- Enhancing electrospray ionization efficiency of peptides by derivatization
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With the advent of electrospray ionization mass spectrometry, the world was given a new way to look at complex peptide mixtures. Identification of proteins via their signature peptides requires ionization of a representative portion of the peptides derived from proteins by proteolysis. Unfortunately, matrix effects prohibited electrospray ionization of many peptides. This paper describes the development of a new labeling reagent that simultaneously adds a permanent positive charge to peptides and increases their hydrophobicity to enhance their ionization efficiency. The labeling agent is preactivated with N-hydroxysuccinimide to react with primary amines to form a peptide bond. In the most dramatic case, ionization efficiency of the peptide ADRDQYELLCLDNTRKPVDEYK increased 500-fold after derivatization as opposed to other peptides where ionization efficiency was impacted little. Ionization efficiency of peptides was enhanced roughly 10-fold in general by derivatization. Peptides of less than 500 Da experienced the greatest increase in ionization efficiency by derivatization. Poor ionization efficiency of native peptides was found to be due more to their inherent structural properties than the matrix in which ionization occurs.
- Mirzaei, Hamid,Regnier, Fred
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Read Online
- Nanoscale Biodegradable Organic–Inorganic Hybrids for Efficient Cell Penetration and Drug Delivery
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We report a comprehensive study on novel, highly efficient, and biodegradable hybrid molecular transporters. To this end, we designed a series of cell-penetrating, cube-octameric silsesquioxanes (COSS), and investigated cellular uptake by confocal microscopy and flow cytometry. A COSS with dense spatial arrangement of guanidinium groups displayed fast uptake kinetics and cell permeation at nanomolar concentrations in living HeLa cells. Efficient uptake was also observed in bacteria, yeasts, and archaea. The COSS-based carrier was significantly more potent than cell-penetrating peptides (CPPs) and displayed low toxicity. It efficiently delivered a covalently attached cytotoxic drug, doxorubicin, to living tumor cells. As the uptake of fluorescently labeled carrier remained in the presence of serum, the system could be considered particularly attractive for the in vivo delivery of therapeutics.
- H?rner, Sebastian,Knauer, Sascha,Uth, Christina,J?st, Marina,Schmidts, Volker,Frauendorf, Holm,Thiele, Christina Marie,Avrutina, Olga,Kolmar, Harald
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supporting information
p. 14842 - 14846
(2016/11/23)
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- Online monitoring of hydroformylation intermediates by ESI-MS
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Self-assembling ligands bearing permanently charged moieties have been synthesized and investigated in the Rh-catalyzed hydroformylation of terminal alkenes. By coupling a high-pressure autoclave directly to an ESI mass spectrometer hydroformylation reactions applying self-assembling 6-DPPon ligands could be studied in an online fashion. The live-streaming of the reaction mixture to the spectrometer revealed a series of different complexes not observed by other methods before, the structures of which were corroborated by CID experiments. Under CO/H2 atmosphere, new complexes that are predicted by the Wilkinson catalytic cycle could be identified and studied by CID experiments, too. Especially the ion at m/z 848, a square-planar hydrido-carbonyl complex that is normally not detectable by other methods, was investigated in detail. Collision experiments of this complex resulted in the loss of CO and H2, the latter being quite unusual, and points to the involvement of the hydrogen bond framework. These findings were further supported by deuteration experiments that revealed a clear incorporation of deuterium into the ligands. From these findings a new hydrogen-activation mechanism was proposed. Furthermore, substrate-containing complexes could be generated too, though a huge excess of substrate was necessary. CID experiments either with D2 or Ar yielded nearly identical spectra, hinting at a complex that might result either from a β-hydride elimination or from intramolecular oxidative addition of one of the ligands.
- Beierlein, Christian H.,Breit, Bernhard,Paz Schmidt, Roberto A.,Plattner, Dietmar A.
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scheme or table
p. 2521 - 2532
(2010/08/04)
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- Multiple isotopic labels for quantitative mass spectrometry
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Quantitative mass spectrometry is often performed using isotopicalty labeled samples. Although the 4-trimethylammoniumbutyryl (TMAB) labels have many advantages over other isotopic tags, only two forms have previously been synthesized (i.e., a heavy form containing nine deuteriums and a light form without deuterium). In the present report, two additional forms containing three and six deuteriums have been synthesized and tested. These additional isotopic tags perform identically to the previously reported tags; peptides labeled with the new TMAB reagents coelute from reversed-phase HPLC columns with peptides labeled with the lighter and heavier TMAB reagents. Altogether, these four tags allow for multivariate analysis in a single liquid chromatography/mass spectrometry analysis, with each isotopically tagged peptide differing in mass by 3 Da per tag incorporated. The synthetic scheme is described in simple terms so that a biochemist without specific training in organic chemistry can perform the synthesis. The interpretation of tandem mass spectrometry data for the TMAB-labeled peptides is also described in more detail. The additional TMAB isotopic reagents described here, together with the additional description of the synthesis and analysis, should allow these labels to be more widely used for proteomics and peptidomics analyses.
- Morano, Cain,Zhang, Xin,Fricker, Lloyd D.
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experimental part
p. 9298 - 9309
(2009/07/04)
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- Exploiting neighboring-group interactions for the self-selection of a catalytic unit
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(Figure Presented) A good neighbor is better than a far-away friend: A tethering strategy is used to self-select groups that assist in the cleavage of a neighboring carboxylic ester moiety (see picture, TSA=transition-state analogue). A correlation is observed between the amplification at thermodynamic equilibrium and the catalytic efficiency.
- Gasparini, Giulio,Prins, Leonard J.,Scrimin, Paolo
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supporting information; experimental part
p. 2475 - 2479
(2009/02/06)
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- Differences in proton-proton coupling constants of N+-CH2-CH2 protons of some betaines, N+-(CH2)2-3-COO-, and their complexes in aqueous solution
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Synthesis and 1H NMR spectra in D2O of 4 betaines and 19 betaine complexes with mineral acids containing 2 or 3 CH2 groups in the tether, N+-(CH2)n-COO-, n=2,3, and diverse volume of the positively charged groups are reported. In compounds containing three CH2 groups in the tether and three substituents at the nitrogen atom or α, α′-disubstituted pyridine ring, a characteristic multiplet for an AA′MM′X2 spin system is observed. This is consistent with preference for trans conformation (68-85%). In the spectra of compounds with two CH2 groups in the tether or three CH2 groups and unsubstituted pyridine ring, the multiplet changes to a triplet and gives apparent A2X2 and A2M2X2 spectra, respectively, consistent with no significant conformational preference. Both the number of CH2 groups in tether and the bulkiness of the charged groups are responsible for the observed differences of N+CH2 multiplicity and reflect changes in conformational preferences. According to the PM3 calculations, in the gas phase a gauche-like conformer is more stable than the trans, but in aqueous solution it is reverse.
- Szafran, Miroslaw,Dega-Szafran, Zofia,Nowak-Wydra, Barbara,Pietrzak, Mariusz
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p. 555 - 564
(2007/10/03)
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