It is known that in humans taking soy food, the phytoestrogens, daidzein (DZ) and genistein (GS), exist as sulfates and glucuronides in the plasma and are excreted as conjugates in urine. To investigate which human sulfotransferase (SULT) isoforms participate in the sulfation of these phytoestrogens, the four major cytosolic SULTs, SULT1A1, SULT1A3, SULT1E1, and SULT2A1, occurring in the human liver were bacterially expressed as His-tagged proteins and chromatographically purified to homogeneity in the presence of Tween 20 and glycerol as highly efficient agents for stabilizing the recombinant enzymes. All the SULTs showed sulfating activity toward both DZ and GS. However, k(cat)/K(m) values observed indicated that these phytoestrogens were sulfated predominantly by SULT1A1 and SULT1E1 with K(m) values of 0.3 and 0.7 microM for GS and 1.9 and 3.4 microM for DZ, respectively. DZ and GS strongly inhibited the sulfation of the endogenous substrate, beta-estradiol, by SULT1E1 in a non-competitive manner with K(i) values of 14 and 7 microM, respectively, suggesting that these phytoestrogens might affect tissue levels of beta-estradiol in the human. The phenolic endocrine-disrupting chemicals, bisphenol A (BPA), 4-n-nonylphenol (NP), and 4-t-octylphenol (t-OP), were used as substrates to investigate the possible participation of human SULTs in their metabolism for excretion. High k(cat)/K(m) values were observed for the sulfation of BPA by SULT1A1, NP by SULT1A1 and SULT1E1, and t-OP by SULT1E1 and SULT2A1.
Control/structure interaction problems are much concerned with the atti tude stability of space structures and the accuracies of on-board instruments as the sizes and flexibilities of structures increase. In this paper, an attempt to integrate collocated actuators and sensors into truss structures and to suppress the vibration or to adjust the truss geometry is investigated. For both functions of vibration suppression and shape adjustment, piezoelectric actuator Type-I was manufactured. And, for the purpose of increasing the abilities of vibration suppression, another type of actuator (Type-II) was designed. Some experimental results and analyses show the capabilities of vibration sup pression and precise adjustment of truss geometry by these piezoelectric actuators.
This paper describes investigations on adaptive vibration control and shape adjustment of truss structures making use of the active member actuator. The actuator was manufactured in an attempt to achieve these functions by linear actuating. Fundamental characteristics were examined statically and dynamically. Numerical simulations of planar truss model with the configuration of one pair of collocated actuator and sensor shows that a state observer can estimate truncated modes well and the excited vibration can be controlled rapidly. ,1. of IN TELL.
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