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51.
For a large class of quantum mechanical models of matter and radiation we develop an analytic perturbation theory for non-degenerate
ground states. This theory is applicable, for example, to models of matter with static nuclei and non-relativistic electrons
that are coupled to the UV-cutoff quantized radiation field in the dipole approximation. If the lowest point of the energy
spectrum is a non-degenerate eigenvalue of the Hamiltonian, we show that this eigenvalue is an analytic function of the nuclear
coordinates and of α3/2, α being the fine structure constant. A suitably chosen ground state vector depends analytically on α3/2 and it is twice continuously differentiable with respect to the nuclear coordinates.
Submitted: November 24, 2008. Accepted: March 4, 2009. 相似文献
52.
Marcelín-Jiménez G Morales-Martínez M Angeles-Moreno AP Mendoza-Morales L 《Biomedical chromatography : BMC》2008,22(10):1143-1148
Pharmacokinetics of diphenidol (DPN) is limited due to the lack of analytical methodology. Here, a micro-assay for DPN quantification was developed, by coupling ultra-performance liquid chromatography with tandem mass spectrometry. The procedure involved plasma precipitation and injection of supernatant into UPLC with an Acquitytrade mark C18 column. Detection was in positive electrospray, following transitions of m/z 310.3 --> 292.3 and m/z 275.3 --> 230.2 for DPN and chlorphenamine (internal standard), respectively. The method was linear with a range of 4-400 ng/mL, and a 2 min run time. This method was applied in a switchability trial, where both formulations of DPN were bioequivalent. 相似文献
53.
A reaction of trans-[Ir(H)(5)(PiPr(3))(2)] (1) with 2,3,5,6-tetrafluoropyridine, pentafluorobenzene or 1,3-difluorobenzene in the presence of neohexene affords the square-pyramidal C-H activation products cis-trans-[Ir(4-C(5)NF(4))(H)(2)(PiPr(3))(2)] (2), cis-trans-[Ir(C(6)F(5))(H)(2)(PiPr(3))(2)] (4) and cis-trans-[Ir(2-C(6)H(3)F(2))(H)(2)(PiPr(3))(2)] (6). Irradiation of complex 1 with 2,3,5,6-tetrafluoropyridine or pentafluorobenzene gave the hydrides cis-trans-[Ir(4-C(5)NF(4))(H)(2)(H(2))(PiPr(3))(2)] (3) or cis-trans-[Ir(C(6)F(5))(H)(2)(H(2))(PiPr(3))(2)] (5). The presence of non-classical bound H(2) moieties has been demonstrated by the measurement of T(1) times at different temperatures. For 3 the H-H distance in the H(2) ligand can be estimated to be 0.82 A. The dihydride compounds 2, 4 and 6 react with CO to yield the complexes cis-trans-[Ir(Ar)(H)(2)(CO)(PiPr(3))(2)] (7: Ar = 4-C(5)NF(4), 8: Ar = C(6)F(5), 9: Ar = 2-C(6)H(3)F(2)). A reaction of 2 or 3 with an excess of ethylene leads to the formation of ethane and the Ir(i) ethylene complex trans-[Ir(4-C(5)NF(4))(eta(2)-C(2)H(4))(PiPr(3))(2)] (10). Treatment of 10 with CO furnishes the Ir(i) complex trans-[Ir(4-C(5)NF(4))(CO)(PiPr(3))(2)] (11). 相似文献
54.
Moreira LM Santiago PS de Almeida EV Tabak M 《Colloids and surfaces. B, Biointerfaces》2008,61(2):153-163
The present work focuses on the interaction between the zwitterionic surfactant N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (HPS) and the giant extracellular hemoglobin of Glossoscolex paulistus (HbGp). Electronic optical absorption, fluorescence emission and circular dichroism spectroscopy techniques, together with Gel-filtration chromatography, were used in order to evaluate the oligomeric dissociation as well as the autoxidation of HbGp as a function of the interaction with HPS. A peculiar behavior was observed for the HPS–HbGp interaction: a complex ferric species formation equilibrium was promoted, as a consequence of the autoxidation and oligomeric dissociation processes. At pH 7.0, HPS is more effective up to 1 mM while at pH 9.0 the surfactant effect is more intense above 1 mM. Furthermore, the interaction of HPS with HbGp was clearly less intense than the interaction of this hemoglobin with cationic (CTAC) and anionic (SDS) surfactants. Probably, this lower interaction with HPS is due to two factors: (i) the lower electrostatic attraction between the HPS surfactant and the protein surface ionic sites when compared to the electrostatic interaction between HbGp and cationic and anionic surfactants, and (ii) the low cmc of HPS, which probably reduces the interaction of the surfactant in the monomeric form with the protein. The present work emphasizes the importance of the electrostatic contribution in the interaction between ionic surfactants and HbGp. Furthermore, in the whole HPS concentration range used in this study, no folding and autoxidation decrease induced by this surfactant were observed. This is quite different from the literature data on the interaction between surfactants and tetrameric hemoglobins, that supports the occurrence of this behavior for the intracellular hemoglobins at low surfactant concentration range. Spectroscopic data are discussed and compared with the literature in order to improve the understanding of hemoglobin–surfactant interaction as well as the acid isoelectric point (pI) influence of the giant extracellular hemoglobins on their structure–activity relationship. 相似文献
55.
Marcel Meiland 《Tetrahedron letters》2009,50(4):469-3893
MS and 1H, 13C and 11B NMR results are presented revealing the formation of cyclic seven-membered boronate structures at trans-1,2-diol moieties of carbohydrates providing new opportunities for the activation, protection and analysis of glucopyranose-based oligomers and polymers such as cellulose or starch. ‘Coordination-induced shifts’ in 13C NMR spectra were identified for the esterification by boronic acids of carbohydrates, which can be applied for further studies. 相似文献
56.
57.
Köcher T Pichler P Mazanek M Swart R Mechtler K 《Analytical and bioanalytical chemistry》2011,400(8):2339-2347
The Mascot search algorithm is one of the most commonly used tools for protein identification. Tandem mass spectrometry data
searched against a protein sequence database is utilized for identifying peptides and proteins, each reported with a score.
Higher Mascot scores are associated with lower chances of random hits. The process of peak selection performed by the search
engine prior to the search is a critical aspect of the process. Here, we show that Mascot divides the MS/MS spectrum into
fixed m/z regions for peak selection, starting at the lowest m/z value of the peak list. Therefore, modifying the m/z range of the peak lists by insertion of a dummy peak with low m/z value changes the ensemble of peaks used for searching. As a consequence, Mascot peptide scores and search results are altered
significantly and a different subset of the peptides present in the sample is identified after processing. We further show
that the effect can be exploited and additional proteins and peptides can be identified by repeating the search with a combined
set of differently processed files, even when applying identical false-positive rates. 相似文献
58.
Min Tu Helge Reinsch Sabina Rodríguez‐Hermida Rhea Verbeke Timothe Stassin Werner Egger Marcel Dickmann Bjorn Dieu Johan Hofkens Ivo F. J. Vankelecom Norbert Stock Rob Ameloot 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2445-2449
Metal–organic frameworks (MOFs) enable the design of host–guest systems with specific properties. In this work, we show how the confinement of anthracene in a well‐chosen MOF host leads to reversible yellow‐to‐purple photoswitching of the fluorescence emission. This behavior has not been observed before for anthracene, either in pure form or adsorbed in other porous hosts. The photoresponse of the host–guest system is caused by the photodimerization of anthracene, which is greatly facilitated by the pore geometry, connectivity, and volume as well as the structural flexibility of the MOF host. The photoswitching behavior was used to fabricate photopatternable and erasable surfaces that, in combination with data encryption and decryption, hold promise in product authentication and secure communication applications. 相似文献
59.
Lemasson FA Strunk T Gerstel P Hennrich F Lebedkin S Barner-Kowollik C Wenzel W Kappes MM Mayor M 《Journal of the American Chemical Society》2011,133(4):652-655
Physico-chemical methods to sort single-walled carbon nanotubes (SWNTs) by chiral index are presently lacking but are required for in-depth experimental analysis and also for potential future applications of specific species. Here we report the unexpected selectivity of poly(N-decyl-2,7-carbazole) to almost exclusively disperse semiconducting SWNTs with differences of their chiral indices (n - m) ≥ 2 in toluene. The observed selectivity complements perfectly the dispersing features of the fluorene analogue poly(9,9-dialkyl-2,7-fluorene), which disperses semiconducting SWNTs with (n - m) ≤ 2 in toluene. The dispersed samples are further purified by density gradient centrifugation and analyzed by photoluminescence excitation spectroscopy. All-atom molecular modeling with decamer model compounds of the polymers and (10,2) and (7,6) SWNTs suggests differences in the π-π stacking interaction as origin of the selectivity. We observe energetically favored complexes between the (10,2) SWNT and the carbazole decamer and between the (7,6) SWNT and the fluorene decamer, respectively. These findings demonstrate that subtle structural changes of polymers lead to selective solvation of different families of carbon nanotubes. Furthermore, chemical screening of closely related polymers may pave the way toward simple, low-cost, and index-specific isolation of SWNTs. 相似文献
60.
An air-stable palladium catalyst formed in situ from commercially available components efficiently catalyzed the transfer vinylation between butyl vinyl ether and various allyl and alkyl alcohols to give the corresponding allyl and alkyl vinyl ethers in 61-98% yield in a single step. 相似文献