The reversible formation of a glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-CP12-phosphoribulokinase (PRK) supramolecular complex, identified in oxygenic photosynthetic organisms, provides light-dependent Calvin cycle regulation in a coordinated manner. An intrinsically disordered protein (IDP) CP12 acts as a linker to sequentially bind GAPDH and PRK to downregulate both enzymes. Here, we report the crystal structures of the ternary GAPDH-CP12-NAD and binary GAPDH-NAD complexes from Synechococcus elongates. The GAPDH-CP12 complex structure reveals that the oxidized CP12 becomes partially structured upon GAPDH binding. The C-terminus of CP12 is inserted into the active-site region of GAPDH, resulting in competitive inhibition of GAPDH. This study also provides insight into how the GAPDH-CP12 complex is dissociated by a high NADP(H)/NAD(H) ratio. An unexpected increase in negative charge potential that emerged upon CP12 binding highlights the biological function of CP12 in the sequential assembly of the supramolecular complex.

Stable blast furnace operation is required to reduce energy consumption in iron and steelmaking industry. For the stable blast furnace operation, precise controlled drainage is one of the important factors. However, the effects of the various in-furnace conditions on the stable operation were not examined well. Therefore, in this work, basic characteristic features of drainage in a blast furnace hearth were examined.Two-and three-dimensional mathematical model were developed based on the finite difference method to simulate molten iron and slag flow in a hearth of a blast furnace. Pressure drop evaluation model in a taphole was developed to reflect pressure variation in a blast furnace hearth on drainage rate of molten iron and slag for the three-dimensional mathematical model.The two-dimensional mathematical model results were validated with measured interfaces shapes obtained using an experimental model. The three-dimensional mathematical model results were validated with measured total, iron and slag drainage rate of Chiba No. 6 blast furnace. The results indicate that the drainage behavior and residual iron and slag volume were affected by the conditions in the hearth. The taphole conditions dominate the total drainage rate under the term of assumed blast furnace conditions. In order to reduce the residual slag volume, the taphole diameter change during the tap should be controlled. The decrease of the coke diameter causes increase of the residual slag volume, decrease of the residual iron volume.KEY WORDS: iron and slag flow; residual slag volume; numerical simulation; VOF method; blast furnace hearth; ironmaking.faces shapes of immiscible fluids having different properties. Two-dimensional Mathematical ModellingThe governing equations for fluid flow used in the twodimensional mathematical model are based on the HSMAC method, 8) ... (3) where u is the horizontal velocity (m/s), v is vertical velocity (m/s), x and y are coordinates (m), t is time (s), r is density of fluids (kg/m 3 ), p is pressure of fluids (Pa), m is viscosity (Pa · s), g is acceleration due to gravity (m/s 2 ), and S is an interaction force between fluid and 2 flat parallel plates (m/s 2 ). In the two-dimensional mathematical model, gas, slag and iron were treated as one fluid having local properties, which correspond to each phase. Representation of InterfacesFor the determination of the fluid properties in each computational cell, it is necessary to compute the proportion of gas, iron and slag in each cell. Therefore, gas-slag and slag-iron interfaces should be identified exactly. To distinguish the interfaces, the VOF method 9) was applied for the calculation of interfaces (gas-slag, slag-iron). Generally, the VOF method is used to track free boundaries in two-or three-dimensional meshes. Although, in this work, VOF is also used to identify slag-iron interface, as shown in Fig. 1. A unit value of VOF 1 would correspond to a cell full of liquid. A unit value of VOF 2 would correspond to a cell full of iron. Cells with VOF 2 values betw...

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