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151.
The fluorescence dynamics parameters of the fluorescent transient flavin-luciferase species from the typesVibrio fischeri andPhotobacterium leiognathi are presented. The fluorescence anisotropy decay is a single exponential function for both types. The correlation time is 70 ns for theP. leiognathi fluorescent transient intermediate (2°C, aqueous buffer, pH 7.0), consistent with the rotational correlation time of the luciferase macromolecule (77 kD) to which the flavin fluorophore is rigidly attached. In contrast, for theV. fischeri species the observed correlation time for the anisotropy decay function is 133 ns. This suggests that protein self-association occurs in theV. fischeri case and this is confirmed by filtration, where the fluorescent transient fromV. fischeri does not pass through a 100,000 molecular weight cutoff membrane, whereas theP. leiognathi species does. The filtration method also demonstrates self-association in the luciferase peroxyflavin and photoflavin fromV. fischeri. A monomer-dimer equilibrium also explains the previously reported high correlation times for theV. harveyi luciferase-flavin species. It is proposed that the self-association competes with the lumazine protein interaction in the bioluminescence reaction. 相似文献
152.
153.
Nonequilibrium statistical mechanics close to equilibrium is studied using SRB states and a formula [10] for their derivatives
with respect to parameters. We write general expressions for the thermodynamic fluxes (or currents) and the transport coefficients,
generalizing the results of [4, 5]. In this framework we give a general proof of the Onsager reciprocity relations.
Received: 2 December 1996 / Accepted: 13 March 1997 相似文献
154.
155.
In this paper a statistical multiplexer that processes a mixture of real-time and non-real-time traffic is studied under bursts of traffic. Different scheduling algorithms are compared under conditions when one of the classes of traffic has a sudden increase in its arrival rate during a short period of time. The results show a difference in the way the scheduling disciplines studied behave under short overloads of traffic even though the scheduling algorithms had been set up to give similar performance under steady-state arrivals. The lifetime of real-time packets is shown to have a great effect on the way in which the performance of the scheduling algorithms compare.Robert Lackman is an IBM employee in the IBM Resident Study Program. 相似文献
156.
157.
David E. Griffiths 《应用有机金属化学》1994,8(2):149-161
Dibutyltin-3-hydroxyflavone, Bu2Sn(of), is a new fluorescence probe inhibitor of F1F0-ATPase and oxidative phosphorylation which inhibits by titration of an unidentified component of F0. Its site of action is closely related to that of the trialkyltins and of venturicidin. This F0 component is part of a pool of this component which is present in the heart mitochondrial inner membrane at levels of 5–7 nmol (mg protein)?1 [18 ± 3 Bu2Sn(of) sites per mol F1F0-ATPase]. However, ATPase activity in submitochondrial particles is near maximally inhibited by titration of approx. three Bu2Sn(of) sites per mol F1F0-ATPase. Over 60% (60–80%) of the Bu2Sn(of) interaction sites can be lost during the purification of F1F0-ATPase from submitochondrial particles. The number of Bu2Sn(of) interaction sites in various F1F0-ATPase preparations is variable. The high numbers of Bu2Sn(of) sites per mol F1F0-ATPase for heart mitochondria (18–21) and submitochondrial particles (15–19.5) decline in ATP synthase (11–15) to the low values obtained in Complex V (7–10.5) and the minimal values observed in highly purified F1F0?ATPase (3.5–5.6), thus indicating a variable dissociable component or cofactor of ATP synthase. The Bu2Sn(of) interaction site, a component of ATP synthase, is responsive to the redox status of the respiratory chain and the interaction with Bu2Sn(of) is with the reduced form of this component. Fluorescence titration studies show that this component is in redox equilibrium with the ubiquinone pool of the respiratory chain. It is proposed that this redox component serves as an inhibitor titratable cofactor pool which cycles through an F0 interaction site (or sites) via a system which serves as an energy-transfer link between the respiratory chain and ATP synthase. 相似文献
158.
It is thought that the extensive industrial use of arsenic, gallium and indium, which have applications as the materials for III–V semiconductors, will increase human exposure to these compounds in the near future. We have undertaken the development of new biological indicators for assessing exposure to these elements. Element-specific alterations in protein synthesis patterns were expected to occur following exposure to arsenic compounds. We examined alterations in protein synthesis in primary cultures of rat kidney proximal tubule epithelial cells by sodium arsenite, gallium chloride and indium chloride, utilizing two-dimensional gel electrophoresis. After incubation with the chemicals for 20 h, newly synthesized proteins were labeled with [35S]methionine. A protein with a molecular weight (Mr) of 30 000 was markedly induced on exposure to 10 μM arsenite or 300 μM gallium chloride, and synthesis of proteins with Mr values of 85 000, 71 000, 65 000, 51 000, 38 000 and 28 000 were also increased by exposure to arsenite and gallium chloride. No significant changes were observed upon exposure to indium. Some of these increased proteins could be heat-shock proteins. 相似文献
159.
Dai Lu David Rutledge Milan Kovacevic Jon Hacker 《International Journal of Infrared and Millimeter Waves》2002,23(5):693-704
This paper presents an active patch array designed at 24 GHz. It can be used as a front-end component for a phased array. A series resonant array structure is chosen which is compact and easy excite. With 5 elements, the array proved a 12-dB antenna gain. A power amplifier and a low noise amplifier are designed on a single GaAs chip (PALNA). Bias switch is used in the PALNA, which greatly reduces the switch loss in a transceiver and increases the efficiency. 20-dB small signal gain is achieved in both power amplifier and low noise amplifier. The active patch array is built by the combination of the patch array and PALNA. The measured active gain of this antenna is 35-dB for the PA mode and 31-dB for the LNA mode. This active patch array can obtain an EIRP of 34 dBm with a total radiated power of 22dBm and a maximum PAE of 32%. To check the noise performance, we applied sources at both normal temperature and 77K (liquid nitrogen) and extracted the noise figure (3.5 dB) of the active antenna by the Y factor method. The results proved that the active antenna is working efficiently as both a transmitting and receiving antenna. 相似文献
160.