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61.
Dr. Lucie Rivier Dr. Pekka Peljo Sunny Maye Dr. Manuel A. Méndez Dr. Heron Vrubel Dr. Laurent A. C. Vannay Prof. Clémence Corminboeuf Dr. Micheál D. Scanlon Prof. Hubert H. Girault 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(55):12769-12779
Detailed studies on hydrogen evolution by decamethylruthenocene ([Cp*2RuII]) highlighted that metallocenes are capable of photoreducing hydrogen without the need for an additional sensitizer. Electrochemical, gas chromatographic, and spectroscopic (UV/Vis, 1H and 13C NMR) measurements corroborated by DFT calculations indicated that the production of hydrogen occurs by a two-step process. First, decamethylruthenocene hydride [Cp*2RuIV(H)]+ is formed in the presence of an organic acid. Subsequently, [Cp*2RuIV(H)]+ is reversibly reduced in a heterolytic reaction with one-photon excitation leading to a first release of hydrogen. Thereafter, the resultant decamethylruthenocenium ion [Cp*2RuIII]+ is further reduced with a second release of hydrogen by deprotonation of a methyl group of [Cp*2RuIII]+. Experimental and computational data show spontaneous conversion of [Cp*2RuII] to [Cp*2RuIV(H)]+ in the presence of protons. Calculations highlight that the first reduction is endergonic (ΔG0=108 kJ mol−1) and needs an input of energy by light for the reaction to occur. The hydricity of the methyl protons of [Cp*2RuII] was also considered. 相似文献
62.
Summary This note presents estimates of hourly averages of insolation, net radiation and soil heat flux during daytime from solar-elevation
angle and routine weather data on cloud cover and screen level air temperature using a formulation procedure generally adopted
in surface layer parametrisation schemes. The estimation procedure employs commonly used forms of empirical relationships
and the estimates are compared with the concurrent field observations at Trombay site in Bombay (19.1° N, 72.8° E) India.
Wherever possible site-specific empirical coefficients are derived. Using the observed insolation, the net radiation and soil
heat flux are respectively estimated within ±18% and ±14% of their observed values. Estimated insolation was found to be within
±37% of the observed values and, when used to derive the fluxes, the uncertainty increases to ±25% and ±27%, respectively. 相似文献
63.
Zhouxi Wang Tomas Rejtar Zhaohui Sunny Zhou Barry L. Karger 《Rapid communications in mass spectrometry : RCM》2010,24(3):267-275
In this study, we have examined two cysteine modifications resulting from sample preparation for protein characterization by mass spectrometry (MS): (1) a previously observed conversion of cysteine into dehydroalanine, now found in the case of disulfide mapping and (2) a novel modification corresponding to conversion of cysteine into alanine. Using model peptides, the conversion of cysteine into dehydroalanine via β‐elimination of a disulfide bond was seen to result from the conditions of typical tryptic digestion (37°C, pH 7.0–9.0) without disulfide reduction and alkylation. Furthermore, the surprising conversion of cysteine into alanine was shown to occur by heating cysteine‐containing peptides in the presence of a phosphine (tris(2‐carboxyethyl)phosphine hydrochloride (TCEP)). The formation of alanine from cysteine, investigated by performing experiments in H2O or D2O, suggested a radical‐based desulfurization mechanism unrelated to β‐elimination. Importantly, an understanding of the mechanism and conditions favorable for cysteine desulfurization provides insight for the establishment of improved sample preparation procedures of protein analysis. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
64.
The purine riboswitch is a genetic regulatory element found in the 5'-untranslated regions of Gram-positive bacteria that regulates expression of the mRNA specifically in response to either guanine or adenine. We report that the adenine-responsive RNA element is also capable of specifically recognizing pyrimidine compounds bearing modifications at the 6- or 5,6-positions in a fashion similar to that of purine compounds. Using isothermal titration calorimetry and X-ray crystallography, the binding of these compounds is characterized. 相似文献
65.
The role of store brand positioning for appropriating supply chain profit under shelf space allocation 总被引:1,自引:0,他引:1
We consider a retailer’s decision of developing a store brand (SB) version of a national brand (NB) and the role that its positioning strategy plays in appropriating the supply chain profit. Since the business of the retailer can be regarded as selling to NB manufacturers the shelf space at its disposal, we formulate a game-theoretical model of a single-retailer, single-manufacturer supply chain, where the retailer can decide whether to launch its own SB product and sells scarce shelf-space to a competing NB in a consumer good category. As a result, the most likely equilibrium outcome is that the available selling amount of each brand is constrained by the shelf-space available for its products and both brands coexist in the category. In this paper, we conceptualize the SB positioning that involves both product quality and product features. Our analysis shows that when the NB cross-price effect is not too large, the retailer should position its SB’s quality closer to the NB, more emphasize its SB’s differences in features facing a weaker NB, and less emphasize its SB’s differences in features facing a stronger NB. Our results stress the importance of SB positioning under the shelf-space allocation, in order to maximize the retailer’s value appropriation across the supply chain. 相似文献
66.
In the present work, chromophoric system (E)‐4‐(naphthalen‐1‐yl diazenyl)benzoic acid was synthesized and incorporated into lignin core. The end hydroxyl group of lignin was modified with the free carboxyl group of the chromophoric systems by dicyclohexylcarbodiimide coupling. The products were characterized by means of UV–visible, fluorescence, FT‐IR, and NMR spectroscopic methods and subjected to photoresponsive studies. The results show that modification enhances the light absorption and light fastening properties of the chromophoric system. The photoinduced trans–cis isomerization on the newly developed photosensitive biopolymeric system and the chromophoric system were investigated. Results also show that the trans–cis photoisomerization and the reverse cis–trans thermal conversions of the photoactive groups were also assisted by the incorporation onto biopolymeric core. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
67.
Jente Boelaert Frédéric Lynen Griet Glorieux Sunny Eloot Maria Van Landschoot Marie-Anne Waterloos Pat Sandra Raymond Vanholder 《Analytical and bioanalytical chemistry》2013,405(6):1937-1947
Chronic kidney disease (CKD) is a devastating illness characterized by accumulation of uremic retention solutes in the body. The objective of this study was to develop and validate a simple, rapid, and robust UPLC–MS–MS method for simultaneous determination, in serum, of seven organic acid uremic retention toxins, namely uric acid (UA), hippuric acid (HA), indoxylsulfate (IS), p-cresylglucuronide (pCG), p-cresylsulfate (pCS), indole-3-acetic acid (IAA), and 3-carboxy-4-methyl-5-propyl-2-furanpropionic acid (CMPF). Isotopically labeled internal standards (d5-HA; 1,3-15N2-UA, and d5-IAA) were used to correct for variations in sample preparation and system performance. Separation on a C18 column was followed by negative electrospray ionization and tandem mass spectrometric detection. Accuracy was below the 15 % threshold. Within-day precision varied from 0.60 to 4.54 % and between-day precision was below 13.33 % for all compounds. The applicability of the method was evaluated by analyzing 78 serum samples originating both from healthy controls and from patients at different stages of CKD. These results were compared with those obtained by use of conventional HPLC–PDA–FLD methods. A good correlation was obtained between both methods for all compounds. 相似文献
68.
Amissi Sadiki Eric M. Kercher Haibin Lu Ryan T. Lang Bryan Q. Spring Zhaohui Sunny Zhou 《Photochemistry and photobiology》2020,96(3):596-603
Photosensitizer (PS)–antibody conjugates (photoimmunoconjugates, PICs) enable cancer cell-targeted photodynamic therapy (PDT). Nonspecific chemical bioconjugation is widely used to synthesize PICs but gives rise to several shortcomings. The conjugates are heterogeneous, and the process is not easily reproducible. Moreover, modifications at or near the binding sites alter both binding affinity and specificity. To overcome these limitations, we introduce convergent assembly of PICs via a chemo-enzymatic site-specific approach. First, an antibody is conjugated to a clickable handle via site-specific modification of glutamine (Gln) residues catalyzed by transglutaminase (TGase, EC 2.3.2.13). Second, the modified antibody intermediate is conjugated to a compatible chromophore via click chemistry. Utilizing cetuximab, we compared this site-specific conjugation protocol to the nonspecific chemical acylation of amines using N-hydroxysuccinimide (NHS) chemistry. Both the heavy and light chains were modified via the chemical route, whereas, only a glutamine 295 in the heavy chain was modified via chemo-enzymatic conjugation. Furthermore, a 2.3-fold increase in the number of bound antibodies per cell was observed for the site-specific compared with nonspecific method, suggesting that multiple stochastic sites of modification perturb the antibody–antigen binding. Altogether, site-specific bioconjugation leads to homogenous, reproducible and well-defined PICs, conferring higher binding efficiency and probability of clinical success. 相似文献
69.
Journal of Cluster Science - In the present study we have synthesized α-Fe2O3 nanoparticles in a more conventionally established NaBH4 reduction, but using a bio-macromolecule, starch. The... 相似文献
70.