Our previous studies have reported the presence of "chain delivery" effects of protein adsorption onto ion exchangers with polymer-grafted ion-exchange groups, such as dextran-grafted and poly(ethylenimine)-...Our previous studies have reported the presence of "chain delivery" effects of protein adsorption onto ion exchangers with polymer-grafted ion-exchange groups, such as dextran-grafted and poly(ethylenimine)-modified Sepharose gels. However, it is unclear if the "chain delivery" occurs on affinity adsorption with specific interactions. This work is designed to address this issue. A dextran-grafted Sepharose gel was prepared, and then the matrix was modified using diethylaminoethyl, a typical ion-exchange group, or octapeptide(FYCHWQDE), an affinity ligand for human immunoglobulin G(h Ig G) to prepare ion-exchange or affinity adsorbents, respectively.Results of h Ig G adsorption showed that the uptake rate represented by the effective diffusivity of h Ig G onto the dextran-grafted ion exchangers was obviously enhanced by the dextran grafting, indicating the presence of"chain delivery" of the bound proteins on the charged groups on the dextran chains. By contrast, the effective diffusivity of h Ig G changed little as ligand density increased on the dextran-grafted FYCHWQDE adsorbents.Their adsorption capacities decreased and effective diffusivities were not accelerated by the dextran grafting.Thus, this work clarified that grafted dextran could not accelerate h Ig G uptake rate on the affinity resins, or in other words, chain delivery did not occur on the specific interaction-based affinity adsorption.展开更多
As a member of the inwardly rectifying channel (Kir) family, Kir2.1 allows to influx the cell more easily than to efflux, a biophysical phenomenon named inward rectification. The function of Kir2.1 is to set the resti...As a member of the inwardly rectifying channel (Kir) family, Kir2.1 allows to influx the cell more easily than to efflux, a biophysical phenomenon named inward rectification. The function of Kir2.1 is to set the resting membrane potential and modulate membrane excitability. It has been reported that residue E224 plays a key role in regulating inward rectification. The mutant Kir2.1 (E224G) displays weaker inward rectification than the WT channel. Gating of Kir2.1 depends on the membrane lipid, PIP<sub>2</sub>, such that the channel gates are closed in the absence of PIP<sub>2</sub>. Here we perform electrophysiological and computational approaches, and demonstrate that E224 also plays an important role in the PIP<sub>2</sub>-dependent activation of Kir2.1 in addition to its influence on inward rectification. The E224G mutant takes 4.5 times longer to be activated by PIP<sub>2</sub>. To probe the mechanism by which E224G slows the channel opening kinetics, we perform targeted molecular dynamics simulations and find that the mutant weakens the interactions between CD-loop and C-linker (H221-R189) and the adjacent G-loops (R312-E303) which are thought to stabilize the open state of the channel in our previous work. These data provide new insights into the regulation of Kir2.1 channel activity and suggest that a common mechanism may be involved in the distinct biophysical processes, such as inward rectification and PIP<sub>2</sub>-induced gating.展开更多
Photocatalysis. which utilizes solar energy to trigger chemical reactions, is one of the most desirable solar-energy-conversion approaches. Graphitic carbon nitride （g-C3N4）. as an attractive metal-free photocatalys...Photocatalysis. which utilizes solar energy to trigger chemical reactions, is one of the most desirable solar-energy-conversion approaches. Graphitic carbon nitride （g-C3N4）. as an attractive metal-free photocatalyst, has drawn worldwide research interest in the area of solar energy conversion due to its easy synthesis, earth-abundant nature, physicochemical stability and visible-light-responsive properties. Over the past ten years, g-C3N4 based photocatalysts have experienced intensive exploration, and great progress has been achieved. However, the solar conversion efficiency is still far from industrial applications due to the wide bandgap, severe charge recombination, and lack of surface active sites. Many strategies have been proposed to enhance the light absorption, reduce the recombination of charge carriers and accelerate the surface kinetics. This work makes a crucial review about the main contributions of various strategies to the light harvesting, charge separation and surface kinetics of g-C3N4 photocatalyst. Furthermore, the evaluation measurements for the enhanced light harvesting, reduced charge recombination and accelerated surface kinetics will be discussed. In addition, this review proposes future trends to enhance the photocatalytic performance of g-C3N4 photocatalyst for the solar energy conversion.展开更多
基金Supported by the National Natural Science Foundation of China(21236005,21621004)
文摘Our previous studies have reported the presence of "chain delivery" effects of protein adsorption onto ion exchangers with polymer-grafted ion-exchange groups, such as dextran-grafted and poly(ethylenimine)-modified Sepharose gels. However, it is unclear if the "chain delivery" occurs on affinity adsorption with specific interactions. This work is designed to address this issue. A dextran-grafted Sepharose gel was prepared, and then the matrix was modified using diethylaminoethyl, a typical ion-exchange group, or octapeptide(FYCHWQDE), an affinity ligand for human immunoglobulin G(h Ig G) to prepare ion-exchange or affinity adsorbents, respectively.Results of h Ig G adsorption showed that the uptake rate represented by the effective diffusivity of h Ig G onto the dextran-grafted ion exchangers was obviously enhanced by the dextran grafting, indicating the presence of"chain delivery" of the bound proteins on the charged groups on the dextran chains. By contrast, the effective diffusivity of h Ig G changed little as ligand density increased on the dextran-grafted FYCHWQDE adsorbents.Their adsorption capacities decreased and effective diffusivities were not accelerated by the dextran grafting.Thus, this work clarified that grafted dextran could not accelerate h Ig G uptake rate on the affinity resins, or in other words, chain delivery did not occur on the specific interaction-based affinity adsorption.
基金Supported by the National Natural Science Foundation for Distinguished Young Scholars of Hebei Province under Grant Nos C2015202340 and C2013202244the Foundation for Outstanding Talents of Hebei Province under Grant No C201400305+3 种基金the National Natural Science Foundation of China under Grant Nos 11247010,11175055,11475053,11347017,31400711 and 11647121the NIH R01 under Grant No HL059949-18the Foundation for the Science and Technology Program of Higher Education Institutions of Hebei Province under Grant No QN2016113the Scientific Innovation Fund for Excellent Young Scientists of Hebei University of Technology under Grant No 2015010
文摘As a member of the inwardly rectifying channel (Kir) family, Kir2.1 allows to influx the cell more easily than to efflux, a biophysical phenomenon named inward rectification. The function of Kir2.1 is to set the resting membrane potential and modulate membrane excitability. It has been reported that residue E224 plays a key role in regulating inward rectification. The mutant Kir2.1 (E224G) displays weaker inward rectification than the WT channel. Gating of Kir2.1 depends on the membrane lipid, PIP<sub>2</sub>, such that the channel gates are closed in the absence of PIP<sub>2</sub>. Here we perform electrophysiological and computational approaches, and demonstrate that E224 also plays an important role in the PIP<sub>2</sub>-dependent activation of Kir2.1 in addition to its influence on inward rectification. The E224G mutant takes 4.5 times longer to be activated by PIP<sub>2</sub>. To probe the mechanism by which E224G slows the channel opening kinetics, we perform targeted molecular dynamics simulations and find that the mutant weakens the interactions between CD-loop and C-linker (H221-R189) and the adjacent G-loops (R312-E303) which are thought to stabilize the open state of the channel in our previous work. These data provide new insights into the regulation of Kir2.1 channel activity and suggest that a common mechanism may be involved in the distinct biophysical processes, such as inward rectification and PIP<sub>2</sub>-induced gating.
基金the Australian Research Council for the financial support through its DP and FF programsthe Australian Government for the financial support through the Australian Government Research Training Program ScholarshipThe financial support from National Science Foundation of China(No.513228201)
文摘Photocatalysis. which utilizes solar energy to trigger chemical reactions, is one of the most desirable solar-energy-conversion approaches. Graphitic carbon nitride （g-C3N4）. as an attractive metal-free photocatalyst, has drawn worldwide research interest in the area of solar energy conversion due to its easy synthesis, earth-abundant nature, physicochemical stability and visible-light-responsive properties. Over the past ten years, g-C3N4 based photocatalysts have experienced intensive exploration, and great progress has been achieved. However, the solar conversion efficiency is still far from industrial applications due to the wide bandgap, severe charge recombination, and lack of surface active sites. Many strategies have been proposed to enhance the light absorption, reduce the recombination of charge carriers and accelerate the surface kinetics. This work makes a crucial review about the main contributions of various strategies to the light harvesting, charge separation and surface kinetics of g-C3N4 photocatalyst. Furthermore, the evaluation measurements for the enhanced light harvesting, reduced charge recombination and accelerated surface kinetics will be discussed. In addition, this review proposes future trends to enhance the photocatalytic performance of g-C3N4 photocatalyst for the solar energy conversion.
