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61.
The detailed structural characterization of complex polymer architectures, like copolymers and polymer mixtures, by mass spectrometry
presents a challenge. Even though soft ionization analyses revolutionized the characterization of large molecules and provided
a means for determining the polymer’s molecular weight distribution, polydispersity, and end groups, full microstructure elucidation
and monomer sequencing by soft ionization alone is not possible. The combination of high-resolution Fourier transform mass
spectrometry (FTMS) and tandem mass spectrometry (MSn) provides a powerful analytical tool for addressing these challenges. This tool was used in our work to separate and identify
the products of polymerization between 12-hydroxystearic acid (HSA) and stearic acid (SA), to provide precise information
about the exact location of caprolactones on the Tris(2-hydroxyethyl)isocyanurate (THEIC) molecule, and to sequence a glycidyl
methacrylate/methyl methacrylate (GMA/MMA) copolymer. The results highlight the value of ultrahigh resolution and tandem mass
spectrometry for fine structural characterization and sequencing of polymers. 相似文献
62.
Sinan Faiad Dr. Quentin Laurent Dr. Alexander L. Prinzen Jathavan Asohan Dr. Daniel Saliba Dr. Violeta Toader Prof. Hanadi F. Sleiman 《Angewandte Chemie (International ed. in English)》2023,62(51):e202315768
Nucleic acid therapeutics (NATs), such as mRNA, small interfering RNA or antisense oligonucleotides are extremely efficient tools to modulate gene expression and tackle otherwise undruggable diseases. Spherical nucleic acids (SNAs) can efficiently deliver small NATs to cells while protecting their payload from nucleases, and have improved biodistribution and muted immune activation. Self-assembled SNAs have emerged as nanostructures made from a single DNA-polymer conjugate with similar favorable properties as well as small molecule encapsulation. However, because they maintain their structure by non-covalent interactions, they might suffer from disassembly in biologically relevant conditions, especially with regard to their interaction with serum proteins. Here, we report a systematic study of the factors that govern the fate of self-assembled SNAs. Varying the core chemistry and using stimuli-responsive disulfide crosslinking, we show that extracellular stability upon binding with serum proteins is important for recognition by membrane receptors, triggering cellular uptake. At the same time, intracellular dissociation is required for efficient therapeutic release. Disulfide-crosslinked SNAs combine these two properties and result in efficient and non-toxic unaided gene silencing therapeutics. We anticipate these investigations will help the translation of promising self-assembled structures towards in vivo gene silencing applications. 相似文献
63.
Ana‐Maria Acu Carmen Violeta Muraru Daniel Florin Sofonea Voichiţa Adriana Radu 《Mathematical Methods in the Applied Sciences》2016,39(18):5636-5650
In this paper, we will propose a Durrmeyer variant of q‐Bernstein–Schurer operators. A Bohman–Korovkin‐type approximation theorem of these operators is considered. The rate of convergence by using the first modulus of smoothness is computed. The statistical approximation of these operators is also studied. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
64.
Let E be a Banach space of functions on a locally compact Abeliangroup G satisfying certain conditions. It has been proved thatfor every bounded operator M on E commuting with translationsthere exists such that , where is a suitable subset of the group of the continuous morphismsfrom G into * and is a generalized Fourier transform of g defined on . 相似文献
65.
66.
Stepwise Strategy to Cyclometallated PtII Complexes with N‐Heterocyclic Carbene Ligands: A Luminescence Study on New β‐Diketonate Complexes
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Dr. Sara Fuertes Dr. Hector García Dr. Mariano Perálvarez Wim Hertog Dr. Josep Carreras Dr. Violeta Sicilia 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(4):1620-1631
The imidazolium salt 3‐methyl‐1‐(naphthalen‐2‐yl)‐1H‐imidazolium iodide ( 2 ) has been treated with silver(I) oxide and [{Pt(μ‐Cl)(η3‐2‐Me‐C3H4)}2] (η3‐2‐Me‐C3H4=η3‐2‐methylallyl) to give the intermediate N‐heterocyclic carbene complex [PtCl(η3‐2‐Me‐C3H4)(H$\widehat{CC}$ *‐κC*)] ( 3 ) (H$\widehat{CC}$ *‐κC*=3‐methyl‐1‐(naphthalen‐2‐yl)‐1H‐imidazol‐2‐ylidene). Compound 3 undergoes regiospecific cyclometallation at the naphthyl ring of the NHC ligand to give the five‐membered platinacycle compound [{Pt(μ‐Cl)($\widehat{CC}$ *)}2] ( 4 ). Chlorine abstraction from 4 with β‐diketonate Tl derivatives rendered the corresponding neutral compounds [Pt($\widehat{CC}$ *)(L‐O,O′)] {L=acac (HL=acetylacetone) 5 , phacac (HL=1,3‐diphenyl‐1,3‐propanedione) 6 , hfacac (HL=hexafluoroacetylacetone) 7 }. All of the compounds ( 3 – 7 ) were fully characterized by standard spectroscopic and analytical methods. X‐ray diffraction studies were performed on 5 – 7 , revealing short Pt?Pt and π–π interactions in the solid‐state structure. The influence of the R‐substituents of the β‐diketonate ligand on the photophysical properties and the use of the most efficient emitter, 5 , as phosphor converter has also been studied. 相似文献
67.
Koleva V Zhecheva E Stoyanova R 《Dalton transactions (Cambridge, England : 2003)》2011,40(28):7385-7394
Dittmarite-type compound KMnPO(4)·H(2)O was used as a new precursor for the synthesis of nanostructured LiMnPO(4) phospho-olivines with a plate-like morphology at low temperature (about 200 °C) and a short reaction time (90-180 min). The dehydration of KMnPO(4)·H(2)O was studied by DTA and TG analysis. Structural and morphological characterization of both KMnPO(4)·H(2)O and LiMnPO(4) was performed by powder XRD, SEM and TEM analyses. The formation of nanostructured LiMnPO(4) was examined by electron paramagnetic resonance spectroscopy and TEM. It was found that the reaction between KMnPO(4)·H(2)O with the LiCl-LiNO(3) mixture includes a fast ionic exchange of K(+) with Li(+) in the framework of the dittmarite structure, followed by H(2)O release and the formation of the olivine-type structure. The morphology and texture of the dittmarite-type precursor results in a plate-like morphology of LiMnPO(4) with a preferred orientation along the [100] direction. The plate-like morphology of LiMnPO(4) is stable after annealing at 500 °C. The plates are composed of nanocrystallites, with various sizes in the range 10-20 nm. The EPR signal of LiMnPO(4) is due to the exchange-coupled Mn(2+) ions. It was demonstrated that the EPR line-width correlates with the Scherrer crystallite size. 相似文献
68.
S-Alkyl O,O-dialkyl thiophosphates are prepared by alkylation of the triethylammonium salt of O,O-diisopropyl thiophosphoric acid. S-Benzyl thiophosphate was metallated at temperatures of ≥-45 °C by trityllithium and LiTMP (lithium 2,2,6,6-tetramethylpiperidide) and S-alkyl thiophosphates only by LiTMP to give dipole-stabilised carbanions which rearrange to α-mercaptophosphonates in yields of up to 45%. Metallation occurs with a high primary kinetic isotope effect (k(H)/k(D) up to ≈50). When the lithium (R)-N-isopropyl-1-phenylethylamide was used to induce the isomerisation of S-pentyl thiophosphate an α-mercaptophosphonate with an ee of 22% was isolated. (R)-S-[1-D(1)]hexyl O,O-diisopropyl thiophosphate was rearranged to a dextrorotary α-mercapto-[1-D(1)]hexylphosphonate, whose (R)-configuration was determined by chemical correlation. The thiophosphate-mercaptophosphonate rearrangement proceeds with retention of configuration. 相似文献
69.
Juan Forniés Violeta Sicilia Pilar Borja José M. Casas Alvaro Díez Elena Lalinde Carmen Larraz Antonio Martín M. Teresa Moreno 《化学:亚洲杂志》2012,7(12):2813-2823
The neutral compounds [Pt(bzq)(CN)(CNR)] (R=tBu ( 1 ), Xyl ( 2 ), 2‐Np ( 3 ); bzq= benzoquinolate, Xyl=2,6‐dimethylphenyl, 2‐Np=2‐napthyl) were isolated as the pure isomers with a trans‐Cbzq,CNR configuration, as confirmed by 13C{1H} NMR spectroscopy in the isotopically marked [Pt(bzq)(13CN)(CNR)] (R=tBu ( 1′ ), Xyl ( 2′ ), 2‐Np ( 3′ )) derivatives (δ13CCN≈110 ppm; 1J(Pt,13C)≈1425 Hz]. By contrast, complex [Pt(bzq)(C≡CPh)(CNXyl)] ( 4 ) with a trans‐Nbzq,CNR configuration, has been selectively isolated from [Pt(bzq)Cl(CNXyl)] (trans‐Nbzq,CNR) using Sonogashira conditions. X‐ray diffraction studies reveal that while 1 adopts a columnar‐stacked chain structure with Pt–Pt distances of 3.371(1) Å and significant π???π interactions (3.262 Å), complex 2 forms dimers supported only by short Pt???Pt (3.370(1) Å) interactions. In complex 4 the packing is directed by weak bzq???Xyl and bzq???C≡E (C, N) interactions. In solid state at room temperature, compounds 1 and 2 both show a bright red emission (?=42.1 % 1 , 57.6 % 2 ). Luminescence properties in the solid state at 77 K and concentration‐dependent emission studies in CH2Cl2 at 298 K and at 77 K are also reported for 1 , 1·CHCl3 , 2 , 2' , 2·CHCl3 , 3 , 4 . 相似文献
70.
Amer?Baniodeh Abhishake?Mondal Ravil?GaleevEmail authorView authors OrcID profile Andrei?Sukhanov Rushana?Eremina Violeta?Voronkova Christopher?E.?Anson Annie?K.?Powell 《Applied magnetic resonance》2017,48(1):101-113
The DyIII ions in the dimer [Dy2(H2tea)2(O2CPh)4]·2H2O (1) (H3tea = triethanolamine) have the 9-coordinate monocapped square-antiprismatic ligand field environment. Compound 1 shows slow relaxation of magnetization which is observable only with applied magnetic fields. This is consistent with the idea that low-symmetry ligand fields allow for the quantum tunneling of magnetization. This is reflected by the fact that there are no observable maxima in the out-of-phase ac susceptibility above 1.8 K. The {g}-tensor of the DyIII ions {g x = 11, g y = 8.2, g z = 1} further underlying the reduced uniaxiality in this system was determined in electron paramagnetic resonance (X- and Q-band) studies of 1 at temperatures down to 4 K. 相似文献