The atomic structures of Zr-Ni and Zr-Ti-Al-Cu-Ni metallic glasses were investigated by using classical molecular dynamic (MD),reverse Monte Carlo (RMC),ab initio MD (AIMD) simulations and high resolution transmission...The atomic structures of Zr-Ni and Zr-Ti-Al-Cu-Ni metallic glasses were investigated by using classical molecular dynamic (MD),reverse Monte Carlo (RMC),ab initio MD (AIMD) simulations and high resolution transmission electron microscopy (HRTEM) techniques. We focused on the short-range order (SRO) and medium-range order (MRO) in the glassy structure. It is shown that there are icosahedral,FCC-and BCC-type SROs in the Zr-based metallic glasses. A structural model,characterized by imperfect ordered packing (IOP),was proposed based on the MD simulation and confirmed by the HRTEM observation. Furthermore,the evolution from IOP to nanocrystal during the crystallization of metallic glasses was also ex-plored. It is found that the growth from IOP to nanocrystal proceeds through three distinct stages: the formation of quasi-ordered structure with one-dimensional (1D) periodicity,then 2D periodicity,and finally the formation of 3D nanocrystals. It is also noted that these three growth steps are crosslinked.展开更多
The dynamics of water within a nanopool of a reverse micelle is heavily affected by the amphiphilic interface.In this work,the terahertz(THz)spectra of cyclohexane/Igepal/water nonionic reverse micelle mixture are mea...The dynamics of water within a nanopool of a reverse micelle is heavily affected by the amphiphilic interface.In this work,the terahertz(THz)spectra of cyclohexane/Igepal/water nonionic reverse micelle mixture are measured by THz timedomain spectroscopy and analyzed with two Debye models and complex permittivity of background with volume ratios.Based on the fitted parameters of bulk and fast water,the molar concentration of all kinds of water molecules and hydration water molecule number per Igepal molecule are calculated.We find that slow hydration water has the highest proportion in water when the radius parameterω_(0)<10,while bulk water becomes the main component whenω_(0)≥10.The feature radius ratio of nonhydrated and hydrated water to total water nanopool is roughly obtained from 0.39 to 0.85 with increasingω_(0).展开更多
Poly(N-isopropylacrylamide)(PNIPAAm) grafted onto silica,which may be used for reverse phase chromatography(RPC),was simulated and synthesized for protein separation with temperature-triggered adsorption and desorptio...Poly(N-isopropylacrylamide)(PNIPAAm) grafted onto silica,which may be used for reverse phase chromatography(RPC),was simulated and synthesized for protein separation with temperature-triggered adsorption and desorption.Molecular dynamics simulation at an all-atom level was performed to illustrate the adsorption/desorption behavior of cytochrome c,the model protein,on PNIPAAm-grafted-silica,a temperature responsive adsorbent.At a temperature above the lower critical solution temperature(LCST),the PNIPAAm chains aggregate on the silica surface,forming a hydrophobic surface that is favorable for the hydrophobic adsorption of cytochrome c,which has a high exposure of hydrophobic patches.At temperatures below the LCST,the PNIPAAm chains stretch,forming hydrophilic surface due to hydrogen bonding between PNIPAAm and surrounding water.Desorption of cytochrome c on the PNIPAAm-grafted-silica surface occurs as a result of competition with water,which forms hydrogen bonds with the protein.The conformational transitions of both cytochrome c and PNIPAAm are monitored,providing molecular insight into this temperature-responsive RPC technique.PNIPAAm-grafted-silica beads were synthesized and used for the adsorption and desorption of cytochrome c at approximately 313 K and 290 K,respectively.The experimental results validate the molecular dynamics simulation.In comparison to conventional RPC,using temperature as a driving force for RPC reduces the risk of protein denaturation caused by exposure to chaotropic solvents.Moreover,it simplifies the separation process by avoiding the buffer exchange operations between the steps.展开更多
基金the National Natural Science Foundation of China (Grant Nos. 50431030 and 50471097)the National Basic Research Program of China (Grant No. 2007CB613901)the Programme of Introducing Talents of Discipline to Universities (Grant No. B07003)
文摘The atomic structures of Zr-Ni and Zr-Ti-Al-Cu-Ni metallic glasses were investigated by using classical molecular dynamic (MD),reverse Monte Carlo (RMC),ab initio MD (AIMD) simulations and high resolution transmission electron microscopy (HRTEM) techniques. We focused on the short-range order (SRO) and medium-range order (MRO) in the glassy structure. It is shown that there are icosahedral,FCC-and BCC-type SROs in the Zr-based metallic glasses. A structural model,characterized by imperfect ordered packing (IOP),was proposed based on the MD simulation and confirmed by the HRTEM observation. Furthermore,the evolution from IOP to nanocrystal during the crystallization of metallic glasses was also ex-plored. It is found that the growth from IOP to nanocrystal proceeds through three distinct stages: the formation of quasi-ordered structure with one-dimensional (1D) periodicity,then 2D periodicity,and finally the formation of 3D nanocrystals. It is also noted that these three growth steps are crosslinked.
基金supported by the National Natural Science Foundation of China(No.62175185)。
文摘The dynamics of water within a nanopool of a reverse micelle is heavily affected by the amphiphilic interface.In this work,the terahertz(THz)spectra of cyclohexane/Igepal/water nonionic reverse micelle mixture are measured by THz timedomain spectroscopy and analyzed with two Debye models and complex permittivity of background with volume ratios.Based on the fitted parameters of bulk and fast water,the molar concentration of all kinds of water molecules and hydration water molecule number per Igepal molecule are calculated.We find that slow hydration water has the highest proportion in water when the radius parameterω_(0)<10,while bulk water becomes the main component whenω_(0)≥10.The feature radius ratio of nonhydrated and hydrated water to total water nanopool is roughly obtained from 0.39 to 0.85 with increasingω_(0).
基金Supported by State Key Laboratory of Chemical Engineering (SKL-ChE-09A05)the National Excellent Doctoral Dissertation Special Fund (200956)
文摘Poly(N-isopropylacrylamide)(PNIPAAm) grafted onto silica,which may be used for reverse phase chromatography(RPC),was simulated and synthesized for protein separation with temperature-triggered adsorption and desorption.Molecular dynamics simulation at an all-atom level was performed to illustrate the adsorption/desorption behavior of cytochrome c,the model protein,on PNIPAAm-grafted-silica,a temperature responsive adsorbent.At a temperature above the lower critical solution temperature(LCST),the PNIPAAm chains aggregate on the silica surface,forming a hydrophobic surface that is favorable for the hydrophobic adsorption of cytochrome c,which has a high exposure of hydrophobic patches.At temperatures below the LCST,the PNIPAAm chains stretch,forming hydrophilic surface due to hydrogen bonding between PNIPAAm and surrounding water.Desorption of cytochrome c on the PNIPAAm-grafted-silica surface occurs as a result of competition with water,which forms hydrogen bonds with the protein.The conformational transitions of both cytochrome c and PNIPAAm are monitored,providing molecular insight into this temperature-responsive RPC technique.PNIPAAm-grafted-silica beads were synthesized and used for the adsorption and desorption of cytochrome c at approximately 313 K and 290 K,respectively.The experimental results validate the molecular dynamics simulation.In comparison to conventional RPC,using temperature as a driving force for RPC reduces the risk of protein denaturation caused by exposure to chaotropic solvents.Moreover,it simplifies the separation process by avoiding the buffer exchange operations between the steps.
