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91.
Collision-induced reporter fragmentations of the currently most important covalent peptide modifications as detected by tandem
mass spectrometry are summarized. These fragmentations comprise the formation of reporter ions, which are preferentially immonium
ions, immonium ion-derived fragments or side chain fragments. In addition, the reporter neutral loss reactions for covalently
modified amino acid residues are summarized. For each individual covalent modification which can be recognized by a reporter
fragmentation, the accurate mass shift and the gross formula shift of the modified amino acid residue are given. The same
set of data is provided for the reporter fragmentations. Finally, an extensive accurate mass and gross formula list is presented
as supplementary material, describing mostly regular and modified y1 and dipeptide a and b ions, which are helpful for identification of the peptide ends of covalently modified peptides.
Figure When modified peptides are fragmented by collision-induced dissociation in a tandem mass spectrometer, the modification is
either lost as part of a charged fragment, so that a reporter ion for the modification is generated or it is lost as part of a neutral fragment, so that a modification-specific reporter neutral loss is observed in the fragment ion spectrum.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.
Chien-Wen Hung and Andreas Schlosser contributed equally to this work. 相似文献
92.
93.
Wang Q Deredas D Huynh C Schlosser M 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(2):570-574
The key step in the trans-selective modification of the Wittig reaction is the alpha-lithiation of the lithium bromide coordinated ylide-aldehyde adduct (the so-called "P-betaine"). Only phenyllithium effects this deprotonation rapidly and cleanly. Alkyllithiums (in particular, butyl-, sec-butyl-, and tert-butyllithium) react only sluggishly and incompletely, being tied up in very stable mixed aggregates with the lithium alkoxide part of the betaines. 相似文献
94.
Using 13C-chemical shifts as a probe for the electronic environment of carbon centers, triphenylphosphoniomethanide, the model case of a “reactive” phosphorus ylid, was found to have much more zwitterion than PC double bond character (resonance structure 1a being dominant). Triphenylphosphonio-propenide (“triphenylphosphonium-allylid”), a “moderated” ylid, accumulates electron excess mainly at the α-carbon atom (resonance structure 6a being dominant) whereas triphenylphosphonio-ethenoate (formyl-methylene-triphenylphosphorane) and other “stabilized” ylids carry roughly equal fractions of negative charge at the α-carbon and the oxygen atom (resonance formulas a and b being of comparable importance). The one-bond C,H coupling constant of triphenylphosphonio-methanide ( 1 ) argues against a perfectly planar ylid center. The three-bond P,C coupling constants permit the assignment of endo- or exo-configurations to ylids having an allyl-type side-chain. 相似文献
95.
The New Mixed Valent Chalcogenoindates MIn7X9 (M = Rb, Cs; X = S, Se): Structural Chemistry, X‐Ray and HRTEM Investigations Systematic X‐ray and HRTEM investigations on the ternary systems alkali metal (or thallium)–indium–chalcogen proved the existence of mixed valent solids with the simultaneous occurrence of indium species in different states of oxidation. Additionally to the earlier described solids MIn5S7 (M: Na, K, Tl: isotypic to InIn5S7 = In6S7 and TlIn5S7) and KIn5S6 (isotyp to TlIn5S6) in the actual work we present with MIn7X9 (M: Rb, Cs; X: S, Se) a new structure type which also contains indium in the states of oxidation +3 and +2. The formal state of oxidation In2+ corresponds to (In2)4+ ions. A reasonable ionic formulation of these structures is given by: MIn5S7 = M+ 3[In3+] [(In2)4+] 7[S2–] (M = Na, K, Tl), MIn5S6 = M+ [In3+] 2[(In2)4+] 6[S2–] (M = K, Tl), MIn7X9 = M+ 3[In3+] 2[(In2)4+] 9[S2–]. The three structure types show common two dimensional structure elements which contain ethane analogous In2X6 units and cis and trans edge sharing double octahedron chains. The main interest of this work is a crystalchemical discussion taking into account the new compounds MIn7X9 and the results of special HRTEM investigations on MIn7X9. The HRTEM investigations aim on the identification and subsequent preparation of new phases which initially might be visible as nano size crystals or inclusions in the HRTEM only. 相似文献
96.
Nelson Libardi Junior Regina Maria Miranda Gern Sandra Aparecida Furlan Dietmar Schlosser 《Applied biochemistry and biotechnology》2012,167(5):1144-1156
This work aimed to study the production of laccase from Pleurotus ostreatus DSM 1833 and Phoma sp. UHH 5-1-03 using banana peels as alternative carbon source, the subsequent partial purification and characterization of the enzyme, as well the applicability to degrade endocrine disruptors. The laccase stability with pH and temperature, the optimum pH, the K m and V max parameters, and the molar mass were determined. Tests were conducted for assessing the ability of degradation of the endocrine disruptors t-nonylphenol, bisphenol A, and 17??-ethinylestradiol. Laccase production of 752 and 1,117?U?L?1 was obtained for Phoma sp. and P. ostreatus, respectively. Phoma sp. laccase showed higher stability with temperature and pH. The laccase from both species showed higher affinity by syringaldazine. The culture broth with banana peels induced the production of two isoforms of P. ostreatus (58.7 and 21?kDa) and one of Phoma sp. laccase (72?kDa). In the first day of incubation, the concentrations of bisphenol A and 17??-ethinylestradiol were reduced to values close to zero and after 3?days the concentration of t-nonylphenol was reduced in 90% by the P. ostreatus laccase, but there was no reduction in its concentration by the Phoma sp. laccase. 相似文献
97.
Pisamai Kittipoom Gitta Kutyniok Wang-Q Lim 《Journal of Fourier Analysis and Applications》2011,17(4):604-639
Recently, shearlet systems were introduced as a means to derive efficient encoding methodologies for anisotropic features in 2-dimensional data with a unified treatment of the continuum and digital setting. However, only very few construction strategies for discrete shearlet systems are known so far. 相似文献
98.
Robert Calderbank Peter G. Casazza Andreas Heinecke Gitta Kutyniok Ali Pezeshki 《Advances in Computational Mathematics》2011,35(1):1-31
Fusion frame theory is an emerging mathematical theory that provides a natural framework for performing hierarchical data processing. A fusion frame can be regarded as a frame-like collection of subspaces in a Hilbert space, and thereby generalizes the concept of a frame for signal representation. However, when the signal and/or subspace dimensions are large, the decomposition of the signal into its fusion frame measurements through subspace projections typically requires a large number of additions and multiplications, and this makes the decomposition intractable in applications with limited computing budget. To address this problem, in this paper, we introduce the notion of a sparse fusion frame, that is, a fusion frame whose subspaces are generated by orthonormal basis vectors that are sparse in a ‘uniform basis’ over all subspaces, thereby enabling low-complexity fusion frame decompositions. We study the existence and construction of sparse fusion frames, but our focus is on developing simple algorithmic constructions that can easily be adopted in practice to produce sparse fusion frames with desired (given) operators. By a desired (or given) operator we simply mean one that has a desired (or given) set of eigenvalues for the fusion frame operator. We start by presenting a complete characterization of Parseval fusion frames in terms of the existence of special isometries defined on an encompassing Hilbert space. We then introduce two general methodologies to generate new fusion frames from existing ones, namely the Spatial Complement Method and the Naimark Complement Method, and analyze the relationship between the parameters of the original and the new fusion frame. We proceed by establishing existence conditions for 2-sparse fusion frames for any given fusion frame operator, for which the eigenvalues are greater than or equal to two. We then provide an easily implementable algorithm for computing such 2-sparse fusion frames. 相似文献
99.
We derive combinatorial identities for variables satisfying specific systems of commutation relations, in particular elliptic commutation relations. The identities thus obtained extend corresponding ones for -commuting variables and satisfying . In particular, we obtain weight-dependent binomial theorems, functional equations for generalized exponential functions, we derive results for an elliptic derivative of elliptic commuting variables, and finally study weight-dependent extensions of the Weyl algebra which we connect to rook theory. 相似文献
100.
Gitta Kutyniok 《Journal of Mathematical Analysis and Applications》2003,277(2):589-608
In this paper we construct a general class of time-frequency representations for LCA groups which parallel Cohen's class for the real line. For this, we generalize the notion of ambiguity function and Wigner distribution to the setting of general LCA groups in such a way that the Plancherel transform of the ambiguity function coincides with the Wigner distribution. Furthermore, properties of the general ambiguity function and Wigner distribution are studied. In detail we characterize those groups whose ambiguity functions and Wigner distributions vanish at infinity or are square-integrable. Finally, we explicitly construct Cohen's class for the group of p-adic numbers, p prime. 相似文献