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https://www.readbyqxmd.com/read/28643349/a-qm-mm-study-of-the-catalytic-mechanism-of-sam-methyltransferase-rlmn-from-escherichia-coli
#1
Chenxiao Zhao, Lihua Dong, Yongjun Liu
RlmN is a radical S-adenosylmethionine (SAM) enzyme that catalyzes the C2 methylation of adenosine 2503 (A2503) in 23S rRNA and adenosine 37 (A37) in several Escherichia coli transfer RNAs (tRNA). The catalytic reaction of RlmN is distinctly different from that of typical SAM-dependent methyltransferases that employs an SN 2 mechanism, but follows a ping-pong mechanism which involves the intermediate methylation of a conserved cysteine residue. Recently, the x-ray structure of a key intermediate in the RlmN reaction has been reported, allowing us to perform combined quantum mechanics and molecular mechanics (QM/MM) calculations to delineate the reaction details of RlmN at atomic level...
June 23, 2017: Proteins
https://www.readbyqxmd.com/read/28633829/different-valence-sn-doping-a-simple-way-to-detect-oxygen-concentration-variation-of-zno-quantum-dots-synthesized-under-ultrasonic-irradiation
#2
Weimin Yang, Bing Zhang, Qitu Zhang, Lixi Wang, Bo Song, Fan Wu, C P Wong
An ultrasonic method is employed to synthesize the Sn doped Zn0.95Sn0.05O quantum dots with green light emission. Sn(2+) and Sn(4+) ions are used to create different optical defects inside Zn0.95Sn0.05O quantum dots and the changing trend of oxygen concentration under different ultrasonic irradiation power are investigated. The photoluminescence spectra are employed to characterize the optical defects of Zn0.95Sn0.05O quantum dots. The UV-vis spectra are used to study the band gap of Zn0.95Sn0.05O quantum dots, which is influenced by their sizes...
September 2017: Ultrasonics Sonochemistry
https://www.readbyqxmd.com/read/28627471/phospholipid-drug-conjugates-as-a-novel-oral-drug-targeting-approach-for-the-treatment-of-inflammatory-bowel-disease
#3
Arik Dahan, Milica Markovic, Svetlana Epstein, Noa Cohen, Ellen M Zimmermann, Aaron Aponick, Shimon Ben-Shabat
The enzyme phospholipase A2 (PLA2) is overexpressed in the inflamed intestine in inflammatory bowel disease (IBD) patients, and in this work we aimed to exploit PLA2 as a prodrug-activating enzyme for a novel PL-drug conjugate, thereby liberating the free drug specifically in the targeted diseased tissue(s). The proposed prodrug contains a drug moiety covalently bound through a linker to the sn-2 position of a phospholipid (PL). The NSAID diclofenac was used as model molecule, and four different linker lengths (2, 4, 6 and 8 -CH2 units) were studied...
June 13, 2017: European Journal of Pharmaceutical Sciences
https://www.readbyqxmd.com/read/28621355/penta-and-hexaorganostannate-iv-complexes-based-on-o-heterocyclic-ligands
#4
Ireen Gebauer, Daniel Gräsing, Jörg Matysik, Stefan Zahn, Kornelia Zeckert
In the present study, the synthesis of homoleptic five- and six-coordinate heteroaryl tin(iv) compounds using two O-heterocyclic substituents, 2-furyl (2-fu) and 2-benzofuryl (2-fu(Bz)) ligands is described. The compounds were obtained as their lithium salts [Li2(OEt2)2Sn(2-fu)6] (1), [Li(tmeda)2][Sn(2-fu)5] (tmeda = N,N,N',N'-tetramethylethylenediamine) (2) and [Li(thf)4][Sn(2-fu(Bz))5] (3), featuring both an intramolecular coordination of the counterions by the anionic hypercoordinate tin(iv) species found in 1 as well as solvent separated cation/anion pairs for compounds 2 and 3...
June 16, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28590551/ozone-induced-dissociation-on-a-traveling-wave-high-resolution-mass-spectrometer-for-determination-of-double-bond-position-in-lipids
#5
Ngoc Vu, Jeffery Brown, Kevin Giles, Qibin Zhang
RATIONALE: The position of C=C within fatty acyl chains affects the biological function of lipids. Ozone induced dissociation-mass spectrometry (OzID-MS) has great potential in determination of lipid double bond position, but has only been implemented on low resolution ion trap mass spectrometers. In addition, most of the OzID-MS experiments carried out so far were focused on the sodiated adducts of lipids, fragmentation of the most commonly observed protonated ions generated in LC-MS based lipidomics workflow has been less explored...
June 7, 2017: Rapid Communications in Mass Spectrometry: RCM
https://www.readbyqxmd.com/read/28573851/screening-of-lipases-with-unusual-high-activity-in-the-sn-2-esterification-of-1-3-dicaprin-under-mild-operating-conditions
#6
Daniel Alberto Sánchez, Gabriela Marta Tonetto, María Luján Ferreira
In this work, the synthesis of acylglycerides with high nutritional value was carried out by enzymatic esterification at sn-2 position of 1,3-dicaprin with palmitic acid. A comparative study of the performance of several biocatalysts according to the obtained products was carried out. The results obtained with several of the biocatalysts evaluated are very interesting, and it would be possible to use them to obtain a mixture of acylglycerides to act as a fat substitute. The final product was composed of about 90% of nutritionally attractive glycerides...
June 21, 2017: Journal of Agricultural and Food Chemistry
https://www.readbyqxmd.com/read/28552363/in-situ-evaluation-of-fluoride-stannous-and-polyphosphate-containing-solutions-against-enamel-erosion
#7
Samira Helena João-Souza, Sávio José C Bezerra, Patrícia Moreira de Freitas, Nelson B de Lima, Ana Cecília Corrêa Aranha, Anderson T Hara, Taís Scaramucci
OBJECTIVE: To evaluate the anti-erosive effect of solutions containing sodium fluoride (F: 225ppm of fluoride), sodium fluoride+stannous chloride (F+Sn: 225ppm of fluoride+800ppm of stannous), sodium fluoride+stannous chloride+sodium linear polyphosphate (F+Sn+LPP: 225ppm of fluoride+800ppm of stannous+2% of sodium linear polyphosphate), and deionized water (C: control), using a four-phase, single-blind, crossover in situ clinical trial. METHODS: In each phase, 12 volunteers wore appliances containing 4 enamel specimens, which were submitted to a 5-day erosion-remineralization phase that consisted of 2h of salivary pellicle formation with the appliance in situ, followed by 2min extra-oral immersion in 1% citric acid (pH 2...
May 25, 2017: Journal of Dentistry
https://www.readbyqxmd.com/read/28551261/production-of-sn-1-3-distearoyl-2-oleoyl-glycerol-rich-fats-from-mango-kernel-fat-by-selective-fractionation-using-2-methylpentane-based-isohexane
#8
Jun Jin, Liyou Zheng, Warda Mwinyi Pembe, Jinfang Zhang, Dan Xie, Xiaosan Wang, Jianhua Huang, Qingzhe Jin, Xingguo Wang
High-purity isohexane containing 88.12% 2-methylpentane, which has a higher polarity than industrial hexane, was selected to selectively fractionate mango kernel fat to produce 1,3-distearoyl-2-oleoyl-glycerol (SOS)-rich fat. The three-stage fractionation process was optimized by considering the stearin yield and its SOS content to obtain a third stearin (TS). This fat contained a high percentage of SOS (69.2%) with only 0.8% diacylglycerol. Mass spectra and sn-2 fatty acid analyses further revealed that the TS was mainly composed of symmetrical monounsaturated triacylglycerols...
November 1, 2017: Food Chemistry
https://www.readbyqxmd.com/read/28541675/prediction-of-bond-vector-autocorrelation-functions-from-larmor-frequency-selective-order-parameter-analysis-of-nmr-relaxation-data
#9
Janet S Anderson, Griselda Hernández, David M LeMaster
Protein molecular dynamics interpretation of the standard R1, R2, and heteronuclear NOE relaxation measurements has typically been limited to a single S(2) order parameter which is often insufficient to characterize the rich content of these NMR experiments. In the absence of exchange linebroadening, an optimized reduced spectral density analysis of these measurements can yield spectral density values at three distinct frequencies. Surprisingly, these three discrete spectral density values have proven to be sufficient for a Larmor frequency-selective order parameter analysis of the 223 methine and methylene H-C bonds of the B3 domain of Protein G (GB3) to accurately back-calculate the entire curve of the corresponding bond vector autocorrelation functions upon which the NMR relaxation behavior depends...
June 6, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28538167/understanding-the-bioavailability-and-sequestration-of-different-metal-cations-in-the-presence-of-a-biodegradable-chelant-mgda-in-biological-fluids-and-natural-waters
#10
Clemente Bretti, Rosalia Maria Cigala, Concetta De Stefano, Gabriele Lando, Silvio Sammartano
Thermodynamic information about the metal-ligand interaction between Fe(3+), Zn(2+), Cu(2+) and Sn(2+), and a biodegradable ligand as MGDA is reported. The speciation scheme was obtained by means of potentiometric measurements and isothermal titration calorimetry (to determine enthalpy changes) in NaCl medium. The formation of the ML and MLOH species was evidenced for all the metal cations, and for Fe(3+) also the ML2 and ML(OH)2 were found. The relative stability, for the ML species, follows the order: Sn(2+) > Fe(3+) > Cu(2+) > Zn(2+)...
May 16, 2017: Chemosphere
https://www.readbyqxmd.com/read/28535603/realizing-full-coverage-of-stable-perovskite-film-by-modified-anti-solvent-process
#11
Long Ji, Ting Zhang, Yafei Wang, Peng Zhang, Detao Liu, Zhi Chen, Shibin Li
Lead-free solution-processed solid-state photovoltaic devices based on formamidinium tin triiodide (FASnI3) and cesium tin triiodide (CsSnI3) perovskite semiconductor as the light harvester are reported. In this letter, we used solvent engineering and anti-solvent dripping method to fabricate perovskite films. SnCl2 was used as an inhibitor of Sn(4+) in FASnI3 precursor solution. We obtained the best films under the function of toluene or chlorobenzene in anti-solvent dripping method and monitored the oxidation of FASnI3 films in air...
December 2017: Nanoscale Research Letters
https://www.readbyqxmd.com/read/28532794/immunogenicity-of-phospholipase-a2-toxins-and-their-role-in-streptococcus-equi-pathogenicity
#12
M R López-Álvarez, M Salze, A Cenier, C Robinson, R Paillot, A S Waller
Streptococcus equi subsp. equi (S. equi) is the causative agent of strangles, one of the most frequently diagnosed infectious diseases of horses worldwide. Phospholipase A2 toxins (PLA2) cleave phospholipid molecules at position sn-2 contributing to the production of leukotrienes that are important inflammatory mediators. Two homologous phospholipases, SlaA and SlaB are encoded by the S. equi genome suggesting that PLA2 toxins may contribute to its pathogenicity. Here we report the immunogenicity and role of PLA2 toxins during natural and experimental infection of horses with S...
May 2017: Veterinary Microbiology
https://www.readbyqxmd.com/read/28530584/triacylglycerol-regioisomers-in-human-milk-resolved-with-an-algorithmic-novel-electrospray-ionization-tandem-mass-spectrometry-method
#13
Heikki Kallio, Matts Nylund, Pontus Boström, Baoru Yang
A highly sensitive mass spectrometric (MS) method was developed and validated to analyze ratios of regioisomeric triacylglycerols (TAGs) in fats and oils. UPLC resolution of lithiated TAGs followed by daughter scan MS/MS of positive ions revealed several indicative ions for quantitative analysis. Reference TAGs containing C14-C20 fatty acids (FAs) showed good linear response. Analysis of Finnish and Chinese pooled human milk samples revealed hundreds of regioisomeric TAGs. At least 64mol% of the TAGs were quantified with relative standard deviation <17%...
October 15, 2017: Food Chemistry
https://www.readbyqxmd.com/read/28494407/streptococcus-mutans-membrane-lipid-composition-virulence-factors-and-structural-parameters
#14
M A Bojanich, R O Calderón
OBJECTIVE: The aim of the present work was to analyze whether the location of the dental biofilm was associated with shifts in the membrane fatty acid profile, and whether such shifts could affect certain virulence factors of strains of Streptococcus mutans. DESIGN: An experimental study was conducted to assess the behavior of S. mutans strains isolated from dental biofilm collected from sound and carious smooth and occlusal surfaces of the oral cavity of children...
April 21, 2017: Archives of Oral Biology
https://www.readbyqxmd.com/read/28484778/strikingly-diverse-reactivity-of-structurally-identical-silylene-and-stannylene
#15
Nasrina Parvin, Rajarshi Dasgupta, Shiv Pal, Sakya S Sen, Shabana Khan
The reactivity of structurally identical silylene and stannylene [PhC(NtBu)2EN(SiMe3)2] (E = Si (1) and Sn (2)) towards coinage metals has been explored. While 1 has the propensity to form an adduct with coinage metals (4 and 5), 2 undergoes a ligand exchange reaction with copper halides and silver triflate leading to PhC(NtBu)2SnX (X = Br (6), Cl (7), and OSO2CF3 (8)) with concomitant formation of [M{N(SiMe3)2}] (M = Cu, Ag). However, with AgSbF6 both 1 and 2 led to ion pairs, 9(+)·SbF6(-)and 10(+)·SbF6(-) displaying weaker Ag·F interactions in the latter...
May 9, 2017: Dalton Transactions: An International Journal of Inorganic Chemistry
https://www.readbyqxmd.com/read/28457130/azide-modified-membrane-lipids-synthesis-properties-and-reactivity
#16
Sindy Lindner, Kai Gruhle, Rico Schmidt, Vasil M Garamus, Daniel Ramsbeck, Gerd Hause, Annette Meister, Andrea Sinz, Simon Drescher
In the present work, we describe the synthesis and the temperature-dependent behavior of photoreactive membrane lipids as well as their capability to study peptide/lipid interactions. The modified phospholipids contain an azide group either in the middle part or at the end of an alkyl chain and also differ in the linkage (ester vs ether) of the second alkyl chain. The temperature-dependent aggregation behavior of the azidolipids was studied using differential scanning calorimetry (DSC), Fourier-transform infrared (FTIR) spectroscopy, and small-angle X-ray scattering (SAXS)...
May 10, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28443847/the-impact-of-dietary-sn-2-palmitic-triacylglycerols-in-combination-with-docosahexaenoic-acid-or-arachidonic-acid-on-lipid-metabolism-and-host-faecal-microbiota-composition-in-sprague-dawley-rats
#17
Jianchun Wan, Songyou Hu, Jörg J Jacoby, Jie Liu, Yaqiong Zhang, Liangli Lucy Yu
Sn-2 palmitic acid triacylglycerols (sn2PA fat) and polyunsaturated fatty acids are thought to influence the metabolic status and intestinal bacterial population of the host. In this study, the impact of sn2PA fat in combination with DHA or ARA in the diet on lipid metabolism in the liver and faecal microbiota composition were investigated in rats fed diets containing sn2PA fat, 90% sn2PA fat + 10% DHA oil (wt%), or 90% sn2PA fat + 10% ARA oil (wt%). Tissue fatty acid composition was measured using gas chromatography (GC), whereas the faecal microbial composition was assessed using 16S rRNA high-throughput sequencing technology...
May 24, 2017: Food & Function
https://www.readbyqxmd.com/read/28433900/production-of-new-human-milk-fat-substitutes-by-enzymatic-acidolysis-of-microalgae-oils-from-nannochloropsis-oculata-and-isochrysis-galbana
#18
Yongjin He, Changyang Qiu, Zheng Guo, Jian Huang, Mingzi Wang, Bilian Chen
Human milk fat substitutes (HMFs) with four kinds of n-3 fatty acid for infant formula were firstly synthesized using triacylglycerols (TAGs) from Nannochloropsis oculata rich in PA at the sn-2 position and free fatty acids (FFAs) from Isochrysis galbana rich in n-3 polyunsaturated fatty acids (n-3 PUFAs-ALA/SDA/DHA) via solvent-free acidolysis with Novozym 435, Lipozyme 435, TL-IM and RM-IM as biocatalysts. The results show that the resulting HMFs contain total n-3 PUFA of 13.92-17.12% and PA of 59.38-68.13% at the sn-2 position under the optimal conditions (mole ratio FFAs/TAG 3:1, 60°C (Novozym 435 and Lipozyme TL-IM) and 50°C (Lipozyme 435 and RM-IM), lipase loading 10%, reaction time 24h)...
August 2017: Bioresource Technology
https://www.readbyqxmd.com/read/28430435/cu-in-halide-perovskite-solar-absorbers
#19
Xin-Gang Zhao, Dongwen Yang, Yuanhui Sun, Tianshu Li, Lijun Zhang, Liping Yu, Alex Zunger
The long-term chemical instability and the presence of toxic Pb in otherwise stellar solar absorber APbX3 made of organic molecules on the A site and halogens for X have hindered their large-scale commercialization. Previously explored ways to achieve Pb-free halide perovskites involved replacing Pb(2+) with other similar M(2+) cations in ns(2) electron configuration, e.g., Sn(2+) or by Bi(3+) (plus Ag(+)), but unfortunately this showed either poor stability (M = Sn) or weakly absorbing oversized indirect gaps (M = Bi), prompting concerns that perhaps stability and good optoelectronic properties might be contraindicated...
May 4, 2017: Journal of the American Chemical Society
https://www.readbyqxmd.com/read/28416864/synthesis-of-structured-lipids-containing-behenic-acid-from-fully-hydrogenated-crambe-abyssinica-oil-by-enzymatic-interesterification
#20
Marilene D M Morselli Ribeiro, Chiu Chih Ming, Thiago I B Lopes, Renato Grimaldi, Anita J Marsaioli, Lireny A G Gonçalves
Low-calorie structured lipids (SLs) rich in behenic and oleic acids were produced by enzymatic (EI) and chemical interesterification (CI) of high oleic sunflower oil and fully hydrogenated Crambe abyssinica oil in proportions of 60:40, 50:50, 40:60 and 30:70 (w/w), respectively. The immobilized lipase from Thermomyces lanuginosus (Lipozyme TL IM) was used for 3 h at 70 °C at a dosage of 7% (w/w) free of organic solvents. The original blend (BE) and the reaction products were evaluated for their fatty acid (FA) and triacylglycerols (TAG) compositions, solid fat contents, thermal analysis, regiospecific distribution of the FA, microstructure and polymorphism...
April 2017: Journal of Food Science and Technology
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