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941.
942.
943.
944.
Laran T. Jensen J. M. Peltier Dennis R. Winge 《Journal of biological inorganic chemistry》1998,3(6):627-631
Mammalian metallothioneins (MT) are known to maximally bind 12 copper ions in two six-Cu(I) ion clusters. Using electrospray
ionization mass spectrometry of MT at pH 4.5, a four-Cu(I) ion cluster was observed intermediate to a fully formed six Cu(I)
in a single domain or a fully formed Cu12MT species. The four-Cu(I) cluster was observed in both MT1 and MT3 isoforms. Addition of increasing amounts of Cu(I) to MT
at pH 4.5 resulted in prominent ions whoses masses were consistent with apo-MT, Cu4MT, Cu6MT, and Cu12MT. The cooperativity of cluster formation was reduced at pH 2.5. Addition of Cu(I) to apo-MT at a reduced pH resulted in
a series of ions consistent with Cu4 to Cu12MT species. However, formation of the tetracopper MT species remained cooperative at low pH, suggesting that this species
is very stable. To determine whether the tetracopper cluster was formed in either the α or β domain, domain peptides of MT3
were used. Addition of Cu(I) to the apo β domain resulted in a peak consistent with the formation of a four-Cu(I) cluster.
This is consistent with reports that Cu(I) ions bind preferentially to the β domain of MTs.
Received: 2 June 1998 / Accepted: 21 August 1998 相似文献
945.
946.
A. V. Timofeev 《Plasma Physics Reports》2003,29(8):683-687
The conditions under which the energy of the electron Langmuir oscillations can escape from the plasma into vacuum are determined in the simplest model of a plane slab of an inhomogeneous cold magnetized plasma in a uniform magnetic field. 相似文献
947.
I. Denholm 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》1998,353(1376):1757-1767
For many key agricultural pests, successful management of insecticide resistance depends not only on modifying the way that insecticides are deployed, but also on reducing the total number of treatments applied. Both approaches benefit from a knowledge of the biological characteristics of pests that promote or may retard the development of resistance. For the whitefly Bemisia tabaci (Gennadius), these factors include a haplodiploid breeding system that encourages the rapid selection and fixation of resistance genes, its breeding cycle on a succession of treated or untreated hosts, and its occurrence on and dispersal from high-value crops in greenhouses and glasshouses. These factors, in conjunction with often intensive insecticide use, have led to severe and widespread resistance that now affects several novel as well as conventional control agents. Resistance-management strategies implemented on cotton in Israel, and subsequently in south-western USA, have nonetheless so far succeeded in arresting the resistance treadmill in B. tabaci through a combination of increased chemical diversity, voluntary or mandatory restrictions on the use of key insecticides, and careful integration of chemical control with other pest-management options. In both countries, the most significant achievement has been a dramatic reduction in the number of insecticide treatments applied against whiteflies on cotton, increasing the prospect of sustained use of existing and future insecticides. 相似文献
948.
949.
T L Marshak M Sh Avrushchenko 《Biulleten' eksperimental'no? biologii i meditsiny》1986,102(10):477-479
The changes in the size of Purkinje cell (PC) nucleolus in the lateral and medial cerebellum zones were studied in dogs with different degree of neurologic status recovery after clinical death of various etiology and duration. PC always possess one nucleolus in the control and experimental groups. In the case of complete neurologic status recovery of animals the area of PC nucleolus increases in both zones studied, irrespective of the cause of clinical death. In the case of neurologic disorders the increase in PC nucleolus area is clearly expressed only in the medial zone of the cerebellum, being insignificant in the lateral zone. It is suggested that adaptive characteristics of PC are distinct in the two compared zones, which leads to greater PC vulnerability in the lateral zone during deep hypoxia. 相似文献
950.
Detection of albumin mRNAs in rat liver by in situ hybridization: usefulness of paraffin embedding and comparison of various fixation procedures 总被引:3,自引:0,他引:3
I Tournier D Bernuau A Poliard D Schoevaert G Feldmann 《The journal of histochemistry and cytochemistry》1987,35(4):453-459
Our aim was to define optimal conditions for efficient and reproducible albumin mRNA detection in rat liver by in situ hybridization. We used an albumin-specific [3H]-labeled cDNA probe with a specific activity of 6-8.10(6) cpm/microgram DNA. In situ hybridization is as efficient on paraffin sections as on cryostat sections for detecting albumin mRNAs. Perfusion fixation with a 4% paraformaldehyde solution results in homogeneous RNA retention within tissue blocks, in contrast with immersion fixation, which yields heterogeneous RNA preservation. Comparison of immersion fixation with three different fixatives (paraformaldehyde, ethanol-acetic acid, and Bouin's fixative) shows that the highest level of hybridization signal is obtained with paraformaldehyde. Ethanol-acetic acid and Bouin's fixative appear less efficient for albumin mRNA detection. Loss of mRNAs within liver tissue blocks over time is largely although not completely prevented by paraffin embedding. 相似文献