＜正＞The kinetics of loop closure sets the"speed limit"for protein folding.Single molecule fluorescence resonanc...
Ze Yong Zhi,Peng Cheng Liu,and Xin Sheng Zhao~* Beijing National Laboratory for Molecular Sciences,State Key Laboratory for Structural Chemistry of Unstable and Stable Species,and Department of Chemical Biology,College of Chemistry and Molecular Engineering,Peking University,Beijing 100871,China
Xin-Xing Yang~(§1),Jing-Qi Duan~(§2),Ye-Ke Qiong~2,Xin-Sheng Zhao~(*1) 1 State Key Laboratory for Structural Chemistry of Unstable and Stable Species,and Department of Chemical Biology,College of Chemistry and Molecular Engineering,Peking University,Beijing,100871, China 2 National Institute of Biological Sciences,Beijing 102206,China§The authors contributed equally to this work
Room-temperature Ionic Liquids(ILs) have numerous unique properties that differ from those of conventional molecular solvents.Although the unique properties of ILs have been suggested to origin from their microscopic interionic interaction,detailed dynamics of interionic interaction of ILs has not been fully understood.Here,with the Femtosecond Optical Heterodyne-Detected Raman Induced Kerr Effect Spectroscopy(fs-OHD-RIKES),we measured the ultrafast dynamics of the interionic interaction of three typical imidazolium based ILs,1-butyl-3-methylimidazolium tetrafluoroborate([bmim][BF4]),1-butyl-3-methylimidazolium hexafluorophosphate([bmim][PF6]),and 1-decyl-3-methylimidazolium tetrafluoroborate([dmim][BF4]).We observed several periods of subpicosecond oscillation in their fs-OHD-RIKES signals.Through decomposing their fs-OHD-RIKES signals into four Brownian oscillators in time domain,we explored the cation and anion substitution effects on the ultrafast dynamics of interionic interaction of ILs.We found that the cation substitution affected all the low frequency motions we observed,while the anion substitution only affected the two higher low frequency motions.
A1KB is a kind of enzyme that repairs MethyNA.The phenomenon that double strand DNA(dsDNA) will be contorted w...
Xun Li,Xin Sheng Zhao~* Beijing National Laboratory for Molecular Sciences,State Key Laboratory for Structural Chemistry of Unstable and Stable Species,and Department of Chemical Biology,College of Chemistry and Molecular Engineering,Peking University,Beijing 100871,China
The photophysical property of the tricarbocyanine dye IR144 has been extensively studied in non-aqueous solvents. However, as a potential near-infrared biomedical imaging probe, the photophysical property of IR144 in water is still little known. So, the aggregation behaviors of IR144 in water with steady-state absorption spectroscopy and integrated polarization dependent femtosecond pump-probe spectroscopy were investigated. Through comparing the absorption spectral bandshape of IR144 in water and in water pool of AOT reverse micelles, It is found that IR144 form dimer aggregates in water even at very low concentration （〈 1.0× 10^- 7 moloL 1）. And the absorption spectrum of the IR144 aggregates always displays a bimodal feature, which is independent of the dye concentration ranging from 1.0 × 10^-7 to 1.0 × 10^-4 mol·L^-1. For better understanding the aggregation behaviors of IR144 in water, we measured the ground state recovery kinetics and the reorientation kinetics of IR144 in water and in water pool of AOT reverse micelles （W0= [H2O]/[AOT], W0=40）. It is found that the fluorescence quantum yield of 1R144 in water is lower than that in water pool of AOT reverse micelles, and the reorientation time of IR144 in water is slower than that in water pool of AOT reverse micelles. Those kinetic measurements also verify that IR144 exists as dimer aggregates in water.
We developed an integrated microfluidic chip for long-term culture of isolated single cells. This polydimethylsiloxane (PDMS) based device could accurately seed each single cell into different culture chambers, and isolate one chamber from each other with monolithically integrated pneumatic valves. We optimized the culture conditions, including the frequency of medium replacement and the introduction of conditioned medium, to keep the single cells alive for 4 days. We cultured a few hundred cells in a separated chamber on the same chip to continuously supply the conditioned medium into the culture chambers for single cells. This approach greatly facilitated the growth of single cells, and created a suitable microenvironment for observing cells' autonomous process in situ without the interference of other adjacent cells. This single cell colony assay is expandable to higher throughput, fitting the needs in the studies of drug screening and stem cell differentiation.
