Secondary Amine Groups Research Articles

Enantioseparation of chiral β-blockers using polynorepinephrine-coated nanoparticles and chiral capillary electrophoresis.

A method of combining magnetic solid-phase separation (MSPE) and chiral capillary electrophoresis (CE) is developed for enantioseparation of trace amounts of β-blockers. Polynorepinephrine-functionalized magnetic nanoparticles (polyNE-MNPs) are synthesized and applied to simultaneously extract three β-blockers (carteolol, metoprolol, and betaxolol). The prepared polyNE-MNPs are spherical with a diameter of 198 ± 17nm and the thickness of the polyNE coating is about 14nm. PolyNE possesses abundant catechol hydroxyl and secondary amine groups, endowing the MNPs with excellent hydrophilicity. Under the optimum conditions, the extraction efficiencies of polyNE-MNPs for β-blockers are in the range of 89.6 to 100%, with relative standard deviations (RSDs) below 3.5%. The extraction process can be finished in 4min. Field-enhanced sample injection (FESI) in chiral CE is constructed to further enhance the sensitivities of β-blocker enantiomers. The limits of detection for β-blocker enantiomers by the FESI-CE with polyNE-MNPs are in the range of 0.401 to 1.59ngmL-1. The practicability of this method in real samples is evaluated by analysis of human urine samples. The recoveries for each enantiomer of β-blockers in the real samples range from 89.5 to 92.8%, with RSDs ranging from 0.37 to 5.9%. The whole detection process can be finished in less than 0.5h. The method demonstrates its great potential in the pharmacokinetic and pharmacodynamic studies of chiral drugs in humans. Graphical abstract ᅟ.

Solution degradant of mirabegron extended release tablets resulting from a Strecker-like reaction between mirabegron, minute amounts of hydrogen cyanide in acetonitrile, and formaldehyde in PEG during sample preparation

During the related substances testing of mirabegron extended release tablets, an unknown peak was observed in HPLC chromatograms in a level exceeding the identification threshold. By using a strategy that combines LC–PDA/UV-MSn with mechanism-based stress studies, the unknown peak was rapidly identified as cyanomethyl mirabegron, a solution degradant that is caused by a Strecker-like reaction between the API, formaldehyde (an impurity in PEG), and HCN (an impurity in HPLC grade acetonitrile). The mechanism of the solution degradation chemistry was verified by stressing mirabegron with formaldehyde and trimethylsilyl cyanide (TMSCN, a synthetic reagent that generates HCN upon contact with water), in which the secondary amine group of mirabegron first reacts with formaldehyde to form the iminium ion intermediate; the latter then undergoes a nucleophilic attack by cyanide to yield the cyanomethyl mirabegron. The structure of the impurity was further confirmed through the synthesis of the impurity and subsequent structure characterization by 1D and 2D NMR. Due to the ubiquitous presence of formaldehyde in pharmaceutical excipients (e.g., PEG and polysorbate) and trace amount of HCN in HPLC grade acetonitrile, this type of solution degradation would likely occur in sample preparations of pharmaceutical finished products containing APIs with primary and secondary amine moieties. In a GMP environment, such an event may trigger undesirable out-of-specification (OOS) investigations; the results of this paper should help resolve such OOS investigations or even prevent these events from happening in the first place.

Synthesis of N-doped carbon quantum dots from bio-waste lignin for selective irons detection and cellular imaging.

Facile synthesis of carbon quantum dots with high fluorescence and excellent biocompatibility from plentiful and biocompatible materials still attracts much attention because of their great potential value in sensors and imaging. In this study, a highly fluorescent and super biocompatible N-doped carbon quantum dots derived from green precursor of aminated alkali lignin has been synthesized for cellular imaging. The amine-rich lignin carbon quantum dots (AL-CQDs) was firstly synthesized by introduction of secondary amine groups into lignin backbones via both Mannich and Machael addition reaction. The resulted AL-CQDs within the range of 4-10 nm exhibited excitation-dependent and pH-stable fluorescence properties and was employed for the detection of irons with a wide range from 100 nM to 1 mM and a low detection limit of 8 nM, in which the Fe3+ ions could be captured by the amine groups of the AL-CQDs to form an absorbent complex, resulting in a significant fluorescence quenching. Meanwhile, the AL-CQDs were successfully applied to cell imaging and intracellular irons detection benefited from low cytotoxicity and good biocompatibility. This work would shed much light on converting agricultural waste into bio-based nanomaterials and their potential applications.

Synthesis, Characterization, and Pickering Emulsifier Performance of Anisotropic Cross-Linked Block Copolymer Worms: Effect of Aspect Ratio on Emulsion Stability in the Presence of Surfactant.

Reversible addition-fragmentation chain transfer (RAFT) aqueous dispersion polymerization is used to prepare epoxy-functional PGMA-P(HPMA- stat-GlyMA) diblock copolymer worms, where GMA, HPMA, and GlyMA denote glycerol monomethacrylate, 2-hydroxypropyl methacrylate, and glycidyl methacrylate, respectively. The epoxy groups on the GlyMA residues were ring-opened using 3-aminopropyltriethoxysilane (APTES) in order to cross-link the worm cores via a series of hydrolysis-condensation reactions. Importantly, the worm aspect ratio can be adjusted depending on the precise conditions selected for covalent stabilization. Relatively long cross-linked worms are obtained by reaction with APTES at 20 °C, whereas much shorter worms with essentially the same copolymer composition are formed by cooling the linear worms from 20 to 4 °C prior to APTES addition. Small-angle X-ray scattering (SAXS) studies confirmed that the mean aspect ratio for the long worms is approximately eight times greater than that for the short worms. Aqueous electrophoresis studies indicated that both types of cross-linked worms acquired weak cationic surface charge at low pH as a result of protonation of APTES-derived secondary amine groups within the nanoparticle cores. These cross-linked worms were evaluated as emulsifiers for the stabilization of n-dodecane-in-water emulsions via high-shear homogenization at 20 °C and pH 8. Increasing the copolymer concentration led to a reduction in mean droplet diameter, indicating that APTES cross-linking was sufficient to allow the nanoparticles to adsorb intact at the oil/water interface and hence produce genuine Pickering emulsions, rather than undergo in situ dissociation to form surface-active diblock copolymer chains. In surfactant challenge studies, the relatively long worms required a thirty-fold higher concentration of a nonionic surfactant (Tween 80) to be displaced from the n-dodecane-water interface compared to the short worms. This suggests that the former nanoparticles are much more strongly adsorbed than the latter, indicating that significantly greater Pickering emulsion stability can be achieved by using highly anisotropic worms. In contrast, colloidosomes prepared by reacting the hydroxyl-functional adsorbed worms with an oil-soluble polymeric diisocyanate remained intact when exposed to high concentrations of Tween 80.

Enhancing the CO2 separation performance of SPEEK membranes by incorporation of polyaniline-decorated halloysite nanotubes

Polyaniline-decorated halloysite nanotubes (PANI-d-HNTs) having a multilayer hollow tubular structure were incorporated into sulfonated poly(ether ether ketone) (SPEEK) to prepare high-performance mixed matrix membranes (MMMs) for CO2/N2 separation. Scanning electron microscopy images revealed that PANI-d-HNTs were tightly wrapped by SPEEK chains. The strong interfacial interaction between PANI-d-HNTs and SPEEK, as confirmed by attenuated total-reflectance Fourier-transform infrared spectroscopy and differential scanning calorimetry, led to excellent miscibility between the polymer and halloysite nanotubes, which in turn, resulted in improved mechanical properties for the MMMs. The highest CO2 permeability of 1260 Barrer and a CO2/N2 selectivity of 87 were achieved for MMMs loaded with 0.9 wt% PANI-d-HNTs; these values exceeded the Robeson's upper bound proposed in 2008, and were also much higher than those of MMMs containing 0.9 wt% HNTs, for which, a CO2 permeability of 1093 Barrer and CO2/N2 selectivity of 74 were observed. It is proposed that PANI-d-HNTs with a multilayer hollow tubular structure can be used as high-speed facilitated channels for CO2 transport, where densely arranged secondary amine groups readily reacted with CO2 to facilitate transport in the MMMs. Importantly, durability testing indicated that MMMs loaded with 0.9 wt% PANI-d-HNTs maintained outstanding CO2 permselectivity for over 120 h, suggesting the superior stability of the membranes under mixed gas feed conditions.

Experimental measurements and modelling of CO2 solubility in aqueous mixtures of benzylamine and N‐(2‐aminoethyl) ethanolamine

AbstractIn this work, carbon dioxide solubility in N‐(2‐aminoethyl) ethanolamine (AEEA) activated aqueous benzylamine (BZA) solutions are studied using a stirred‐cell reactor in the temperature and pressure range of 313.15–333.15 K and 0.2–219 kPa, respectively. AEEA is a linear diamine with a primary and secondary amine groups, and BZA is a primary cyclic amine. The concentration of the aqueous blends used are (20mass% BZA + 10mass% AEEA), (24mass% BZA + 6mass% AEEA), and (28mass% BZA + 2mass% AEEA). Density and viscosity of unloaded aqueous amine blends are also measured in experimental temperature and concentration ranges and correlated using Joubian–Acree mathematical model. Model‐predicted density and viscosity data are in good agreement with experimental results showing 0.05% and 3.41% AAD, respectively. To correlate experimental vapor–liquid‐equilibrium data, Kent–Eisenberg (KE), artificial neural network (ANN), and soft models are used. Equilibrium constants of monocarbamate formation reaction of BZA and AEEA are regressed as a function of temperature and CO2 loading to fit the experimental data with KE model expression. KE model is also utilized to estimate the pH of CO2 loaded aqueous amine solutions. ANN model is found to predict CO2 solubility with better accuracy (1.56% AAD) in comparison of KE model (8.27% AAD) and soft model (15.5%). The CO2 absorption capacity of (20mass% BZA + 10mass% AEEA) solvent (~0.8 mol CO2/mol amine) is higher than that of monoethanolamine (~0.5 mol CO2/mol amine). Heats of absorption values of (BZA + AEEA) solvents (~25 kJ/mol CO2) predicted from Gibbs–Helmholtz relationship are found to be lower than that of MEA (~87 kJ/mol CO2) and PZ (~66 kJ/mol CO2).

2,2,6,6-Tetramethylpiperidin-1-yloxycarbonyl: A Protecting Group for Primary, Secondary, and Heterocyclic Amines.

The 2,2,6,6-tetramethylpiperidin-1-yloxycarbonyl (Tempoc) protecting group is readily introduced by the reaction of amines with a new acyl transfer reagent, 4-nitrophenyl (2,2,6,6-tetramethylpiperidin-1-yl) carbonate (NPTC). Tempoc has a reactivity profile that complements the commonly used t-butyloxycarbonyl (Boc) and benzyloxycarbonyl (Cbz) protecting groups. Deprotection can be achieved under mild reductive conditions with in situ generated Cu(I) species or by thermolytic cleavage at 135 °C. Mechanistic studies on the deprotection of Tempoc-indole suggest a combination of ionic and radical fragmentation pathways under thermal conditions.

A new approach in functionalization of carbon nanoparticles for optoelectronically relevant carbon dots and beyond

Carbon dots (CDots), generally small carbon nanoparticles with surface passivation by a soft corona-like layer of mostly organic species, have been actively pursued for potential applications in optoelectronics, including various functions that have been served by some popular fullerene derivatives. For the preparation of CDots, chemical functionalization of pre-processed and selected small carbon nanoparticles by organic molecules, so far mostly molecules with primary and secondary amine groups, has been an effective method. In this study, carbon nanoparticles were functionalized by N-ethylcarbazole (NEC) under microwave-assisted reaction conditions for NEC-CDots, analogous but with advantages to the CDots of surface functionalization by poly(N-vinylcarbazole) (PVK, which holds a special place in optoelectronics). NEC molecules can apparently be activated under the reaction conditions for reactive functionalities such as radicals to bind to surface carbons of the nanoparticles, consistent with the observed high stability of NEC-CDots. These dots, likely with a unique surface passivation scheme, exhibited optical properties and photoinduced redox characteristics similar to those found in other high-performance CDots. The potentially broad applicability of the new functionalization approach is discussed, so are implications of the unique surface passivation of carbon nanoparticles by the carbazole moieties.

Linear Bidentate Ligands (L) with Two Terminal Pyridyl N-Donor Groups Forming Pt(II)LCl2 Complexes with Rare Eight-Membered Chelate Rings.

NMR and X-ray diffraction studies were conducted on Pt(II)LCl2 complexes prepared with the new N-donor ligands N(SO2R)Me ndpa (R = Me, Tol; n = 2, 4). These ligands differ from N(H)dpa (di-2-picolylamine) in having the central N within a tertiary sulfonamide group instead of a secondary amine group and having Me groups at the 6,6'-positions ( n = 2) or 3,3',5,5'-positions ( n = 4) of the pyridyl rings. The N(SO2R)3,3',5,5'-Me4dpa ligands are coordinated in a bidentate fashion in Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes, forming a rare eight-membered chelate ring. The sulfonamide N atom did not bind to Pt(II), consistent with indications in the literature that tertiary sulfonamides are unlikely to anchor two meridionally coordinated five-membered chelate rings in solutions of coordinating solvents. The N(SO2R)6,6'-Me2dpa ligands coordinate in a monodentate fashion to form the binuclear complexes [ trans-Pt(DMSO)Cl2]2( N(SO2R)6,6'-Me2dpa). The monodentate instead of bidentate N(SO2R)6,6'-Me2dpa coordination is attributed to 6,6'-Me steric bulk. These binuclear complexes are indefinitely stable in DMF- d7, but in DMSO- d6 the N(SO2R)6,6'-Me2dpa ligands dissociate completely. In DMSO- d6, the bidentate ligands in Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes also dissociate, but incompletely; these complexes provide rare examples of association-dissociation equilibria of N,N bidentate ligands in Pt(II) chemistry. Like typical cis-PtLCl2 complexes, the Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes undergo monosolvolysis in DMSO- d6 to form the [Pt( N(SO2R)3,3',5,5'-Me4dpa)(DMSO- d6)Cl]+ cations. However, unlike typical cis-PtLCl2 complexes, the Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes surprisingly do not react readily with the excellent N-donor bioligand guanosine. A comparison of the structural features of over 50 known relevant Pt(II) complexes having smaller chelate rings with those of the very few relevant Pt(II) complexes having eight-membered chelate rings indicates that the pyridyl rings in Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes are well positioned to form strong Pt-N bonds. Therefore, the dissociation of the bidentate ligand and the poor biomolecule reactivity of the Pt( N(SO2R)3,3',5,5'-Me4dpa)Cl2 complexes arise from steric consequences imposed by the -CH2-N(SO2R)-CH2- chain in the eight-membered chelate ring.

Investigation of low concentration SO2 adsorption performance on different amine-modified Merrifield resins

Three amine-modified Merrifield resins (AMMRs) were synthesized with ethane diamine, methylamine and dimethylamine to assess the impact of amine group on SO2 adsorption under low SO2 concentration. The dimethylamine-modified Merrifield resin (DMAMR) grafting with tertiary amine groups showed the greatest SO2 adsorption compared with ethane diamine-modified Merrifield resin (EDAMR) and methylamine-modified Merrifield resin (MAMR). Different amine groups had different reaction mechanisms with SO2. It was much easier for SO2 to form noncovalent charge transfer complex with tertiary amine group than the zwitterion and ion/counterion products with primary and secondary amine groups under dry condition. The noncovalent charge transfer complex had a relatively weaker thermostability than the zwitterion and ion/counterion products. As the temperature increased from 25 °C to 75 °C, the SO2 adsorption capacity on DMAMR decreased by 78.92%, which was much higher than that of EDAMR and MAMR (63.77% and 63.41% respectively). As SO2 concentration increased from 40 ppm to 100 ppm, significant increase (∼100%) in SO2 adsorption capacity was observed. Lower SO2 flow rate led to a more sufficient reaction between SO2 and amine groups, resulting the increase in SO2 adsorption capacities. Water vapor enhanced the SO2 adsorption performance of AMMRs significantly due to the formation of salt. However, it was more difficult for tertiary amine group to react with SO2 in the presence of water due to its relatively weaker basicity. DMAMR showed a greater regeneration performance than EDAMR and MAMR under dry and humid condition.

A Facile and Scalable Route to the Preparation of Catalytic Membranes with in Situ Synthesized Supramolecular Dendrimer Particle Hosts for Pt(0) Nanoparticles Using a Low-Generation PAMAM Dendrimer (G1-NH2) as Precursor.

Since the first reports of Cu dendrimer-encapsulated nanoparticles (DENs) published in 1998, the dendrimer-templating method has become the best and most versatile method for preparing ultrafine metallic and bimetallic nanoparticles (1-3 nm) with well-defined compositions, high catalytic activity, and tunable selectivity. However, DENs have remained for the most part model systems with limited prospects for scale up and integration into high-performance and reusable catalytic modules and systems for industrial-scale applications. Here, we describe a facile and scalable route to the preparation of catalytic polyvinylidene fluoride (PVDF) membranes with in situ synthesized supramolecular dendrimer particles (SDPs) that can serve as hosts and containers for Pt(0) nanoparticles (2-3 nm). These new catalytic membranes were prepared using a reactive encapsulation process similar to that utilized to prepare Pt DENs by addition of a reducing agent (sodium borohydride) to aqueous complexes of Pt(II) + G4-OH/G6-OH polyamidoamine (PAMAM) dendrimers. However, the SDPs (2.4 μm average diameter) of our new mixed matrix PVDF-PAMAM membranes were synthesized in the dope dispersion without purification prior to film casting using (i) a low-generation PAMAM dendrimer (G1-NH2) as particle precursor and (ii) epichlorohydrin, an inexpensive functional reagent, as cross-linker. In addition, the membrane PAMAM particles contain secondary amine groups (∼1.9 mequiv per gram of dry membrane), which are more basic and thus have higher Pt binding affinity than the tertiary amine groups of the G4-OH and G6-OH PAMAM dendrimers. Proof-of-concept experiments show that our new PVDF-PAMAM-G1-Pt/membranes can serve as highly active and reusable catalysts for the hydrogenation of alkenes and alkynes to the corresponding alkanes using (i) H2 at room temperature and a pressure of 1 bar and (ii) low catalyst loadings of ∼1.4-1.6 mg of Pt. Using cyclohexene as model substrate, we observed near quantitative conversion to cyclohexane (∼98%). The regeneration studies showed that our new Pt/membrane catalysts are stable and can be reused for five consecutive reaction cycles for a total duration of 120 h including 60 h of heating at 100 °C under vacuum for substrate, product, and solvent removal with no detectable loss of cyclohexene hydrogenation activity. The overall results of our study point to a promising, versatile, and scalable path for the integration of catalytic membranes with in situ synthesized SDP hosts for Pt(0) nanoparticles into high-throughput modules and systems for heterogeneous catalytic hydrogenations, an important class of reactions that are widely utilized in industry to produce pharmaceuticals, agrochemicals, and specialty chemicals.

Improved Conjugation, 64-Cu Radiolabeling, in Vivo Stability, and Imaging Using Nonprotected Bifunctional Macrocyclic Ligands: Bis(Phosphinate) Cyclam (BPC) Chelators.

Bifunctional derivatives of bis(phosphinate)-bearing cyclam (BPC) chelators bearing a carboxylate, amine, isothiocyanate, azide, or cyclooctyne in the BP side chain were synthesized. Conjugations required no protection of phosphinate or ring secondary amine groups. The ring amines were not reactive (proton protected) at pH < ∼8. For isothiocyanate coupling, oligopeptide N-terminal α-amines were more suitable than alkyl amines, e.g., Lys ω-amine (p Ka ∼7.5-8.5 and ∼10-11, respectively) due to lower basicity. The Cu-64 labeling was efficient at room temperature (specific activity ∼100 GBq/μmol; 25 °C, pH 6.2, ∼100 ligand equiv, 10 min). A representative Cu-64-BPC was tested in vivo showing fast clearance and no nonspecific radioactivity deposition. The monoclonal anti-PSCA antibody 7F5 conjugates with thiocyanate BPC derivative or NODAGA were radiolabeled and studied in PC3-PSCA tumor bearing mice by PET. The radiolabeled BPC conjugate was accumulated in the prostate tumor with a low off-target uptake, unlike Cu-64-labeled NODAGA-antibody conjugate. The BPC chelators have a great potential for theranostic applications of the Cu-64/Cu-67 matched pair.

Two Propanediurea-based Cucurbituril Analogues: Bis-ns-TD[8] and NH-ns-TD[4

Two new cucurbituril members, one containing two equivalent cavities and the other having an active secondary amine group, were synthesized by condensation of propanediurea (2,4,6,8-tetraazabicyclo[3.3.1]nonane-3,7-dione) with formaldehyde. These two macrocycles exhibit excellent thermal stability, and their structures were confirmed by single-crystal X-ray diffraction, 1H NMR spectroscopy, and high-resolution mass spectrometry.

A resonance-assisted intra-molecular hydrogen bond in compounds containing 2-hy-droxy-3,5-di-nitro-benzoic acid and its various deprotonated forms: redetermination of several related structures.

A large number of structural determinations of compounds containing 2-hy-droxy-3,5-di-nitro-benzoic acid (I) and its various deprotonated forms, 2-hy-droxy-3,5-di-nitro-benzoate (II) or 2-carb-oxy-4,6-di-nitro-phenolate (III), are biased. The reason for the bias follows from incorrectly applied constraints or restraints on the bridging hydrogen, which is involved in the intra-molecular hydrogen bond between the neighbouring carb-oxy-lic/carboxyl-ate and oxo/hy-droxy groups. This hydrogen bond belongs to the category of resonance-assisted hydrogen bonds. The present article suggests corrections for the following structure determinations that have been published in Acta Crystallographica: DUJZAK, JEVNAA, LUDFUL, NUQVEB, QIQJAD, SAFGUD, SEDKET, TIYZIM, TUJPEV, VABZIJ, WADXOR, YAXPOE [refcodes are taken from the Cambridge Structural Database [CSD; Groom et al. (2016 ▸). Acta Cryst. B72, 171-179]. The structural features of the title mol-ecules in all the retrieved structures, together with structures that contain 3,5-di-nitro-2-oxidobenzoate (IV), are discussed. Attention is paid to the localization of the above-mentioned bridging hydrogen, which can be situated closer to the O atom of the carboxyl-ate/carb-oxy-lic group or that of the hy-droxy/oxo group. In some cases, it is disordered between the two O atoms. The position of the bridging hydrogen seems to be dependent on the pKa (base) although with exceptions. A stronger basicity enhances the probability of the presence of a phenolate (III). The present article examines the problem of the refinement of such a bridging hydrogen as well as that of the hydrogen atoms involved in the hy-droxy and primary and secondary amine groups. It appears that the best model, in many cases, is obtained by fixing the hydrogen-atom position found in the difference electron-density map while refining its isotropic displacement parameter.

Bis(3-carbamoylpyridin-1-ium) phosphite mono-hydrate.

Two of the constituent mol-ecules in the title structure, 2C6H7N2O+·HPO32-·H2O, i.e. the phosphite anion and the water mol-ecule, are situated on a symmetry plane. The mol-ecules are held together by moderate N-H⋯O and O-H⋯N, and weak O-H⋯O and C-H⋯Ocarbon-yl hydrogen bonds in which the amide and secondary amine groups, and the water molecules are involved. The structural features are usual, among them the H atom bonded to the P atom avoids hydrogen bonding.

In Situ Cross-Linked Nanofibers by Aqueous Electrospinning of Selenol-Functionalized Poly(2-oxazoline)s

Poly(2-oxazoline)-based biomaterials have shown significant potential for various applications in the past decade. Herein, we present a methodology for the design of degradable diselenide-cross-linked nanofibers by aqueous electrospinning of selenol (SeH)-modified poly(2-ethyl-2-oxazoline) (PEtOx). The selenol groups have been introduced into PEtOx by reacting partially hydrolyzed PEtOx (poly(2-ethyl-2-oxazoline-)-co-ethylenimine (PEtOx-EI)) with γ-butyroselenolactone, whereby ring-opening upon reaction with the secondary amine groups in the polymer backbone yields selenol side chains. Subsequent aqueous electrospinning of the selenol-containing PEtOx was found to lead to in situ cross-linked water-stable nanofibers, ascribed to the formation of diselenide cross-links. The effects of changes in the experimental parameters and the influence of the selenium content on the electrospinning process were investigated in detail. Dynamic exchange between the remaining free SeH groups and diselenide bonds formed u...

Immobilization of Small‐Molecule Ligands Containing Secondary or Tertiary Amine Groups onto TiO2‐Supported Ru Catalysts Driven by the Hydrophobic Effect

AbstractA strategy for effectively immobilizing small‐molecule ligands onto TiO2‐supported Ru catalysts is described. The immobilization was based on a simple two‐phase centrifugation technique and driven by the hydrophobic effect, likely leading to the formation of hydrophobic clusters of small‐molecule ligands. By using this strategy, a library of ligands containing secondary or tertiary amine groups and hydrophobic chains were successfully immobilized onto TiO2‐supported Ru catalysts. Of these ligands, ligands containing 2,2,6,6‐tetramethyl‐1‐piperidine‐N‐oxyl (TEMPO) moieties significantly improved the selectivity for aldehyde at high conversion in aerobic oxidation of alcohols, resulting from the inhibition of auto‐oxidation of aldehydes. This strategy can generate diversity in preparation of organic/inorganic hybrid catalysts.

Superhydrophobic Melamine Sponge Modified by Cross-Linked Urea Network as Recyclable Oil Absorbent Materials

A novel “urea cross-linking reaction”, involving the facile reaction between urea amide and isocyanate groups of an isocyanate-terminated poly(dimethylsiloxane) (iPD), was employed to fabricate superhydrophobic melamine sponge (SMS) as an efficient oil- and organic-solvent-absorbent material. By heating, isocyanate terminals of iPD can react with the secondary amine groups of melamine sponge (MS), rendering covalent urea bonds over the surface of MS skeleton. The resultant SMS exhibits a high water contact angle (WCA) of 153.4°, excellent volumetric absorption capacity (1.163–1.661 m3/m3), superior selectivity, and high absorption capacity retention (85.1–98.7%) over 30 sorption–squeezing cycles for different oils and organic solvents. The fabrication procedure of SMS is simple and cost-effective, and the robust, recyclable SMS is efficient in the separation of various oils and organic solvent/water mixtures. Therefore, a readily available process for environmental cleanup and remediation was provided in ...

Influence of pH on the uptake and toxicity of β-blockers in embryos of zebrafish, Danio rerio

ß-Blockers are weak bases with acidity constants related to their secondary amine group. At environmental pH they are protonated with the tendency to shift to their neutral species at more alkaline pH. Here we studied the influence of pH from 5.5 to 8.6 on the toxicity of the four ß-blockers atenolol, metoprolol, labetalol and propranolol in zebrafish embryos, relating toxicity not only in a conventional way to external aqueous concentrations but also to measured internal concentrations.Besides lethality, we evaluated changes in swimming activity and heartbeat, using the Locomotor Response (LMR) method and the Vertebrate Automated Screening Technology (VAST) for high throughput imaging.Effects of metoprolol, labetalol and propranolol were detected on phenotype, heart rate and swimming activity. External effect concentrations decreased with increasing neutral fraction for all three pharmaceuticals, attributed by an enhanced uptake of the neutral species in comparison to the corresponding charged form. The LC50 of metoprolol decreased by a factor of 35 from 1.91 mM with almost complete cationic state at pH 7.0 to 0.054 mM with 8% neutral fraction at pH 8.6. For propranolol the LC50 of 2.42 mM at pH 5.5 was even 100 fold higher than the LC50 at pH 8 with 0.023 mM where 3% were neutral fraction. No effects were detected in the zebrafish embryo exposed to atenolol.The internal concentrations for metoprolol and propranolol were quantified at non-toxic concentrations and at the LC10. Apparent bioconcentration factors (BCF) ranged from 1.96 at pH 7.0 to 32.0 at pH 8.6 for metoprolol and from 1.86 at pH 5.5 to 169 at pH 8.0 for propranolol. The BCFs served to predict the internal effect concentrations from the measured external effect concentrations.Internal effect concentrations of metoprolol and propranolol were in a similar range for all pH-values and for all endpoints. Interestingly, the internal effect concentrations were in the internal concentration range of baseline toxicity, which suggests that the effects of the ß-blockers are rather unspecific, even for sublethal effects on heart rate. In summary, our data confirm that the pH-dependent toxicity related to external concentrations can be explained by toxicokinetic effects and that the internal effect concentrations are pH-independent.

Albumin solder covalently bound to a polymer membrane: New approach to improve binding strength in laser tissue soldering in-vitro.

Laser tissue soldering (LTS) based on indocyanine green (ICG)-mediated heat-denaturation of proteins might be a promising alternative technique for micro-suturing, but up to now the problem of too weak shear strength of the solder welds in comparison to sutures is not solved. Earlier reports gave promising results showing that solder supported by carrier materials can enhance the cohesive strength of the liquid solder. In these studies, the solder was applied to the carriers by dip coating. Higher reliability of the connection between the solder and the carrier material is expected when the solder is bound covalently to the carrier material. In the present study a poly(ether imide) (PEI) membrane served as carrier material and ICG-supplemented albumin as solder substrate. The latter was covalently coupled to the carrier membrane under physiological conditions to prevent structural protein changes. As laser source a diode continuous-wave laser emitting at 808 nm with intensities between 250 mW and 1500 mW was utilized. The albumin functionalized carrier membrane was placed onto the tunica media of explanted pig thoracic aortae forming an overlapping area of approximately 0.5×0.5 cm2. All tests were performed in a dry state to prevent laser light absorption by water. Infrared spectroscopy, spectro-photometrical determination of the secondary and primary amine groups after acid orange II staining, contact angle measurements, and atomic force microscopy proved the successful functionalization of the PEI membrane with albumin. A laser power of 450 mW LTS could generate a membrane-blood vessel connection which was characterized by a shear strength of 0.08±0.002 MPa, corresponding to 15% of the tensile strength of the native blood vessel. Theoretically, an overlapping zone of 4.1 mm around the entire circumference of the blood vessel could have provided shear strength of the PEI membrane-blood vessel compound identical to the tensile strength of the native blood vessel. These in-vitro results confirmed the beneficial effects of solder reinforcement by carrier membranes, and suggest LTS with covalently bound solders on PEI substrates for further studies in animal models.