Integration of a virus membrane protein into the lipid bilayer of target cells as a prerequisite for immune cytolysis

Structural requirements for membrane antigens on target cells to mediate immune cytolysis were studied in a model system with purified membrane proteins from Semliki Forest virus (SFV). These SFV spike proteins were isolated in the form of detergent- and lipid-free protein micelles (29S complexes) or, after reconstitution into lipid vesicles, in the form of virosomes. Both the 29S complexes and the virosomes were found to bind well to murine tumor cells (P815 or Eb). When these cells, however, were used as target cells in complement-dependent lysis or in antibody-dependent cell- mediated cytotoxicity assays in the presence of anti-SFV serum, they were not lysed, although they effectively bound the antibody and consumed complement. The same tumor cells infected with SFV served as positive controls in both assays. Different results were obtained when inactivated Sendai virus was added as a fusion reagent to the cells coated with either virosomes or 29S complexes. Under these conditions the virosome-coated cells became susceptible to SFV- specific lysis, whereas the 29S complex-coated cells remained resistant. Evidence that the susceptibility to lysis ofvirosome-coated cells was dependent on active fusion and, therefore, integration of the viral antigens into the lipid bilayer of the target cells was derived from control experiments with enzyme-treated Sendai virus preparations. The 29S complexes and the virosomes partially and selectively blocked the target cell lysis by anti-H-2 sera but not by anti-non-H-2 sera confirming our previous finding that major histocompatibility antigens serve as receptors for SFV. The general significance of these findings for mechanisms of immune cytolysis is dicussed

Calculating potentials of mean force and diffusion coefficients from nonequilibirum processes without Jarzynski's equality

In general, the direct application of the Jarzynski equality (JE) to reconstruct potentials of mean force (PMFs) from a small number of nonequilibrium unidirectional steered molecular dynamics (SMD) paths is hindered by the lack of sampling of extremely rare paths with negative dissipative work. Such trajectories, that transiently violate the second law, are crucial for the validity of JE. As a solution to this daunting problem, we propose a simple and efficient method, referred to as the FR method, for calculating simultaneously both the PMF U(z) and the corresponding diffusion coefficient D(z) along a reaction coordinate z for a classical many particle system by employing a small number of fast SMD pullings in both forward (F) and time reverse (R) directions, without invoking JE. By employing Crook's transient fluctuation theorem (that is more general than JE) and the stiff spring approximation, we show that: (i) the mean dissipative work W_d in the F and R pullings are equal, (ii) both U(z) and W_d can be expressed in terms of the easily calculable mean work of the F and R processes, and (iii) D(z) can be expressed in terms of the slope of W_d. To test its viability, the FR method is applied to determine U(z) and D(z) of single-file water molecules in single-walled carbon nanotubes (SWNTs). The obtained U(z) is found to be in very good agreement with the results from other PMF calculation methods, e.g., umbrella sampling. Finally, U(z) and D(z) are used as input in a stochastic model, based on the Fokker-Planck equation, for describing water transport through SWNTs on a mesoscopic time scale that in general is inaccessible to MD simulations.Comment: ReVTeX4, 13 pages, 6 EPS figures, Submitted to Journal of Chemical Physic

Integration of a virus membrane protein intothe lipid bilayer of target cells as a prerequisite for immune cytolysis. Specific cytolysis after virosome- target cell fusion

Structural requirements for membrane antigens on target cells to mediate immune cytolysis were studied in a model system with purified membrane proteins from Semliki Forest virus (SFV). These SFV spike proteins were isolated in the form of detergent- and lipid-free protein micelles (29S complexes) or, after reconstitution into lipid vesicles, in the form of virosomes. Both the 29S complexes and the virosomes were found to bind well to murine tumor cells (P815 or Eb). When these cells, however, were used as target cells in complement-dependent lysis or in antibody-dependent cell- mediated cytotoxicity assays in the presence of anti-SFV serum, they were not lysed, although they effectively bound the antibody and consumed complement. The same tumor cells infected with SFV served as positive controls in both assays. Different results were obtained when inactivated Sendai virus was added as a fusion reagent to the cells coated with either virosomes or 29S complexes. Under these conditions the virosome-coated cells became susceptible to SFV- specific lysis, whereas the 29S complex-coated cells remained resistant. Evidence that the susceptibility to lysis ofvirosome-coated cells was dependent on active fusion and, therefore, integration of the viral antigens into the lipid bilayer of the target cells was derived from control experiments with enzyme-treated Sendai virus preparations. The 29S complexes and the virosomes partially and selectively blocked the target cell lysis by anti-H-2 sera but not by anti-non-H-2 sera confirming our previous finding that major histocompatibility antigens serve as receptors for SFV. The general significance of these findings for mechanisms of immune cytolysis is dicussed

Cavitation and bubble collapse in hot asymmetric nuclear matter

The dynamics of embryonic bubbles in overheated, viscous and non-Markovian nuclear matter is studied. It is shown that the memory and the Fermi surface distortions significantly affect the hinderance of bubble collapse and determine a characteristic oscillations of the bubble radius. These oscillations occur due to the additional elastic force induced by the memory integral.Comment: Revtex file (10 pages) and 3 figure

Size of Fireballs Created in High Energy Lead-Lead Collisions as Inferred from Coulomb Distortions of Pion Spectra

We compute the Coulomb effects produced by an expanding, highly charged fireball on the momentum distribution of pions. We compare our results to data on Au+Au at 11.6 A GeV from E866 at the BNL AGS and to data on Pb+Pb at 158 A GeV from NA44 at the CERN SPS. We conclude that the distortion of the spectra at low transverse momentum and mid-rapidity can be explained in both experiments by the effect of the large amount of participating charge in the central rapidity region. By adjusting the fireball expansion velocity to match the average transverse momentum of protons, we find a best fit when the fireball radius is about 10 fm, as determined by the moment when the pions undergo their last scattering. This value is common to both the AGS and CERN experiments.Comment: Enlarged discussion, new references added, includes new analysis of pi-/pi+ at AGS energies. 12 pages 5 figures, uses LaTex and epsfi

qBitcoin: A Peer-to-Peer Quantum Cash System

A decentralized online quantum cash system, called qBitcoin, is given. We design the system which has great benefits of quantization in the following sense. Firstly, quantum teleportation technology is used for coin transaction, which prevents from the owner of the coin keeping the original coin data even after sending the coin to another. This was a main problem in a classical circuit and a blockchain was introduced to solve this issue. In qBitcoin, the double-spending problem never happens and its security is guaranteed theoretically by virtue of quantum information theory. Making a block is time consuming and the system of qBitcoin is based on a quantum chain, instead of blocks. Therefore a payment can be completed much faster than Bitcoin. Moreover we employ quantum digital signature so that it naturally inherits properties of peer-to-peer (P2P) cash system as originally proposed in Bitcoin.Comment: 11 pages, 2 figure

Thermal Hadron Production in High Energy Heavy Ion Collisions

We provide a method to test if hadrons produced in high energy heavy ion collisions were emitted at freeze-out from an equilibrium hadron gas. Our considerations are based on an ideal gas at fixed temperature $T_f$, baryon number density $n_B$, and vanishing total strangeness. The constituents of this gas are all hadron resonances up to a mass of 2 GeV; they are taken to decay according to the experimentally observed branching ratios. The ratios of the various resulting hadron production rates are tabulated as functions of $T_f$ and $n_B$. These tables can be used for the equilibration analysis of any heavy ion data; we illustrate this for some specific cases.Comment: 12 pages (not included :13 figures + tables) report CERN-TH 6523/92 and Bielefeld preprint BI-TP 92/0

Kinetic Monte Carlo and Cellular Particle Dynamics Simulations of Multicellular Systems

Computer modeling of multicellular systems has been a valuable tool for interpreting and guiding in vitro experiments relevant to embryonic morphogenesis, tumor growth, angiogenesis and, lately, structure formation following the printing of cell aggregates as bioink particles. Computer simulations based on Metropolis Monte Carlo (MMC) algorithms were successful in explaining and predicting the resulting stationary structures (corresponding to the lowest adhesion energy state). Here we present two alternatives to the MMC approach for modeling cellular motion and self-assembly: (1) a kinetic Monte Carlo (KMC), and (2) a cellular particle dynamics (CPD) method. Unlike MMC, both KMC and CPD methods are capable of simulating the dynamics of the cellular system in real time. In the KMC approach a transition rate is associated with possible rearrangements of the cellular system, and the corresponding time evolution is expressed in terms of these rates. In the CPD approach cells are modeled as interacting cellular particles (CPs) and the time evolution of the multicellular system is determined by integrating the equations of motion of all CPs. The KMC and CPD methods are tested and compared by simulating two experimentally well known phenomena: (1) cell-sorting within an aggregate formed by two types of cells with different adhesivities, and (2) fusion of two spherical aggregates of living cells.Comment: 11 pages, 7 figures; submitted to Phys Rev

Relativistic quantum kinetic equation of the Vlasov type for systems with internal degrees of freedom

We present an approach to derive a relativistic kinetic equation of the Vlasov type. Our approach is especially reliable for the description of quantum field systems with many internal degrees of freedom. The method is based on the Heisenberg picture and leads to a kinetic equation which fulfills the conservation laws. We apply the approach to the standard Walecka Lagrangian and an effective chiral Lagrangian.Comment: 11 pages, LaTeX, uses ijmpel.st