Probing the Transition State of the Allosteric Pathway of the Shaker Kv Channel Pore by Linear Free-Energy Relations

Long-range coupling between distant functional elements of proteins may rely on allosteric communication trajectories lying along the protein structure, as described in the case of the Shaker voltage-activated potassium (Kv) channel model allosteric system. Communication between the distant Kv channel activation and slow inactivation pore gates was suggested to be mediated by a network of local pairwise and higher-order interactions among the functionally unique residues that constitute the allosteric trajectory. The mechanism by which conformational changes propagate along the Kv channel allosteric trajectory to achieve pore opening, however, remains unclear. Such conformational changes may propagate in either a concerted or a sequential manner during the reaction coordinate of channel opening. Residue-level structural information on the transition state of channel gating is required to discriminate between these possibilities. Here, we combine patch-clamp electrophysiology recordings of Kv channel gating and analysis using linear free-energy relations, focusing on a select set of residues spanning the allosteric trajectory of the Kv channel pore. We show that all allosteric trajectory residues tested exhibit an open-like conformation in the transition state of channel opening, implying that coupling interactions occur along the trajectory break in a concerted manner upon moving from the closed to the open state. Energetic coupling between the Kv channel gates thus occurs in a concerted fashion in both the spatial and the temporal dimensions, strengthening the notion that such trajectories correspond to pathways of mechanical deformation along which conformational changes propagate.     

Effect of diastolic pressure on MLC2v phosphorylation in the rat left ventricle

The effect of passive muscle stretch on the extent of MLC2v phosphorylation was investigated. We used an isolated rat heart preparation and controlled the passive pressure of the left ventricle (LV) at 0 or 15 mmHg. The hearts were flash frozen and the LV free wall was split into epicardial and the endocardial halves. The samples were solubilized using a novel method that minimizes changes in the phosphate content of MLC2v under non-denaturing conditions. The proteins were separated by urea glycerol PAGE and identified by mass spectrometry and Western blots. At 0 mmHg passive pressure, the extent of MLC2v phosphorylation of the epicardium (34.1+/-1.7%) was the same as that of the endocardium (35.3+/-3.4%). At 15 mmHg passive pressure, we found a significant increase in MLC2v phosphorylation in the epicardium (to 41.5+/-2.0%) and a significant reduction in the endocardium (to 24.2+/-1.2%), giving rise to a gradient in the extent of MLC2v phosphorylation from epicardium (high) to endocardium (low). These changes in MLC2v phosphorylation that take place in response to increased diastolic pressure are likely to impact on the calcium sensitivity of actomyosin interaction (with an increased sensitivity towards the epicardium) and may play a role in the Frank-Starling mechanism of the heart.     

Feedback controlled force enhancement and activation reduction of voluntarily activated quadriceps femoris during sub-maximal muscle action

Stretch of activated muscles leads to enhanced forces compared to isometric contractions at the same muscle length and the same level of activation. This so-called residual force enhancement (RFE) is thought to be a property of all muscles and preparations. However, observations concerning the existence, amount and duration of RFE are inconsistent, especially for voluntary activated large human muscles. Therefore, physiological relevance for daily activity is still questionable and the purpose of this study was to examine whether RFE is present in voluntary sub-maximal activated quadriceps femoris (QF). Seated in a rotational dynamometer with EMG attached to superficial parts of QF, 30 subjects performed isometric and isometric-eccentric-isometric contractions (20° stretch, ω = 60° s⁻¹) at 30% and 60% of maximum voluntary activation (MVA) and contraction (MVC). To account for the complexity of the multi-headed QF, a compensation model based on physiological cross-sectional area and individual EMG-torque relations was used to interpret EMG data. For both levels of intensity and both feedback control strategies, ANOVA identified significant RFE (at the same level of activation) and reduced activation (at the same level of torque). Against expectations, RFE was independent of the level of activation.     

浙江北雁荡山蕨类植物区系特征分析

通过标本和文献查阅以及野外调查,对浙江北雁荡山蕨类植物的区系组成和分布区类型进行了分析.结果显示:北雁荡山共有蕨类植物37科71属156种(含种下分类群);以单种和寡种分布的科和属所占比例最大,分别占总科数和总属数的75.7％和91.5％.该区域蕨类植物科的分布区类型以世界分布型和泛热带分布型为主,分别有14和20科,占总科数的37.8％和54.1％;热带成分总计22科,占总科数的59.5％,而温带成分仅1科.属的分布区类型可划分为9类型2亚型,包含世界分布型17属、热带分布型47属、温带分布型7属;其中,泛热带分布型属数量最多区28属),占总属数的39.4％.种的分布区类型以东亚分布型最多(93种),其中,中国-日本分布亚型有65种,占总种数的41.7％.中国特有种有21种(占总种数的13.5％),其中2种为仅分布于本区域的特有种,分布类型以华东-华南分布最多.由分析结果可见:北雁荡山蕨类植物具有组成丰富、区系起源古老、地理成分多样、热带区系特征明显及特有种数量匮乏等特点,但与周边区域蕨类植物分布有紧密联系.     

Comprehensive evaluation of multiple cropping systems on upland red soil

According to the principles and methods of ecology and system engineering, we set up an evaluation indicator system for multi-component and multiple cropping systems, evaluated the comprehensive benefits of multi-component and multiple cropping systems using grey relation clustering analysis and screened out the optimized model based on research done in the upland red soil in Jiangxi Agricultural University from 1984 to 2004. The results show that the grey relation degree of “cabbage/potato/maize — sesame” was the highest among 23 multi-component and multiple cropping systems and was clustered into the optimized system. This indicates that “cabbage/potato/maize — sesame” can bring the best social, economic and ecological benefits, increase product yield and farmers’ income and promote sustainable development of agricultural production. Therefore, it is suitable for promotion on upland red soil. The grey relation degree of “canola/Chinese milk vetch/maize/mung bean/maize” was second, which is suitable for implementation at the city outskirts. In conclusion, these two planting patterns are expected to play important roles in the reconstruction of the planting structure and optimization of the planting patterns on upland red soil. __________ Translated from Acta Ecologica Sinica, 2006, 26(8): 2532–2539 [译自: 生态学报]     

东北地区部分大型藓类植物遗传多样性的RAPD研究

采用RAPD标记构建了东北地区20种大型藓类植物的系统关系。从200个随机引物中筛选出清晰且多态性高的7个引物,共产生了82条DNA片段,其中79条谱带具有遗传多态性,约占96.34%,平均每个引物扩增的DNA片段数为11.71条。采用NTSYS-pc数据分析软件,计算Nei氏相似性系数,建立了UPGMA聚类图。结果表明：以遗传相似性系数0.27为界限划分,可将20种苔藓植物分为二大类,即泥炭藓类和真藓类。以遗传相似性系数0.42为界限划分,可将20种苔藓植物划分为四大类群,即泥炭藓类、顶蒴单齿亚类、顶蒴双齿亚类和侧蒴双齿类。从整个聚类图可以看出,泥炭藓类是较原始的类群,而金发藓类是较进化的类群,这一结果和大多数苔藓植物经典分类系统相同。     

Comprehensive evaluation of multiple cropping systems on upland red soil

According to the principles and methods of ecology and system engineering,we set up an evaluation indicator system for multi-component and multiple crop-ping systems,evaluated the comprehensive benefits of multi-component and multiple cropping systems using grey relation clustering analysis and screened out the opti-mized model based on research done in the upland red soil in Jiangxi Agricultural University from 1984 to 2004.The results show that the grey relation degree of "cabbage/ potato/maize-sesame" was the highest among 23 multi-component and multiple cropping systems and was clustered into the optimized system.This indicates that "cabbage/potato/maize - sesame" can bring the best social,economic and ecological benefits,increase product yield and farmers' income and promote sustainable development of agricultural production.Therefore,it is suitable for promotion on upland red soil.The grey rela-tion degree of "canola/Chinese milk vetch/maize/mung bean/maize" was second,which is suitable for imple-mentation at the city outskirts.In conclusion,these two planting patterns are expected to play important roles in the reconstruction of the planting structure and optimiza-tion of the planting patterns on upland red soil.     

Floristic richness of three perhumid New Zealand alpine plant communities in comparison with other regions

Abstract Results are presented on vascular species richness in three representative alpine plant communities at 1040–1410 m on Mt Burns in the perhumid Fiordland region, a hotspot of alpine plant diversity, in south‐western South Island, New Zealand. Overall species richness was not dissimilar between the three communities in any of the eight plot sizes (mean values of 20.8–24.4 species in the largest plots of 100 m²), even though coefficients of floristic similarity were small (17.9; 23.5) between both low‐alpine communities (snow tussock‐shrubland and snow tussock grassland) and the high‐alpine cushion fellfield. Vascular species richness was generally similar to that in the few other oceanic New Zealand alpine communities for which data are available. The decline in richness from the low‐alpine to high‐alpine zones, revealed in more comprehensive records from two other regions with generally similar oceanic environments, was not recorded, indeed was reversed, on Mt Burns. Whether the recognized biodiversity hotspot of Fiordland has a generally richer high‐alpine flora than other regions in New Zealand needs further examination. The general pattern of alpine floristic richness in relation to elevation, in New Zealand, also prevails in most alpine regions abroad, usually under much more extreme continental environments. This pattern is usually ascribed to the associated decrease in temperature. Both the small size of the land mass and/or associated environmental conditions may be implicated but clarification awaits further data, preferably collected with standardized procedures.     

千佛山自然保护区种子植物区系特征研究

在对千佛山自然保护区详细调查的基础上,对其种子植物的科、属分布区类型进行了统计分析。结果表明:(1)保护区内种子植物丰富,共153科767属2494种;(2)优势科、属明显;(3)区系起源古老;(4)种子植物地理成分复杂,吴征镒划分的中国种子植物属的15大分布类型在千佛山均有分布;(5)种子植物区系在科和属级水平上均显示出温带性质,温带分布属475属,占总属数的61.9%;(6)特有属、种丰富。     

Effects of Sewage Sludge on Plant Community Composition in Restored Limestone Quarries

The effects of sewage sludge, used to improve fertility of replaced soil, on vegetation were studied in limestone quarry restoration. Plant community growing in the first stages after sludge application was surveyed in six quarries of NE Spain. Areas with a mixture of sewage sludge and residual soil were compared to areas where the application consisted only of residual soil (a mixture of previous top soil and mine spoils). Sewage sludge was hypothesized to increase total biomass and cover, modifying species composition and delaying the early successional recover of the community. The results showed that both biomass and plant cover increased because of sewage sludge addition. The floristic composition was dominated by ruderal species that did not show any dependence on sewage sludge application. Convergence on similarity between sludge and control plots was not detected along a 5‐year period. Although species richness was significantly lower in sludge plots, diversity and equitability indexes did not show differences between treatments. The results did not show differences in the proportion of non‐native species. The proportion of legumes was lower in sludge plots. These results show that the plant communities resulting from the addition of sewage sludge to the soil used in limestone quarry restoration have more biomass and cover, but less number of species, and they do not show a clear trend to converge to those areas restored only with non‐amended soil.