scholarly journals Electric-driven membrane poration: A rationale for water role in the kinetics of pore formation

2021 ◽  
pp. 107987
Author(s):  
Paolo Marracino ◽  
Laura Caramazza ◽  
Maria Montagna ◽  
Ramin Ghahri ◽  
Marco D'Abramo ◽  
...  
Keyword(s):  
Pore Formation ◽  
Membrane Poration ◽  
Kinetics Of

scholarly journals The fusion kinetics of influenza hemagglutinin expressing cells to planar bilayer membranes is affected by HA density and host cell surface.

1995 ◽  
Vol 106 (5) ◽  
pp. 783-802 ◽  
Author(s):  
G B Melikyan ◽  
W D Niles ◽  
F S Cohen
Keyword(s):  
Cell Surface ◽  
Fusion Protein ◽  
Pore Formation ◽  
Surface Proteins ◽  
Fusion Pore ◽  
Planar Bilayer ◽  
Bilayer Membranes ◽  
Pore Evolution ◽  
Fusion Pores ◽  
Kinetics Of

Time-resolved admittance measurements were used to follow formation of individual fusion pores connecting influenza virus hemagglutinin (HA)-expressing cells to planar bilayer membranes. By measuring in-phase, out-of-phase, and dc components of currents, pore conductances were resolved with millisecond time resolution. Fusion pores developed in stages, from small pores flickering open and closed, to small successful pores that remained open until enlarging their lumens to sizes greater than those of viral nucleocapsids. The kinetics of fusion and the properties of fusion pores were studied as functions of density of the fusion protein HA. The consequences of treating cell surfaces with proteases that do not affect HA were also investigated. Fusion kinetics were described by waiting time distributions from triggering fusion, by lowering pH, to the moment of pore formation. The kinetics of pore formation became faster as the density of active HA was made greater or when cell surface proteins were extensively cleaved with proteases. In accord with this faster kinetics, the intervals between transient pore openings within the flickering stage were shorter for higher HA density and more extensive cell surface treatment. Whereas the kinetics of fusion depended on HA density, the lifetimes of open fusion pores were independent of HA density. However, the lifetimes of open pores were affected by the proteolytic treatment of the cells. Faster fusion kinetics correlated with shorter pore openings. We conclude that the density of fusion protein strongly affects the kinetics of fusion pore formation, but that once formed, pore evolution is not under control of fusion proteins but rather under the influence of mechanical forces, such as membrane bending and tension.

Role of Pressure and Amount of Blowing Agent in Molding Microporous Footwear Parts

1960 ◽  
Vol 33 (4) ◽  
pp. 1193-1199
Author(s):  
M. A. Al'bam ◽  
A. P. Pisarenko
Keyword(s):  
Pore Formation ◽  
External Pressure ◽  
Blowing Agent ◽  
Film Forming ◽  
The Press ◽  
Molded Parts ◽  
Artificial Leather ◽  
Method Of Production ◽  
Kinetics Of

Abstract In the All-Union Film-forming Materials and Artificial Leather Research Institute (VNIIPIK) investigations have been in progress for several years with a view to developing a rational method of production of microporous footwear parts, and to eliminating completely expansion of the parts on removal from the press. It had already been demonstrated that to produce microporous molded parts strictly to the set shape they must be vulcanized with an external pressure not exceeding a certain critical value for each stock formula depending upon the amount of blowing agent, the flowability of the stock and the temperature. However the cause of this marked dependence of the process of molding of microporous parts upon the external pressure was not explained. It was merely suggested that a big part was played by the escape of gas from the cells of the molded rubber. In order to work out a theoretical basis for the production of molded parts and for the control of the process of pore formation, it was necessary to study the essential nature of the process. For this purpose we studied the kinetics of the process of pore formation and of the escape of gas from a stock in the process of vulcanization. The method worked out for investigation of the process of pore formation made it possible to study this process under conditions fully corresponding to the actual production conditions of press vulcanization, and to follow simultaneously in one experiment the change in volume of the vulcanization stock and the escape of gas from it. On the basis of these data we plotted the kinetic curves for the processes.

scholarly journals Single-molecule analysis of the entire perfringolysin O pore formation pathway

2021 ◽  
Author(s):  
Conall Mc Guinness ◽  
James Walsh ◽  
Charles Bayly-Jones ◽  
Michelle Dunstone ◽  
Craig Morton ◽  
...  
Keyword(s):  
Single Molecule ◽  
Pore Formation ◽  
Membrane Insertion ◽  
Formation Pathway ◽  
Perfringolysin O ◽  
Assembly Pathway ◽  
Bacterial Virulence Factor ◽  
Membrane Bound ◽  
Single Molecule Analysis ◽  
Kinetics Of

The cholesterol-dependent cytolysin perfringolysin O (PFO) is secreted by Clostridium perfringens as a bacterial virulence factor able to form giant ring-shaped pores that perforate and ultimately lyse mammalian cell membranes. To resolve the kinetics of all steps in the assembly pathway, we have used single-molecule fluorescence imaging to follow the dynamics of PFO on dye-loaded liposomes that lead to opening of a pore and release of the encapsulated dye. Formation of a long-lived membrane-bound PFO dimer nucleates the growth of an irreversible oligomer. The growing oligomer can insert into the membrane and open a pore at stoichiometries ranging from tetramers to full rings (~35-mers), whereby the rate of insertion increases linearly with the number of subunits. Oligomers that insert before the ring is complete continue to grow by monomer addition post insertion. Overall, our observations suggest that PFO membrane insertion is kinetically controlled.

scholarly journals Characterization of the stoichiometry of the complex formed by Staphylococcal LukSF and human C5aR receptor in living cells

2017 ◽  
Author(s):  
Karita Haapasalo ◽  
Adam J.M Wollman ◽  
Carla de Haas ◽  
Kok van Kessel ◽  
Jos van Strijp ◽  
...  
Keyword(s):  
Single Molecule ◽  
Total Internal Reflection ◽  
Pore Formation ◽  
Membrane Receptors ◽  
Host Cell Membrane ◽  
C5a Receptor ◽  
Protein Subunits ◽  
Kinetics Of ◽  
Panton Valentine Leukocidin

SUMMARYStaphylococcus aureusPanton Valentine Leukocidin (PVL) is a pore-forming toxin comprising protein subunits LukS and LukF. Binding of LukS to human C5a receptor (hC5aR) on leukocytes induces secondary binding of LukF and assembly of lytic complexes. Previous analysis suggests that PVL consists of 4-plus-4 LukS/LukF subunits but the exact stoichiometry between LukS, LukF and hC5aR is not yet known. In this study we determine the stoichiometry and spatiotemporal dynamics of functional LukS/LukF-hC5aR complexes in living eukaryotic cells. By using rapid total internal reflection fluorescence (TIRF) and single-molecule photobleaching analysis we found that tetrameric LukS-hC5aR complexes are formed within a cluster of receptors. Upon binding to hC5aR each LukS subunit binds LukF leading to lytic pore formation and simultaneous dissociation of receptors from the complex. Our findings corroborate a hetero-octamer model but provide a new view on the kinetics of crucial virulence factor assembly on integrated host cell membrane receptors.

Residue-Specialized Membrane Poration Kinetics of Melittin and Its Variants: Insight from Mechanistic Landscapes

2019 ◽  
Vol 71 (7) ◽  
pp. 887 ◽  
Author(s):  
Zhi-Xiong Deng ◽  
Jing-Liang Li ◽  
Bing Yuan ◽  
Kai Yang
Keyword(s):  
Membrane Poration ◽  
Kinetics Of

Apparatus Study of Pore Formation Kinetics in Vulcanization

1961 ◽  
Vol 34 (1) ◽  
pp. 357-360
Author(s):  
M. A. Albam ◽  
A. P. Pisarenko
Keyword(s):  
Pore Formation ◽  
External Pressure ◽  
Plastic Properties ◽  
Gaseous Products ◽  
Blowing Agents ◽  
Blowing Agent ◽  
Formation Kinetics ◽  
Complex Matter ◽  
Kinetics Of ◽  
Rubber Stock

Abstract The investigation of the processes of formation of microporous vulcanizates is a complex matter, since pore formation depends upon a whole ensemble of simultaneous chemical and physical processes some of which are : the decomposition of the blowing agent with the formation of gaseous products; the solution of these gases in the rubber hydrocarbon; the formation of an independent gaseous phase inside the compounded rubber stock and the foaming of the vulcanizate, which changes its elastic and plastic properties in the course of vulcanization; the escape of the gas. The biggest difficulty is the lack of a satisfactory procedure for investigation. Many specialists have investigated the kinetics of various pure blowing agents, but this differs from the kinetics of the decomposition of a blowing agent in various media, including a compounded rubber stock. In other investigations the force of the blowing action has been assessed from the size of the pressure exerted from the direction of the compounded stock upon a steel diaphragm. Nevertheless this method does not enable us to investigate the kinetics of the process or the influence of external pressure acting upon the compounded stock. All the methods proposed hitherto for investigation of the decomposition of blowing agents enable us merely to judge the relative amount of gas liberated by the various blowing agents, or else the action of whatever blowing agent in the “foaming” of the compounded stock. But with these methods it is impossible to determine the actual amount of gas formed in the compounded stock in the vulcanization period.

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