Spontaneous formation of giant unilamellar liposomes in a gentle hydration process, as well as the adhesion energy between liposomal membranes, has been found to be dependent on the concentration of divalent alkali ca...
详细信息
Spontaneous formation of giant unilamellar liposomes in a gentle hydration process, as well as the adhesion energy between liposomal membranes, has been found to be dependent on the concentration of divalent alkali cations, Ca2+ or Mg2+, in the medium. With electrically neutral phosphatidylcholine (PC), Ca2+ or M2+ at 1-30 mM greatly promoted liposome formation compared to low yields in nonelectrolyte or potassium chloride solutions. When negatively charged phosphatidylglycerol (PG) was mixed at 10%, the yield was high in nonelectrolytes but liposomes did not form at 3-10 mM CaCl2. In the adhesion test with micropipette manipulation, liposomal membranes adhered to each other only in a certain range of CaCl2 concentrations, which agreed with the range where liposome did not form. The adhesion range shifted to higher Ca2+ concentrations as the amount of PG was increased. These results indicate that the divalent cations bind to and add positive charges to the lipids, and that membranes are separated and stabilized in the form of unilamellar liposomes when net charges on the membranes produce targe enough electrostatic repulsion. Under the assumption that the maximum of adhesion energy within an adhesive range corresponds to exact charge neutralization by added Ca2+, association constants of PC and PG for Ca2+ were estimated at 7.3 M-1 and 86 M-1, respectively, in good agreement with literature values.
A single molecule of F-1-ATPase, a portion of ATP synthase, is by itself a rotary motor in which a central gamma subunit rotates against a surrounding cylinder made of alpha(3)beta(3) subunits. Driven by three catalyt...
详细信息
A single molecule of F-1-ATPase, a portion of ATP synthase, is by itself a rotary motor in which a central gamma subunit rotates against a surrounding cylinder made of alpha(3)beta(3) subunits. Driven by three catalytic beta s, each fueled with ATP, gamma makes discrete 120 degrees steps, occasionally stepping backward. The work done in each step is constant over a broad range of imposed load and is close to the free energy of hydrolysis of one ATP molecule.
Provides information on the synthesis of ATP, a rotary motor made of a single molecule. Details on how ATP is synthesized; Ways of detecting molecular rotation; Information on the F1-ATPase, a portion of ATP synthase.
Provides information on the synthesis of ATP, a rotary motor made of a single molecule. Details on how ATP is synthesized; Ways of detecting molecular rotation; Information on the F1-ATPase, a portion of ATP synthase.
Skinned skeletal and cardiac muscle fibers exhibit spontaneous oscillatory contraction (SPOC) in the presence of MgATP, MgADP, and inorganic phosphate (P(i)), but the molecular mechanism underlying this phenomenon is ...
详细信息
Skinned skeletal and cardiac muscle fibers exhibit spontaneous oscillatory contraction (SPOC) in the presence of MgATP, MgADP, and inorganic phosphate (P(i)), but the molecular mechanism underlying this phenomenon is not yet clear. We have investigated the role of regulatory proteins in SPOC using cardiac muscle fibers of which the actin filaments had been reconstituted without tropomyosin and troponin, according to a previously reported method (Fujita et al., 1996. Biophys. J. 71:2307-2318). That is, thin filaments in glycerinated cardiac muscle fibers were selectively removed by treatment with gelsolin. Then, by adding exogenous actin to these thin filament-free cardiac muscle fibers under polymerizing conditions, actin filaments were reconstituted. The actin filament-reconstituted cardiac muscle fibers generated active tension in a Ca(2+)-insensitive manner because of the lack of regulatory proteins. Herein we have developed a new solvent condition under which SPOC occurs, even in actin filament-reconstituted fibers: the coexistence of 2,3-butanedione 2-monoxime (BDM), a reversible inhibitor of actomyosin interactions, with MgATP, MgADP and P(i). The role of BDM in the mechanism of SPOC in the actin filament-reconstituted fibers was analogous to that of the inhibitory function of the tropomyosin-troponin complex (-Ca(2+)) in the control fibers. The present results suggest that SPOC is a phenomenon that is intrinsic to the actomyosin motor itself.
As a provider of broadcast planning Software for television stations, programmers have to create highly customized software while maintaining the quality standards of an off-the-shelf product. Framework technology pla...
详细信息
As a provider of broadcast planning Software for television stations, programmers have to create highly customized software while maintaining the quality standards of an off-the-shelf product. Framework technology plays a strategic role in our business, because there are many similarities in the complex broadcast planning processes of different stations, yet a standard product would satisfy only 70% to 80% of the needs of a typical station. Thanks to frameworks, customers can be offered a standard product that is easily customizable by a small team of software engineers in a cost-effective way. Moreover, the adaptive nature of frameworks provides another advantage; like any other business, television stations need to respond to new and rapidly changing market opportunities. They are faced with rapidly evolving hardware and rapid evolution of their product. These changes require more malleable software. For broadcasters, the ability to cope with change more efficiently than from similar off-the-shelf applications results in a competitive advantage.
Since the early 1980s, object-oriented (OO) frameworks have demonstrated that OO programmers can encapsulate a reusable, tailorable software architecture as a collection of collaborating, extensible object classes. Su...
详细信息
Since the early 1980s, object-oriented (OO) frameworks have demonstrated that OO programmers can encapsulate a reusable, tailorable software architecture as a collection of collaborating, extensible object classes. Such frameworks are particularly important for developing open systems in which not only functionality but architecture is reused across a family of related applications. Unfortunately, the design of frameworks remains an art rather than a science because of the inherent conflict between reuse packaging software components that can be reused in as many contexts as possible and tailorability designing software architectures that are easily adapted to largest requirements. To cope with this conflict, well-designed OO frameworks must provide a clean conceptual framework that clearly identifies hot spots where tailorability is necessary and desirable and specifies framework contracts that formalize exactly which parts of the framework are to be reused. Tailorable frameworks are Particularly useful for the construction of so-called open systems.
The Data Diffusion Machine (DDM), a cache-only memory architecture (COMA) that relies on a hierarchical network structure, is described. The key ideas behind DDM are introduced by describing a small machine, which cou...
详细信息
The Data Diffusion Machine (DDM), a cache-only memory architecture (COMA) that relies on a hierarchical network structure, is described. The key ideas behind DDM are introduced by describing a small machine, which could be a COMA on its own or a subsystem of a larger COMA, and its protocol. A large machine with hundreds of processors is also described. The DDM prototype project is discussed, and simulated performance results are presented.
暂无评论