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1.
A simple and divergent synthetic strategy of bottlebrush polymers (BBPs) is presented, consisting of postpolymerization modification of a macromonomer and grafting-through polymerization. Beginning with a single macromonomer, its direct modification could build a library of macromonomers with an identical chain length, thus guaranteeing the precision in the synthesis of BBPs. In this study, a newly designed norbornenyl-terminated poly(methyl acrylate) (NB-PMA) is proposed as a chemically robust template. Ti-mediated transesterification of NB-PMA successfully produces structurally diverse polyacrylates while maintaining the terminal norbornenyl group intact. All macromonomers obtained from transesterification possess a good grafting-through ring-opening metathesis polymerization reactivity, furnishing homo, random, and block BBPs in a controllable manner. Moreover, atomic force microscopy analysis supports the controlled side-chain length distribution in the resulting BBPs.  相似文献   
2.
Redox‐inactive metal ions play important roles in tuning chemical properties of metal–oxygen intermediates. Herein we report the effect of water molecules on the redox properties of a nonheme iron(III)–peroxo complex binding redox‐inactive metal ions. The coordination of two water molecules to a Zn2+ ion in (TMC)FeIII‐(O2)‐Zn(CF3SO3)2 ( 1 ‐Zn2+) decreases the Lewis acidity of the Zn2+ ion, resulting in the decrease of the one‐electron oxidation and reduction potentials of 1 ‐Zn2+. This further changes the reactivities of 1 ‐Zn2+ in oxidation and reduction reactions; no reaction occurred upon addition of an oxidant (e.g., cerium(IV) ammonium nitrate (CAN)) to 1 ‐Zn2+, whereas 1 ‐Zn2+ coordinating two water molecules, (TMC)FeIII‐(O2)‐Zn(CF3SO3)2‐(OH2)2 [ 1 ‐Zn2+‐(OH2)2], releases the O2 unit in the oxidation reaction. In the reduction reactions, 1 ‐Zn2+ was converted to its corresponding iron(IV)–oxo species upon addition of a reductant (e.g., a ferrocene derivative), whereas such a reaction occurred at a much slower rate in the case of 1 ‐Zn2+‐(OH2)2. The present results provide the first biomimetic example showing that water molecules at the active sites of metalloenzymes may participate in tuning the redox properties of metal–oxygen intermediates.  相似文献   
3.
In allogeneic transplantation, including the B6 anti-BALB.B settings, H60 and H4 are two representative dominant minor histocompatibility antigens that induce strong CD8 T-cell responses. With different distribution patterns, H60 expression is restricted to hematopoietic cells, whereas H4 is ubiquitously expressed. H60-specific CD8 T-cell response has been known to be dominant in most cases of B6 anti-BALB.B allo-responses, except in the case of skin transplantation. To understand the mechanism underlying the subdominance of H60 during allogeneic skin transplantation, we investigated the dynamics of the H60-specific CD8 T cells in B6 mice transplanted with allogeneic BALB.B tail skin. Unexpectedly, longitudinal bioluminescence imaging and flow cytometric analyses revealed that H60-specific CD8 T cells were not always subdominant to H4-specific cells but instead showed a brief dominance before the H4 response became predominant. H60-specific CD8 T cells could expand in the draining lymph node and migrate to the BALB.B allografts, indicating their active participation in the anti-BALB.B allo-response. Enhancing the frequencies of H60-reactive CD8 T cells prior to skin transplantation reversed the immune hierarchy between H60 and H4. Additionally, H60 became predominant when antigen presentation was limited to the direct pathway. However, when antigen presentation was restricted to the indirect pathway, the expansion of H60-specific CD8 T cells was limited, whereas H4-specific CD8 T cells expanded significantly, suggesting that the temporary immunodominance and eventual subdominance of H60 could be due to their reliance on the direct antigen presentation pathway. These results enhance our understanding of the immunodominance phenomenon following allogeneic tissue transplantation.  相似文献   
4.
5.
Redox‐inactive metal ions and Brønsted acids that function as Lewis acids play pivotal roles in modulating the redox reactivity of metal–oxygen intermediates, such as metal–oxo and metal–peroxo complexes. The mechanisms of the oxidative C?H bond cleavage of toluene derivatives, sulfoxidation of thioanisole derivatives, and epoxidation of styrene derivatives by mononuclear nonheme iron(IV)–oxo complexes in the presence of triflic acid (HOTf) and Sc(OTf)3 have been unified as rate‐determining electron transfer coupled with binding of Lewis acids (HOTf and Sc(OTf)3) by iron(III)–oxo complexes. All logarithms of the observed second‐order rate constants of Lewis acid‐promoted oxidative C?H bond cleavage, sulfoxidation, and epoxidation reactions of iron(IV)–oxo complexes exhibit remarkably unified correlations with the driving forces of proton‐coupled electron transfer (PCET) and metal ion‐coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes were taken into account. The binding of HOTf and Sc(OTf)3 to the metal–oxo moiety has been confirmed for MnIV–oxo complexes. The enhancement of the electron‐transfer reactivity of metal–oxo complexes by binding of Lewis acids increases with increasing the Lewis acidity of redox‐inactive metal ions. Metal ions can also bind to mononuclear nonheme iron(III)–peroxo complexes, resulting in acceleration of the electron‐transfer reduction but deceleration of the electron‐transfer oxidation. Such a control on the reactivity of metal–oxygen intermediates by binding of Lewis acids provides valuable insight into the role of Ca2+ in the oxidation of water to dioxygen by the oxygen‐evolving complex in photosystem II.  相似文献   
6.
A novel nanomagnetic basic catalyst of caesium carbonate supported on hydroxyapatite‐coated Ni0.5Zn0.5Fe2O4 magnetic nanoparticles (Ni0.5Zn0.5Fe2O4@HAP‐Cs2CO3) was prepared. This new catalyst was fully characterized using Fourier transform infrared spectroscopy, transmission and scanning electron microscopy, X‐ray diffraction and vibrating sample magnetometry techniques, and then the catalytic activity of this catalyst was investigated in the synthesis of 1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐dione derivatives. Also, Ni0.5Zn0.5Fe2O4@HAP‐Cs2CO3 could be reused at least five times without significant loss of activity and could be recovered easily by applying an external magnet. Thus, the developed nanomagnetic catalyst is potentially useful for the green and economic production of organic compounds. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   
7.
The main result of this paper is Theorem 1.1 , which shows that it is possible for derived models to satisfy “ω1 is ‐supercompact”. Other constructions of models of this theory are also discussed; in particular, Theorem 4.1 constructs a normal fine measure on and hence a model of “Θ is regular”+“ω1 is ‐supercompact” from a model of “Θ is measurable”.  相似文献   
8.
We have synthesized new magnetic resonance imaging (MRI) T1 contrast agents (CA1 and CA2) that permit the activatable recognition of the cellular vicinal thiol motifs of the protein thioredoxin. The contrast agents showed MR relaxivities typical of gadolinium complexes with a single water molecule coordinated to a Gd3+ center (i.e., ~4.54 mM−1s−1) for both CA1 and CA2 at 60 MHz. The contrast agent CA1 showed a ~140% relaxivity enhancement in the presence of thioredoxin, a finding attributed to a reduction in the flexibility of the molecule after binding to thioredoxin. Support for this rationale, as opposed to one based on preferential binding, came from 1H-15N-HSQC NMR spectral studies; these revealed that the binding affinities toward thioredoxin were almost the same for both CA1 and CA2. In the case of CA1, T1-weighted phantom images of cancer cells (MCF-7, A549) could be generated based on the expression of thioredoxin. We further confirmed thioredoxin expression-dependent changes in the T1-weighted contrast via knockdown of the expression of the thioredoxin using siRNA-transfected MCF-7 cells. The nontoxic nature of CA1, coupled with its relaxivity features, leads us to suggest that it constitutes a first-in-class MRI T1 contrast agent that allows for the facile and noninvasive monitoring of vicinal thiol protein motif expression in live cells.  相似文献   
9.
The reaction pathways of 1-propanethiol, 1-propanol, and propylamine molecules, containing a propyl moiety, on a Ge(100) surface were investigated using high-resolution photoemission spectroscopy (HRPES) experiments and density functional theory (DFT) calculations. Upon analysis of the HRPES data, the adsorption of 1-propanethiol and 1-propanol was found to occur through a dissociation reaction, whereas that of propylamine took place via N dative bonding at room temperature. On the basis of our DFT results, adsorption geometries and transition states for each of these molecules on the Ge(100) surface were confirmed. Systematic studies of S-, O-, and N-containing molecules, composed of an identical propyl moiety, on the Ge(100) surface provide insight into the adsorption mechanism of aliphatic molecules containing alkyl chains on the Ge(100) surface.  相似文献   
10.
Determination of the ligand-binding affinity is an extremely interesting problem. Normally, the free energy perturbation (FEP) method provides an appropriate result. However, it is of great interest to improve the accuracy and precision of this method. In this context, temperature replica exchange molecular dynamics implementation of the FEP computational approach, which we call replica exchange free energy perturbation (REP) was proposed. In particular, during REP simulations, the system can easily escape from being trapped in local minima by exchanging configurations with high temperatures, resulting in significant improvement in the accuracy and precision of protein–ligand binding affinity calculations. The distribution of the decoupling free energy was enlarged, and its mean values were decreased. This results in changes in the magnitude of the calculated binding free energies as well as in alteration in the binding mechanism. Moreover, the REP correlation coefficient with respect to experiment ( RREP = 0.85 ± 0.15 ) is significantly boosted in comparison with the FEP one ( RFEP = 0.64 ± 0.30 ). Furthermore, the root-mean-square error (RMSE) of REP is also smaller than FEP, RMSEREP = 4.28 ± 0.69 versus RMSEFEP = 5.80 ± 1.11 kcal/mol, respectively. © 2019 Wiley Periodicals, Inc.  相似文献   
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