Active human ferritin H/L-hybrid and sequence effect on folding efficiency in Escherichia coli

In Escherichia coli, the recombinant human L-chain ferritin was synthesized in the form of inclusion bodies under the control of T7 promoter system. We developed a recombinant ferritin H/L-hybrid by a direct gene fusion between H- and L-chain subunits. Surprisingly, the presence of heavy-chain polypeptide at the amino terminus of light chain significantly increased the cytoplasmic solubility of the recombinant ferritin hybrid, i.e., more than 80% of synthesized ferritin hybrid was soluble in intracellular region regardless of the changes in cell growth and gene expression conditions such as type of inducer, growth media, culture scale, etc. The soluble ferritin H/L-hybrid was biologically active with the iron storage capacity (295mol Fe(+3) per mol H/L-hybrid) equivalent to ferritin standard. Different types of hybrid mutants were also developed using various H-chain derivatives. Comparison of the intracellular solubilities of the synthesized hybrid mutants showed that the N-terminus four helices of heavy subunit were of crucial importance in maintaining the high solubility in E. coli cytoplasm. Consequently, the increased solubility of the ferritin hybrid seems to be related to such H-chain sequence that forms ferroxidase center and promotes effective intra-molecular interaction with L-chain domain of H/L-hybrid for enhancing the folding efficiency.     

The hatching of common carp (Cyprinus carpio L.) embryos in response to exposure to different concentrations of cryoprotectant at low temperatures

The hatching performance of embryos of the common carp (Cyprinus carpio L.) was examined after 1, 7, 14, 21, or 28 days of storage at -8, -6, -4, -2, 0, 2, or 4 degrees C with different concentrations of methanol (0.5-7.0 M in 0.5 M steps) or varying concentrations of methanol in 0.1 M sucrose or trehalose. Preserved embryos failed to hatch after storage at -8 and -6 degrees C, regardless of the duration of storage or the concentrations tested. Likewise, there was no hatching out above 5.0 M concentration of methanol, even with the addition of sucrose or trehalose. After storage at 2 or 4 degrees C, the hatching rate was higher with mixtures of methanol (1.5 M) and trehalose (0.1 M) than with methanol plus sucrose or methanol alone. At 4 degrees C, the solution containing 1.5 M methanol supplemented with trehalose gave the highest hatching response of embryos stored for 14 days. Comparison of hatching after 24h of storage at the effective temperatures (-4, -2, 0, 2, and 4 degrees C) revealed that low concentrations of methanol were effective at high temperatures and high concentrations at sub-zero temperatures. The combination of 0.1 M trehalose with 1.5 M methanol gave the highest percentage hatching out both at 4 and 2 degrees C. At 0 degrees C, the highest percentage hatching occurred with 0.1 M trehalose plus 2.5 M methanol and at -2 and 4 degrees C, the best results were with 0.1 M trehalose plus 3.0 M methanol.     

The effects of mowing and fertilization on carbohydrate reserves and regrowth of grasses: do they promote plant coexistence in species-rich meadows?

After the cessation of regular management and after fertilization a single clonal species tends to dominate in many types of grasslands, whereas in regularly managed meadows these potential dominants usually attain a low cover. It has been hypothesized that plants reaching a high dominance in abandoned and fertilized meadows are selectively suppressed by mowing so that a balanced competition is maintained and competitive exclusion is postponed. We compared regeneration capacity and carbohydrate reserves accumulated by three species of clonal grasses, which markedly increase their dominance in irregularly mown, un-mown or fertilized meadows. Above-ground biomass and the amount of storage carbohydrates of the two largest species, (Molinia arundinacea, Calamagrostis epigejos) were reduced in a mown meadow. This effect was weaker in Bromus erectus, which produces smaller shoots. Shoots of Molinia were most impacted by mowing but their regeneration was efficient due to the large carbohydrate reserves in the shoot bases. Fertilization did not affect Bromus and Calamagrostis. In contrast, fertilized plants of Molinia produced larger storage organs and accumulated more carbohydrates. We conclude that plant size and growth form are important features promoting the ability of potential dominants to tolerate mowing and regenerate after it. Our results confirm that taller plants are selectively suppressed by this type of disturbance, thereby potentially promoting plant coexistence.     

Effects of wall linings on moisture ingress into traditional grain storage pits

Increasing climate variability, resulting in frequent years of poor rainfall, has recently subjected the traditional subsistence farmers in the Central Clay Plain of the Sudan to longer periods of food shortage. However, excess production in years of good rainfall could bridge the gap of years with poor rainfall if the grain is properly stored. Resource-poor farmers have tried several linings to improve the traditional underground pit (”matmura”) they use for storage of sorghum. In the experimental study described here, pits with two types of lining: (i) a mixture of mud, cow dung and straw and (ii) sorghum chaff, were compared with unlined pits. Six closed pits were used, two for each type, and temperature and moisture content were monitored. It was found that the temperature increased in all pits and at all positions within the pits, with few differences between the linings. Moisture levels also increased everywhere but the sources of moisture were at the sides and bottoms of the pits. The chaff-lined pits were superior to the others because they showed smaller increases in moisture content at all positions and thus maintained a better quality of sorghum. Joint traditional assessments with local farmers after the pits were opened supported these findings. Received: 15 March 2000 / Revised: 4 January 2001 / Accepted: 10 January 2001     

An improved method for determination of ethyl carbamate in Korean traditional rice wine

An improved extraction method for ethyl carbamate, a genotoxic and carcinogenic compound found in various fermented foods and beverages, was investigated for its determination in the two most typical Korean traditional rice wines, takju and yakju. When the rice wines were extracted twice with chloroform at 30°C for 60 min, the recovery of ethyl carbamate was less than 16%. When they were saturated with NaCl before extraction, the recovery of ethyl carbamate increased to 24.4% in takju and 67.2% in yakju. Adjustment of pH to 9.0 after NaCl saturation in takju resulted in a dramatic increase of recovery to 81.2%, but not in yakju. When the contents of ethyl carbamate and its precursor, urea, in various Korean traditional rice wines were determined, there was no correlation between the two contents. This is due to the fact that storage time is more important than urea content in the formation of ethyl carbamate in rice wine. In addition, its storage at high temperature resulted in a dramatic increase in ethyl carbamate content according to the prolonged storage time, suggesting that storage time and temperature play a key role in the formation of ethyl carbamate in Korean traditional rice wine. Journal of Industrial Microbiology & Biotechnology (2001) 26, 363–368. Received 10 January 2001/ Accepted in revised form 17 March 2001     

Seasonal patterns of terpene content and emission from seven Mediterranean woody species in field conditions

The seasonal pattern of terpene content and emission by seven Mediterranean woody species was studied under field conditions. Emission rates were normalized at 30°C and 1000 μmol·m·s PFD (photosynthetic photon flux density). Bupleurum fruticosum, Pinus halepensis, and Cistus albidus stored large amounts of terpenes (0.01-1.77% [dry matter]) with maximum values in autumn and minimum values in spring. They emitted large amounts of terpenes (2-40 μg·g DM·h), but with no clear seasonal trend except for Cistus albidus, which had maximum values in spring and minimum values in autumn. The nonstoring species Arbutus unedo, Erica arborea, Quercus coccifera and Quercus ilex also emitted large amounts of terpenes (0-40 μg·g DM·h) and also tended to present maximum emission rates in spring, although this trend was significant only for A. unedo. At the seasonal scale, emission rates did not follow changes in photosynthetic rates; instead, they mostly followed changes in temperature. From autumn to spring, the least volatile monoterpenes such as limonene were emitted at highest rates, whereas the most volatile monoterpenes such as α-pinene and β-pinene were the most emitted in summer. The monoterpene emission rates represented a greater percentage of the photosynthetic carbon fixation in summer (from 0.51% in Arbutus unedo to 5.64% in Quercus coccifera) than in the rest of the seasons. All these seasonality trends must be considered when inventorying and modeling annual emission rates in Mediterranean ecosystems.     

四川森林植被碳储量的时空变化

利用平均木法建立森林生物量与蓄积量模型,结合四川森林资源二类调查数据,研究了森林碳密度和碳储量的时空变化.结果表明 四川森林碳储量从1974年的300.02 Tg增加到2004年的469.96 Tg,年均增长率1.51%,表明其是CO2的"汇".由于人工林面积的增加,森林植被的平均碳密度从49.91 Mg·hm-2减少到37.39 Mg·hm-2.四川森林碳储量存在空间差异性,表现为川西北高山峡谷区＞川西南山区＞盆周低山区＞盆地丘陵区＞川西平原区.森林碳密度由东南向西北呈现逐渐增加趋势,即盆地丘陵区＜川西平原区＜川西南山区＜盆周低山区＜川西北高山峡谷区.通过分区森林经营与管理将提高四川森林的碳吸存能力.     

南方红壤丘陵区油桐人工林土壤水分动态

利用时域反射仪(TDR)定位监测方法,研究了南方红壤丘陵区油桐人工林土壤水分动态规律.结果表明:不同月份间土壤蓄水量差异达极显著水平,研究时段内土壤水分动态变化可划分为土壤水分积累期、土壤水分消耗期和土壤水分稳定期3个时期;油桐人工林土壤水分垂直变化显著,且不同季节的变化规律各异;土壤蓄水量与大气相对湿度(RH)、大气温度(t)、饱和水汽压差(VPD)、降雨量(R)等气象因子显著相关(P<0.05); 次降雨后,土壤水分损失率与干旱天数呈显著的双曲函数关系,土壤蓄水量与雨后干旱天数呈显著的线性负相关(P<0.05);在次降雨后的持续干旱条件下,土壤水分损失随着土层深度的增加逐渐趋于平缓.