121 research outputs found

    GT2004-53683 OPTIMAL OPERATIONAL PLANNING OF COGENERATION SYSTEMS WITH MICROTURBINE AND DESICCANT AIR-CONDITIONING UNITS

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    ABSTRACT Economic and energy-saving characteristics of cogeneration systems with microturbine and desiccant airconditioning units are investigated on system operational planning. An optimization approach is adopted to rationally evaluate these characteristics. In this approach, on/off and rated/part load status of operation of equipment and energy flow rates are determined so as to minimize the hourly energy charge subject to satisfaction of energy demand requirements. In this optimization problem, performance characteristics of the microturbine and desiccant air-conditioning units are modeled in consideration of the influence due to ambient air temperature. Moreover, the influence due to ambient air humidity is also considered in the desiccant air-conditioning unit using the psychrometric diagram. The implementation of the numerical analysis method, discussed in this paper, to two cogeneration systems, clearly shows economic and operational benefits of using desiccant air-conditioning. NOMENCLATURE A : coefficient for unit conversion from J to Wh, Wh/J a : latent heat of vaporization of water, kJ/kg B, C : coefficients of proportion, kg/m b : specific heat at constant pressure of air, kJ/(kg·°C) c : specific heat of water, kJ/(kg·°C) E : electricity, kWh/h F : natural gas consumption, m 3 /h h : specific enthalpy, kJ/kg J : hourly energy charge, yen/h m : mass flow rate, kg/h p, q, r, p′, q′, r′ : performance characteristic values of equipment Q : heat flow rate, kWh/h s : sensible heat factor t : temperature, °C u : input energy flow rate of equipment, m 3 /h, kWh/h v : velocity of process air, m/h x : absolute humidity, kg/kg y : output energy flow rate of equipment, kWh/h δ : binary variable expressing on/off status of operation η c : evaporative effectiveness of EC2 η e : effectiveness on regeneration air side of SHW η s : effectiveness on process air side of SHW ϕ : unit cost of energy charge, yen/m 3 , yen/kWh ( ), ( ) : lower and upper limit

    Multistep Engineering of Pyrrolysyl-tRNA Synthetase to Genetically Encode Nɛ-(o-Azidobenzyloxycarbonyl) lysine for Site-Specific Protein Modification

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    SummaryPyrrolysyl-tRNA synthetase (PylRS) esterifies pyrrolysine to tRNAPyl. In this study, Nɛ-(tert-butyloxycarbonyl)-L-lysine (BocLys) and Nɛ-allyloxycarbonyl-L-lysine (AlocLys) were esterified to tRNAPyl by PylRS. Crystal structures of a PylRS catalytic fragment complexed with BocLys and an ATP analog and with AlocLys-AMP revealed that PylRS requires an Nɛ-carbonyl group bearing a substituent with a certain size. A PylRS(Y384F) mutant obtained by random screening exhibited higher in vitro aminoacylation and in vivo amber suppression activities with BocLys, AlocLys, and pyrrolysine than those of the wild-type PylRS. Furthermore, the structure-based Y306A mutation of PylRS drastically increased the in vitro aminoacylation activity for Nɛ-benzyloxycarbonyl-L-lysine (ZLys). A PylRS with both the Y306A and Y384F mutations enabled the large-scale preparation (>10 mg per liter medium) of proteins site-specifically containing Nɛ-(o-azidobenzyloxycarbonyl)-L-lysine (AzZLys). The AzZLys-containing protein was labeled with a fluorescent probe, by Staudinger ligation

    Deep Knot Structure for Construction of Active Site and Cofactor Binding Site of tRNA Modification Enzyme

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    AbstractThe tRNA(Gm18) methyltransferase (TrmH) catalyzes the 2′-O methylation of guanosine 18 (Gua18) of tRNA. We solved the crystal structure of Thermus thermophilus TrmH complexed with S-adenosyl-L-methionine at 1.85 Å resolution. The catalytic domain contains a deep trefoil knot, which mutational analyses revealed to be crucial for the formation of the catalytic site and the cofactor binding pocket. The tRNA dihydrouridine(D)-arm can be docked onto the dimeric TrmH, so that the tRNA D-stem is clamped by the N- and C-terminal helices from one subunit while the Gua18 is modified by the other subunit. Arg41 from the other subunit enters the catalytic site and forms a hydrogen bond with a bound sulfate ion, an RNA main chain phosphate analog, thus activating its nucleophilic state. Based on Gua18 modeling onto the active site, we propose that once Gua18 binds, the phosphate group activates Arg41, which then deprotonates the 2′-OH group for methylation
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