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https://www.readbyqxmd.com/read/28922664/patchy-particles-made-by-colloidal-fusion
#1
Zhe Gong, Theodore Hueckel, Gi-Ra Yi, Stefano Sacanna
Patches on the surfaces of colloidal particles provide directional information that enables the self-assembly of the particles into higher-order structures. Although computational tools can make quantitative predictions and can generate design rules that link the patch motif of a particle to its internal microstructure and to the emergent properties of the self-assembled materials, the experimental realization of model systems of particles with surface patches (or 'patchy' particles) remains a challenge. Synthetic patchy colloidal particles are often poor geometric approximations of the digital building blocks used in simulations and can only rarely be manufactured in sufficiently high yields to be routinely used as experimental model systems...
September 18, 2017: Nature
https://www.readbyqxmd.com/read/28922646/synthesis-spectral-characterization-and-computed-optical-analysis-of-potent-triazole-based-compounds
#2
Sajjad H Sumrra, Fazila Mushtaq, Muhammad Khalid, Muhammad Asam Raza, Muhammad Faizan Nazar, Bakhat Ali, Ataualpa A C Braga
Biologically active triazole Schiff base ligand (L) and metal complexes [Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)] are reported herein. The ligand acted as tridentate and coordinated towards metallic ions via azomethine-N, triazolic-N moiety and deprotonated-O of phenyl substituents in an octahedral manner. These compounds were characterized by physical, spectral and analytical analysis. The synthesized ligand and metal complexes were screened for antibacterial pathogens against Chromohalobacter salexigens, Chromohalobacter israelensi, Halomonas halofila and Halomonas salina, antifungal bioassay against Aspergillus niger and Aspergellus flavin, antioxidant (DPPH, phosphomolybdate) and also for enzyme inhibition [butyrylcholinesterase (BChE) and acetylcholinesterase (AChE)] studies...
September 13, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28922644/temperature-dependent-polymorphism-of-pyrazinamide-an-in-situ-raman-and-dft-study
#3
Poornima Sharma, Rajib Nandi, Debraj Gangopadhyay, Anurag Singh, Ranjan K Singh
The α and γ polymorphs of drug pyrazinamide have been detected with the help of temperature dependent Raman spectroscopic technique. Pyrazinamide is a very useful drug used for the treatment of tuberculosis (TB) and plays a significant role in destroying the dormant tubercle bacilli which are not destroyed by other common TB drugs. Temperature dependent Raman spectra suggest polymorphic phase change from α→γ form of pyrazinamide between 145 and 146°C. In situ Raman spectra of pyrazinamide between 145 and 146°C show the conversion of α→γ form by the shift in CO stretching vibration accompanied by several other changes...
September 13, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28922641/structural-luminescence-thermodynamic-and-theoretical-studies-on-mononuclear-complexes-of-eu-iii-with-pyridine-monocarboxylate-n-oxides-in-aqueous-solution
#4
Rama Mohana Rao Dumpala, Neetika Rawat, Anil Boda, Sk Musharaf Ali, B S Tomar
The mononuclear complexes formed by Eu(III) with three isomeric pyridine monocarboxylate-N-oxides namely picolinic acid-N-oxide (PANO), nicotinic acid-N-oxide (NANO) and isonicotinic acid-N-oxide (IANO) in aqueous solutions were studied by potentiometry, luminescence spectroscopy and isothermal titration calorimetry (ITC) to determine the speciation, coordination, luminescence properties and thermodynamic parameters of the complexes formed during the course of the reaction. More stable six membered chelate complexes with stoichiometry (MLi, i=1-4) are formed by Eu(III) with PANO while non chelating ML and ML2 complexes are formed by NANO and IANO...
September 9, 2017: Spectrochimica Acta. Part A, Molecular and Biomolecular Spectroscopy
https://www.readbyqxmd.com/read/28922636/effects-of-mutations-on-active-site-conformation-and-dynamics-of-rna-dependent-rna-polymerase-from-coxsackievirus-b3
#5
Hujun Shen, Mingsen Deng, Yachao Zhang
Recent crystal structures of RNA-dependent RNA polymerase (3D(pol)) from Coxsackievirus B3 (CVB3) revealed that a tyrosine mutation at Phe364 (F364Y) resulted in structures with open active site whereas a hydrophobic mutation at Phe364 (F364A) led to conformations with closed active site. Besides, the crystal structures showed that the F364W mutation had no preference between the open and closed active sites, similar to wild-type. In this paper, we present a molecular dynamics (MD) study on CVB3 3D(pol) in order to address some important questions raised by experiments...
September 12, 2017: Journal of Molecular Graphics & Modelling
https://www.readbyqxmd.com/read/28922615/the-impact-of-incorporating-antimicrobials-into-implant-surfaces
#6
N J Hickok, I M Shapiro, A F Chen
With the increase in numbers of joint replacements, spinal surgeries, and dental implantations, there is an urgent need to combat implant-associated infection. In addition to stringent sterile techniques, an efficacious way to prevent this destructive complication is to create new implants with antimicrobial properties. Specifically, these implants must be active in the dental implant environment where the implant is bathed in the glycoprotein-rich salivary fluids that enhance bacterial adhesion, and propagation, and biofilm formation...
September 1, 2017: Journal of Dental Research
https://www.readbyqxmd.com/read/28922609/serum-proteomic-variability-associated-with-clinical-phenotype-in-familial-transthyretin-amyloidosis-attrm
#7
Gloria G Chan, Clarissa M Koch, Lawreen H Connors
Transthyretin (TTR), normally a plasma circulating protein, can become misfolded and aggregated, ultimately leading to extracellular deposition of amyloid fibrils usually targeted to heart or nerve tissues. Referred to as TTR-associated amyloidoses (ATTR), this group of diseases is frequently life threatening and fatal if untreated. ATTR, caused by amyloid-forming variant TTR proteins (ATTRm) which arise from point mutations in the TTR gene, were classically referred to as familial amyloid cardiomyopathy (FAC) or familial amyloid polyneuropathy (FAP) reflecting the clinical phenotype...
September 18, 2017: Journal of Proteome Research
https://www.readbyqxmd.com/read/28922608/j-si-h-coupling-constants-of-activated-si-h-bonds
#8
Petra Meixner, Kilian Batke, Andreas Fischer, Dominik Schmitz, Georg Eickerling, Marcel Kalter, Klaus Ruhland, Klaus Eichele, José E Barquera-Lozada, Nicola P M Casati, Fabio Montisci, Piero Macchi, Wolfgang Scherer
We outline in this combined experimental and theoretical NMR study that sign and magnitude of J(Si,H) coupling constants provide reliable indicators to evaluate the extent of the oxidative addition of Si-H bonds in hydrosilane complexes. In combination with experimental electron density studies and MO analyses a simple structure-property relationship emerges: positive J(Si,H) coupling constants are observed in cases where M → L π-back-donation (M = transition metal; L = hydrosilane ligand) dominates. The corresponding complexes are located close to the terminus of the respective oxidative addition trajectory...
September 18, 2017: Journal of Physical Chemistry. A
https://www.readbyqxmd.com/read/28922605/alkane-coiling-in-perfluoroalkane-solutions-a-new-primitive-solvophobic-effect
#9
Pedro Morgado, Ana Rosa Garcia, Luís F G Martins, Laura M Ilharco, Eduardo J M Filipe
In this work we demonstrate that n-alkanes coil when mixed with perfluoroalkanes, changing their conformational equilibria to more globular states, with a higher number of gauche conformations. The new coiling effect is here observed in fluids governed exclusively by dispersion interactions, contrarily to other examples in which hydrogen bonding and polarity play important roles. FTIR spectra of liquid mixtures of n-hexane and perfluorohexane unambiguously reveal that the population of n-hexane molecules in all-trans conformation reduces from 32% in the pure n-alkane to practically zero...
September 18, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
https://www.readbyqxmd.com/read/28922598/proteolytic-unlocking-of-ultra-stable-twin-acylhydrazone-linkers-for-lysosomal-acid-triggered-release-of-anticancer-drugs
#10
Yiwu Zheng, Jing Ren, Yaqi Wu, Xiaoting Meng, Yibing Zhao, Chuanliu Wu
Targeted prodrugs exploiting cleavable linkers capable of responding to endogenous stimuli have increasingly been explored for cancer therapy. Successful application of these prodrug designs relies on the manipulation of both stability and responsiveness of the cleavable linkers, which, however, are difficult to be finely regulated, particularly for acid-responsive acylhydrazone bonds. Here we developed a new class of peptide-bridged twin-acylhydrazone linkers (PTA linkers) displaying both an ultrahigh stability and a rapid responsiveness-highly stable in neutral and acidic conditions due to effect of cooperativity between the two acylhydrazone bonds, easily cleavable in acidic conditions after enzymatically-triggered unlocking of the two bonds...
September 18, 2017: Bioconjugate Chemistry
https://www.readbyqxmd.com/read/28922593/cysteine-silac-mass-spectrometry-enables-the-identification-and-quantitation-of-scrambled-inter-chain-disulfide-bonds-preservation-of-native-heavy-light-chain-pairing-in-bispecific-iggs-generated-by-controlled-fab-arm-exchange
#11
Ewald T J van den Bremer, Aran F Labrijn, Ramon van den Boogaard, Patrick Priem, Kai Scheffler, Joost P M Melis, Janine Schuurman, Paul Parren, Rob N de Jong
Bispecific antibodies (bsAbs) are one of the most versatile and promising pharmaceutical innovations for countering heterogeneous and refractory disease by virtue of their ability to bind two distinct antigens. One critical quality attribute of bsAb formation requiring investigation is the potential randomization of cognate heavy chain (H)/light (L) chain pairing, which could occur to a varying extent dependent on bsAb format and the production platform. To assess the content of such HL chain-swapped reaction products with high sensitivity, we developed cysteine-SILAC, a method that facilitates the detailed characterization of disulfide-bridged peptides by mass-spectrometry...
September 18, 2017: Analytical Chemistry
https://www.readbyqxmd.com/read/28922539/structural-characterization-of-a-covalent-monolayer-sheet-obtained-by-two-dimensional-polymerization-at-an-air-water-interface
#12
Vivian Müller, Feng Shao, Milos Baljozovic, Mina Moradi, Yao Zhang, Thomas Jung, William B Thompson, Benjamin T King, Renato Zenobi, A Dieter Schlüter
This work describes a two-dimensional polymerization at an air/water interface and provides, for the first time, direct spectroscopic evidence for the kind of cross-links formed and for the conversion reached in a covalently bonded monolayer sheet. This is achieved by a combination of a variety of monolayer characterization techniques before and after transfer onto solid substrates in particular by tip-enhanced Raman spectroscopy (TERS) and TERS mapping after transfer of both the monomer and polymer monolayer onto Au(111)...
September 18, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28922537/encapsulation-of-isolated-luminophores-within-supramolecular-cages
#13
Marcel Handke, Takuji Adachi, Chunhua Hu, Michael D Ward
The sequestration of luminophores within supramolecular polyhedral compartments of a crystalline zeolite-like hydrogen-bonded framework illustrates a unique approach to limiting the self-quenching ordinarily exhibited at the high concentrations achievable in this framework. A range of differently sized luminescent guests, namely coumarin 1, coumarin 4, fluorescein, [Ru(bpy)3 ]Cl2 , and rhodamine B, can be encapsulated in amounts of up to one molecule per cage, equivalent to a concentration of 0.175 m, which is significantly higher than the concentration at which aggregation-induced quenching occurs in other media...
September 18, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28922529/borane-stabilized-isomeric-dimers-of-the-phosphaethynolate-anion
#14
Kevin Szkop, Andrew Jupp, Riccardo Suter, Hansjorg Gruetzmacher, Douglas Wade Stephan
The reactions of the phosphaethynolate anion ([PCO]-) with a range of boranes were explored. BPh3 and [PCO]- form a dimeric anion featuring P-B bonds and is prone to dissociation at room temperature. The more Lewis acidic borane B(C6F5)3 yields a less symmetric dimer of [PCO]- with P-B and P-O bonds. Less sterically demanding HB(C6F5)2 and H2B(C6F5) boranes form a third isomer with [PCO]- with both boranes bound to the same phosphorus atom. Despite the unexpected thermodynamic preference for P-coordination, computational data illustrate that electronic and steric features impact the binding modes of the resulting dianionic dimers...
September 18, 2017: Angewandte Chemie
https://www.readbyqxmd.com/read/28922503/modulating-the-structural-properties-of-alpha-gamma-hybrid-peptides-by-alpha-amino-acid-residues-uniform-12-helix-versus-mixed-12-10-helix
#15
Rajkumar Misra, K Muruga Poopathi Raja, Hans-Jörg Hofmann, Hosahudya Gopi
The most important natural a- and 310-helices are stabilized by unidirectional intramolecular hydrogen bonds along the helical cylinder. In contrast, we are reporting here on 12/10-helical conformations with alternately changing H-bond directionality in sequences of alpha,gamma-hybrid peptides [P1: Boc-Ala-Aic-Ala-Aic-COOH; P2: Boc-Leu-Aic-Leu-Aic-OEt; P3: Boc-Leu-Aic-Leu-Aic-Leu-Aic-Aib-OMe; P4: Boc-Ala-Aic-Ala-Aic-Ala-Aic-Ala-OMe; P5: Boc-Leu-Aic-Leu-Aic-Leu-Aic-Leu-Aic-Aib-OMe] composed of natural a-amino acids and the achiral gamma4,4-dimethyl substituted g-amino acid Aic in solution and in single crystals...
September 18, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28922498/c-sp%C3%A2-h-bond-activation-by-vinylidene-gold-i-complexes-a-concerted-asynchronous-or-stepwise-process
#16
Johannes E M N Klein, Gerald Knizia, Laura Nunes Dos Santos Comprido, Johannes Kästner, A Stephen K Hashmi
A detailed analysis of the C(sp³)-H activation process by vinylidene Au(I) complexes is described based on an intrinsic bond orbital analysis. Based on our analysis this event can be divided into three phases: (i) hydride transfer, (ii) C-C bond formation, and (iii) σ to π rearrangement of the lone pair coordinated to Au. Small perturbations of the system lead to either a concerted asynchronous reaction, or a stepwise reaction featuring an intermediate with a C-H-C three-centre two-electron (3c-2e) bond...
September 18, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28922481/photo-induced-assembly-of-a-luminescent-tetraruthenium-square
#17
Baptiste Laramée-Milette, Francesco Nastasi, Fausto Puntoriero, Sebastiano Campagna, Garry S Hanan
Self-assembly is a powerful synthetic tool that has led to the development of one-, two- and three-dimensional architectures. From MOFs to molecular flasks, self-assembled materials have proven to be of great interest to the scientific community. Here we describe a strategy for the construction and de-construction of a supramolecular structure through unprecedented photo-induced assembly and dis-assembly. The combination of two approaches, a [n×1]-directional bonding strategy and a ligand photo-dissociation strategy, allows the photo-induced assembly of a polypyridyl Ru(II) precursor into a discrete molecular square...
September 18, 2017: Chemistry: a European Journal
https://www.readbyqxmd.com/read/28922400/protein-folding-misfolding-and-aggregation-the-importance-of-two-electron-stabilizing-interactions
#18
Andrzej Stanisław Cieplak
Proteins associated with neurodegenerative diseases are highly pleiomorphic and may adopt an all-α-helical fold in one environment, assemble into all-β-sheet or collapse into a coil in another, and rapidly polymerize in yet another one via divergent aggregation pathways that yield broad diversity of aggregates' morphology. A thorough understanding of this behaviour may be necessary to develop a treatment for Alzheimer's and related disorders. Unfortunately, our present comprehension of folding and misfolding is limited for want of a physicochemical theory of protein secondary and tertiary structure...
2017: PloS One
https://www.readbyqxmd.com/read/28922152/brain-biomarkers-in-familial-alzheimer-s-disease-mouse-models
#19
Yafit Kuttner-Hirshler, Palamadai N Venkatasubramanian, Joan Apolinario, Jacqueline Bonds, Alice M Wyrwicz, Orly Lazarov
Alzheimer's disease (AD) is characterized by progressive loss of memory and cognitive deterioration. It is thought that the onset of the disease takes place several decades before memory deficits are apparent. Reliable biomarkers for the diagnosis or prognostication of the disease are highly desirable. Neural stem cells (NSC) exist in the adult brain throughout life and give rise to neural progenitor cells (NPC), which differentiate into neurons or glia. The level of NPC proliferation and new neuron formation is significantly compromised in mouse models of familial Alzheimer's disease (FAD)...
September 8, 2017: Journal of Alzheimer's Disease: JAD
https://www.readbyqxmd.com/read/28921981/the-use-of-cyclopentadienone-iron-tricarbonyl-complexes-for-c-n-bond-formation-reactions-between-amines-and-alcohols
#20
Thomas J Brown, Madeleine Cumbes, Louis J Diorazio, Guy J Clarkson, Martin Wills
The application of a series of (cyclopentadienone)iron tricarbonyl complexes to 'borrowing hydrogen' reactions between amines and alcohols was completed in order to assess their catalytic activity. The electronic variation of the aromatic groups flanking the C=O of the cyclopentadienone influenced the efficiency of the reactions, however in other cases the Knölker catalyst 1, containing trimethylsilyl groups flanking the cyclopentadienone ketone, gave the best results. In some cases, the change of the ratio of amine to alcohol improves the conversion significantly...
September 18, 2017: Journal of Organic Chemistry
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