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https://www.readbyqxmd.com/read/28926249/the-trans-effect-in-palladium-phosphine-sulfonate-complexes
#1
Elixabete Rezabal, Jesus M M Ugalde, Gernot Frenking
Palladium phosphine sulfonate complexes constitute an efficient family of catalysts for both homopolymerization of ethylene and copolymerization of ethylene with a number of polar monomers. Their catalytic mechanism have been extensively studied but not fully understood at the electronic structure level. The Energy Decomposition Analysis (EDA), complemented with the inspection of the Natural Orbitals for Chemical Valence (NOCV), reveals that their catalytic activity can be rationalized in terms of the co-called ${\it trans}$ ${\it effect}$...
September 19, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28924046/in-silico-modeling-of-the-cryptic-e2-ubiquitin-binding-site-of-e6-associated-protein-e6ap-ube3a-reveals-the-mechanism-of-polyubiquitin-chain-assembly
#2
Virginia P Ronchi, Elizabeth D Kim, Christopher M Summa, Jennifer M Klein, Arthur L Haas
To understand the mechanism for assembly of Lys(48)-linked polyubiquitin degradation signals, we previously demonstrated the E6AP/UBE3A ligase harbors two functionally-distinct E2~ubiquitin binding sites: a high-affinity Site 1 required for E6AP Cys(820)~ubiquitin thioester formation and a canonical Site 2 responsible for subsequent chain elongation. Ordered binding to Sites 1 and 2 is here revealed by observation of UbcH7~ubiquitin-dependent substrate inhibition of chain formation at micromolar concentrations...
September 18, 2017: Journal of Biological Chemistry
https://www.readbyqxmd.com/read/28923469/thermodynamics-and-kinetics-of-single-chain-monellin-folding-with-structural-insights-into-specific-collapse-in-the-denatured-state-ensemble
#3
Hiranmay Maity, Govardhan Reddy
Proteins, which behave as random coils in high denaturant concentrations undergo collapse transition similar to polymers on denaturant dilution. We study collapse in the denatured ensemble of single chain monellin (MNEI) using a coarse-grained protein model and molecular dynamics simulations. The model is validated by quantitatively comparing the computed Guanidinium Chloride (GuHCl) and pH-dependent thermodynamic properties of MNEI folding with the experiments. The computed properties such as the fraction of the protein in the folded state and radius of gyration (Rg) as function of [GuHCl] are in good agreement with the experiments...
September 15, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28921106/kinetic-stability-of-membrane-proteins
#4
REVIEW
F Luis González Flecha
Although membrane proteins constitute an important class of biomolecules involved in key cellular processes, study of the thermodynamic and kinetic stability of their structures is far behind that of soluble proteins. It is known that many membrane proteins become unstable when removed by detergent extraction from the lipid environment. In addition, most of them undergo irreversible denaturation, even under mild experimental conditions. This process was found to be associated with partial unfolding of the polypeptide chain exposing hydrophobic regions to water, and it was proposed that the formation of kinetically trapped conformations could be involved...
September 18, 2017: Biophysical Reviews
https://www.readbyqxmd.com/read/28919656/direct-valorisation-of-waste-cocoa-butter-triglycerides-via-catalytic-epoxidation-ring-opening-and-polymerisation
#5
Dorota D Plaza, Vinzent Strobel, Parminder Kaur Ks Heer, Andrew B Sellars, Seng-Soi Hoong, Andrew J Clark, Alexei A Lapkin
BACKGROUND: Development of circular economy requires significant advances in the technologies for valorisation of waste, as waste becomes new feedstock. Food waste is a particularly important feedstock, containing large variation of complex chemical functionality. Although most food waste sources are complex mixtures, waste from food processing, no longer suitable for the human food chain, may also represent relatively clean materials. One such material requiring valorisation is cocoa butter...
September 2017: Journal of Chemical Technology and Biotechnology
https://www.readbyqxmd.com/read/28919234/effects-of-periplasmic-chaperones-and-membrane-thickness-on-bama-catalysed-outer-membrane-protein-folding
#6
Bob Schiffrin, Antonio N Calabrese, Anna J Higgins, Julia R Humes, Alison E Ashcroft, Antreas C Kalli, David J Brockwell, Sheena E Radford
The biogenesis of outer membrane proteins (OMPs) in Gram-negative bacteria involves delivery by periplasmic chaperones to the β-barrel assembly machinery (BAM) which catalyses OMP insertion into the outer membrane (OM). Here, we examine the effects of membrane thickness, the E. coli periplasmic chaperones Skp and SurA, and BamA, the central subunit of the BAM complex, on the folding kinetics of a model OMP (tOmpA) using fluorescence spectroscopy, native mass spectrometry, and molecular dynamics (MD) simulations...
September 15, 2017: Journal of Molecular Biology
https://www.readbyqxmd.com/read/28918990/long-term-metabolic-persistence-of-gram-positive-bacteria-on-health-care-relevant-plastic
#7
Loree C Heller, Chelsea M Edelblute
BACKGROUND: Health care-associated opportunistic pathogens Staphylococcus aureus and Enterococcus faecium persist on dry environments and can contribute to organism transmission through contact. These organisms can be monitored on surfaces by culture, molecular methods, or metabolic assays. This study was designed to determine the kinetics of bacterial persistence on acrylonitrile butadiene styrene, a plastic commonly used in the manufacture of bedrails. MATERIALS AND METHODS: Polymerase chain reaction for genomic DNA was used to confirm the presence of bacteria cells on this plastic irrespective of viability...
September 14, 2017: American Journal of Infection Control
https://www.readbyqxmd.com/read/28918930/a-parenteral-docetaxel-loaded-lipid-microsphere-with-decreased-7-epidocetaxel-conversion-in-vitro-and-in-vivo
#8
Lifeng Luo, Xiuzhi Wang, Qiuyue Chen, Linlin Miao, Xuezhi Zhuo, Lu Liu, Jiawen Xu, Yu Zhang, Haibing He, Tian Yin, Xing Tang
The purpose of the study was to develop a parenteral docetaxel lipid microsphere to inhibit its 7-epidocetaxel conversion in vitro and in vivo. 7-epidocetaxel conversion as the main indicator was investigated to optimize the formulation and process. 10% medium-chain triglyceride/long-chain triglyceride (3:1) as the oil phase, egg lecithin E80 as the emulsifier and 0.02% NaHSO3 as the acidity regulator were selected to prepare docetaxel lipid microsphere. This study found that pH and temperature were dominant factors on the epimerization of docetaxel in lipid microsphere, and that optimum conditions were a pH of 5...
September 14, 2017: European Journal of Pharmaceutical Sciences
https://www.readbyqxmd.com/read/28918632/analysis-and-sensory-evaluation-of-the-stereoisomers-of-a-homologous-series-c5-c10-of-4-mercapto-2-alkanols
#9
Svenja Nörenberg, Christiane Kiske, Bastian Reichardt, Verena Andelfinger, Anne Pfeiffer, Franziska Schmidts, Wolfgang Eisenreich, Karl-Heinz Engel
A homologous series of 4-mercapto-2-alkanols (C5-C10) was used to investigate the impact of the stereochemistry on the sensory properties of a class of naturally occurring polyfunctional thiols having a 1,3-oxygen-sulfur functionality. Stereoisomers were obtained via syntheses of racemic mixtures and subsequent lipase-catalyzed kinetic resolutions. Analytical separations of the stereoisomers were achieved by capillary gas chromatography (GC) using chiral stationary phases. The absolute configurations were assigned via NMR analysis...
September 17, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28917731/chain-length-dependent-interfacial-immunoreaction-kinetics-on-self-assembled-monolayers-revealed-by-surface-enhanced-infrared-absorption-spectroscopy
#10
Wen-Jing Bao, Jian Li, Tian-Yuan Cao, Jin Li, Xing-Hua Xia
Self-assembled monolayer (SAM) has been extensively applied as ideal interface layer for construction of biosensors. Its chain length and end functional groups determine the physical and chemical properties of the modified surfaces, which will affect the performance of constructed biosensors. Herein, we studied the influence of chain length of n-alkanethiols SAMs on the immunoreaction kinetics employing attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS). Antibody (rabbit immunoglobulin) is assembled on carboxyl terminated SAMs of n-alkanethiols with different chain lengths (n = 3, 6, 11, 16)...
January 1, 2018: Talanta
https://www.readbyqxmd.com/read/28917116/thermal-and-photo-induced-degradation-of-perfluorinated-carboxylic-acids-kinetics-and-mechanism
#11
Jiaoqin Liu, Ruijuan Qu, Zunyao Wang, Itza Mendoza-Sanchez, Virender K Sharma
Perfluorinated carboxylic acids (PFCAs) of different carbon chain lengths are chemicals of concern to human health and their removal, using conventional remediation technologies, is challenging. The present paper pursuits thermal and photo-induced degradation of PFCAs (F(CF2)nCOOH, n = 1-9) under various concentrations of four different acids (HNO3, H2SO4, HCl, and H3PO4) covering a range of strong acidic to basic pH. For thermal-induced experiments, the temperature was set at 40 °C, 60 °C, and 80 °C at acid strengths of 0...
September 6, 2017: Water Research
https://www.readbyqxmd.com/read/28916410/kinetic-stability-and-sequence-structure-studies-of-urine-derived-bence-jones-proteins-from-multiple-myeloma-and-light-chain-amyloidosis-patients
#12
Luis M Blancas-Mejía, Emily B Martin, Angela Williams, Jonathan S Wall, Marina Ramirez-Alvarado
It is now accepted that the ability of a protein to form amyloid fibrils could be associated both kinetic and thermodynamic protein folding parameters. A recent study from our laboratory using recombinant full-length (encompassing the variable and constant domain) immunoglobulin light chains found a strong kinetic control of the protein unfolding for these proteins. In this study, we are extending our analysis by using urine-derived Bence Jones proteins (BJPs) from five patients with light chain (AL) amyloidosis and four patients with multiple myeloma (MM)...
September 1, 2017: Biophysical Chemistry
https://www.readbyqxmd.com/read/28915560/pharynx-mitochondrial-ca-2-dynamics-in-live-c-elegans-worms-during-aging
#13
Pilar Alvarez-Illera, Paloma García-Casas, Jessica Arias-Del-Val, Rosalba I Fonteriz, Javier Alvarez, Mayte Montero
Progressive decline in mitochondrial function is generally considered one of the hallmarks of aging. We have expressed a Ca(2+) sensor in the mitochondrial matrix of C. elegans pharynx cells and we have measured for the first time mitochondrial [Ca(2+)] ([Ca(2+)]M) dynamics in the pharynx of live C. elegans worms during aging. Our results show that worms stimulated with serotonin display a pharynx [Ca(2+)]M oscillatory kinetics that includes both high frequency oscillations (up to about 1Hz) and very prolonged "square-wave" [Ca(2+)]M increases, indicative of energy depletion of the pharynx cells...
August 22, 2017: Oncotarget
https://www.readbyqxmd.com/read/28913413/open-versus-closed-kinetic-chain-exercises-following-an-anterior-cruciate-ligament-reconstruction-a-systematic-review-and-meta-analysis
#14
REVIEW
Daniel Jewiss, Cecilia Ostman, Neil Smart
BACKGROUND: There is no consensus on whether closed kinetic chain (CKC) or open kinetic chain (OKC) exercises should be the intervention of choice following an anterior cruciate ligament (ACL) injury or reconstruction. METHODS: A systematic search identified randomized controlled trials of OKC versus CKC exercise training in people who had undergone ACL reconstructive surgery. All published studies in this systematic review were comparisons between OKC and CKC groups...
2017: Journal of Sports Medicine (Hindawi Publishing Corporation)
https://www.readbyqxmd.com/read/28912867/protective-effect-of-controlled-release-of-cytokine-response-modifier-a-from-chitosan-microspheres-on-rat-chondrocytes-from-interleukin-1%C3%AE-induced-inflammation-and-apoptosis
#15
Pang-Hu Zhou, Lei Shi, Bo Qiu
The aim of the present study was to investigate the protective effect of cytokine response modifier A (CrmA) released from chitosan (CS) microspheres in a controlled manner on interleukin (IL)-1β-induced inflammation and apoptosis in chondrocytes. The CrmA release kinetics were characterized by an initial burst release, which was reduced to a linear release over 8 days. Furthermore, chondrocytes were isolated from 1-week-old Sprague Dawley rats. The cell culture was established by stimulation with 10 ng/ml IL-1β and subsequent incubation with CS-CrmA microspheres...
October 2017: Experimental and Therapeutic Medicine
https://www.readbyqxmd.com/read/28912830/in-vitro-oxidative-decarboxylation-of-free-fatty-acids-to-terminal-alkenes-by-two-new-p450-peroxygenases
#16
Huifang Xu, Linlin Ning, Wenxia Yang, Bo Fang, Cong Wang, Yun Wang, Jian Xu, Severine Collin, Frederic Laeuffer, Laurent Fourage, Shengying Li
BACKGROUND: P450 fatty acid decarboxylases represented by the unusual CYP152 peroxygenase family member OleTJE have been receiving great attention recently since these P450 enzymes are able to catalyze the simple and direct production of 1-alkenes for potential applications in biofuels and biomaterials. To gain more mechanistic insights, broader substrate spectra, and improved decarboxylative activities, it is demanded to discover and investigate more P450 fatty acid decarboxylases. RESULTS: Here, we describe for the first time the expression, purification, and in vitro biochemical characterization of two new CYP152 peroxygenases, CYP-Aa162 and CYP-Sm46Δ29, that are capable of decarboxylating straight-chain saturated fatty acids...
2017: Biotechnology for Biofuels
https://www.readbyqxmd.com/read/28912575/thermodynamics-of-nanodisc-formation-mediated-by-styrene-maleic-acid-2-1-copolymer
#17
Anne Grethen, Abraham Olusegun Oluwole, Bartholomäus Danielczak, Carolyn Vargas, Sandro Keller
Styrene/maleic acid copolymers (SMA) have recently attracted great interest for in vitro studies of membrane proteins, as they self-insert into and fragment biological membranes to form polymer-bounded nanodiscs that provide a native-like lipid-bilayer environment. SMA copolymers are available in different styrene/maleic acid ratios and chain lengths and, thus, possess different charge densities, hydrophobicities, and solubilisation properties. Here, we studied the equilibrium solubilisation properties of the most commonly used copolymer, SMA(2:1), by monitoring the formation of nanodiscs from phospholipid vesicles using (31)P nuclear magnetic resonance spectroscopy, dynamic light scattering, and differential scanning calorimetry...
September 14, 2017: Scientific Reports
https://www.readbyqxmd.com/read/28902217/a-bifunctional-old-yellow-enzyme-from-penicillium-roqueforti-is-involved-in-ergot-alkaloid-biosynthesis
#18
Nina Gerhards, Shu-Ming Li
The blue cheese-making fungus Penicillium roqueforti produces isofumigaclavine A as the main ergot alkaloid. Recently, genome mining revealed the presence of two DNA loci bearing the genetic potential for its biosynthesis. In this study, a short-chain dehydrogenase/reductase (SDR) from one of the loci was proved to be responsible for the conversion of chanoclavine-I to its aldehyde. Furthermore, a putative gene coding for an enzyme with high homology to Old Yellow Enzymes (OYEs) involved in the ergot alkaloid biosynthesis was found outside the two clusters...
September 13, 2017: Organic & Biomolecular Chemistry
https://www.readbyqxmd.com/read/28891636/cuaac-based-click-chemistry-in-self-healing-polymers
#19
Diana Döhler, Philipp Michael, Wolfgang H Binder
Click chemistry has emerged as a significant tool for materials science, organic chemistry, and bioscience. Based on the initial concept of Barry Sharpless in 2001, the copper(I)-catalyzed azide/alkyne cycloaddition (CuAAC) reaction has triggered a plethora of chemical concepts for linking molecules and building blocks under ambient conditions, forming the basis for applications in autonomous cross-linking materials. Self-healing systems on the other hand are often based on mild cross-linking chemistries that are able to react either autonomously or upon an external trigger...
September 11, 2017: Accounts of Chemical Research
https://www.readbyqxmd.com/read/28890968/ultrafast-flavin-photoreduction-in-an-oxidized-animal-6-4-photolyase-through-an-unconventional-tryptophan-tetrad
#20
Ryan Martin, Fabien Lacombat, Agathe Espagne, Nadia Dozova, Pascal Plaza, Junpei Yamamoto, Pavel Müller, Klaus Brettel, Aurélien de la Lande
Photolyases are flavoenzymes repairing UV-induced lesions in DNA, which may be activated by a photoreduction of their FAD cofactor. In most photolyases, this photoreduction proceeds by electron transfer along a chain of three tryptophan (Trp) residues, connecting the flavin to the protein surface. Much less studied, animal (6-4) photolyases (repairing pyrimidine-pyrimidone (6-4) photoproducts) are particularly interesting as they were recently shown to have a longer electron transfer chain, counting four Trp residues...
September 11, 2017: Physical Chemistry Chemical Physics: PCCP
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