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排序方式: 共有315条查询结果,搜索用时 15 毫秒
1.
This work describes a new electrochemical sensor for hydrogen peroxide based on tin pentacyanonitrosylferrate (SnPCNF)-modified carbon ceramic electrode (CCE). The modified electrode was constructed by using a sol-gel technique involving two steps: construction of CCE containing metallic tin (Sn) powder and then electrochemical creation of SnPCNF film on the surface of CCE. The modified electrode was characterized by energy-dispersive X-ray, Fourier transform infrared, scanning electron microscopy, and cyclic voltammetry (CV) techniques. The charge transfer coefficient (α) and charge transfer rate constant (ks) for the modifying film were calculated. The electrocatalytic activity of the modified electrode toward the reduction of hydrogen peroxide was studied by CV and chronoamperometry. A linear calibration curve was obtained over the hydrogen peroxide concentration range of 0.5 to 69.4 μM using a hydrodynamic amperometric technique. The limit of detection (for a signal-to-noise ratio of 3) and sensitivity were found to be 92 nM and 0.89 μA/μM, respectively. Furthermore, the diffusion coefficient of hydrogen peroxide (D) and catalytic rate constant (kcat) were calculated. 相似文献
2.
Germinal vesicle migration (GVM) and dissolution (GVD) were studied in goldfish oocytes treated with 17-α,20–β-dihydroxyprogesterone (DHP) and/or demecolcine (DE; a colchicine derivative also known as colcemid) in vitro. DE (100 μg/ml) in the presence of DHP, enhanced steroid-induced GVM, after both 24 and 48 hr of incubation and significantly reduced the DHP ED50 value for GVM. Similarly, administration of DE alone elicited a significant, dose-related increase in GVM after 24 or 48 hr of incubation. The presence of DE, either alone or in combination with DHP, was without effect on GVD. The effect of DE was also tested on ooplasmic viscoelasticity in goldfish follicles subjected to a centrifugal force (160g for 1 min). Preincubation (24 hr) of goldfish follicles in DE significantly influenced the direction and the extent of the centrifugally induced GV movement along the axis of centrifugal force in a dose-related fashion. The present results provide support for the hypothesis that cytoskeletal components, such as microtubules that are sensitive to DE, are involved in the mechanism of GVM in goldfish oocytes. 相似文献
3.
Behavioural observations of both captive and free-ranging sand and mountain gazelles revealed differences in group size and composition, territory size and agonistic behaviour. Sand gazelles are seasonal breeders and form large herds (maximum = 56) during rut and post-rut as compared to mountain gazelles, which breed throughout the year in smaller groups (maximum = 5). As a result, mountain gazelle males maintain their territories year round, whereas sand gazelle rams show marked morphological changes and defend a territory only during the rut. Mountain gazelle males exhibited threat displays rather than engaging in actual combat more often than did sand gazelles. Although subject to the same environmental conditions, sand gazelles are seasonal breeders and the young are born in March-April, whereas mountain gazelles give birth throughout the year. 相似文献
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Esmaeil Fallahi Brenda R. Simons John K. Fellman W. Michael Colt 《Plant Growth Regulation》1992,11(4):435-439
Effects of various concentrations of Dormex (a.i. 49% hydrogen cyanamide) on fruit thinning of Rome Beauty apple (Malus domestica Borkh.), Friar and Simka plums (Prunus salicina Lindley) were studied. A full bloom application of Dormex at all tested concentrations decreased Rome Beauty apple fruit set and yield, and increased fruit weight. Dormex at 0.25% (v/v) resulted in adequate apple thinning, indicated by production of an optimum fruit weight (320 g). Prebloom and full bloom applications of Dormex at greater than 0.75% reduced plum fruit set and yield in Friar. Full bloom application of Dormex at 0.50% showed a satisfactory fruit set, yield, and fruit weight in Friar plum. Prebloom Dormex application had no significant effect on `Simka' plum fruit set or yield, but full bloom application decreased fruit set and yield. 相似文献
6.
H R Habibi T A Marchant C S Nahorniak H Van der Loo R E Peter J E Rivier W W Vale 《Biology of reproduction》1989,40(6):1152-1161
The relationship between gonadotropin-releasing hormone (GnRH) receptor binding and biological activity in the goldfish pituitary for mammalian and salmon GnRH (sGnRH) analogs with structural modification at the C terminus involving replacement of glycine amide with an alkyl amine and replacement of the Gly6 residue with D amino acids was examined. The GnRH receptor binding data were analyzed with a computerized curve-fitting program (LIGAND) for a single as well as two classes of binding sites; analysis based on one site fit estimated binding affinity and capacity for one class of binding site, and analysis based on two-site fit estimated binding affinity and capacity for two classes of binding sites (high-affinity/low-capacity and low-affinity/high-capacity binding sites). The estimated receptor affinity values were then used to determine the correlation between binding affinity and gonadotropin (GTH)-release potency in vitro. The highest correlation between biological activity and receptor binding affinity was obtained for the high-affinity/low-capacity binding sites and GnRH analogs containing Trp7 and Leu8 residues (i.e., the salmon GnRH structural format) (R = 0.940 +/- 0.150). For the same group of GnRH analogs, there was no significant correlation between the relative GTH-release potency and binding affinity of the low-affinity/high-capacity sites (R = 0.159 +/- 0.434), or that obtained from a one-site fit (R = 0.198 +/- 0.431). Similarly, for mammalian GnRH analogs, significant correlation between binding affinity and biological activity (R = 0.406 +/- 0.049) was only obtained for the high-affinity sites, although the degree of correlation was significantly lower than that obtained for salmon GnRH analogs. The present findings provide strong support for the hypothesis that high-affinity GnRH receptors are involved in the control of GTH release in the goldfish pituitary. In addition, the results demonstrate clearly that the presence of Trp7, Leu8 residues in salmon GnRH molecule, a native peptide in goldfish, is important for recognition of the ligand by the GnRH receptors in the goldfish pituitary, and that structural modifications at positions 6 and 10 in this peptide can increase receptor binding affinity and biological activity at the pituitary level. The most active sGnRH analog identified to date is [D-Arg6, Pro9-NEt]-sGnRH. 相似文献
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Hosseini Zohreh Habibi Najafi Mohammad Bagher Yavarmanesh Masoud Ataei-Pirkooh Angila 《International journal of peptide research and therapeutics》2020,26(2):911-919
International Journal of Peptide Research and Therapeutics - LL-37 is a 37 amino acid long cationic peptide belonging to the cathelicidin family of antimicrobial peptides. Limited investigations... 相似文献
9.
Plasma Physics Reports - The evaluation of the Coulomb logarithm (CL) for different coupled plasma regimes is examined using generalized CL, effective CL, and conventional CL models. To find out... 相似文献
10.
Mahbobeh Zamani Babgohari Ali Niazi Ali Asghar Moghadam Tahereh Deihimi Esmaeil Ebrahimie 《In vitro cellular & developmental biology. Plant》2013,49(2):97-106
Exclusion of sodium ions from cells is one of the key salinity tolerance mechanisms in plants. The high-affinity cation transporter (HKT1;5) is located in the plasma membrane of the xylem, excluding Na+ from the parenchyma cells to reduce Na+ concentration. The regulatory mechanism and exact functions of HKT genes from different genotypic backgrounds are relatively obscure. In this study, the expression patterns of HKT1;5 in A and D genomes of wheat were investigated in root and leaf tissues of wild and domesticated genotypes using real-time PCR. In parallel, the K+/Na+ ratio was measured in salt-tolerant and salt-sensitive cultivars. Promoter analysis were applied to shed light on underlying regulatory mechanism of the HKT1;5 expression. Gene isolation and qPCR confirmed the expression of HKT1;5 in the A and D genomes of wheat ancestors (Triticum boeoticum, AbAb and Aegilops crassa, MMDD, respectively). Interestingly, earlier expression of HKT1;5 was detected in leaves compared with roots in response to salt stress. In addition, the salt-tolerant genotypes expressed HKT1;5 before salt-sensitive genotypes. Our results suggest that HKT1;5 expression follows a tissue- and genotype-specific pattern. The highest level of HKT1;5 expression was observed in the leaves of Aegilops, 6 h after being subjected to high salt stress (200 mM). Overall, the D genome allele (HKT1;5-D) showed higher expression than the A genome (HKT1;5-A) allele when subjected to a high NaCl level. We suggest that the D genome is more effective regarding Na+ exclusion. Furthermore, in silico promoter analysis showed that TaHKT1;5 genes harbor jasmonic acid response elements. 相似文献