Search results for "Proton"

Cationic Copolymerization of 3,3-Bis(hydroxymethyl)oxetane and Glycidol: Biocompatible Hyperbranched Polyether Polyols with High Content of Primary H…

2015

The cationic ring-opening copolymerization of 3,3-bis(hydroxymethyl)oxetane (BHMO) with glycidol using different comonomer ratios (BHMO content from 25 to 90%) and BF3OEt2 as an initiator has been studied. Apparent molecular weights of the resulting hyperbranched polyether copolymers ranged from 1400 to 3300 g mol(-1) (PDI: 1.21-1.48; method: SEC, linear PEG standards). Incorporation of both comonomers is evidenced by MALDI-TOF mass spectroscopy. All hyperbranched polyether polyols with high content of primary hydroxyl groups portray good solubility in water, which correlates with an increasing content of glycerol units. Detailed NMR characterization was employed to elucidate the copolymer …

Biodegradable pH-Sensitive Poly(ethylene glycol) Nanocarriers for Allergen Encapsulation and Controlled Release

2015

In the last decades, the number of allergic patients has increased dramatically. Allergen-specific immunotherapy (SIT) is the only available cause-oriented therapy so far. SIT reduces the allergic symptoms, but also exhibits some disadvantages; that is, it is a long-lasting procedure and severe side effects like anaphylactic shock can occur. In this work, we introduce a method to encapsulate allergens into nanoparticles to avoid severe side effects during SIT. Degradable nanocarriers combine the advantage of providing a physical barrier between the encapsulated cargo and the biological environment as well as responding to certain local stimuli (like pH) to release their cargo. This work int…

Poly(Ethylene Glycol) Dimethacrylates with Cleavable Ketal Sites: Precursors for Cleavable PEG-Hydrogels.

2017

The authors introduce poly(ethylene glycol) (PEG) based macromonomers containing acid-labile ketal moieties as well as terminal methacrylate units that are amenable to radical polymerization. The synthesis of PEGs of different molecular weights (ranging from 2000 to 13 000 g mol-1 with polydispersities <1.15) with a central ketal unit (PEG-ketal-diol) and their conversion to PEG-ketal-dimethacrylates (PEG-ketal-DMA) is introduced. Degradation rates of both PEG-ketal-diols and PEG-ketal-DMA are investigated by in situ 1 H NMR kinetic studies in deuterated phosphate buffer. Hydrogels containing 0, 5, or 10 wt% of PEG-ketal-DMA and 100, 95, or 90 wt% of PEG-DMA, respectively, are synthesized a…

pH-responsive physically and chemically cross-linked glutamic-acid-based hydrogels and nanogels

2018

Abstract Given the great demand for polymers prepared from renewable materials, the synthesis of a glutamic-acid-based hydrogel by solution and inverse miniemulsion polymerization is herein presented. Free radical initiated homopolymerizations of N-acryloyl- l -glutamic acid (l- AGA) resulted in either a readily water-soluble polymer or a physically cross-linked hydrogel, being the formation of physical cross-linking junctions closely related to monomer concentration and mixture viscosity. Chemically cross-linked poly( l -AGA-co-BIS) hydrogels were also synthesized by copolymerization of l -AGA and N,N′-methylenebis(acrylamide) (BIS). Both poly (l- AGA) and poly( l -AGA-co-BIS) swelling beh…

Zn-Enhanced Asp-Rich Antimicrobial Peptides N-Terminal Coordination by Zn(II) and Cu(II), Which Distinguishes Cu(II) Binding to Different Peptides

2021

The antimicrobial activity of surfactant-associated anionic peptides (SAAPs), which are isolated from the ovine pulmonary surfactant and are selective against the ovine pathogen Mannheimia haemolytica, is strongly enhanced in the presence of Zn(II) ions. Both calorimetry and ITC measurements show that the unique Asp-only peptide SAAP3 (DDDDDDD) and its analogs SAAP2 (GDDDDDD) and SAAP6 (GADDDDD) have a similar micromolar affinity for Zn(II), which binds to the N-terminal amine and Asp carboxylates in a net entropically-driven process. All three peptides also bind Cu(II) with a net entropically-driven process but with higher affinity than they bind Zn(II) and coordination that involves the N…

Improvements in H2/O2 thin film fuel cell working with Porous Anodic Alumina-supported electrolytes

2009

Novel meso-substituted porphyrins: Synthesis, characterization and photocatalytic activity of their TiO2-based composites

2009

Abstract Two series of novel meso-substituted porphyrins, namely 5,10,15,20-tetra[4-(3-phenoxy)-propoxy]phenyl porphyrin, the structural analogue 5,10,15,20-tetra[2-(3-phenoxy)-propoxy]phenyl porphyrin and their Co(II) Cu(II) and Zn(II) complexes were synthesized. The compounds were characterized using various spectroscopic techniques and their molecular structure was proposed based on density functional theory calculations. The diverse properties of the porphyrin derivatives result from the different stereochemistry of the particular substituents at the meso site on the macrocycle and are controlled also by the coordinated metal. The 1H NMR spectrum of the free-base porphyrin showed a comp…

Lapatiniba protolītisko īpašību izpēte un sāļu iegūšana

2016

Maģistra darba ietvaros veikta lapatiniba potenciometriskā titrēšana neūdens vidē, izmantojot divas šķīdinātāju sistēmas: N,N-dimetilformamīda un ūdens maisījums; metanola, acetonitrila, 1,4 dioksāna un ūdens maisījums. Protonēšanās konstante ūdens vidē noteikta, izmantojot Yasuda Shedlovsky ekstrapolāciju. Veikta lapatiniba sāļu sintēze, izmantojot sālsskābi, p-toluolsulfonskābi, citronskābi, maleīnskābi, vīnskābi, skābeņskābi. Iegūtie produkti analizēti, izmantojot pulvera rentgendifraktometriju, diferenciāli termisko analīzi un kodolmagnētiskās rezonanses spektroskopiju. Atsevišķiem paraugiem pārbaudīta stabilitāte paaugstināta gaisa relatīvā mitruma apstākļos.

Fuel cells for household appliances: Experimental test of power management algorithms

2013

In this paper, fuel cell - based hybrid power supplies for household appliances are addressed. The profile of residential power consumption is evaluated during working, non-working days in both summer and winter periods. The worst-case load power demand is therefore highlighted. A 5kW Nuvera PowerFlow proton exchange membrane fuel cell for household appliances is tested. On the basis of the characterization of the fuel cell stack under test, stand-alone and fuel cell - battery active hybrid power supply architectures are both considered. Experimental validation of three power management algorithms is proposed in terms of hydrogen consumption, cost and energy saving. Power management algorit…

ChemInform Abstract: Synthesis of 1,2-Disubstituted Indoles from α-Aminonitriles and 2-Halobenzyl Halides.

2016

The α-alkylation of deprotonated Strecker products derived from primary amines and aromatic aldehydes with 2-halobenzyl halides furnishes intermediates that can be cyclized to 1,2-disubstituted indoles in moderate to high yields (up to 94% over two steps) by microwave-assisted copper- or palladium-catalyzed intramolecular cross-coupling.