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71.
Syed R. Haider Helen J. Reid Barry L. Sharp 《Analytical and bioanalytical chemistry》2010,397(2):655-664
This study describes a modification to tricine sodium dodecyl sulphate polyacrylamide gel electrophoresis to make it more
effective for the separation of low molecular mass proteins and for coupling with inductively coupled plasma mass spectrometry
(ICP-MS). The modified method employs low-percentage polyacrylamide gels (7–10%) (w/v) and low reagent concentrations that
provide efficient separations, good quantitation and low matrix levels that are compatible with ICP-MS. Using phosphopeptides
as a model system, and offline analysis, we obtained recoveries of 73% (w/v) in a 9% gel compared with 55% in a conventional
16% gel. Online coupling was achieved by modification of a standard commercially available gel electroelution apparatus and
casting of the gel into a 7.3-cm-long tube. Online separation of a digest of β-casein was demonstrated with recovery of the
mono- and tetraphosphopeptides, which were identified by comparison with peptide standards. A mass balance study with the
standards yielded recoveries of 95% for tetraphosphopeptides and 48% for monophosphopeptides. The factors affecting the separations
and recoveries are discussed in detail. The detection limits for 10-μL samples of the mono- and tetraphosphopeptides were
0.7 μM (7 pmol) and 0.2 μM (2 pmol) respectively. 相似文献
72.
Xiao Zhou Yali Lu Wenjing Wang Babak Borhan Gavin E. Reid 《Journal of the American Society for Mass Spectrometry》2010,21(8):1339-1351
Protein surface accessible residues play an important role in protein folding, protein-protein interactions and protein-ligand
binding. However, a common problem associated with the use of selective chemical labeling methods for mapping protein solvent
accessible residues is that when a complicated peptide mixture resulting from a large protein or protein complex is analyzed,
the modified peptides may be difficult to identify and characterize amongst the largely unmodified peptide population (i.e.,
the ‘needle in a haystack’ problem). To address this challenge, we describe here the development of a strategy involving the
synthesis and application of a novel ‘fixed charge’ sulfonium ion containing lysine-specific protein modification reagent,
S,S′-dimethylthiobutanoylhydroxysuccinimide ester (DMBNHS), coupled with capillary HPLC-ESI-MS, automated CID-MS/MS, and data-dependant
neutral loss mode MS3 in an ion trap mass spectrometer, to map the surface accessible lysine residues in a small model protein, cellular retinoic
acid binding protein II (CRABP II). After reaction with different reagent:protein ratios and digestion with Glu-C, modified
peptides are selectively identified and the number of modifications within each peptide are determined by CID-MS/MS, via the
exclusive neutral loss(es) of dimethylsulfide, independently of the amino acid composition and precursor ion charge state
(i.e., proton mobility) of the peptide. The observation of these characteristic neutral losses are then used to automatically
‘trigger’ the acquisition of an MS3 spectrum to allow the peptide sequence and the site(s) of modification to be characterized. Using this approach, the experimentally
determined relative solvent accessibilities of the lysine residues were found to show good agreement with the known solution
structure of CRABP II. 相似文献
73.
We present here a study of the phase behavior of mixed component NaNO(3)-Na(2)SO(4) (SNS) droplets with NaNO(3) to Na(2)SO(4) molar ratios of 1:1, 3:1, and 10:1, comparing observations with thermodynamic predictions. Measurements are made by Fourier transform infrared attenuated total reflection and micro-Raman spectroscopy for SNS droplets deposited on ZnSe and quartz substrates, respectively. The conventional deliquescence/efflorescence hysteresis in phase behavior is observed. On drying, heterogeneous crystallization leads to phase behavior that is consistent with bulk solution thermodynamics, with the formation of the mixed salt NaNO(3)·Na(2)SO(4)·H(2)O, Na(2)SO(4) (s), and NaNO(3) (s) all observed to form at relative humidities that coincide with predictions by the aerosol inorganics model. However, conditioning of the droplet at high relative humidity prior to drying is observed to lead to quantitative differences between the fractions of different salts formed. When substrate effects do not influence the crystallization process, supersaturated solutions are formed, and this leads to the observation of contact ion pairs. Such measurements of the phase behavior of mixed component droplets are important for testing the reliability of thermodynamic models. 相似文献
74.
Blanchard F Golde D Su FH Razzari L Sharma G Morandotti R Ozaki T Reid M Kira M Koch SW Hegmann FA 《Physical review letters》2011,107(10):107401
The anisotropic effective mass of energetic electrons in an isotropic, nonparabolic conduction band is revealed using ultrafast THz-pump-THz-probe techniques in a n-doped InGaAs semiconductor thin film. A microscopic theory is applied to identify the origin of the observed anisotropy and to show that the self-consistent light-matter coupling contributes significantly to the THz response. 相似文献
75.
76.
In a previous paper the authors, together with Balwant Singh, introduced an elementwisc characterization of weak subintegrality for an extension A?B of commutative rings. In the present paper we improve our methods for working with this characterization. This leads us to propose two new types of “elementary weakly subintegral extension”. 相似文献
77.
Ohne Zusammenfassung 相似文献
78.
Given a digraph D on vertices v1, v2, ?, vn, we can associate a bipartite graph B(D) on vertices s1, s2, ?, sn, t1, t2, ?, tn, where sitj is an edge of B(D) if (vi, vj) is an arc in D. Let OG denote the set of all orientations on the (undirected) graph G. In this paper we will discuss properties of the set S(G) := {β1 (B(D))) | D ? OG}, where β1 is the edge independence number. In the first section we present some background and related concepts. We show that sets of the form S(G) are convex and that max S(G) ≦ 2 min S(G). Furthermore, this completely characterizes such sets. In the second section we discuss some bounds on elements of S(G) in terms of more familiar graphical parameters. The third section deals with extremal problems. We discuss bounds on elements of S(G) if the order and size of G are known, particularly when G is bipartite. In this section we exhibit a relation between max S(G) and the concept of graphical closure. In the fourth and final section we discuss the computational complexity of computing min S(G) and max S(G). We show that the first problem is NP-complete and that the latter is polynomial. 相似文献
79.
80.
Coherent synthesis using carrier-envelope phase-controlled pulses from a dual-color femtosecond optical parametric oscillator 总被引:3,自引:0,他引:3
By using a dual-color femtosecond optical parametric oscillator (OPO), a coherent waveform was synthesized from two coresonant near-infrared signal pulses whose center wavelengths had a separation of 100 nm. Immediately after the OPO cavity the pulses had independent carrier-envelope phase-slip frequencies, and synthesis was achieved by shifting these frequencies using an acousto-optic modulator driven by an internally generated difference frequency. Soliton self-frequency shifted pulses from a photonic crystal fiber and a cross-correlation frequency-resolved optical gating (XFROG) measurement were used to analyze the result of the synthesis experiment and revealed that the synthesized waveform was a train of high-contrast 30 fs pulses. 相似文献