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排序方式: 共有212条查询结果,搜索用时 31 毫秒
41.
Annamaria Guagliardi Laura Cerchia Mosè Rossi 《Applied biochemistry and biotechnology》1997,62(1):37-46
The chaperonin of the hyperthermophilic archaeonSulfolobus solfataricus, briefly Ssocpn, was purified by a fast and high-yield procedure. Ssocpn, a 920 kDa-complex of two different subunits, displays
a potassium-dependent ATPase activity with a temperature optimum at 80°C. The ability of Ssocpn to function in vitro was investigated
using different protein substrates. Ssocpn promotes correct refolding of thermophilic and mesophilic enzymes from their chemically
unfolded state; moreover, Ssocpn prevents the irreversible inactivation of native proteins by suppressing their precipitation
upon heating. Both the activity in assisting refolding of unfolded proteins and that in preventing heat denaturation of native
proteins require the hydrolysis of ATP.
The chaperone-based strategies in different technological fields are discussed, and the advantages in using archaeal chaperonins
are underlined. 相似文献
42.
Anna Maria Manotti Lanfredi Franco Ugozzoli Annamaria Camus Nazario Marsich 《Journal of chemical crystallography》1995,25(1):37-41
The title compound was synthesized by CS2 insertion in the C-M bonds of the corresponding AgLi ate organomental compound. It contains flattened tetrahedral Ag4 units, connected in polymeric chains by intermolecular Ag...S interactions. Two Ag atoms and three S atoms are in a distorted square pyramidal arrangement around each silver atom. The crystals are tetragonal, space group 141/a witha=23.706(2) andc=12.934(2) Å. The structure was refined toR=0.032 for 889 reflections. 相似文献
43.
Henri Brunner Rainer Lukas Annamaria Woditsch 《Journal of organometallic chemistry》1978,161(2):C49-C52
(η-C5H5)(CO)2W[(η3-C5H5)(C5H5)2], I, containing two tilted five-membered rings, is converted into the bridged ferrocene derivative (η-C5H5)(CO)2W{(η3-C5H5)}[(η-C5 H4)2Fe]} II by successive reaction with Na and FeCl2. 相似文献
44.
Violeta Lazic Sonja Jovicevic Roberta Fantoni Francesco Colao 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007,62(12):1433-1442
Laser-induced breakdown spectroscopy (LIBS) measurements were performed on bulk water solutions by applying a double-pulse excitation from a Q-Switched (QS) Nd:YAG laser emitting at 1064 nm. In order to optimize the LIBS signal, laser pulse energies were varied through changing of the QS trigger delays with respect to the flash-lamp trigger. We had noted that reduction of the first pulse energy from 92 mJ to 72 mJ drastically improves the signal, although the second pulse energy was also lowered from 214 mJ to 144 mJ. With lower pulse energies, limit of detection (LOD) for Mg in pure water was reduced for one order of magnitude (34 ppb instead of 210 ppb). In order to explain such a phenomenon, we studied the dynamics of the gas bubble generated after the first laser pulse through measurements of the HeNe laser light scattered on the bubble. The influence of laser energy on underwater bubble and plasma formation and corresponding plasma emission intensity were also studied by photographic technique. From the results obtained, we conclude that the optimal first pulse energy should be kept close to the plasma elongation threshold, in our case about 65 mJ, where the gas bubble has its maximum lateral expansion and the secondary plasma is still well-localized. The importance of a multi-pulse sequence on the LIBS signal was also analyzed, where the pulse sequence after the first QS aperture was produced by operating the laser close to the lasing threshold, with the consequent generation of relaxation oscillations. Low-energy multi-pulses might keep the bubble expansion large prior to the probing pulse, but preventing the formation of secondary weak plasmas in multiple sites, which reduces the LIBS signal. The short interval between the pre-pulses and the probing pulse is another reason for the observed LIBS signal enhancement. 相似文献
45.
Occhiato EG Prandi C Ferrali A Guarna A Deagostino A Venturello P 《The Journal of organic chemistry》2002,67(20):7144-7146
Alkoxydienyl- and alkoxystyrylboronates were used for Pd-catalyzed cross-coupling reactions with lactam-derived vinyl triflates. The hydrolysis of the coupling products with alkoxystyrylboronates provided the corresponding alpha-acyl-substituted 3,4-dihydro-(2H)-pyridines and 2,3,4,5-tetrahydroazepines in good to high yields. The hydrolysis of the coupling products with alkoxydienylboronates, performed in the presence of Amberlyst 15, resulted in a Nazarov-type cyclization that afforded hexahydro[1]pyrindin-7-ones and 3,4,5,6,7,8-hexahydro-(2H)-cyclopenta[b]azepin-8-ones. This methodology represents a novel and efficient procedure for the preparation of these classes of azacyclic compounds. 相似文献
46.
47.
48.
L. Caneve F. Colao R. Fantoni V. Spizzichino 《Applied Physics A: Materials Science & Processing》2006,85(2):151-157
Single and double pulse laser induced breakdown spectroscopy was applied to the analysis of copper based alloys samples, in order to investigate the material ablation process under two different experimental conditions. An Nd:YAG laser, emitting at the fundamental wavelength (1064 nm) for a fixed value of total energy with the same pulse width, has been used for both set-up configurations. Certified samples of copper based alloys were examined in order to investigate the effect of their different compositions on the ablation process efficiency. The craters produced by the laser on the samples surfaces were measured by a contact profilometer in order to evaluate the mass of ablated material. In this respect the differences in behaviour of the single and the double pulse ablation for Laser Induced Breakdown Spectroscopy (LIBS), respectively, have been considered. The dependence, under the same experimental conditions, of the LIBS background emission of the different ablated masses of the material has also been investigated, by looking for normalization algorithms for quantitative data reduction.The behaviour of some peculiar intensity ratios, suitable for building calibration curves, has been studied in order to evaluate the trend in fractionated evaporation on going from the single pulse to the double pulse technique. PACS 52.70.-m; 52.50.Jm; 42.62.Fi 相似文献
49.
Annamaria Barbagallo 《Journal of Global Optimization》2008,40(1-3):29-39
The aim of this paper is to obtain the continuity of solutions to time-dependent nonlinear variational and quasi-variational
inequalities which express many dynamic equilibrium problems. To prove our results, we make use of Minty’s Lemma and of the
notion of the Mosco’s convergence. 相似文献
50.
The cellular plasma membrane plays a fundamental role in biological processes, including cell growth, signaling and transport. The labelling of the plasma membrane with targeted fluorescent probes offers a convenient and non-invasive way to image the morphological changes and dynamics of a membrane in real-time and, despite many examples of fluorescent plasma membrane probes, a “universal targeting/anchoring moiety” is still required. In this study, a small number of stearic acid-based probes labelled with 6-carboxyfluorescein was designed and fabricated via solid-phase synthesis in which variations in both charge and hydrophobicity were explored. To ease the synthesis process, a gram-scale synthesis of the Fmoc-Lys(6-carboxyfluoresein diacetate)-OH building block was developed, allowing the discovery of optimal probes that carried a positively charged amino group and a stearic acid tail that exhibited intense plasma membrane brightness and robust retention. 相似文献