The Experts below are selected from a list of 56799 Experts worldwide ranked by ideXlab platform
Jeifu Shaw - One of the best experts on this subject based on the ideXlab platform.
-
enhanced preference for π bond containing substrates is correlated to pro110 in the substrate binding tunnel of escherichia coli thioesterase i protease i lysophospholipase l1
Biochimica et Biophysica Acta, 2007Co-Authors: Lichiun Lee, Yenchywan Liaw, Yalin Lee, Jeifu ShawAbstract:Abstract Escherichia coli thioesterase I/protease I/lysophospholipase L1 (TAP) possesses multifunctional enzyme with thioesterase, esterase, arylesterase, protease, and lysophospholipase activities. Leu109, located at the substrate-binding tunnel, when substituted with proline (Pro) in TAP, shifted the substrate-preference from medium-to-long acyl chains to shorter acyl chains of triglyceride and p-nitrophenyl ester, and increased the preference for Aromatic-amino acid-derived esters. In the three-dimensional TAP structures, the only noticeable alteration of backbone and side chain conformation was located at the downstream Pro110–Ala123 region rather than at Pro109 itself. The residue Pro110, adjacent to Leu109 or Pro109, was found to contribute to the substrate preference of TAP enzymes for esters containing acyl Groups with π bond(s) or Aromatic Group(s). Some of the interactions between the enzyme protein and the substrate may be contributed by an attractive force between the Pro110 C–H donor and the substrate π-acceptor.
Igor V. Trushkov - One of the best experts on this subject based on the ideXlab platform.
-
lewis acid triggered vinylcyclopropane cyclopentene rearrangement
Journal of Organic Chemistry, 2017Co-Authors: Olga A Ivanova, Alexey O. Chagarovskiy, Vasiliy D. Krasnobrov, I. I. Levina, Alexey Shumsky, Igor V. TrushkovAbstract:We report a mild Lewis acid induced isomerization of donor–acceptor cyclopropanes, containing an alkenyl moiety and diverse electron-withdrawing Group(s) at the adjacent positions, into substituted cyclopentenes. We have found that 1,1,2-trisubstituted cyclopent-3-enes were exclusively obtained in yield of 51–99% when cyclopropanes with a 2-substituted alkenyl Group as a donor underwent isomerization. For cyclopropanes bearing a trisubstituted alkenyl Group either the corresponding cyclopent-3-enes or isomeric cyclopent-2-enes having two acceptor Groups at the C(1) atom were formed, with the reaction selectivity being determined by the applied Lewis acid. We have shown that the reactivity of the donor–acceptor cyclopropane increases with the increase of the electron-donating character of (hetero)Aromatic Group attached to the alkenyl moiety. The synthetic utility of the developed methodology was also demonstrated through the synthesis of polysubstituted cyclopentane and piperidine derivatives.
Olga A Ivanova - One of the best experts on this subject based on the ideXlab platform.
-
lewis acid triggered vinylcyclopropane cyclopentene rearrangement
Journal of Organic Chemistry, 2017Co-Authors: Olga A Ivanova, Alexey O. Chagarovskiy, Vasiliy D. Krasnobrov, I. I. Levina, Alexey Shumsky, Igor V. TrushkovAbstract:We report a mild Lewis acid induced isomerization of donor–acceptor cyclopropanes, containing an alkenyl moiety and diverse electron-withdrawing Group(s) at the adjacent positions, into substituted cyclopentenes. We have found that 1,1,2-trisubstituted cyclopent-3-enes were exclusively obtained in yield of 51–99% when cyclopropanes with a 2-substituted alkenyl Group as a donor underwent isomerization. For cyclopropanes bearing a trisubstituted alkenyl Group either the corresponding cyclopent-3-enes or isomeric cyclopent-2-enes having two acceptor Groups at the C(1) atom were formed, with the reaction selectivity being determined by the applied Lewis acid. We have shown that the reactivity of the donor–acceptor cyclopropane increases with the increase of the electron-donating character of (hetero)Aromatic Group attached to the alkenyl moiety. The synthetic utility of the developed methodology was also demonstrated through the synthesis of polysubstituted cyclopentane and piperidine derivatives.
Wim E Hennink - One of the best experts on this subject based on the ideXlab platform.
-
π π stacked poly e caprolactone b poly ethylene glycol micelles loaded with a photosensitizer for photodynamic therapy
Pharmaceutics, 2020Co-Authors: Marcel H A M Fens, Wim E Hennink, Nicky C H Van Kronenburg, Roel F Maasbakker, Sabrina Oliveira, Cornelus F Van NostrumAbstract:To improve the in vivo stability of poly(-caprolactone)-b-poly(ethylene glycol) (PCL-PEG)-based micelles and cargo retention by π-π stacking interactions, pendant Aromatic rings were introduced by copolymerization of -caprolactone with benzyl 5-methyl-2-oxo-1,3-dioxane-5-carboxylate (TMC-Bz). It was shown that the incorporation of Aromatic rings yielded smaller micelles (18-30 nm) with better colloidal stability in PBS than micelles without Aromatic Groups. The circulation time of i.v. injected micelles containing multiple pendant Aromatic Groups was longer (t½-α: ~0.7 h; t½-β: 2.9 h) than that of micelles with a single terminal Aromatic Group (t½ < 0.3 h). In addition, the in vitro partitioning of the encapsulated photosensitizer (meta-tetra(hydroxyphenyl)chlorin, mTHPC) between micelles and human plasma was favored towards micelles for those that contained the pendant Aromatic Groups. However, this was not sufficient to fully retain mTHPC in the micelles in vivo, as indicated by similar biodistribution patterns of micellar mTHPC compared to free mTHPC, and unequal biodistribution patterns of mTHPC and the host micelles. Our study points out that more detailed in vitro methods are necessary to more reliably predict in vivo outcomes. Furthermore, additional measures beyond π-π stacking are needed to stably incorporate mTHPC in micelles in order to benefit from the use of micelles as targeted delivery systems.
-
small oligomeric micelles based on end Group modified mpeg oligocaprolactone with monodisperse hydrophobic blocks
Macromolecules, 2007Co-Authors: Myrra G Carstens, Jan J L Bevernage, Cornelus F Van Nostrum, Mies J Van Steenbergen, Frits M Flesch, Ruud Verrijk, Leo G J De Leede, Daan J A Crommelin, Wim E HenninkAbstract:To design stable biodegradable micelles with a size smaller than 20 nm, the self-assembly of methoxypoly(ethylene glycol)-b-oligocaprolactones (mPEG-b-OCLs), and the effect of OCL block length and terminal derivatization with an Aromatic Group were studied. The studied oligomers consisted of an mPEG block with a molecular weight of 750 Da and a monodisperse OCL block of 1−7 units with a hydroxyl end Group that was either unmodified, benzoylated or naphthoylated. They were prepared by preparative HPLC of the polydisperse block oligomers. Differential scanning calorimetry demonstrated that the two blocks were phase separated and crystallized separately. These block oligomers formed small and almost monodisperse oligomeric micelles with a hydrodynamic diameter of 8−15 nm, which could be tailored by the size of the hydrophobic block. The critical aggregation concentration (CAC) of the unmodified mPEG-b-OCLs was 0.03−4 mg/mL, and it decreased with increasing length of the OCL chain. End Group modification resu...
Jeyoung Park - One of the best experts on this subject based on the ideXlab platform.
-
Sustainable and recyclable super engineering thermoplastic from biorenewable monomer
Nature Communications, 2019Co-Authors: Seul A Park, Hyeonyeol Jeon, Seunghwan Choy, Jun Mo Koo, Dong Soo Hwang, Jong-geon Jegal, Sung Yeon Hwang, Hyungjun Kim, Sung-ho Shin, Jeyoung ParkAbstract:Environmental and health concerns force the search for sustainable super engineering plastics (SEPs) that utilise bio-derived cyclic monomers, e.g. isosorbide instead of restricted petrochemicals. However, previously reported bio-derived thermosets or thermoplastics rarely offer thermal/mechanical properties, scalability, or recycling that match those of petrochemical SEPs. Here we use a phase transfer catalyst to synthesise an isosorbide-based polymer with a high molecular weight >100 kg mol^−1, which is reproducible at a 1-kg-scale production. It is transparent and solvent/melt-processible for recycling, with a glass transition temperature of 212 °C, a tensile strength of 78 MPa, and a thermal expansion coefficient of 23.8 ppm K^−1. Such a performance combination has not been reported before for bio-based thermoplastics, petrochemical SEPs, or thermosets. Interestingly, quantum chemical simulations show the alicyclic bicyclic ring structure of isosorbide imposes stronger geometric restraint to polymer chain than the Aromatic Group of bisphenol-A.Super engineering plastics that utilise bio-derived cyclic monomers rarely offer the same thermal/mechanical properties, scalability and recyclability as petrochemical derived plastics. Here the authors use a phase transfer catalyst to synthesise a transparent, recyclable and tough isosorbide-based polymer with a high molecular weight.