Search results for " modifica"

Second harmonic generation in SiO2 sol-gel films functionalized with Ethyl-[4-(4-nitro-phenylazo)-phenyl]-(2-oxiranylmethoxy-ethyl)-amine (ENPMA) mol…

2010

Abstract High concentrations of Ethyl-[4-(4-nitro-phenylazo)-phenyl]-(2-oxiranylmethoxy-ethyl)-amine (ENPMA) chromophores were linked covalently to two different kinds of SiO 2 matrices prepared by the sol–gel method. The matrices differed in their reticulation level, determined by the organometallic precursor used during the synthesis. The materials were deposited as films by spin-coating. The chromophores in the films were oriented in a non-centrosymmetric way by a modified Corona poling set-up, and the nonresonant second order non-linear optical coefficient d 33 (0) of the films was determined by means of the Maker fringe technique. It was found that there is an optimum concentration of …

Nanoreactors for the multi-functionalization of poly-histidine fragments

2019

Water-soluble MBHA derivatives were found to self-assemble in a water environment to generate aggregates showing core–shell architectures. The aggregates appeared to be capable of working as nanoreactors performing a multi-functionalization of poly-histidine fragments, which after an initial interaction with the solvated oligo(ethylene glycol) shell reach the reactive core.

Cover Picture: Photo-Chromium: Sensitizer for Visible-Light-Induced Oxidative C−H Bond Functionalization-Electron or Energy Transfer? (ChemPhotoChem …

2017

Chromatin dynamics of the developmentally regulated P. lividus neural alpha tubulin gene

2011

Over 40 years ago, Allfrey and colleagues (1964) suggested that two histone modifications, namely acetylation and methylation, might regulate RNA synthesis. Nowadays it is universally accepted that activation of gene expression strictly depends on enzymatic mechanisms able to dynamically modify chromatin structure. Here, using techniques including DNaseI hypersensitive site analysis, chomatin immunoprecipitation and quantitative PCR analysis, we have analyzed the dynamics of histone post-translation modifications involved in developmentally/spatially controlled activation of the sea urchin PlTalpha2 tubulin gene. We have demonstrated that only when the PlTalpha2 core promoter chromatin is a…

The Sea Urchin sns5 Insulator Protects Retroviral Vectors From Chromosomal Position Effects by Maintaining Active Chromatin Structure

2009

Silencing and position-effect (PE) variegation (PEV), which is due to integration of viral vectors in heterochromatin regions, are considered significant obstacles to obtaining a consistent level of transgene expression in gene therapy. The inclusion of chromatin insulators into vectors has been proposed to counteract this position-dependent variegation of transgene expression. Here, we show that the sea urchin chromatin insulator, sns5, protects a recombinant gamma-retroviral vector from the negative influence of chromatin in erythroid milieu. This element increases the probability of vector expression at different chromosomal integration sites, which reduces both silencing and PEV. By chr…

Epigenetic Transcriptional Regulation of the Growth Arrest-Specific gene 1 (Gas1) in Hepatic Cell Proliferation at Mononucleosomal Resolution

2011

Background Gas1 (growth arrest-specific 1) gene is known to inhibit cell proliferation in a variety of models, but its possible implication in regulating quiescence in adult tissues has not been examined to date. The knowledge of how Gas1 is regulated in quiescence may contribute to understand the deregulation occurring in neoplastic diseases. Methodology/Principal Findings Gas1 expression has been studied in quiescent murine liver and during the naturally synchronized cell proliferation after partial hepatectomy. Chromatin immunoprecipitation at nucleosomal resolution (Nuc-ChIP) has been used to carry out the study preserving the in vivo conditions. Transcription has been assessed at real …

Synthesis and properties of chemically modified dihydroxy-, hydroxyamino- and amino-functional silica packings in adsorption chromatography

1980

1,2-Dihydroxy-3-propoxypropyl (HPP), 1-amino-2-hydroxy-3-propoxypropyl (AHP) and 3-(2-aminoethylamino)propyl (AEAP) silica packings were synthesized by means of both a surface modification and a bulk modification procedure. In surface modification a complete monolayer of bonded groups could be achieved. The modifiers reacted with the silanol groups according to a bifunctional mechanism. Eluotropic series of solvents were established on these polar modified silicas referring to n-heptane having ɛ∘=0. The solvent parameter ratio of modified to bare silica was found to be constant over a wide range of solvent compositions as \(\varepsilon _{{\text{HPP - silica}}}^ \circ = 0.26\varepsilon _{{\t…

EVALUATION OF THE ELUTION STRENGTH OF THE SURFACTANT AND ORGANIC SOLVENT IN HYBRID MICELLAR MOBILE PHASES

2001

The global ability of a mixed mobile phase (with two or more modifiers) to elute a solute is often measured without distinguishing between the elution strength of each modifier. An algorithm is proposed to evaluate the elution strength of the modifiers in hybrid micellar mobile phases containing a surfactant and an organic solvent. The algorithm is based on a mechanistic retention model that takes into account the competing equilibria of solutes among aqueous-organic phase, micelle, and stationary phase. The change in the elution strength of surfactant and organic solvent with respect to the concentration of both modifiers is also examined. The results are discussed according to the values …

Column technology in liquid chromatography

2017

This chapter deals with the most important part of the liquid chromatography (LC) system: the column enabling the efficient and fast resolution of complex mixtures. It is divided into seven sections under the overall aspects of manufacture, operation, and evaluation of analytical columns for the user. The first three sections highlight the column design and hardware, followed by a thorough treatment of the properties of microparticulate silica adsorbents as packing material, stationary phases performed by surface functionalization, and the column filling process. Then, the implementation of the column into the LC system is discussed, leading into chromatographic column testing as a C18-bond…

Hydrolytically stable chemically bonded silica supports with metal complexating ligands: Synthesis, characterization and use in high-performance liga…

1982

A silica of 14 nm pore size was reacted according to two procedures with the following silanes: γ-aminopropyltriethoxysilane (1), N-aminoethyl-N′-aminopropyltrimethoxysilane (2), N-aminoethyl-N′-aminoethyl-N″-aminopropyltrimethoxysilane (3), N-(3-triethoxysilanepropyl)-N, N-diacetic dimethylester (4), N-(3-trisodiumsilanolatepropyl)-N, N-diacetic acid disodium salt (5) and N-(3-trisodiumsilanolatepropyl)-ethylenediamine-N, N′, N′-triacetic acid trisodium salt (6). The reaction of silanes 1–4 with the silica was carried out under anhydrous conditions (procedure A). Silanes 1–6 were subjected to surface modification under essentially hydrous conditions applying a two-step procedure (procedure…