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排序方式: 共有670条查询结果,搜索用时 31 毫秒
71.
Tian X Field T Mazur AW Ebetino FH Wos JA Crossdoersen D Pinney BB Sheldon RJ 《Bioorganic & medicinal chemistry letters》2005,15(11):2819-2823
A series of proline based melanocortin ligands has been developed on the basis of initial piperazine leads by using a more conformationally rigid scaffold. A number of these novel ligands showed significant binding affinity for MC3 and MC4 receptors. 相似文献
72.
MII mouse oocytes in 1 and 1.5M ethylene glycol(EG)/phosphate buffered saline have been subjected to rapid freezing at 50 degrees C/min to -70 degrees C. When this rapid freezing is preceded by a variable hold time of 0-3 min after the initial extracellular ice formation (EIF), the duration of the hold time has a substantial effect on the temperature at which the oocytes subsequently undergo intracellular ice formation (IIF). For example, in 1M EG, the IIF temperatures are -23.7 and -39.2 degrees C with 0 and 2 min hold times; in 1.5M EG, the corresponding IIF temperatures are -29.1 and -40.8 degrees C. 相似文献
73.
74.
High ice nucleation temperature of zebrafish embryos: slow-freezing is not an option 总被引:4,自引:0,他引:4
Although fish embryos have been used in a number of slow-freezing cryopreservation experiments, they have never been successfully cryopreserved. In part this is because little is known about whether ice forms within the embryo during the slow-freezing dehydration process. Therefore, we examined the temperature of intraembryonic ice formation (T(IIF)) and the temperature of extraembryonic ice formation (T(EIF)), using a cryomicroscope. We used both unmodified zebrafish embryos and those with water channels (aquaporin-3 or AQP3) inserted into their membranes to increase permeability to water and cryoprotectants, examined at 100% epiboly to the 6-somite stage. In these experiments we examined: (1) the spontaneous freezing of (external) solutions; (2) the spontaneous freezing of solutions containing embryos; (3) the effect of preloading the embryos with cryoprotectants on T(IIF); (4) whether preloading the embryos with cryoprotectant helps in survival after nucleating events in the solution; and (5) the damaging effects of extracellular nucleation events versus solution toxicity on the embryos. The solutes alone (embryo medium--EM, sucrose culture medium, 1 M propylene glycol in EM, and 1 M propylene glycol in a sucrose culture medium) froze at -14.9 +/- 1.1, -17.0 +/- 0.3, -17.8 +/- 1.0, and -17.7 +/- 1.4, respectively. There was no difference amongst these means (P > 0.05), thus adding cryoprotectant did not significantly lower the nucleation point. Adding embryos (preloaded with cryoprotectant or not) did not change the basic freezing characteristics of these solutes. In all these experiments, (T(EIF)) equaled (T(IIF)), and there was no difference in the freezing point of the solutions with or without the embryos (P > 0.05). Additionally, there was no difference in the freezing characteristics of embryos with and without aquaporins (P > 0.05). The formation of intraembryonic ice was lethal to the zebrafish embryos in all cases. But this lethal outcome was not related to solution injury effects, because 88-98% of embryos survived when exposed to a higher solute concentration with no ice present. Taken together, these data suggest that slow-freezing is not a suitable option for zebrafish embryos. The mechanism of this high temperature nucleation event in zebrafish embryos is still unknown. 相似文献
75.
Jan Moncol Barbora Kalinakova Miroslava Kleinova Daniela Hudecova Milan Mazur 《Inorganica chimica acta》2004,357(11):3211-3222
New copper(II) clofibriates (clof, {2-(4-chlorophenoxy)-2-methylpropionic or 2-(4-chlorophenoxy)isobutyric acid}) of composition Cu(clof)2L2 (where L=2-pyridylmethanol (2-pymeth) (1), N-methylnicotinamide (Menia) (4), N,N-diethylnicotinamide (Et2nia) (5), isonicotinamide (isonia) (7) or methyl-3-pyridylcarbamate (mpc) (8)), [Cu(clof)2(4-pymeth)2(H2O)] · 2H2O (4-pymeth=4-pyridylmethanol) (2 · 2H2O) and Cu(clof)2L (where L=4-pymeth (3) or Et2nia (6)) have been prepared and spectroscopically characterized. All the Cu(clof)2L2 compounds seem to possess distorted octahedral copper(II) stereochemistry with differing tetragonal distortions. An X-ray analysis of 1 was carried out and it featured a tetragonal-bipyramidal geometry around the copper(II) atom. X-ray analysis of 2 · 2H2O featured a square-pyramidal geometry around copper(II) atom. Both the Cu(clof)2L compounds seem to consist of a binuclear unit of tetracarboxylate type bridging. An X-ray analysis of 6 revealed typical binuclear paddle-wheel type structure, consisting of two copper(II) atoms in square-pyramidal geometry bridged by four carboxylate anions in the xy-plane. All complexes under study were characterized by EPR and electronic spectroscopy. The antimicrobial effects have been tested on various strains of bacteria, yeasts and filamentous fungi. 相似文献
76.
Marek Lisowski Łukasz Jaremko Mariusz Jaremko Adam Mazur Rafał Latajka Maciej Makowski 《Biopolymers》2010,93(12):1055-1064
Conformations of two pairs of dehydropeptides with the opposite configuration of the ΔPhe residue, Boc‐Gly‐ΔZPhe‐Gly‐Phe‐OMe ( Z‐ OMe ), Boc‐Gly‐ΔEPhe‐Gly‐Phe‐OMe ( E‐ OMe ), Boc‐Gly‐ΔZPhe‐Gly‐Phe‐p‐NA ( Z‐p‐ NA ), and Boc‐Gly‐ΔEPhe‐Gly‐Phe‐p‐NA ( E‐p‐ NA ) were compared on the basis of CD and NMR studies in MeOH, trifluoroethanol (TFE), MeCN, chloroform, and dimethylsulfoxide (DMSO). The CD results were used as the additional input data for the NMR‐based determination of the detailed solution conformations of the peptides. It was found that E‐ OMe is unordered and Z‐ OMe , Z‐p‐ NA , and E‐p‐ NA adopt the β‐turn conformation. There are two overlapping β‐turns in each of those peptides: type II and type III′ in Z‐ OMe and Z‐p‐ NA , and two type III in E‐p‐ NA . The ordered structure‐inducing properties of ΔZPhe and ΔEPhe in the peptides studied depend on the C‐terminal blocking group. In methyl esters, the ΔZPhe residue is a strong inducer of ordered conformations whereas the ΔEPhe one has no such properties. In p‐nitroanilides, both isomers of ΔPhe cause the peptides to adopt ordered structures to a similar extent. © 2010 Wiley Periodicals, Inc. Biopolymers 93: 1055–1064, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com 相似文献
77.
Mazur A 《Social biology》2006,53(1-2):24-29
Usually face-to-face dominance contests between humans are nonviolent, even amiable. Most violence between young men occurs when dominance contests infrequently escalate beyond their usually bounds. Heightened testosterone is not a direct cause of male violence. Occasional outbreaks of violence occur for other reasons, and are often random outcomes. However testosterone does encourage (nonviolent) dominant behavior among young men, increasing the frequency of dominance contests, hence increasing the likelihood of violent outcomes. "Honor subcultures" such as are found in our inner cities place inordinate importance on the enhancement of personal reputations and the humiliation of losing face. This atmosphere of persistent challenge produces heightened testosterone in young black men of the inner city, raising the likelihood that they will engage in dominance competition, which in turn raises the likelihood of a violent, even fatal, outcome. 相似文献
78.
Zirah S Kozin SA Mazur AK Blond A Cheminant M Ségalas-Milazzo I Debey P Rebuffat S 《The Journal of biological chemistry》2006,281(4):2151-2161
Amyloid deposits within the cerebral tissue constitute a characteristic lesion associated with Alzheimer disease. They mainly consist of the amyloid peptide Abeta and display an abnormal content in Zn(2+) ions, together with many truncated, isomerized, and racemized forms of Abeta. The region 1-16 of Abeta can be considered the minimal zinc-binding domain and contains two aspartates subject to protein aging. The influence of zinc binding and protein aging related modifications on the conformation of this region of Abeta is of importance given the potentiality of this domain to constitute a therapeutic target, especially for immunization approaches. In this study, we determined from NMR data the solution structure of the Abeta-(1-16)-Zn(2+) complex in aqueous solution at pH 6.5. The residues His(6), His(13), and His(14) and the Glu(11) carboxylate were identified as ligands that tetrahedrally coordinate the Zn(II) cation. In vitro aging experiments on Abeta-(1-16) led to the formation of truncated and isomerized species. The major isomer generated, Abeta-(1-16)-l-iso-Asp(7), displayed a local conformational change in the His(6)-Ser(8) region but kept a zinc binding propensity via a coordination mode involving l-iso-Asp(7). These results are discussed here with regard to Abeta fibrillogenesis and the potentiality of the region 1-16 of Abeta to be used as a therapeutic target. 相似文献
79.
Improved methods for preservation of honey bee, Apis mellifera L., germplasm would be very welcome to beekeeping industry queen breeders. The introduction of two parasites and the emergence of an antibiotic resistant disease have increased demands for resistant stock. Techniques for artificial insemination of queens are available, and semen has been cryopreserved with limited success. However, cryopreservation of embryos for rearing queens would mesh well with current practices and also provide drones (haploid males). Eggs at five ages between twenty-four hours and sixty-two hours were exposed to 0, -6.6, and/or -15 degrees C for various times, and successful hatch measured. Honey bee embryos show chill sensitivity as do other insect embryos, and the rate of chill injury increases dramatically with decrease in holding temperature. The 48 h embryos in both groups showed the greatest tolerance to chilling, although 44 h embryos were only slightly less so. 相似文献
80.
Effect of nickel on antioxidative enzyme activities, proline and chlorophyll contents in wheat shoots 总被引:12,自引:0,他引:12
Effect of two Ni concentrations (10 and 200 μM) on growth, Ni accumulation, chlorophyll and proline contents, relative water
content (RWC) as well as the activities of superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) and glutathione S-transferase
(GST) were studied in shoots of wheat plants. Treatments caused a considerable accumulation of Ni in the shoots. However,
exposure of plants to 10 μM Ni did not lead to significant alterations in shoot growth except for a slight increase in fresh
mass. The other parameters studied were not affected by treatment of plants with 10 μM Ni. In contrast, 200 μM Ni caused inhibition
of shoot growth, a decline in RWC and chlorophyll content, accumulation of proline and occurrence of visible symptoms of Ni
toxicity. The activities of SOD and CAT decreased in response to 200 μM Ni. Conversely, several-fold enhancements of POD and
GST activities were observed following the 3rd day of 200 μM Ni treatment. 相似文献