Lys-373 of actin is involved in binding to caldesmon

AbstractLimited proteolysis of actin with trypsin removes its two or three C-terminal amino acid residues [Proc. Natl. Acad. Sci. USA 81 (1984) 3680–3684]. Carboxypeptidase B-treatment of G- and F-actin previously digested with trypsin revealed that in the first case preferential release of three and in the second two C-terminal amino acid residues takes place. Tryptic removal of three but not two C-terminal amino acid residues of actin causes weakening of its interaction with caldesmon and lowering of the caldesmon-induced inhibitory effect on actomyosin ATPase activity. Therefore, it is concluded that the third amino acid residue from the C terminus of actin, Lys-373, is important for the interaction with caldesmon

Thermodynamics of stationary states of the ideal gas in a heat flow

There is a long-standing question as to whether and to what extent it is possible to describe nonequilibrium systems in stationary states in terms of global thermodynamic functions. The positive answers have been obtained only for isothermal systems or systems with small temperature differences. We formulate thermodynamics of the stationary states of the ideal gas subjected to heat flow in the form of the zeroth, first, and second law. Surprisingly, the formal structure of steady state thermodynamics is the same as in equilibrium thermodynamics. We rigorously show that $U$ satisfies the following equation $dU=T^{*}dS^{*}-pdV$ for a constant number of particles, irrespective of the shape of the container, boundary conditions, size of the system, or mode of heat transfer into the system. We calculate $S^{*}$ and $T^{*}$ explicitly. The theory selects stable nonequilibrium steady states in a multistable system of ideal gas subjected to volumetric heating. It reduces to equilibrium thermodynamics when heat flux goes to zero

Parameters of state in the global thermodynamics of binary ideal gas mixtures in a stationary heat flow

We formulate the first law of global thermodynamics for stationary states of the binary ideal gas mixture subjected to heat flow. We map the non-uniform system onto the uniform one and show that the internal energy $U(S^*,V,N_1,N_2,f_1^*,f_2^*)$ is the function of the following parameters of state: a non-equilibrium entropy $S^*$, volume $V$, number of particles of the first component, $N_1$, number of particles of the second component $N_2$ and the renormalized degrees of freedom. The parameters $f_1^*,f_2^*$, $N_1, N_2$ satisfy the relation $x_1f_1^*/f_1+x_2f_2^*/f_2=1$ ($f_1$, where $x_i$ is the fraction of $i$ component, and $f_2$ are the degrees of freedom for each component respectively). Thus only 5 parameters of state describe the non-equilibrium state of the binary mixture in the heat flow. We calculate the non-equilibrium entropy $S^{*}$ and new thermodynamic parameters of state $f_1^*, f_2^*$ explicitly. The latter are responsible for heat generation due to the concentration gradients. The theory reduces to equilibrium thermodynamics, when the heat flux goes to zero. As in equilibrium thermodynamics, the steady-state fundamental equation also leads to the thermodynamic Maxwell relations for measurable steady-state properties.Comment: 8 pages, 1 figur

Steady state thermodynamics of ideal gas in shear flow

Equilibrium thermodynamics describes the energy exchange of a body with its environment. Here, we describe the global energy exchange of an ideal gas in the Coutte flow in a thermodynamic-like manner. We derive a fundamental relation between internal energy as a function of parameters of state. We analyze a non-equilibrium transition in the system and postulate the extremum principle, which determines stable stationary states in the system. The steady-state thermodynamic framework resembles equilibrium thermodynamics

Thermodynamics of stationary states of the ideal gas in a heat flow

There is a long-standing question as to whether and to what extent it is possible to describe nonequilibrium systems in stationary states in terms of global thermodynamic functions. The positive answers have been obtained only for isothermal systems or systems with small temperature differences. We formulate thermodynamics of the stationary states of the ideal gas subjected to heat flow in the form of the zeroth, first, and second law. Surprisingly, the formal structure of steady state thermodynamics is the same as in equilibrium thermodynamics. We rigorously show that U satisfies the following equation dU= T* dS* -pdV for a constant number of particles, irrespective of the shape of the container, boundary conditions, size of the system, or mode of heat transfer into the system. We calculate S* and T* explicitly. The theory selects stable nonequilibrium steady states in a multistable system of ideal gas subjected to volumetric heating. It reduces to equilibrium thermodynamics when heat flux goes to zero

Current dietary recommendations for patients with cystic fibrosis

Cystic fibrosis (CF) is classified as metabolic and multisystem disease with autosomal recessive inheritance caused by mutations in the gene located on chromosome 7 encoding cystic fibrosis transmembrane conductance regulator (CFTR) protein. CFTR is a transmembrane chloride channel of epithelial cells and affects the activity of the mucous membrane of the sweat glands, airway epithelium, pancreatic ducts, vas deferens, bile ducts and intestines. In CF, increased concentration of chlorides in the sweat, pancreatic insufficiency and impaired absorption are observed as well as changes in the respiratory system related to, among others, impaired airway patency, weakening of the mucociliary clearance mechanism and the development of bacterial infections. CF is a chronic condition requiring comprehensive therapy. Nutritional treatment is an essential element of CF therapy. Malnutrition is a common complication in patient with CF and eating disorders. The majority of patients with CF have higher energy, protein and fat needs. In addition, supplementation with enzyme preparations, vitamins, sodium chloride, as well as the use of high-energy nutrients is recommended. The aim of the study was to evaluate current nutritional recommendations of patients with CF

Diffusion and flow in complex liquids

Thermal motion of particles and molecules in liquids underlies many chemical and biological processes. Liquids, especially in biology, are complex due to structure at multiple relevant length scales. While diffusion in homogeneous simple liquids is well understood through the Stokes–Einstein relation, this equation fails completely in describing diffusion in complex media. Modeling, understanding, engineering and controlling processes at the nanoscale, most importantly inside living cells, requires a theoretical framework for the description of viscous response to allow predictions of diffusion rates in complex fluids. Here we use a general framework with the viscosity η(k) described by a function of wave vector in reciprocal space. We introduce a formulation that allows one to relate the rotational and translational diffusion coefficients and determine the viscosity η(k) directly from experiments. We apply our theory to provide a database for rotational diffusion coefficients of proteins/protein complexes in the bacterium E. coli. We also provide a database for the diffusion coefficient of proteins sliding along major grooves of DNA in E. coli. These parameters allow predictions of rate constants for association of proteins. In addition to constituting a theoretical framework for description of diffusion of probes and viscosity in complex fluids, the formulation that we propose should decrease substantially the cost of numerical simulations of transport in complex media by replacing the simulation of individual crowding particles with a continuous medium characterized by a wave-length dependent viscosity η(k)

Continuous non-equilibrium transition driven by the heat flow

We discovered an out-of-equilibrium transition in the ideal gas between two walls, divided by an inner, adiabatic, movable wall. The system is driven out-of-equilibrium by supplying energy directly into the volume of the gas. At critical heat flux, we have found a continuous transition to the state with a low-density, hot gas on one side of the movable wall and a dense, cold gas on the other side. Molecular dynamic simulations of the soft-sphere fluid confirm the existence of the transition in the interacting system. We introduce a stationary state Helmholtz-like function whose minimum determines the stable positions of the internal wall. This transition can be used as a paradigm of transitions in stationary states and the Helmholtz-like function as a paradigm of the thermodynamic description of these states