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951.
Artacho E 《Physical review letters》2011,107(18):188901; discussion 188902
952.
Muñoz-Úbeda M Misra SK Barrán-Berdón AL Aicart-Ramos C Sierra MB Biswas J Kondaiah P Junquera E Bhattacharya S Aicart E 《Journal of the American Chemical Society》2011,133(45):18014-18017
The most important objective of the present study was to explain why cationic lipid (CL)-mediated delivery of plasmid DNA (pDNA) is better than that of linear DNA in gene therapy, a question that, until now, has remained unanswered. Herein for the first time we experimentally show that for different types of CLs, pDNA, in contrast to linear DNA, is compacted with a large amount of its counterions, yielding a lower effective negative charge. This feature has been confirmed through a number of physicochemical and biochemical investigations. This is significant for both in vitro and in vivo transfection studies. For an effective DNA transfection, the lower the amount of the CL, the lower is the cytotoxicity. The study also points out that it is absolutely necessary to consider both effective charge ratios between CL and pDNA and effective pDNA charges, which can be determined from physicochemical experiments. 相似文献
953.
Cocinero EJ Çarçabal P Vaden TD Davis BG Simons JP 《Journal of the American Chemical Society》2011,133(12):4548-4557
The physical basis of carbohydrate-peptide interactions has been explored by probing the structures of a series of complexes generated in a solvent-free environment under molecular beam conditions. A combination of double-resonance IR-UV spectroscopy and quantum-chemical calculations has established the structures of complexes of the model, N-acetyl-L-phenylalanine methylamide, bound to the α and β anomers of methyl D-gluco- and D-galactopyranoside as guests. In all cases, the carbohydrates are bound through hydrogen bonding to the dipeptide chain, although with some differing patterns. The amino acid host "engages" with the most suitable pair of neighboring conjugate sites on each carbohydrate; the specific choice depends on the conformation of the peptide backbone and the configuration and conformation of the carbohydrate ligand. None of the structures is supported by "stacking" interactions with the aromatic ring, despite their common occurrence in bound carbohydrate-protein structures. 相似文献
954.
Cristina Rodríguez‐Seco Maria Mndez Cristina Roldn‐Carmona Ravi Pudi Mohammad Khaja Nazeeruddin Emilio Jose Palomares 《Angewandte Chemie (International ed. in English)》2020,59(13):5303-5307
Three hole transport materials (HTMs) based on a substituted triphenylamine moiety have been synthesized and successfully employed in triple‐cation mixed‐halide PSCs, reaching efficiencies of 19.4 %. The efficiencies, comparable to those obtained using spiro‐OMeTAD, point them out as promising candidates for easily attainable and cost‐effective alternatives for PSCs, given their facile synthesis from commercially available materials. Interestingly, although all these HTMs show similar chemical and physical properties, they provide different carrier recombination kinetics. Our results demonstrate that is feasible through the molecular design of the HTM to minimize carrier losses and, thus, increase the solar cell efficiencies. 相似文献
955.
Dr. Olga A. Stasyuk Prof. Dr. Miquel Solà Prof. Dr. Marcel Swart Prof. Dr. Célia Fonseca Guerra Prof. Dr. Tadeusz Marek Krygowski Prof. Dr. Halina Szatylowicz 《Chemphyschem》2020,21(18):2112-2126
For many years, non-covalently bonded complexes of nucleobases have attracted considerable interest. However, there is a lack of information about the nature of hydrogen bonding between nucleobases when the bonding is affected by metal coordination to one of the nucleobases, and how the individual hydrogen bonds and aromaticity of nucleobases respond to the presence of the metal cation. Here we report a DFT computational study of nucleobase pairs interacting with alkali metal cations. The metal cations contribute to the stabilization of the base pairs to varying degrees depending on their position. The energy decomposition analysis revealed that the nature of bonding between nucleobases does not change much upon metal coordination. The effect of the cations on individual hydrogen bonds were described by changes in VDD charges on frontier atoms, H-bond length, bond energy from NBO analysis, and the delocalization index from QTAIM calculations. The aromaticity changes were determined by a HOMA index. 相似文献
956.
Sergi Hernàndez‐Navarro Dr. Pietro Tierno Prof. Joan Anton Farrera Prof. Jordi Ignés‐Mullol Prof. Francesc Sagués 《Angewandte Chemie (International ed. in English)》2014,53(40):10696-10700
Different phoretic driving mechanisms have been proposed for the transport of solid or liquid microscopic inclusions in integrated chemical processes. It is now shown that a substrate that was chemically modified with photosensitive self‐assembled monolayers enables the direct control of the assembly and transport of large ensembles of micrometer‐sized particles and drops that were dispersed in a thin layer of anisotropic fluid. This strategy separates particle driving, which was realized by AC electrophoresis, and steering, which was achieved by elastic modulation of the nematic host fluid. Inclusions respond individually or in collective modes following arbitrary reconfigurable paths that were imprinted by irradiation with UV or blue light. Relying solely on generic material properties, the proposed procedure is versatile enough for the development of applications that involve either inanimate or living materials. 相似文献
957.
OH⋅⋅⋅N and CH⋅⋅⋅O Hydrogen Bonds Control Hydration of Pivotal Tropane Alkaloids: Tropinone⋅⋅⋅H2O Complex
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Dr. Patricia Écija Montserrat Vallejo‐López Dr. Luca Evangelisti Dr. José A. Fernández Prof. Dr. Alberto Lesarri Prof. Dr. Walther Caminati Dr. Emilio J. Cocinero 《Chemphyschem》2014,15(5):918-923
The effect of monohydration in equatorial/axial isomerism of the common motif of tropane alkaloids is investigated in a supersonic expansion by using Fourier‐transform microwave spectroscopy. The rotational spectrum reveals the equatorial isomer as the dominant species in the tropinone???H2O complex. The monohydrated complex is stabilized primarily by a moderate O?H???N hydrogen bond. In addition, two C?H???O weak hydrogen bonds also support this structure, blocking the water molecule and avoiding any molecular dynamics in the complex. The water molecule acts as proton donor and chooses the ternary amine group over the carbonyl group as a proton acceptor. The experimental work is supported by theoretical calculations; the accuracy of the B3LYP, M06‐2X, and MP2 methods is also discussed. 相似文献
958.
Exploring the Potential Energy Surface of E2P4 Clusters (E=Group 13 Element): The Quest for Inverse Carbon‐Free Sandwiches
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Abril C. Castro Dr. Edison Osorio Dr. José Luis Cabellos Dr. Erick Cerpa Dr. Eduard Matito Prof. Dr. Miquel Solà Prof. Dr. Marcel Swart Prof. Dr. Gabriel Merino 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(16):4583-4590
Inverse carbon‐free sandwich structures with formula E2P4 (E=Al, Ga, In, Tl) have been proposed as a promising new target in main‐group chemistry. Our computational exploration of their corresponding potential‐energy surfaces at the S12h/TZ2P level shows that indeed stable carbon‐free inverse‐sandwiches can be obtained if one chooses an appropriate Group 13 element for E. The boron analogue B2P4 does not form the D4h‐symmetric inverse‐sandwich structure, but instead prefers a D2d structure of two perpendicular BP2 units with the formation of a double B?B bond. For the other elements of Group 13, Al–Tl, the most favorable isomer is the D4h inverse‐sandwich structure. The preference for the D2d isomer for B2P4 and D4h for their heavier analogues has been rationalized in terms of an isomerization‐energy decomposition analysis, and further corroborated by determination of aromaticity of these species. 相似文献
959.
Long‐Range Effects in Anion–π Interactions: Their Crucial Role in the Inhibition Mechanism of Mycobacterium Tuberculosis Malate Synthase
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Antonio Bauzá Dr. David Quiñonero Prof. Dr. Pere M. Deyà Prof. Antonio Frontera 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(23):6985-6990
The glyoxylate shunt is an anaplerotic bypass of the traditional Krebs cycle. It plays a prominent role in Mycobacterium tuberculosis virulence, so it can be exploited for the development of antitubercular therapeutics. The shunt involves two enzymes: isocitrate lyase (ICL) and malate synthase (GlcB). The shunt bypasses two steps of the tricarboxylic acid cycle, allowing the incorporation of carbon, and thus, refilling oxaloacetate under carbon‐limiting conditions. The targeting of ICL is complicated; however, GlcB, which accommodates the pantothenate tail of acetyl‐CoA in the active site, is easier to target. A catalytic Mg2+ unit is located at the bottom of the cavity, and plays a very important role. Recently, the development of effective antituberculosis drugs based on phenyldiketo acids (PDKAs) has been reported. Interestingly, all the crystal structures of GlcB–inhibitor complexes exhibit close contact between the carboxylate of Asp633 and the face of the aromatic ring of the inhibitor. Remarkably, the replacement of the phenyl ring in PDKA by aliphatic moieties yields inactive inhibitors, suggesting that the aromatic moiety is crucial for inhibition. However, the aromatic ring of PDKA is not electron‐deficient, and consequently, the anion–π interaction is expected to be very weak (dominated only by polarization effects). Herein, through a combination analysis of the recent X‐ray structures of GlcB–PDKA complexes retrieved from the protein data bank (PDB) and computational ab initio studies (RI‐MP2/def2‐TZVP level of theory), we demonstrate the prominent role of the Mg2+ ion in the active site, which promotes long‐range enhancement of the anion–π interaction. 相似文献
960.
Aqueous Self‐Assembly and Cation Selectivity of Cobaltabisdicarbollide Dianionic Dumbbells
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Màrius Tarrés Prof. Clara Viñas Patricia González‐Cardoso Dr. Mikko M. Hänninen Prof. Reijo Sillanpää Vladimír Ďorďovič Dr. Mariusz Uchman Prof. Francesc Teixidor Dr. Pavel Matějíček 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(22):6786-6794
The anion [3,3′‐Co(C2B9H11)2]? ([COSAN]?) produces aggregates in water. These aggregates are interpreted to be the result of C?H???H?B interactions. It is possible to generate aggregates even after the incorporation of additional functional groups into the [COSAN]? units. The approach is to join two [COSAN]? anions by a linker that can adapt itself to act as a crown ether. The linker has been chosen to have six oxygen atoms, which is the ideal number for K+ selectivity in crown ethers. The linker binds the alkaline metal ions with different affinities; thus showing a distinct degree of selectivity. The highest affinity is shown towards K+ from a mixture containing Li+, Na+, K+, Rb+ and Cs+; this can be indicative of pseudo‐crown ether performance of the dumbbell. One interesting possibility is that the [COSAN]? anions at the two ends of the linker can act as a hook‐and‐loop fastener to close the ring. This facet is intriguing and deserves further consideration for possible applications. The distinct affinity towards alkaline metal ions is corroborated by solubility studies and isothermal calorimetry thermograms. Furthermore, cryoTEM micrographs, along with light scattering results, reveal the existence of small self‐assemblies and compact nanostructures ranging from spheres to single‐/multi‐layer vesicles in aqueous solutions. The studies reported herein show that these dumbbells can have different appearances, either as molecules or aggregates, in water or lipophilic phases; this offers a distinct model as drug carriers. 相似文献