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https://www.readbyqxmd.com/read/29149720/a-robust-strategy-for-preparation-of-sequential-stimuli-responsive-block-copolymer-prodrugs-via-thiolactone-chemistry-to-overcome-multiple-anticancer-drug-delivery-barriers
#1
Wendong Ke, Wei Yin, Zengshi Zha, Jean Felix Mukerabigwi, Weijian Chen, Yuheng Wang, Chuanxin He, Zhishen Ge
Block copolymer prodrugs (BCPs) have attracted considerable attentions in clinical translation of nanomedicine owing to their self-assembly into well-defined core-shell nanoparticles for improved pharmacokinetics, stability in blood circulation without drug leakage, and optimized biodistribution. However, a cascade of physiological barriers against specific delivery of drugs into tumor cells limit the final therapeutic efficacy. Herein, we report a robust and facile strategy based on thiolactone chemistry to fabricate well-defined BCPs with sequential tumor pH-promoted cellular internalization and intracellular stimuli-responsive drug release...
November 9, 2017: Biomaterials
https://www.readbyqxmd.com/read/29149671/silver-nanoparticles-stimulate-the-proliferation-of-sulfate-reducing-bacterium-desulfovibrio-vulgaris
#2
Zhaoyu Chen, Ji Lu, Shu-Hong Gao, Min Jin, Philip L Bond, Ping Yang, Zhiguo Yuan, Jianhua Guo
The intensive use of silver nanoparticles (AgNPs) in cosmetics and textiles causes their release into sewer networks of urban water systems. Although a few studies have investigated antimicrobial activities of nanoparticles against environmental bacteria, little is known about potential impacts of the released AgNPs on sulfate reducing bacteria in sewers. Here, we investigated the effect of AgNPs on Desulfovibrio vulgaris Hidenborough (D. vulgaris), a typical sulfate-reducing bacterium (SRB) in sewer systems...
November 8, 2017: Water Research
https://www.readbyqxmd.com/read/29149637/antiviral-potential-of-natural-compounds-against-influenza-virus-hemagglutinin
#3
S Kannan, P Kolandaivel
Influenza virus of different subtypes H1N1, H2N2, H3N2 and H5N1 cause many human pandemic deaths and threatening the people worldwide. The Hemagglutinin (HA) protein mediates viral attachment to host receptors act as an attractive target. The sixteen natural compounds have been chosen to target the HA protein. Molecular docking studies have been performed to find binding affinity of the compounds. Out of the sixteen, three compounds CI, CII and CIII found to posses a higher binding affinity. The molecular dynamics (MD) simulation has been performed to study the structural, dynamical properties for the nine different complexes CI, CII, CIII bound with H1, H2, H3 proteins and the results were compared...
November 4, 2017: Computational Biology and Chemistry
https://www.readbyqxmd.com/read/29149589/bond-with-me-if-you-can-natural-product-covalent-ligand-and-reactivity-based-probe-compete-for-cysteine-in-pp2a-complex
#4
Douglas S Johnson, Jaimeen D Majmudar
In this issue of Cell Chemical Biology, Grossman et al. (2017) disclose a chemoproteomics-enabled strategy to identify the cysteine-reactive target(s) of the anti-cancer natural product withaferin A and then screen a cysteine-reactive fragment library to discover a covalent ligand for the same target.
November 16, 2017: Cell Chemical Biology
https://www.readbyqxmd.com/read/29149569/blue-thermally-activated-delayed-fluorescence-polymers-with-nonconjugated-backbone-and-through-space-charge-transfer-effect
#5
Shiyang Shao, Jun Hu, Xingdong Wang, Lixiang Wang, Xiabin Jing, Fosong Wang
We demonstrate a novel molecular design concept for thermally activated delayed fluorescence (TADF) polymers based on a nonconjugated polyethylene backbone with through-space charge transfer effect between pendant electron donor (D) and electron acceptor (A) units. Different from conventional conjugated D-A polymers with through-bond charge transfer effect, the nonconjugated architecture avoids the direct conjugation between D and A units, enabling us to realize blue emission. Meanwhile, the spatial π-π interaction between the physically separated D and A units results in both small singlet-triplet energy splitting (0...
November 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29149566/iedda-reaction-of-molecular-iodine-catalyzed-synthesis-of-1-3-5-triazines-via-functionalization-of-sp-3-c-h-bond-of-acetophenones-with-amidines-an-experimental-investigation-and-dft-study
#6
Abhishek Rajesh Tiwari, Shilpa Raveendra Nath, Kaustubh Ashok Joshi, Bhalchandra Mahadeo Bhanage
The present work reports an inverse electron demand Diels Alder (iEDDA) type reaction to synthesize 1,3,5-trizines from acetophenones and amidines. The use of molecular iodine in catalytic amount facilitates the functionalization of sp3 C-H bond of acetophenones. This is a simple and efficient methodology for the synthesis of 1,3,5-triazines in good to excellent yields under transition metal-free and peroxide-free conditions. The reaction is believed to take place via an in situ iodination-based oxidative elimination of formaldehyde...
November 17, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/29149564/binding-thermodynamics-and-kinetics-calculations-using-chemical-host-and-guest-a-comprehensive-picture-of-molecular-recognition
#7
Zhiye Tang, Chia-En A Chang
Understanding the fine balance between changes of entropy and enthalpy and the competition between a guest and water molecules in molecular binding is crucial in fundamental studies and practical applications. Experiments provide measurements. However, illustrating the binding/unbinding processes gives a complete picture of molecular recognition not directly available from experiments, and computational methods bridge the gaps. Here, we investigated guest association/dissociation with β-cyclodextrin (β-CD) by using microsecond-timescale molecular dynamics (MD) simulations, post-analysis and numerical calculations...
November 17, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/29149560/the-extended-zinc-amber-force-field-ezaff
#8
Zhuoqin Yu, Pengfei Li, Kenneth M Merz
An empirical approach based on the previously developed zinc AMBER force field (ZAFF) is proposed for the determination of the parameters for bonds and angles involving zinc. We call it the extended ZAFF (EZAFF) model because the original ZAFF model was only formulated for 4-coordinated systems, while EZAFF additionally can tackle 5- and 6-coordinated systems. Tests were carried out for 6 metalloproteins and 5 organometallic compounds with different coordination spheres. Results validated the reliability of the current model to handle a variety of zinc containing complexes...
November 17, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/29149557/enantiospecific-and-iterative-suzuki-miyaura-cross-couplings
#9
Jason P G Rygus, Cathleen M Crudden
The Suzuki-Miyaura cross-coupling reaction has emerged as one of the most powerful methods for the construction of carbon-carbon bonds. Though most widely utilized for the synthesis of sp2-sp2 linkages, the use of this reaction to form stereochemistry-bearing sp2-sp3 bonds has received widespread attention over the past decade. This Perspective highlights approaches to the synthesis of enantioenriched molecules via the Suzuki-Miyaura reaction. Particular focus is placed on the use of enantiomerically enriched organoboron compounds as coupling partners in stereospecific processes, as well as the development of enantioconvergent and group-selective reactions...
November 17, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/29149535/a-valence-delocalised-osmium-dimer-capable-of-dinitrogen-photocleavage-ab-initio-insights-into-its-electronic-structure
#10
Vera Krewald, Leticia Gonzalez
The search for molecular catalysts that efficiently activate or cleave the dinitrogen molecule is ongoing. While many thermal dinitrogen cleavage catalysts are known, the photochemical activation of N₂ has received considerably less attention. In this paper, we present the first computational study of the osmium dimer [Os(II,III)₂(µ-N₂)(NH₃)₁₀]5+, which was shown to be capable of dinitrogen photocleavage. Despite its deceptively simple geometry, it has a complex electronic structure with a valence-delocalized and electronically degenerate ground state...
November 17, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/29149487/fabrication-of-chelate-setting-%C3%AE-tricalcium-phosphate-cement-using-sodium-citrate-and-sodium-alginate-as-mixing-solution-and-its-in-vivo-osteoconductivity
#11
Toshiisa Konishi, Poon Nian Lim, Michiyo Honda, Masaki Nagaya, Hiroshi Nagashima, Eng San Thian, Mamoru Aizawa
Moldable and injectable calcium-phosphate cements (CPCs) are material candidates for bone replacement applications. In the present study, we examined the effectiveness of sodium alginate and sodium citrate additives to the liquid phase of CPC, in improving its handling property as well as mechanical strength. The use of these additives enhanced the handling property significantly, in terms of consistency as compared to CPC without additives due to the liquefying effect caused by the adsorption of citrate ions on the cement particles...
November 17, 2017: Journal of Biomedical Materials Research. Part B, Applied Biomaterials
https://www.readbyqxmd.com/read/29149235/isolated-complexes-of-the-amino-acid-arginine-with-polyether-and-polyamine-macrocycles-the-role-of-proton-transfer
#12
Juan Ramón Avilés-Moreno, Giel Berden, Jos Oomens, Bruno Martínez-Haya
The distinct basicity of the guanidinium side-group of arginine (Arg) sustains specific interactions involved in essential biochemical processes. The sensing of arginine is therefore key in modern biotechnology and bioanalysis. In this context, the development of molecular receptors based on crown ether building blocks has demonstrated great potential. We investigate the complexes formed by arginine with two benchmark macrocycles, 12-crown-4 (1,4,7,10-tetraoxacyclododecane) and its N-substituted analog cyclen (1,4,7,10-tetraazacyclododecane)...
November 17, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/29149176/a-simple-way-for-targeted-delivery-of-an-antibiotic-in-vitro-evaluation-of-a-nanoclay-based-composite
#13
Leslie Valdés, Irela Pérez, Louis Charles de Ménorval, Ernesto Altshuler, Jon Otto Fossum, Aramis Rivera
The sodium-modified form of fluorohectorite nanoclay (NaFh) is introduced as a potential drug carrier, demonstrating its ability for the controlled release of the broad-spectrum antibiotic Ciprofloxacin through in vitro tests. The new clay-drug composite is designed to target the local infections in the large intestine, where it delivers most of the incorporated drug thanks to its pH-sensitive behavior. The composite has been conceived to avoid the use of coating technology and to decrease the side-effects commonly associated to the burst-release of the ciprofloxacin at the stomach level...
2017: PloS One
https://www.readbyqxmd.com/read/29148795/bromide-mediated-c-h-bond-functionalization-intermolecular-annulation-of-phenylethanone-derivatives-with-alkynes-for-the-synthesis-of-1-naphthols
#14
Tao Lu, Ya-Ting Jiang, Feng-Ping Ma, Zi-Jing Tang, Liu Kuang, Yu-Xuan Wang, Bin Wang
Bromide-mediated intermolecular annulation of phenylethanone derivatives with alkynes has been developed, which allows for the regioselective formation of polysubstituted 1-naphthols. The usage of readily available bromine catalyst, broad substrate scope, and mild conditions make this protocol very practical. Mechanistic investigations reveal that the bromination of phenylethanone derivatives occurs to yield bromo-substituted intermediates, which react in situ with alkynes to furnish the desired 1-naphthols...
November 17, 2017: Organic Letters
https://www.readbyqxmd.com/read/29148794/preparation-and-formation-process-of-zn-ii-coordinated-nanovesicles
#15
Wuxiao Ding, Naohiro Kameta, Hiroyuki Minamikawa, Mitsutoshi Masuda, Masaki Kogiso
Mixing a glycylglycine-lipid and zinc acetate has been reported to form novel supramolecular Zn(II)-coordinated nanovesicles in ethanol. In this study, we investigate in detail the formation of nanovesicles by using three lipids at different temperatures and discuss their formation process. The original lipids show extremely low solubilities and appear as plate structures in ethanol. Within a small window of lipid solubility, the formation of lipid-Zn(II) complexes occurs mainly on the solid surfaces of plate structures...
November 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29148786/n-alkanethiols-directly-grown-on-a-bare-si-111-surface-from-disordered-to-ordered-transition
#16
Lo-Yueh Chang, Yen-Chien Kuo, Hung Wei Shiu, Chia-Hsin Wang, Yao-Chang Lee, Yaw-Wen Yang, Shangjr Gwo, Chia-Hao Chen
We observed the growth phase transition of n-alkanethiols (AT), CH3(CH2)n-1SH, n = 4 ~16, directly implanted on a bare Si(111) surface, forming an AT monolayer. These monolayers were characterized with static water-contact angle, high-resolution X-ray photoelectron spectroscopy, near-edge X-ray fine-structure spectroscopy and grazing-angle reflection absorption Fourier-transform infrared spectroscopy. The integrated spectral results indicated that the implanted n-AT molecules formed a self-oriented and densely packed monolayer through formation of an S-Si bond...
November 17, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/29148774/the-atmospheric-oxidation-of-furan-and-methyl-substituted-furans-initiated-by-hydroxyl-radicals
#17
Yi Yuan, Xiaocan Zhao, Sainan Wang, Liming Wang
Atmospheric oxidation mechanism of furan and methyl furans (MFs) initiated by OH radicals is studied using high-level quantum chemistry and kinetic calculations. The reaction starts mainly with OH addition to C2/C5-position, forming highly chemically activated adduct radical R2*/R5*, which would either be stabilized by collision or promptly isomerize to R2B*/R5B* by breaking the C2-O/C5-O bond and then isomerize to other conformers of R2B/R5B by internal rotations. Under the atmospheric conditions, the ring-retaining radical R2/R5 would recombine with O2 and be converted to a 5-hydroxy-2-furanone compound and a compound containing epoxide, ester, and carbonyl functional groups, while the ring-opening radicals R2B/R5B would react with O2 and form unsaturated 1,4-dicarbonyl compounds...
November 17, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29148771/an-qm-mm-study-of-the-reaction-catalyzed-by-alkyladenine-dna-glycosylase-examination-of-the-substrate-specificity-of-a-dna-repair-enzyme
#18
Stefan A P Lenz, Stacey D Wetmore
Human alkyladenine DNA glycosylase (AAG) functions as part of the base excision repair pathway to excise structurally diverse oxidized and alkylated DNA purines. Specifically, AAG uses a water molecule activated by a general base and a non-specific active site lined with aromatic residues to cleave the N-glycosidic bond. Despite broad substrate specificity, AAG does not target the natural purines (adenine (A) and guanine (G)). Using the ONIOM(QM:MM) methodology, we provide fundamental atomic level details of AAG bound to DNA-containing a neutral substrate (hypoxanthine (Hx)), a non-substrate (G), or a cationic substrate (7-methylguanine (7MeG)), and probe changes in the reaction pathway that occur when AAG targets different nucleotides...
November 17, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/29148770/covalent-bonding-in-the-hydrogen-molecule
#19
George Bajan Bacskay, Sture Nordholm
This work addresses the continuing disagreement between two schools of thought concerning the mechanism of covalent bonding. According to Hellmann, Ruedenberg and Kutzelnigg, covalent bonding is a quantum mechanical phenomenon whereby lowering of the kinetic energy associated with electron sharing, i.e. delocalization, is the key stabilization mechanism. The opposing view of Slater, Feynman and Bader has maintained that the source of stabilization is electrostatic potential energy lowering due to electron density redistribution to binding regions between nuclei...
November 17, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/29148764/synthesis-of-allylic-amines-by-asymmetric-transfer-hydrogenation-of-%C3%AE-%C3%AE-unsaturated-n-tert-butylsulfinyl-imines
#20
Elisabet Selva, Yeshua Sempere, Débora Ruiz-Martínez, Oscar Pablo, David Guijarro
Primary allylic amines with enantiomeric excesses from 97 to > 99% have been prepared by asymmetric transfer hydrogenation of α,β-unsaturated N-(tert-butylsulfinyl)ketimines followed by removal of the sulfinyl group. The effect caused by different substituents at the C=C bond and at the iminic carbon atom on the chemoselectivity of the reduction has been studied. The desired enantiomer of the final allylic amine can be synthesized by choosing the sulfinyl group with the appropriate absolute configuration...
November 17, 2017: Journal of Organic Chemistry
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