排序方式: 共有2条查询结果,搜索用时 0 毫秒
1
1.
Omolara Titilayo Akinsiku Femi Kayode Agboola Adenike Kuku Adeyinka Afolayan 《Fish physiology and biochemistry》2010,36(3):573-586
Two forms of rhodanese were purified from the liver of Clarias gariepinus Burchell, designated catfish rhodanese I (cRHD I) and rhodanese II (cRHD II), by ion-exchange chromatography on a CM-Sepharose
CL-6B column and gel filtration through a Sephadex G-75 column. The apparent molecular weight obtained for cRHD I and cRHD
II was 34,500 ± 707 and 36,800 ± 283 Da, respectively. The subunit molecular weight determined by sodium dodecyl sulphate–polyacrylamide
gel electrophoresis was 33,200 ± 283 and 35,100 ± 141 Da for cRHD I and cRHD II, respectively. Atomic absorption spectrophotometric
analysis revealed that cRHD II contained a high level of iron (Fe), which presumably was responsible for the brownish colour
of the preparation. In contrast, no Fe was identified in cRHD I, and its preparation was colourless. Further characterization
of cRHD II gave true Michaelis–Menten constant (K
m) values of 25.40 ± 1.70 and 18.60 ± 1.68 mM for KCN and Na2S2O3, respectively, an optimum pH of 6.5 and an optimum temperature of 40°C. The Arrhenius plot of the effects of temperature
on the reaction rate consisted of two linear segments with a break occurring at 40°C. The apparent activation energy values
from these slopes were 7.3 and 72.9 kcal/mol. Inhibition studies on the cRHD II enzyme showed that the activity of the enzyme
was not affected by Mn2+, Co2+, Sn2+, Ni2+ and NH4
+, but Zn2+ inhibited the enzyme considerably. 相似文献
2.
This study evaluated physical properties of selected soil series and their implications on the soil compaction and erosion in Abeokuta, southwestern Nigeria. Daily rainfall data (1999–2007) were collected to estimate the rainfall erosivity. Seven soil series (Iwo, Iseyin, Ekiti, Jago, Okemesi, Apomu, and Egbeda) were sampled from 0–15, 15–30, and 30–50 cm depths for particle size distribution, organic carbon, pH, upper plastic limit, and compactibility (Proctor test). Microtopographical changes along and across toposequences of two farmers’ fields cleared mechanically and manually, respectively, were monitored using the erosion pin method. Mean annual erosivity (EI30) was high (7646 MJ mm ha?1 hr?1). Particle size, organic carbon, and pH were similar (p ≥ 0.05), while upper plastic moisture was ≤?2% among different soil series. Soil-moisture density curves indicated a maximum bulk density of 1.77–1.99 g cm?3 for a moisture range of 7.6–14%; while the soils were prone to compaction at low moisture content. Microtopographic changes were found between –2 and 0 cm and –8 and –2 cm on mechanically and manually cleared farmland, respectively. Spatial dependence showed that the soil erosion could be predicted within 5–8 m distance. To avoid erosion and compaction, soil water content should be less than 7.6% before the introduction of mechanical tillage. 相似文献
1