97 research outputs found
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 satisfies the following equation
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 and 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
is the function of the following parameters of
state: a non-equilibrium entropy , volume , number of particles of the
first component, , number of particles of the second component and
the renormalized degrees of freedom. The parameters ,
satisfy the relation (, where is the
fraction of component, and 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 and new thermodynamic parameters of state
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
The first law of thermodynamics in hydrodynamic steady and unsteady flows
We studied planar compressible flows of ideal gas as models of a
non-equilibrium thermodynamic system. We demonstrate that internal energy
of such systems in stationary and non-stationary states is the
function of only three parameters of state, i.e. non-equilibrium entropy
, volume and number of particles in the system. Upon transition
between different states, the system obeys the first thermodynamic law, i.e.
, where and
. Placing a cylinder inside the channel, we find that U depends
on the location of the cylinder only via the parameters of state, i.e.
at V=const. Moreover, when the flow around the
cylinder becomes unstable, and velocity, pressure, and density start to
oscillate as a function of time, t, U depends on t only via the parameters of
state, i.e. for V=const. These examples show that such a
form of internal energy is robust and does not depend on the particular
boundary conditions even in the unsteady flow.Comment: 17 pages, 9 figure
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)
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