Structural Insights into the Epimerization of β-1,4-Linked Oligosaccharides Catalyzed by Cellobiose 2-Epimerase, the Sole Enzyme Epimerizing Non-anomeric Hydroxyl Groups of Unmodified Sugars

Cellobiose 2-epimerase (CE) reversibly converts d-glucose residues into d-mannose residues at the reducing end of unmodified β1,4-linked oligosaccharides, including β-1,4-mannobiose, cellobiose, and lactose. CE is responsible for conversion of β1,4-mannobiose to 4-O-β-d-mannosyl-d-glucose in mannan metabolism. However, the detailed catalytic mechanism of CE is unclear due to the lack of structural data in complex with ligands. We determined the crystal structures of halothermophile Rhodothermus marinus CE (RmCE) in complex with substrates/products or intermediate analogs, and its apo form. The structures in complex with the substrates/products indicated that the residues in the β5-β6 loop as well as those in the inner six helices form the catalytic site. Trp-322 and Trp-385 interact with reducing and non-reducing end parts of these ligands, respectively, by stacking interactions. The architecture of the catalytic site also provided insights into the mechanism of reversible epimerization. His-259 abstracts the H2 proton of the d-mannose residue at the reducing end, and consistently forms the cis-enediol intermediate by facilitated depolarization of the 2-OH group mediated by hydrogen bonding interaction with His-200. His-390 subsequently donates the proton to the C2 atom of the intermediate to form a d-glucose residue. The reverse reaction is mediated by these three histidines with the inverse roles of acid/base catalysts. The conformation of cellobiitol demonstrated that the deprotonation/reprotonation step is coupled with rotation of the C2-C3 bond of the open form of the ligand. Moreover, it is postulated that His-390 is closely related to ring opening/closure by transferring a proton between the O5 and O1 atoms of the ligand

The Computer Programs of Layout Methods Based on Decision Making Theory

We tried to look at the allocation techniques in plant layout from the point of view of decision making theory. And it was made clear that Laplace, Minimax and Hurwicz princilpe can be applied to the allocation techniques. The techniques based on these principles were called Laplace method, Minimax method and Hurwicz method. In this paper algorithms and computer programs of these methods were described in order to solve the layout problems effectively

Allocation Technique Using Relative Distance and Relative Volume Estimated by Statistical Procedure

This paper deals with the allocation technique of the layout whose solution it takes as a little computation time as possible to obtain and which becomes as near to the optimal method as possible. In this method, the relative transport distance of each location and the relative transport volume of each department are calculated from the distance matrix and the volume matriX by the statistical procedures. And allocating departments to locations is determined by one to one correspondence between the arranged relative transport distances and the arranged relative transport volumes. This method was called the allocation technique by the statistical procedure ( ATSP in short ). This method doesn't use the heuristic algorithm. Therefore the calculation time can be reduced much in comparison with any other methods. As the algorithm of ATSP method is very simple, the sub-optimal layout can be determined easily by using the desk-calculator in cases of any layout problems

Coarse-graining and Self-similarity of Price Fluctuations

We propose a new approach for analyzing price fluctuations in their strongly correlated regime ranging from minutes to months. This is done by employing a self-similarity assumption for the magnitude of coarse-grained price fluctuation or volatility. The existence of a Cramer function, the characteristic function for self-similarity, is confirmed by analyzing real price data from a stock market. We also discuss the close interrelation among our approach, the scaling-of-moments method and the multifractal approach for price fluctuations.Comment: 9 pages, 3 figure

"Communication and Coordination in Organizations" (in Japanese)

This paper analyzes a model of coordination where two agents attempt to coordinate their actions through communication. One agent (Sender) is engaged in finding the true state of nature in a stochastic environment and the action that best fits the state. The other agent (Receiver) in turn tries to ``understand'' the Sender's message and chooses his own action. Since the communication succeeds only probilistically, so does the coordination. In our model, two different modes of coordination are identified: the integral-type coordination based on the communication of soft information and the default-type coordination based on the predetermined default value. We find that the agents might choose the latter mode of coordination when the cost arising from the failed communication is high relative to the benefit from coordinating on the state-contingent best actions. Applications to the economics of organization are also discussed.