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31.
Hybrid phospholipid bilayer coatings for separations of cationic proteins in capillary zone electrophoresis
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Elyssia S. Gallagher Seid M. Adem Leonard K. Bright Isen A. C. Calderon Elisabeth Mansfield Craig A. Aspinwall 《Electrophoresis》2014,35(8):1099-1105
Protein separations in CZE suffer from nonspecific adsorption of analytes to the capillary surface. Semipermanent phospholipid bilayers have been used to minimize adsorption, but must be regenerated regularly to ensure reproducibility. We investigated the formation, characterization, and use of hybrid phospholipid bilayers (HPBs) as more stable biosurfactant capillary coatings for CZE protein separations. HPBs are formed by covalently modifying a support with a hydrophobic monolayer onto which a self‐assembled lipid monolayer is deposited. Monolayers prepared in capillaries using 3‐cyanopropyldimethylchlorosilane (CPDCS) or n‐octyldimethylchlorosilane (ODCS) yielded hydrophobic surfaces with lowered surface free energies of 6.0 ± 0.3 or 0.2 ± 0.1 mJ m?2, respectively, compared to 17 ± 1 mJ m?2 for bare silica capillaries. HPBs were formed by subsequently fusing vesicles comprised of 1,2‐dilauroyl‐sn‐glycero‐3‐phosphocholine or 1,2‐dioleoyl‐sn‐glycero‐3‐phosphocholine to CPDCS‐ or ODCS‐modified capillaries. The resultant HPB coatings shielded the capillary surface and yielded reduced electroosmotic mobility (1.3–1.9 × 10?4 cm2 V?1s?1) compared to CPDCS‐ and ODCS‐modified or bare capillaries (3.6 ± 0.2 × 10?4 cm2 V?1s?1, 4.8 ± 0.4 × 10?4 cm2 V?1s?1, and 6.0 ± 0.2 × 10?4 cm2 V?1s?1, respectively), with increased stability compared to phospholipid bilayer coatings. HPB‐coated capillaries yielded reproducible protein migration times (RSD ≤ 3.6%, n ≥ 6) with separation efficiencies as high as 200 000 plates/m. 相似文献
32.
Nolan M. Gallagher Hong-Zhou Ye Shuting Feng Jeffrey Lopez Yun Guang Zhu Troy Van Voorhis Yang Shao-Horn Jeremiah A. Johnson 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(10):3980-3983
We present the discovery of a novel radical cation formed through one-electron oxidation of an N-heterocyclic carbene–carbodiimide (NHC–CDI) zwitterionic adduct. This compound possesses a distonic electronic structure (spatially separate spin and charge regions) and displays persistence under ambient conditions. We demonstrate its application in a redox-flow battery exhibiting minimal voltage hysteresis, a flat voltage plateau, high Coulombic efficiency, and no performance decay for at least 100 cycles. The chemical tunability of NHCs and CDIs suggests that this approach could provide a general entry to redox-active NHC–CDI adducts and their persistent radical ions for various applications. 相似文献
33.
Wing Ying Chow Brendan P. Norman Norman B. Roberts Lakshminarayan R. Ranganath Christian Teutloff Robert Bittl Melinda J. Duer James A. Gallagher Hartmut Oschkinat 《Angewandte Chemie (International ed. in English)》2020,59(29):11937-11942
Alkaptonuria (AKU) is a rare disease characterized by high levels of homogentisic acid (HGA); patients suffer from tissue ochronosis: dark brown pigmentation, especially of joint cartilage, leading to severe early osteoarthropathy. No molecular mechanism links elevated HGA to ochronosis; the pigment's chemical identity is still not known, nor how it induces joint cartilage degradation. Here we give key insight on HGA‐derived pigment composition and collagen disruption in AKU cartilage. Synthetic pigment and pigmented human cartilage tissue both showed hydroquinone‐resembling NMR signals. EPR spectroscopy showed that the synthetic pigment contains radicals. Moreover, we observed intrastrand disruption of collagen triple helix in pigmented AKU human cartilage, and in cartilage from patients with osteoarthritis. We propose that collagen degradation can occur via transient glycyl radicals, the formation of which is enhanced in AKU due to the redox environment generated by pigmentation. 相似文献
34.
Meier MS Bergosh RG Gallagher ME Spielmann HP Wang Z 《The Journal of organic chemistry》2002,67(17):5946-5952
The fulleride dianions C(60)(2-) and C(70)(2-) were generated by deprotonation of the corresponding hydrogenated fullerenes, 1,2-C(60)H(2) and 1,2-C(70)H(2). These anions were prepared in the presence of a variety of alkylating agents, and mono- or dialkylated products were obtained. Alkylation was not successful with sulfonate ester alkylating agents. Deprotonation of monoalkylated compounds, followed by second alkylation with a different alkylating agent, produced heterodialkylated compounds. The monoalkyated material was invariably the 1,2-isomers, while the dialkylated materials were generally 1,4-isomers, although some 1,2-isomer was observed in the C(70) context. The major product from alkylation of C(70)(2-) was the 7,23-isomer 13a, a structure where the alkylation took place near the equator of the fullerene cage, rather than at the more strained carbons near the poles. 相似文献
35.
H. Selig W.A. Sunder M.J. Vasile F.A. Stevie P.K. Gallagher L.B. Ebert 《Journal of fluorine chemistry》1978,12(5):397-412
IF7 intercalates into graphite accompanied by the partial fluorination of the graphite host. The intercalated species was identified as IF5 by IR and 19F nmr spectroscopies. Mass spectrometric analyses of the gases evolved from the intercalate showed only IF5 and fluorocarbons. Iodine pentafluoride intercalates only in the presence of HF, yielding a compound with the stoichiometry C8IF5 and no fluorination of the graphite host. Careful elimination of even traces of HF resulted in no intercalation. Evolved gas analysis showed that the only species recovered from the intercalation was IF5. The remaining interhalogens, ClF5, ClF3, BrF5 and BrF3 all intercalate into graphite with extensive fluorination of the lattice. In the case of these four compounds, the intercalate proved to be more difficult to characterize, e.g. stoichiometry was often variable, and 19F nmr yielded resonances that did not agree with any known halogen fluorides. Thermal decomposition of these intercalates showed little or no gas evolution until relatively high temperatures were reached, whereupon Cl2 or Br2 was evolved, followed by fluorocarbons. 相似文献
36.
Harvey Robin J. Lutz Michael A. Gallagher Hayden E. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1978,6(3):248-255
This paper describes the current interruption and voltage holdoff capabilities of a wide range of crossed-field tubes (XFTs). The XFTs investigated have active electrode areas ranging from 96 to 8000 cm2 with mean diameters from 2 to 56 cm. For the larger XFTs, currents up to 10 kA have been interrupted at voltages up to 100 kV, corresponding to a switched power of 1 GW. Experiments have shown the peak interruptible current to vary linearly with tube radius. The mechanism responsible for the limitation may be related to the self-generated magnetic field, but other factors are also shown to play a role. 相似文献
37.
38.
S-Alkyl dithioformates, generated by a cycloreversion process, react as 1,3-dipolarophiles with beta-lactam-based azomethine ylids to provide, after (net) elimination of MeSH, C(2)-unsubstituted penems. The overall cycloreversion/cycloaddition sequence was accelerated by microwave irradiation. [reaction: see text] 相似文献
39.
Microwave ionization of Rydberg atoms is well described as the onset of classical chaos when the microwave frequency omega is less than the Kepler frequency 1/n(3). However, when omega>1/n(3), i.e., at high scaled frequency Omega=omegan(3)>1, classical ionization is predicted to be suppressed by quantum interference, an analogue to Anderson localization in a solid. Using 17.55 GHz microwave fields we have observed the ionization of Sr Rydberg atoms in the regime 1=Omega=5 . Our measurements demonstrate the quantum suppression of classical diffusive ionization and show the ionization field to be n independent in this regime. 相似文献
40.
Hevia E Gallagher DJ Kennedy AR Mulvey RE O'Hara CT Talmard C 《Chemical communications (Cambridge, England)》2004,(21):2422-2423
Only two-fold amination occurs when 3 molar equivalents of TMPH are offered to a 1:1 BuNa-Bu2Mg mixture; adding TMEDA gives the mixed alkyl amide [(TMEDA)Na(mu-Bu)(mu-TMP)Mg(TMP)], which itself affords the phenyl-bridged analogue when reacted with benzene. 相似文献