An antibacterial protein was isolated from the cultured mycelia of Cordyceps sinensis, and was designated as Cordyceps sinensis Antibacterial Protein （CSAP）. CSAP was single-chained, with an apparent molecular mass ...An antibacterial protein was isolated from the cultured mycelia of Cordyceps sinensis, and was designated as Cordyceps sinensis Antibacterial Protein （CSAP）. CSAP was single-chained, with an apparent molecular mass of 35 × 10^3 revealed by SDS-PAGE and a novel hydrophobic N-terminal sequence N-ALATQHGAP. The antimicrobial assays showed CSAP could inbibit the growth of Gram-positive and Gram-negative bacteria but no significant inhibition against fungi or yeasts. Further more, the antibacterial activity of CSAP was not bactericidal but bacteriostatic. It was the first time that an antibacterial protein was described in the Cordyceps species, which might involve in the chemical defense mechanism of the hosts.展开更多
Supported cell membrane coatings meet many requirements set to bioactive nanocarriers and materials,provided sidedness and fluidity of the natural membrane are maintained upon coating.However,the properties of a suppo...Supported cell membrane coatings meet many requirements set to bioactive nanocarriers and materials,provided sidedness and fluidity of the natural membrane are maintained upon coating.However,the properties of a support-surface responsible for maintaining correct sidedness and fluidity are unknown.Here,we briefly review the properties of natural membranes and membrane-isolation methods,with focus on the asymmetric distribution of functional groups in natural membranes(sidedness)and the ability of molecules to float across a membrane to form functional domains(fluidity).This review concludes that hydrophilic sugar-residues of glycoproteins in the outer-leaflet of cell membranes direct the more hydrophobic inner-leaflet towards a support-surface to create a correctly-sided membrane coating,regardless of electrostatic double-layer interactions.On positively-charged support-surfaces however,strong,electrostatic double-layer attraction of negatively-charged membranes can impede homogeneous coating.In correctly-sided membrane coatings,fluidity is maintained regardless of whether the surface carries a positive or negative charge.However,membranes are frozen on positively-charged,highly-curved,small nanoparticles and localized nanoscopic structures on a support-surface.This leaves an unsupported membrane coating in between nanostructures on planar support-surfaces that is in dual-sided contact with its aqueous environment,yielding enhanced fluidity in membrane coatings on nanostructured,planar support-surfaces as compared with smooth ones.展开更多
Unicellular cyanobacteria Synechocystis 6803 were fixed using high-pressure freezing （HPF） and freeze substitution without any chemical cross-linkers. Immunoelectron microscopy of these cells showed that five sequen...Unicellular cyanobacteria Synechocystis 6803 were fixed using high-pressure freezing （HPF） and freeze substitution without any chemical cross-linkers. Immunoelectron microscopy of these cells showed that five sequential enzymes of the Calvin cycle （phosphoriboisomerase, phosphoribulokinase, ribulose-1,5-bisphosphate carboxylase/oxygenase （RuBisCO）, 3-phosphoglyceratekinase and glyceraldehyde-3-phosphate dehydrogenase） and the catalytic portion of the chloroplast H^＋-ATP synthase （CF1） are located adjacent to the thylakoid membranes. Cell-free extracts of Synechocystis were processed by ultracentrifugation to isolate thylakoid fractions sedimenting at 40 000, 90 000, and 150 000 g. Among these, the 150 000-g fraction showed the highest linked activity of the above five sequential Calvin cycle enzymes and also the highest coordinated activity of light and dark reactions as assessed by ribose-5-phosphate （R-5-P） ＋ADP dependent CO2 fixation. Immunogold labeling of this membrane fraction confirmed the presence of the above five enzymes as well as the catalytic portion of the CF1 ATP synthase. Notably, the protein A-gold labeling of the thylakoids was observed without use of chemical cross-linkers and in spite of the normal washing steps used during standard immunolabeling. The results showed that soluble Calvin cycle enzymes might be organized along the thylakoid membranes.展开更多
基金Supported by the National Natural Science Foundation of China(39770200) the Natural Science Foundation of Hubei Province (2004ABA228)
文摘An antibacterial protein was isolated from the cultured mycelia of Cordyceps sinensis, and was designated as Cordyceps sinensis Antibacterial Protein （CSAP）. CSAP was single-chained, with an apparent molecular mass of 35 × 10^3 revealed by SDS-PAGE and a novel hydrophobic N-terminal sequence N-ALATQHGAP. The antimicrobial assays showed CSAP could inbibit the growth of Gram-positive and Gram-negative bacteria but no significant inhibition against fungi or yeasts. Further more, the antibacterial activity of CSAP was not bactericidal but bacteriostatic. It was the first time that an antibacterial protein was described in the Cordyceps species, which might involve in the chemical defense mechanism of the hosts.
基金financially supported by the National Key Research and Development Program of China(2017YFE0131700)the National Natural Science Foundation of China(52293383)the Soochow University,the Nankai University,and UMCG,Groningen,The Netherlands.
文摘Supported cell membrane coatings meet many requirements set to bioactive nanocarriers and materials,provided sidedness and fluidity of the natural membrane are maintained upon coating.However,the properties of a support-surface responsible for maintaining correct sidedness and fluidity are unknown.Here,we briefly review the properties of natural membranes and membrane-isolation methods,with focus on the asymmetric distribution of functional groups in natural membranes(sidedness)and the ability of molecules to float across a membrane to form functional domains(fluidity).This review concludes that hydrophilic sugar-residues of glycoproteins in the outer-leaflet of cell membranes direct the more hydrophobic inner-leaflet towards a support-surface to create a correctly-sided membrane coating,regardless of electrostatic double-layer interactions.On positively-charged support-surfaces however,strong,electrostatic double-layer attraction of negatively-charged membranes can impede homogeneous coating.In correctly-sided membrane coatings,fluidity is maintained regardless of whether the surface carries a positive or negative charge.However,membranes are frozen on positively-charged,highly-curved,small nanoparticles and localized nanoscopic structures on a support-surface.This leaves an unsupported membrane coating in between nanostructures on planar support-surfaces that is in dual-sided contact with its aqueous environment,yielding enhanced fluidity in membrane coatings on nanostructured,planar support-surfaces as compared with smooth ones.
文摘Unicellular cyanobacteria Synechocystis 6803 were fixed using high-pressure freezing （HPF） and freeze substitution without any chemical cross-linkers. Immunoelectron microscopy of these cells showed that five sequential enzymes of the Calvin cycle （phosphoriboisomerase, phosphoribulokinase, ribulose-1,5-bisphosphate carboxylase/oxygenase （RuBisCO）, 3-phosphoglyceratekinase and glyceraldehyde-3-phosphate dehydrogenase） and the catalytic portion of the chloroplast H^＋-ATP synthase （CF1） are located adjacent to the thylakoid membranes. Cell-free extracts of Synechocystis were processed by ultracentrifugation to isolate thylakoid fractions sedimenting at 40 000, 90 000, and 150 000 g. Among these, the 150 000-g fraction showed the highest linked activity of the above five sequential Calvin cycle enzymes and also the highest coordinated activity of light and dark reactions as assessed by ribose-5-phosphate （R-5-P） ＋ADP dependent CO2 fixation. Immunogold labeling of this membrane fraction confirmed the presence of the above five enzymes as well as the catalytic portion of the CF1 ATP synthase. Notably, the protein A-gold labeling of the thylakoids was observed without use of chemical cross-linkers and in spite of the normal washing steps used during standard immunolabeling. The results showed that soluble Calvin cycle enzymes might be organized along the thylakoid membranes.
