' Journal of Analytical Chemistry》1961,179(3):175-186
Zusammenfassung Es wird eine Arbeitsvorschrift zur photometrischen Bestimmung kleiner Mengen Antimon mit Methylfluoron beschrieben. Die günstigsten Arbeitsbedingungen und die Störung durch Fremdionen werden untersucht. Das Extinktionsmaximum liegt bei 530 nm. Die photometrische Bestimmung wird bei 495 nm durchgeführt. Das Beersche Gesetz ist im Bereich von 0,2– 4 g Sb/ml erfüllt, die Bestimmungsgrenze liegt bei 0,21 g Sb/ml · cm. Der Zeitbedarf einer Einzelbestimmung beträgt 15–20 min.Für die sorgfältige Durchführung der zahlreichen Versuche sprechen wir Herrn H. Siffrin unseren Dank aus. 相似文献
87.
Terrence G. Vargo Daniel J. Hook Joseph A. Gardella Mary A. Eberhardt Anne E. Meyer Robert E. Baier 《Journal of polymer science. Part A, Polymer chemistry》1991,29(4):535-545
Recent work in our laboratories has fully characterized the surface region of a segmented poly(ether-urethane) (PEU) extending from the air/polymer interfacial region through bulk depths in the micron range. This characterization utilized energy and angle dependent Electron Spectroscopy for Chemical Analysis (ESCA), Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR–FTIR), and Comprehensive Wettability Profiling (contact angle using a homologous series of liquids) as defined by Zisman. In this study this same multi-analytical-technique approach is used to elucidate changes in these PEU surfaces induced through an H2O Radio Frequency Glow Discharge (RFGD) plasma. This investigation reports both qualitative and quantitative changes due to the modification treatments as well as the permanency of the changes effected on these surfaces through the plasma treatment. From our analyses, the amount of surface residing polyurethane (hard segment) is observed to increase due to a proposed plasma etching mechanism. Further, the addition of oxygen containing functionality is detected at the modified surfaces unique with respect to the unmodified PEU. These surface modifications which show large increases in wettability, are finally observed to be semi-permanent over a time period of 6 months. 相似文献
88.
NMR spectroscopy techniques for screening and identifying ligand binding to protein receptors 总被引:9,自引:0,他引:9
Binding events of ligands to receptors are the key for an understanding of biological processes. Gaining insight into protein-protein and protein-ligand interactions in solution has recently become possible on an atomic level by new NMR spectroscopic techniques. These experiments identify binding events either by looking at the resonance signals of the ligand or the protein. Ideally, both techniques together deliver a complete picture of ligand binding to a receptor. The approaches discussed in this review allow screening of compound libraries as well as a detailed identification of the groups involved in the binding events. Also, characterization of the binding strength and kinetics is possible, competitive binding as well as allosteric effects can be identified, and it has even been possible to identify ligand binding to intact viruses and membrane-bound proteins. 相似文献
89.
Amatzya Y. Meyer 《Theoretical chemistry accounts》1971,22(3):271-282
Two methods are proposed for dealing with a three-membered ring which is incorporated into a large molecule. The first, an all-valence electron approach, is an iterative CNDO/2 which provides, through bond indices, self-consistent hybridizations and valency angles. The second is compatible with -electron approaches and aims at the study of conjugation and transmission of conjugation. The methods are illustrated by application to the unsubstituted cyclopropane molecule.
For Part V, see Ref. [1]. 相似文献
Zusammenfassung Es werden zwei Methoden zur Behandlung von Molekülen, die einen Dreiring enthalten, vorgeschlagen. Die eine besteht in der iterativen Anwendung des CNDO/2-Verfahrens mit selbst-konsistenten Hybridisierungen und Valenzwinkeln. Die zweite entspricht etwa einem -Elektronenverfahren und dient besonders dem Studium von Konjugationseffekten. Illustriert werden beide am Beispiel des einfachen Cyclopropan.
Résumé On propose deux méthodes pour étudier les molécules contenant une composante cyclopropanique. La première, qui tient compte de tous les électrons de valence, est une CNDO/2 itérative qui fournit — par l'intermédiaire des indices carrés de liaison — des valeurs auto-cohérentes pour l'hybridation et les angles de valence. L'autre, compatible avec les techniques -électroniques, a pour but l'étude de la conjugaison et de la transmission de conjugaison. Les méthodes sont illustrées par application au cyclopropane non-substitué.
For Part V, see Ref. [1]. 相似文献
90.
Single crystals of Sm4OCl6 and KSm2Cl5 have been obtained by metallothermic reductions of SmCl3 with lithium (in the presence of Sm2O3 or SmOCl) and potassium, respectively, at elevated temperatures in sealed tantalum containers. Sm4OCl6 (hexagonal, P63mc, Z = 2, a = 946.59(4), c = 717.88(4) pm) and KSm2Cl5 (monoclinic, P21/c, Z = 4, a = 888.06(6), b = 784.81(5), c = 1262.77(8) pm, ß = 90.085(6)°) are true divalent samarium compounds, Sm4OCl6 with remarkably short Sm2+–O2? distances (236.0, 237.6 (3x) pm) within the [Sm4O] tetrahedron. 相似文献