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https://www.readbyqxmd.com/read/28441731/polyphenolic-compounds-and-digestive-enzymes-in-vitro-non-covalent-interactions
#1
REVIEW
Alejandra I Martinez-Gonzalez, Ángel G Díaz-Sánchez, Laura A de la Rosa, Claudia L Vargas-Requena, Ismael Bustos-Jaimes, And Emilio Alvarez-Parrilla
The digestive enzymes-polyphenolic compounds (PCs) interactions behind the inhibition of these enzymes have not been completely studied. The existing studies have mainly analyzed polyphenolic extracts and reported inhibition percentages of catalytic activities determined by UV-Vis spectroscopy techniques. Recently, pure PCs and new methods such as isothermal titration calorimetry and circular dichroism have been applied to describe these interactions. The present review focuses on PCs structural characteristics behind the inhibition of digestive enzymes, and progress of the used methods...
April 22, 2017: Molecules: a Journal of Synthetic Chemistry and Natural Product Chemistry
https://www.readbyqxmd.com/read/28441719/suppression-of-oxidative-stress-and-nf%C3%AE%C2%BAb-mapk-signaling-by-lyophilized-black-raspberries-for-esophageal-cancer-prevention-in-rats
#2
Ni Shi, Fang Chen, Xiaoli Zhang, Steven K Clinton, Xiaofei Tang, Zheng Sun, Tong Chen
Research in the laboratory has shown that lyophilized black raspberries (BRB) significantly inhibit N-nitrosomethylbenzylamine (NMBA)-induced esophageal squamous cell carcinogenesis in rats. The objective of the present study is to characterize the underlying mechanism(s) of anti-cancer action of BRB in this preclinical animal model focusing on oxidative stress and its related oncogenic signaling pathways. Esophageal epithelial tissues were collected and assessed for markers of oxidative stress and nuclear factor κB (NFκB) and mitogen-activated protein kinase (MAPK)...
April 22, 2017: Nutrients
https://www.readbyqxmd.com/read/28441541/molecular-interaction-of-2-4-diacetylphloroglucinol-dapg-with-human-serum-albumin-hsa-the-spectroscopic-calorimetric-and-computational-investigation
#3
Pragna Lakshmi T, Moumita Mondal, Krishna Ramadas, Sakthivel Natarajan
Drug molecule interaction with human serum albumin (HSA) affects the distribution and elimination of the drug. The compound, 2,4-diacetylphloroglucinol (DAPG) has been known for its antimicrobial, antiviral, antihelminthic and anticancer properties. However, its interaction with HSA is not yet reported. In this study, the interaction between HSA and DAPG was investigated through steady-state fluorescence, time-resolved fluorescence (TRF), circular dichroism (CD), Fourier transform infrared (FT-IR) spectroscopy, isothermal titration calorimetry (ITC), molecular docking and molecular dynamics simulation (MDS)...
April 18, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28441057/oxidative-stress
#4
Helmut Sies, Carsten Berndt, Dean P Jones
Oxidative stress is two sided: Whereas excessive oxidant challenge causes damage to biomolecules, maintenance of a physiological level of oxidant challenge, termed oxidative eustress, is essential for governing life processes through redox signaling. Recent interest has focused on the intricate ways by which redox signaling integrates these converse properties. Redox balance is maintained by prevention, interception, and repair, and concomitantly the regulatory potential of molecular thiol-driven master switches such as Nrf2/Keap1 or NF-κB/IκB is used for system-wide oxidative stress response...
April 24, 2017: Annual Review of Biochemistry
https://www.readbyqxmd.com/read/28441032/observation-of-intermolecular-hydrogen-bonding-interactions-in-biosynthesized-and-biodegradable-poly-r-3-hydroxybutyrate-co-r-3-hydroxyhexanoate-in-chloroform-and-1-1-1-3-3-3-hexafluoro-2-propanol-hfip
#5
Brian J Sobieski, Isao Noda, John F Rabolt, D Bruce Chase
In this work, we describe polymer-solvent interactions in biosynthesized and biodegradable poly[(R)-3-hydroxybutyrate- co-(R)-3-hydroxyhexanoate] (PHBHx) and the atactic homopolymer, poly(3-hydroxybutyrate) (a-PHB), which were studied both as neat polymers and in solutions of chloroform and 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP). Specifically, infrared frequency shifts of the carbonyl band were observed in semi-crystalline PHBHx, but not in a-PHB, because it cannot form the helical conformation required for crystallization...
January 1, 2017: Applied Spectroscopy
https://www.readbyqxmd.com/read/28441028/application-of-gc-ms-soft-ionization-for-isomeric-biological-compound-analysis
#6
Takeshi Furuhashi, Koji Okuda
Isomers are compounds with the same molecular formula. Many different types of isomers are ubiquitous and play important roles in living organisms. Despite their early discovery, the actual analysis of isomers has been tricky and has confounded researchers. Using mass spectrometry (MS) to distinguish or identify isomers is an emergent topic and challenge for analytical chemists. We review some techniques for analyzing isomers with emphasis on MS, e.g., the roles of ion reaction, hydrogen-deuterium exchange, ion mobility mass spectrometry, ion spectroscopy and energy change in producing isomer-specific fragments...
April 25, 2017: Critical Reviews in Analytical Chemistry
https://www.readbyqxmd.com/read/28441019/catalytic-enantioselective-%C3%AE-protonation-through-a-cooperative-activation-strategy
#7
Michael H Wang, David Barsoum, C Benjamin Schwamb, Daniel T Cohen, Brian C Goess, Matthias Riedrich, Audrey Chan, Brooks E Maki, Rama K Mishra, Karl A Scheidt
The NHC-catalyzed transformation of unsaturated aldehydes into saturated esters through an organocatalytic homoenolate process has been thoroughly studied. Leveraging a unique "Umpolung"-mediated β-protonation, this process has evolved from a test bed for homoenolate reactivity to a broader platform for asymmetric catalysis. Inspired by our success in using the β-protonation process to generate enals from ynals with good E/Z selectivity, our early studies found that an asymmetric variation of this reaction was not only feasible, but also adaptable to a kinetic resolution of secondary alcohols through NHC-catalyzed acylation...
April 25, 2017: Journal of Organic Chemistry
https://www.readbyqxmd.com/read/28440901/examining-student-heuristic-usage-in-a-hydrogen-bonding-assessment
#8
Kathryn Miller, Thomas Kim
This study investigates the role of representational competence in student responses to an assessment of hydrogen bonding. The assessment couples the use of a multiple-select item ("Choose all that apply") with an open-ended item to allow for an examination of students' cognitive processes as they relate to the assignment of hydrogen bonding within a structural representation. Response patterns from the multiple-select item implicate heuristic usage as a contributing factor to students' incorrect responses...
April 25, 2017: Biochemistry and Molecular Biology Education
https://www.readbyqxmd.com/read/28440821/dft-d3-study-of-h2-and-n2-chemisorption-over-cobalt-promoted-ta3n5-100-010-and-001-surfaces
#9
Constantinos D Zeinalipour-Yazdi, Justin S J Hargreaves, Said Laassiri, C Richard A Catlow
The reactants for ammonia synthesis have been studied, employing density functional theory (DFT), with respect to their adsorption on tantalum nitride surfaces. The adsorption of nitrogen was found to be mostly molecular and non-activated with side-on, end-on and tilt configurations. At bridging nitrogen sites (Ta-N-Ta) it results in an azide functional group formation with a formation energy of 205 kJ mol(-1). H2 was found also to chemisorb molecularly with an adsorption energy in the range -81 to -91 kJ mol(-1)...
April 25, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28440739/featured-article-pharmacological-postconditioning-with-delta-opioid-attenuates-myocardial-reperfusion-injury-in-isolated-porcine-hearts
#10
Maria Seewald, James A Coles, Daniel C Sigg, Paul A Iaizzo
Ischemic preconditioning has been utilized to protect the heart from ischemia prior to ischemia onset, whereas postconditioning is employed to minimize the consequences of ischemia at the onset of reperfusion. The underlying mechanisms and pathways of ischemic pre- and postconditioning continue to be investigated as therapeutic targets. We evaluated the administration of a delta opioid agonist or cariporide on various parameters associated with myocardial reperfusion injury upon reperfusion of isolated porcine hearts...
May 2017: Experimental Biology and Medicine
https://www.readbyqxmd.com/read/28440636/probing-and-comparing-the-photobromination-and-photoiodination-of-dissolved-organic-matter-by-using-ultrahigh-resolution-mass-spectrometry
#11
Zhineng Hao, Yongguang Yin, Dong Cao, Jing-Fu Liu
Photochemical halogenation of dissolved organic matter (DOM) may represent an important abiotic source of natural organobromine compounds (OBCs) and natural organoiodine compounds (OICs) within surface waters. Here we report the significantly enhanced formation of OBCs and OICs by photohalogenating DOM in freshwater and seawater, as well as the noticeable difference in distribution and composition pattern of newly formed OBCs and OICs. By using the negative ion electrospray ionization coupled with Fourier transform ion cyclotron resonance mass spectrometry, numerous OBCs and OICs were identified during the photo halogenation processes in sunlit waters...
April 25, 2017: Environmental Science & Technology
https://www.readbyqxmd.com/read/28440624/acid-base-catalysis-in-glycosidations-a-nature-derived-alternative-to-the-generally-employed-methodology
#12
Peng Peng, Richard R Schmidt
Inverting glycosyltransferases enforce in the active site an intramolecular, acid-base catalyzed glycosidation that, due to proximity of the donor anomeric carbon and the acceptor hydroxyl group, follows an SN2-type reaction. Spacers, tethering donor and acceptor via nonreacting functional groups, led in intramolecular glycosidations to excellent yields and, independent of the donor anomeric configuration, to either the α- or the β-anomer. The requirement of a demanding protecting group pattern confines the application of this efficient method...
April 25, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28440616/discovery-and-characterization-of-a-eukaryotic-initiation-factor-4a-3-selective-inhibitor-that-suppresses-nonsense-mediated-mrna-decay
#13
Misa Iwatani-Yoshihara, Masahiro Ito, Yoshihiro Ishibashi, Hideyuki Oki, Toshio Tanaka, Daisuke Morishita, Takashi Ito, Hiromichi Kimura, Yasuhiro Imaeda, Samuel A Aparicio, Atsushi Nakanishi, Tomohiro Kawamoto
Eukaryotic initiation factor 4A-3 (eIF4A3) is an Asp-Glu-Ala-Asp (DEAD) box-family adenosine triphosphate (ATP)-dependent RNA helicase. Subtypes eIF4A1 and eIF4A2 are required for translation initiation, but eIF4A3 participates in the exon junction complex (EJC) and functions in RNA metabolism including nonsense-mediated RNA decay (NMD). No small molecules for NMD inhibition via selective inhibition of eIF4A3 have been discovered. Here we identified allosteric eIF4A3 inhibitors from a high-throughput screening campaign...
April 25, 2017: ACS Chemical Biology
https://www.readbyqxmd.com/read/28440566/c%C3%A2-%C3%A2-c%C3%A2-helical-folding-in-%C3%AE-%C3%AE-hybrid-peptides-containing-1-aminocyclohexane-acetic-acid-%C3%AE-%C3%A2-%C3%A2-%C3%A2-ac%C3%A2-c
#14
Naiem Ahmad Wani, Srinivasarao Raghothama, Umesh Prasad Singh, Rajkishor Rai
The present study describes the solid state conformation of αβ hybrid peptides, Boc-Leu-β³,³-Ac₆c-OH, P1; Boc-Leu-β³,³-Ac₆c-Leu-β³,³-Ac₆c-OMe, P2 and Boc-Leu-β³,³-Ac₆c-Leu-β³,³-Ac₆c-Leu-OMe, P3. The dipeptide P1 adopts extended conformations, while tetrapeptide P2 and peptapeptide P3 favor helical conformation stabilized by C₁₁/C₉ intramolecular hydrogen bonds. In peptide P3, amino group of β³,³-Ac₆c(2) and β³,³-Ac₆c(4) residues occupies axial orientation, while in P2, it occupies axial and equatorial orientations for residues β³,³-Ac₆c(2) and β³,³-Ac₆c(4), respectively...
April 25, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28440512/astemizole-protects-against-human-umbilical-vein-endothelial-cell-injury-induced-by-hydrogen-peroxide-via-the-p53-signaling-pathway
#15
Jia-Nan Tian, Xiao-Dong Shi, Xiao-Kun Wang, Shuang Wang, Jing-Xue Xu, Chun-Xiao Yang
Astemizole has gained attention as an antineoplastic drug that targets important ion channels. The present study aimed to investigate the protective effects of astemizole against hydrogen peroxide (H2O2)‑induced oxidative damage to human umbilical vein endothelial cells (HUVECs). HUVECs were pretreated with astemizole (0.5 and 1 µM) for 12 h, then exposed to H2O2 (200 µM) for 12 h. Cell viability was measured using the MTT assay. The levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH‑Px), reactive oxygen species (ROS) and apoptotic percentage were determined...
April 21, 2017: Molecular Medicine Reports
https://www.readbyqxmd.com/read/28440458/role-of-the-cystathionine-%C3%AE-synthase-h2s-system-in-liver-cancer-cells-and-the-inhibitory-effect-of-quinolone-indolone-conjugate-qic2-on-the-system
#16
Huina Jia, Juan Ye, Jing You, Xiaoyan Shi, Wenyi Kang, Tianxiao Wang
Hydrogen sulfide (H2S), the third gasotransmitter, plays important roles in cancer biological processes. As endogenous H2S exerts pro-cancer functions, inhibition of its production in cancer cells may provide a new cancer treatment strategy and be achieved via regulation of the function of cystathionine β-synthase (CBS), one of the main metabolic enzymes synthesizing H2S. This enzyme plays important roles in the development and progression of colon and ovarian cancer, primarily regulating mitochondrial bioenergetics and accelerating cell cycle progression...
May 2017: Oncology Reports
https://www.readbyqxmd.com/read/28440382/ph-dependent-structural-diversity-of-a-2-pyridinemethanol-cu-complex-and-its-relatively-strong-magnetic-exchange-coupling-via-hydrogen-bonding
#17
Tomohiko Hamaguchi, Tomoko Nagata, Shinya Hayami, Satoshi Kawata, Isao Ando
The diversity of the self-assembled structures of a Cu complex via hydrogen bonding, including a square planar unit, is reported. The Cu complex forms two self-assembled structures by hydrogen bonding, depending on the acidity of the recrystallization conditions. A linear chain structure can be produced under acidic conditions, and a three-dimensional network structure is observed under basic conditions. The linear chain structure is constructed from intermolecular sharing of a hydrogen atom between two 2-pyridinemethanolate units, with an OO distance of 2...
April 25, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28440370/structure-of-liquid-water-a-dynamical-mixture-of-tetrahedral-and-ring-and-chain-like-structures
#18
Jinfeng Liu, Xiao He, John Z H Zhang
The nature of the dynamical hydrogen-bond network of liquid water under ambient conditions has challenged both experimental and theoretical researchers for decades and remains a topic of intense debate. In this work, we addressed the structural issue of the hydrogen-bond network of liquid water based on an accurate ab initio molecular dynamics simulation. The present work showed clearly that liquid water is neither accurately described by a static picture of mostly tetrahedral water molecules nor dominated by "ring-and-chain" like structures...
April 25, 2017: Physical Chemistry Chemical Physics: PCCP
https://www.readbyqxmd.com/read/28440366/improved-electrical-conductivity-of-tpu-carbon-black-composites-by-addition-of-copa-and-selective-localization-of-carbon-black-at-the-interface-of-sea-island-structured-polymer-blends
#19
Qiyan Zhang, Jingxia Wang, Jian Yu, Zhao-Xia Guo
The electrical percolation threshold of carbon black (CB) in thermoplastic polyurethane (TPU) decreases by 46% with the incorporation of 20 wt% polyamide copolymer (COPA) through selective localization of CB particles at the interface of sea-island structured TPU/COPA blends. Composites with a composition of TPU/20 wt% COPA/9 wt% CB were prepared by four different mixing sequences and their morphologies were investigated by FESEM and TEM. The majority of CB particles were observed at the interface of sea-island structured blends irrespective of the compounding sequence used, although the percentage of CB particles at the interface is considerably less in the composite prepared by adding COPA to premixed TPU/CB...
April 25, 2017: Soft Matter
https://www.readbyqxmd.com/read/28440269/ruthenium-cobalt-nanoalloys-encapsulated-in-nitrogen-doped-graphene-as-active-electrocatalysts-for-producing-hydrogen-in-alkaline-media
#20
Jianwei Su, Yang Yang, Guoliang Xia, Jitang Chen, Peng Jiang, Qianwang Chen
The scalable production of hydrogen could conveniently be realized by alkaline water electrolysis. Currently, the major challenge confronting hydrogen evolution reaction (HER) is lacking inexpensive alternatives to platinum-based electrocatalysts. Here we report a high-efficient and stable electrocatalyst composed of ruthenium and cobalt bimetallic nanoalloy encapsulated in nitrogen-doped graphene layers. The catalysts display remarkable performance with low overpotentials of only 28 and 218 mV at 10 and 100 mA cm(-2), respectively, and excellent stability of 10,000 cycles...
April 25, 2017: Nature Communications
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