1,2,4‐triazole‐functional PGMA polymers have been synthesized and their anhydrous proton‐conducting properties were investigated after doping with phosphoric acid and triflic acid. PGMA was prepared by solution polymerization and then modified with 1H‐1,2,4‐triazole (Tri) and 3‐amino‐1,2,4‐triazole (ATri). FT‐IR, 13C NMR and elemental analysis verify the high immobilization of the triazoles in the polymer chain. Phosphoric‐acid‐doped polymers showed lower Tg and higher proton conductivities. PGMA‐Tri 4 H3PO4 showed a maximum water‐free proton conductivity of approximately 10?2 S · cm?1 while that of PGMA‐ATri 2 H3PO4 was 10?3 S · cm?1. The structure and dynamics of the polymers were explored by 1H MAS and 13C CP‐MAS solid‐state NMR.
An amphiphilic graft copolymer using chitosan (CS) as a hydrophilic main chain and poly(lactic‐co‐glycolic acid) (PLGA) as a hydrophobic side chain is prepared through an emulsion self‐assembly synthesis. CS aqueous solution is used as a water phase and PLGA in chloroform is served as an oil phase. A water‐in‐oil (W/O) emulsion is fabricated in the presence of the surfactant span‐80. The self‐assembly reaction is performed between PLGA and CS under the condensation of EDC. Fourier transform IR (FTIR) spectroscopy reveals that PLGA is grafted onto the backbone of CS through the interactions between end carboxyl and amino groups of the two components. 1H NMR spectroscopy directly indicates the grafting content of PLGA in the CS‐graft‐PLGA (CS‐g‐PLGA) copolymer is close to 25%. X‐ray diffraction (XRD) confirms that the copolymer exhibits an amorphous structure. The CS‐g‐PLGA amphiphile can self‐assemble to form micelles with size in the range of ≈100–300 nm, which makes it easy to apply in various targeted‐drug‐release and biomaterial fields. 相似文献
The polymerization of 3,4‐ethylenedioxythiophene (EDOT)‐based two‐monomer‐connected precursors in various solvent systems leads to improved crystallinity, compared to poly(3,4‐ethylenedioxythiophene) synthesized from traditional route. The P(EDOT:BPDSA:EDOT) is ordered by using 4,4‐biphenyldisulfonic acid (BPDSA) that is a connector and dopant linking EDOT monomers. The crystallinity, measured from X‐ray diffraction studies, is increased when using short chain or hydrophobic solvents. The crystallinity of P(EDOT:BPDSA:EDOT) significantly increases up to 45.0% compared to polymer with other sulfonic acids, bifunctional 1,2‐ethanesulfonic acid, and monofunctional methanesulfonic acid (MSA). The crystal structure is also confirmed from high‐voltage electron microscope. From these studies, it is confirmed that P(EDOT:BPDSA:EDOT) has an orthorhombic structure, which has the unit cell lattice parameters of a = 1.44 nm, b = 0.98 nm, and c = 1.18 nm from fast Fourier transform pattern images. The electrical conductivity is increased about four times with BPDSA (0.21 S cm?1) when compared using MSA (0.06 S cm?1). 相似文献
The combination of stimuli‐responsive polymers and proteins that can transport drugs is a promising approach for drug delivery. The formation of ferritin–poly(2‐dimethylaminoethyl methacrylate) (PDMAEMA) conjugates by atom‐transfer radical polymerization from the protein macroinitiator is described. PDMAEMA is a dual‐stimuli‐responsive polymer and the thermo‐ and pH‐responsive properties of the resulting conjugates are studied in detail with dynamic light scattering (DLS). Additionally, it is demonstrated that the lower critical solution temperature (LCST) of the protein–polymer conjugates can be further adjusted by the ionic strength of the solution. The conjugates are also characterized by sodium dodecyl sulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE), matrix‐assisted laser desorption ionization‐time of flight (MALDI‐ToF) mass spectrometry, and NMR spectroscopy. The obtained MALDI‐ToF mass spectra are exceptional for protein–polymer conjugates and have not been so often reported.
Four poly(N,N‐dimethylacrylamide)‐block‐poly(L ‐lysine) (PDMAM‐block‐PLL) hybrid diblock copolymers and two PLL homo‐polypeptides are prepared via ROP of ε‐trifluoroacetyl‐L ‐lysine N‐carboxyanhydride initiated by primary amino‐terminated PDMAM and n‐hexylamine respectively. The PLL blocks render the copolymers a multi‐responsive behavior in aqueous solution due to their conformational transitions from random coil to α‐helix with increasing pH, and from α‐helix to β‐sheet upon heating. The random coil‐to‐α‐helix transition is found to depend on the PLL length: the longer the peptide segment, the more readily the transition occurred. The same trend was observed for the α‐helix‐to‐β‐sheet transition, which was found to be inhibited for short polypeptides unless conjugated with the PDMAM block.
When γ‐CDs are added to an aqueous solution of PNIPAAm‐b‐PEG‐b‐PNIPAAm block copolymer, they are threaded onto the polymer chains to give loose‐fit polypseudorotaxanes (PPRs). The inclusion complexation shows a marked dependence on the length of the PNIPAAm blocks although the threaded γ‐CDs are preferably located on the central PEG block. The structure of the resulting PPRs is characterized by using XRD, 1H and 13C CP/MAS NMR, TGA FTIR, and DSC analyses. Because of the mismatched fit between the guest polymer chain and the cavity of the host γ‐CDs, these PPRs may be promising in applications as solid stimuli‐responsive materials. 相似文献
Summary: Sarcosine‐N‐carboxyanhydride (Sar‐NCA), L ‐alanine‐NCA and D,L ‐alanine‐NCA were polymerized with benzylamine as initiator in three different solvents: dichloromethane (CH2Cl2), 1,4‐dioxane and dimethylformamide (DMF). The isolated polyaminoacids were characterized by 1H NMR spectroscopy and MALDI‐TOF mass spectrometry. High conversions and degrees of polymerization s close to the monomer‐initiator (M/I) ratios were found for all polypeptides. For polysarcosine which was soluble under the given reaction conditions a narrow monomodal frequency distribution was found. In contrast, a broad frequency distribution was observed, when L ‐alanine NCA was polymerized in dioxane and DMF. These results were attributed to a partial precipitation of oligopeptides in the β‐sheet structure, which reduces the reactivity of endgroups for steric reasons. The polymerizations of D,L ‐alanine‐NCA showed features in between the extremes of Sar‐NCA and L ‐Ala‐NCA.
Schematic illustration of the secondary structures formed in a primary amine initiated polymerization of L ‐Ala‐NCA. 相似文献
The present study examined the nature of the apical inward L ‐3,4‐dihydroxyphenylalanine (L ‐DOPA) transporter in human intestinal epithelial Caco‐2 cells, and whether protein kinases modulate the activity of this transporter. The apical inward transfer of L ‐DOPA was promoted through an energy‐dependent and sodium‐insensitive transporter (Km=33 μM ; Vmax=2932 pmol/mg protein/6 min). This transporter was insensitive to N‐(methylamino)‐isobutyric acid, but competitively inhibited by 2‐aminobicyclo(2,2,1)‐heptane‐2‐carboxylic acid (BCH; IC50=83 μM ). The organic cation inhibitor decynium 24 failed to affect the accumulation of L ‐DOPA, whereas the organic anion inhibitor 4,4′‐diisothiocynatostilbene‐2,2′‐disulphonic acid (DIDS) competitively inhibited L ‐DOPA uptake (IC50=83 μM ). However, the apical‐to‐basal and basal‐to‐apical transepithelial transport and the cell accumulation of [3H]‐PAH was close to that of [14C]‐sorbitol and insensitive to DIDS (300 μM ). Modulators of protein kinase A (PKA) [cyclic adenosine monophosphate (cAMP), forskolin, H‐89 and cholera toxin], protein kinase G (PKG) [cyclic guanosine monophosphate (GMP), zaprinast, LY 83583 and sodium nitroprusside] and protein kinase C (PKC) (phorbol 12,13‐dibutirate and chelerythrine) failed to affect the accumulation of L ‐DOPA. The Ca2+/calmodulin inhibitors calmidazolium and trifluoperazine inhibited L ‐DOPA uptake (IC50s of 53 and 252 μM , respectively), but the rise of intracellular Ca2+ by A23187 (1 μM ) and thapsigargin (1 μM ) played no role on L ‐DOPA uptake. It is concluded that Caco‐2 cells take up L ‐DOPA over the apical cell border through the sodium‐independent and pH‐sensitive L‐type amino acid transporter. 相似文献
Novel optically active monomers, based on different L ‐amino acid residues such as trans‐(S)‐4‐(2‐methacryloylamino‐3‐methylbutanoylamino)azobenzene, trans‐(S)‐4‐(2‐methacryloylamino‐4‐methylpentanoylamino)azobenzene and trans‐(S)‐4‐(N‐methacryloyl‐2‐pyrrolidinoylamino)azobenzene, have been prepared and homopolymerized by free radical initiation. Circular dichroism spectra of the resulting polymers, as compared with those of the corresponding low molecular weight analogues, purposely synthesized, allow one to suggest that the macromolecules assume in solution achiral or chiral conformations with a prevailing screw sense, depending on the bulkiness and rigidity of the L ‐amino acid residue present in the side chains. The role of intra‐ and/or inter‐molecular hydrogen bonding between side‐chain amido groups along the backbone and the structural requirements of the chiral groups in determining the macromolecular arrangement is also discussed. 相似文献
Aminoacyl‐tRNA synthetases (ARSs) are ubiquitously expressed enzymes that ligate amino acids onto tRNA molecules. Genes encoding ARSs have been implicated in phenotypically diverse dominant and recessive human diseases. The charging of tRNAPHE with phenylalanine is performed by a tetrameric enzyme that contains two alpha (FARSA) and two beta (FARSB) subunits. To date, mutations in the genes encoding these subunits (FARSA and FARSB) have not been implicated in any human disease. Here, we describe a patient with a severe, lethal, multisystem, developmental phenotype who was compound heterozygous for FARSB variants: p.Thr256Met and p.His496Lysfs*14. Expression studies using fibroblasts isolated from the proband revealed a severe depletion of both FARSB and FARSA protein levels. These data indicate that the FARSB variants destabilize total phenylalanyl‐tRNA synthetase levels, thus causing a loss‐of‐function effect. Importantly, our patient shows strong phenotypic overlap with patients that have recessive diseases associated with other ARS loci; these observations strongly support the pathogenicity of the identified FARSB variants and are consistent with the essential function of phenylalanyl‐tRNA synthetase in human cells. In sum, our clinical, genetic, and functional analyses revealed the first FARSB variants associated with a human disease phenotype and expand the locus heterogeneity of ARS‐related human disease. 相似文献
γ‐Glutamic acid 16‐mer α‐ethyl ester was synthesized in stepwise transesterification of the ethyl ester group into benzyl ester group, followed by hydrogenation afforded γ‐glutamic acid 16‐mer with free carboxyl groups. Alkaline hydrolysis of γ‐glutamic acid 16‐mer α‐ethyl ester also afforded 16‐mer with free carboxyl groups. The two 16‐mers showed similar circular dichroism spectra. The structures and optical properties of γ‐glutamic acid dimer, trimer, tetramer, octamer, and 16‐mer were elucidated by 1H NMR, 13C NMR, IR, circular dichroism spectra, and X‐ray. Specific rotation of the intermediates of 16‐mer increased as the number of the glutamate unit. 相似文献
Relatively few MHC class I epitopes have been identified from Mycobacterium tuberculosis, but during the late stage of infection, CD8+ T‐cell responses to these epitopes are often primed at an extraordinary high frequency. Although clearly available for recognition during infection, their role in resistance to mycobacterial infections still remain unclear. As an alternative to DNA and viral vaccination platforms, we have exploited a novel CD8+ T‐cell‐inducing adjuvant, cationic adjuvant formulation 05 (dimethyldioctadecylammonium/trehalose dibehenate/poly (inositic:cytidylic) acid), to prime high‐frequency CD8 responses to the immunodominant H2‐Kb‐restricted IMYNYPAM epitope contained in the vaccine Ag tuberculosis (TB)10.4/Rv0288/ESX‐H (where ESX is mycobacterial type VII secretion system). We report that the amino acid C‐terminal to this minimal epitope plays a decisive role in proteasomal cleavage and epitope priming. The primary structure of TB10.4 is suboptimal for proteasomal processing of the epitope and amino acid substitutions in the flanking region markedly increased epitope‐specific CD8+ T‐cell responses. One of the optimized sequences was contained in the closely related TB10.3/Rv3019c/ESX‐R Ag and when recombinantly expressed and administered in the cationic adjuvant formulation 05 adjuvant, this Ag promoted very high CD8+ T‐cell responses. This abundant T‐cell response was functionally active but provided no protection against challenge, suggesting that CD8+ T cells play a limited role in protection against M. tuberculosis in the mouse model. 相似文献
Smart organic–inorganic hybrids are prepared using non‐covalent interactions between water‐soluble silsesquioxane nanoparticles and two amino acid‐based block copolymers prepared by reversible addition–fragmentation chain transfer (RAFT) polymerization. A block copolymer displaying lower critical solution temperature (LCST) and upper critical solution temperature (UCST) is employed, in which only poly(N‐acryloyl‐4‐trans‐hydroxy‐L ‐proline) segment could interact with the nanoparticles, whereas another poly(N‐acryloyl‐L ‐proline methyl ester) segment shows a thermoresponsive property without any interaction. The complexation of another type of dual thermosensitive block copolymer with two different LCSTs and the silsesquioxane nanoparticles is also investigated. 相似文献
Summary: Advanced 1H solid‐state NMR methods are applied for studying the hydrogen bond formation occurring in polymer hydrogels based on N‐isopropylacrylamide (NIPAAm) and methacrylic acid (MAA). For P(NIPAAm‐co‐MAA) copolymers collapsed at low pH, two populations of water can be distinguished in 1H magic‐angle spinning (MAS) NMR spectra, one of which is probably situated near stable hydrogen‐bonded regions, while the other behaves similarly to free water. The pH‐induced polymer collapse can be followed in detail using 2D 1H‐1H double quantum (DQ) MAS NMR experiments on dried samples. For collapsed copolymers as well as interpenetrating polymer networks, the appearance of characteristic signals shows that hydrogen bonding takes place between NIPAAm and MMA monomers. The temperature dependence of the DQ spectra indicates that acid‐amide hydrogen bonds formed between both comonomers are more stable than the acid‐acid hydrogen bonds formed among MAA moieties alone. Correspondingly, by analyzing 1H‐1H DQ sideband patterns, a relatively short distance of 270 pm is found for the NIPAAm‐MMA hydrogen bond. Finally, the pH dependence of the DQ spectra demonstrates that hydrogen bonding phenomena are directly related to the polymer collapse.
Hybrid copolymers constituted by short l ‐phenylalanine (Phe) blocks (i.e., Phen with n ranging from 2 to 25) and l ‐lactide blocks of different length are synthesized and characterized. The diblock structure is obtained by ring opening polymerization of lactide using a Phe‐oligopeptide as macroinitiator. The length of the poly(l ‐lactide) (PLLA) block is controlled through the [lactide]/[macroinitiator] ratio. Morphologic studies of such hybrid copolymers indicate that the assembly of PLLA can be controlled by introducing short Phe blocks. Spherulites with both positive and negative birefringence are achieved in melt crystallization as a consequence of different lamellar distributions. Instead, a high variety of structures are detected in solution‐crystallized samples. Specifically, lozenge single crystals, flower‐like crystals, fibrillar structures, compact spheres, ringed sperulites, dendritic structures, microfibers, and braid‐like microstructures are observed. Some of the detected morphologies are characteristic of self‐assembled Phe‐oligopeptides, suggesting that Phe‐blocks play a crucial role in the self‐assembly properties. 相似文献
We have synthesized polyethoxysiloxanes starting from the AB3‐type monomers triethoxysilanol and acetoxytriethoxysilane. The polymers are liquid and soluble in organic solvents. 29Si NMR spectroscopy and MALDI‐ToF mass spectrometry analyses show that the polymers have a hyperbranched structure with additional internal cyclization. 29Si NMR spectroscopy indicates that the polymer synthesized from acetoxytriethoxysilane is less branched than the polymer synthesized from triethoxysilanol. Analysis of the molar mass and mass distribution of the polymers via size exclusion chromatography (calibrated via MALDI‐ToF MS and viscosimetry) yields a molar mass of Mn ≈ 2 kg · mol?1 and Mw ≈ 8 kg · mol?1 for polymers synthesized from triethoxysilanol. The molar mass of the polymers synthesized from acetoxytriethoxysilane can be controlled by variation of the polymerization time in the range of Mn ≈ 1.8–12 kg · mol?1 and Mw ≈ 2.1–2 200 kg · mol?1.
Photograph of a vial containing polyethoxysiloxane obtained from triethoxysilanol and a schematic drawing of the proposed molecular structure of the polymer. 相似文献
Highly uniform and conductive single crystals of poly(3‐hexylthiophene) (P3HT)‐based homo and block copolymers with the end coily blocks of polystyrene, poly(methyl methacrylate), and poly(ethylene glycol) are developed using self‐seeding method from varied quality solvents. Edge‐on and flat‐on orientations are detected depending on the thickness and width of single crystals. Coily blocks are excluded from the P3HT crystalline structures, leading to brush‐like or hairy regions on surface of grown single crystals in the longitude of P3HT chains. The larger single crystals possessing flat‐on orientation are obtained from weaker solvents at higher seeding temperatures. The longer P3HT chains are folded, however, the shorter backbones are laminated on each other. The highest backbone lamination occurs for homo‐P3HT7150 (M n of P3HT = 7150 g mol−1) single crystals grown at 20 °C from anisole, the weakest employed solvent. In contract, highly ordered and folded hairy single crystals are acquired from better solvents and high molecular weight P3HTs. In these conditions, the crystallographic features of the hairy block copolymer single crystals are similar to those of nonhairy homo‐P3HT ones. The coily brush‐covered P3HT48 800 single crystals have more foldings compared to the homo‐P3HT48 800 ones, whereas only two laminated backbones in shorter P3HT blocks are detected.