Carbohydrates on cell surfaces play a crucial role in a wide variety of biological processes,including cell adhesion,recognition and signaling,viral and bacterial infection,in°ammation and metastasis.However,owing to the large diversity and complexity of carbohydrate structure and nongenetically synthesis,glycoscience is the least understood¯eld compared with genomics and proteomics.Although the structures and functions of carbohydrates have been investigated by various conventional analysis methods,the distribution and role of carbohydrates in cell membranes remain elusive.This review focuses on the developments and challenges of super-resolution imaging in glycoscience through introduction of imaging principle and the available°uorescent probes for super-resolution imaging,the labeling strategies of carbohydrates,and the recent applications of super-resolution imaging in glycoscience,which will promote the super-resolution imaging technology as a promising tool to provide new insights into the study of glycoscience.
Advanced fluorescence microscopy including single-molecule localization-based super-resolution imaging techniques requires bright and photostable dyes orproteins asfluorophores.The photophysical properties of fluorophores have been proven to be crucial for super-resolution microscopy's localization precision and imaging resolution.Fluorophores TAMRA and Atto Rho6 G,which can interact with macrocyclic host cucurbit[7]uril(CB7) to form host-guest compounds,were found to improve the fluorescence intensity and lifetimes of these dyes.We enhanced the localization precision of direct stochastic optical reconstruction microscopy(dSTORM) by introducing CB7 into the imaging buffer,and showed that the number of photons as well as localizations of both TAMRA and Atto Rho6 G increase over 2 times.
Min ZhangJing GaoJunling ChenMingjun CaiJunguang JiangZhiyuan TianHongda Wang
The 4N1K peptide,which is derived from the C-terminal domain of thrombospondin-1(TSP-1),is usually used as a functional mimic peptide for TSP-1.Knowledge about the interaction force of 4N1K/CD47 is important in explaining how TSP-1 affects the biological effect of CD47.Here we used a single-molecule force spectroscopy(SMFS)technique to explore the interaction of 4N1K/CD47 on both normal and oxidative human red blood cells(h RBCs)at single-molecule level.There was no interaction force between 4N1K and CD47 on normal h RBCs;however,we did find 4N1K-bound CD47 on oxidative h RBCs.We also detected interaction forces for 4N1K/CD47ex(extracellular domain of human CD47),and 4N1K/oxidative CD47ex.The interaction forces of 4N1K/CD47ex were almost consistent with those of 4N1K/oxidative CD47ex at the same loading rate.These results suggest that the conformational change of CD47 is critical for 4N1K-CD47 interaction on oxidative h RBCs.
PAN Yan GangWANG FengLIU Yan HouYANG Yong-GuangWANG Hong Da
Cell membranes play a key role in cellular activities.Fish erythrocytes,prototype of the nucleated erythrocytes of lower vertebrates,are predominantly oval,biconvex discs with elliptical nucleus and much larger in size than human erythrocytes.In attempts to disclose the correlation of membrane structure between fish and human erythrocytes,we used in situ atomic force microscope(AFM)combined with single-molecule force spectroscopy to study the membrane structure of Crucian carp erythrocytes under quasi-native conditions.Our results revealed the asymmetric distribution of proteins in Crucian carp erythrocyte membrane:the outer leaflet of membrane is rather smooth without any proteins,whereas the inner leaflet of membrane is very rough with dense proteins.The asymmetry of fish erythrocyte membrane structure fits well with the semi-mosaic model of human erythrocyte membrane structure.This similarity of membrane structure between human and fish erythrocytes extends the semimosaic model of erythrocytes membrane structure to a wider range of species.
Yong-Mei TianMing-Jun CaiWei-Dong ZhaoShao-Wen WangQi-Wei QinHong-Da Wang
