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161.
162.
Sara N. Pratt Daniel E. Austin 《Journal of the American Society for Mass Spectrometry》2014,25(5):712-721
The survivability of Bacillus subtilis spores and vegetative Escherichia coli cells after electrospray from aqueous suspension was tested using mobility experiments at atmospheric pressure. E. coli did not survive electrospray charging and desolvation, but B. subtilis did. Experimental conditions ensured that any surviving bacteria were de-agglomerated, desolvated, and electrically charged. Based on mobility measurements, B. subtilis spores survived even with 2,000–20,000 positive charges. B. subtilis was also found to survive introduction into vacuum after either positive or negative electrospray. Attempts to measure the charge distribution of viable B. subtilis spores using electrostatic deflection in vacuum were inconclusive; however, viable spores with low charge states (less than 42 positive or less than 26 negative charges) were observed. Graphical Abstract
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163.
Liquid chromatography-electrospray ionization-infrared multiphoton dissociation (IRMPD) mass spectrometry was developed to investigate the distributions of intrastrand crosslinks formed between cisplatin and two oligodeoxynucleotides (ODNs), d(A1T2G3G4G5T6A7C8C9C10A11T12) (G3-D) and its analog d(A1T2G3G4G5T6T7C8C9C10A11T12) (G3-H), which have been reported to adopt different secondary structures in solution. Based on the formation of site-specific fragment ions upon IRMPD, two isobaric crosslink products were differentiated for each ODN. The preferential formation of G3G4 and G4G5 crosslinks was determined as a function of reaction conditions, including incubation temperature and presence of metal ions. G3-D consistently exhibited a greater preference for formation of the G4G5 crosslink compared with the G3-H ODN. The ratio of G3G4:G4G5 crosslinks increased for both G3-D and G3-H at higher incubation temperatures or when metal salts were added. Comparison of the IRMPD fragmentation patterns of the unmodified ODNs and the intramolecular platinated crosslinks indicated that backbone cleavage was significantly suppressed near the crosslink. Figure
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164.
Infrared Detection of Criegee Intermediates Formed during the Ozonolysis of β‐Pinene and Their Reactivity towards Sulfur Dioxide 下载免费PDF全文
Jennifer Ahrens Philip T. M. Carlsson Nils Hertl Prof. Dr. Matthias Olzmann Mark Pfeifle Dr. J. Lennard Wolf Dr. Thomas Zeuch 《Angewandte Chemie (International ed. in English)》2014,53(3):715-719
Recently, direct kinetic experiments have shown that the oxidation of sulfur dioxide to sulfur trioxide by reaction with stabilized Criegee intermediates (CIs) is an important source of sulfuric acid in the atmosphere. So far, only small CIs, generated in photolysis experiments, have been directly detected. Herein, it is shown that large, stabilized CIs can be detected in the gas phase by FTIR spectroscopy during the ozonolysis of β‐pinene. Their transient absorption bands between 930 and 830 cm?1 appear only in the initial phase of the ozonolysis reaction when the scavenging of stabilized CIs by the reaction products is slow. The large CIs react with sulfur dioxide to give sulfur trioxide and nopinone with a yield exceeding 80 %. Reactant consumption and product formation in time‐resolved β‐pinene ozonolysis experiments in the presence of sulfur dioxide have been kinetically modeled. The results suggest a fast reaction of sulfur dioxide with CIs arising from β‐pinene ozonolysis. 相似文献
165.
Laura L. Adduci Dr. Matthew P. McLaughlin Trandon A. Bender Dr. Jennifer J. Becker Prof. Dr. Michel R. Gagné 《Angewandte Chemie (International ed. in English)》2014,53(6):1646-1649
The conversion of readily available cellulosic biomass to valuable feedstocks and fuels is an attrative goal but a challenging transformation that requires the cleavage of multiple nonactivated C? O bonds. Herein, the Lewis acid trispentafluorophenylborane (B(C6F5)3) is shown to catalyze the metal‐free hydrosilylative reduction of monosaccharides and polysaccharides to give hydrocarbons with reduced oxygen content. The choice of the silane reductant influences the degree of deoxygenation, with diethylsilane effecting the complete reduction to produce hexanes while tertiary silanes give partially deoxygenated tetraol and triol products. 相似文献
166.
Dr. Bidraha Bagh Saeid Sadeh Prof. Dr. Jennifer C. Green Prof. Dr. Jens Müller 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(8):2318-2327
Indium‐bridged [1]ferrocenophanes ([1]FCPs) and [1.1]ferrocenophanes ([1.1]FCPs) were synthesized from dilithioferrocene species and indium dichlorides. The reaction of Li2fc?tmeda (fc=(H4C5)2Fe) and (Mamx)InCl2 (Mamx=6‐(Me2NCH2)‐2,4‐tBu2C6H2) gave a mixture of the [1]FCP (Mamx)Infc ( 41 ), the [1.1]FCP [(Mamx)Infc]2 ( 42 ), and oligomers [(Mamx)Infc]n ( 4 n ). In a similar reaction, employing the enantiomerically pure, planar‐chiral (Sp,Sp)‐1,1′‐dibromo‐2,2′‐diisopropylferrocene ( 1 ) as a precursor for the dilithioferrocene derivative Li2fciPr2, equipped with two iPr groups in the α position, gave the inda[1]ferrocenophane 51 [(Mamx)InfciPr2] selectively. Species 51 underwent ring‐opening polymerization to give the polymer 5 n . The reaction between Li2fciPr2 and Ar′InCl2 (Ar′=2‐(Me2NCH2)C6H4) gave an inseparable mixture of the [1]FCP Ar′InfciPr2 ( 61 ) and the [1.1]FCP [Ar′InfciPr2]2 ( 62 ). Hydrogenolysis reactions (BP86/TZ2P) of the four inda[1]ferrocenophanes revealed that the structurally most distorted species ( 51 ) is also the most strained [1]FCP. 相似文献
167.
[(IPent)PdCl2(morpholine)]: A Readily Activated Precatalyst for Room‐Temperature,Additive‐Free Carbon–Sulfur Coupling 下载免费PDF全文
Jennifer L. Farmer Matthew Pompeo Dr. Alan J. Lough Prof. Michael G. Organ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(48):15790-15798
A series of new, easily activated NHC–PdII precatalysts featuring a trans‐oriented morpholine ligand were prepared and evaluated for activity in carbon‐sulfur cross‐coupling chemistry. [(IPent)PdCl2(morpholine)] (IPent=1,3‐bis(2,6‐di(3‐pentyl)phenyl)imidazol‐2‐ylidene) was identified as the most active precatalyst and was shown to effectively couple a wide variety of deactivated aryl halides with both aryl and alkyl thiols at or near ambient temperature, without the need for additives, external activators, or pre‐activation steps. Mechanistic studies revealed that, in contrast to other common NHC–PdII precatalysts, these complexes are rapidly reduced to the active NHC–Pd0 species at ambient temperature in the presence of KOtBu, thus avoiding the formation of deleterious off‐cycle PdII–thiolate resting states. 相似文献
168.
Jennifer Paola Hernández Mancera Francisco Núñez-Zarur Soledad Gutiérrez-Oliva Alejandro Toro-Labbé Ricardo Vivas-Reyes 《Journal of computational chemistry》2020,41(23):2022-2032
Quantum chemical calculations were used to study the mechanism of Diels-Alder reactions involving chiral anthracenes as dienes and a series of dienophiles. The reaction force analysis was employed to obtain a detailed scrutiny of the reaction mechanisms, it has been found that thermodynamics and kinetics of the reactions are quite consistent: the lower the activation energy, the lower the reaction energy, thus following the Bell-Evans-Polanyi principle. It has been found that activation energies are mostly due to structural rearrangements that in most cases represented more than 70% of the activation energy. Electronic activity mostly due to changes in σ and π bonding were revealed by the reaction electronic flux (REF), this property helps identify whether changes on σ or π bonding drive the reaction. Additionally, new global indexes describing the behavior of the electronic activity were introduced and then used to classify the reactions in terms of the spontaneity of their electronic activity. Local natural bond order electronic population analysis was used to check consistency with global REF through the characterization of specific changes in the electronic density that might be responsible for the activity already detected by the REF. Results show that reactions involving acetoxy lactones are driven by spontaneous electronic activity coming from bond forming/strengthening processes; in the case of maleic anhydrides and maleimides it appears that both spontaneous and non-spontaneous electronic activity are quite active in driving the reactions. 相似文献
169.
Martin-del-Campo Jennifer Coulombe Sylvain Kopyscinski Jan 《Plasma Chemistry and Plasma Processing》2020,40(4):857-881
Plasma Chemistry and Plasma Processing - The environmental impact of greenhouse gases such as carbon dioxide and methane can be reduced if they are used as feedstock to synthesize chemical building... 相似文献
170.
Therese Planke Katarina Cirnski Dr. Jennifer Herrmann Prof. Dr. Rolf Müller Prof. Dr. Andreas Kirschning 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(19):4289-4296
Cystobactamids belong to the group of arene-based oligoamides that effectively inhibit bacterial type IIa topoisomerases. Cystobactamid 861-2 is the most active member of these antibiotics. Most amide bonds present in the cystobactamids link benzoic acids with anilines and it was found that some of these amide bonds undergo chemical and enzymatic hydrolysis, especially the one linking ring C with ring D. This work reports on the chemical synthesis and biological evaluation of thirteen new cystobactamids that still contain the methoxyaspartate hinge. However, we exchanged selected amide bonds either by the urea or the triazole groups and modified ring A in the latter case. While hydrolytic stability could be improved with these structural substitutes, the high antibacterial potency of cystobactamid 861-2 could only be preserved in selected cases. This includes derivatives, in which the urea group is positioned between rings A and B and where the triazole is found between rings C and D. 相似文献