EFFECTS OF POTASSIUM ON THE PHOTOSYNTHETIC RECOVERY OF THE TERRESTRIAL CYANOBACTERIUM,NOSTOC FLAGELLIFORME (CYANOPHYCEAE) DURING REHYDRATION1

Effects of potassium on the photosynthetic recovery of Nostoc flagelliforme (Berk. & Curtis) Bornet & Flahault were investigated to determine its exact role during rehydration. Potassium enhanced recovery of the ability to reduce the primary quinone‐type acceptor (Q_A) and plastoquinone (PQ) pool and the area over the fluorescence rise curve was increased by 127%. The proportions of closed PSII reaction centers at phases J and I and the net rate of closure of PSII reaction centers were decreased by, respectively, 19%, 8%, and 23% with the addition of potassium, due to changes in the ability of PSII for multiple turnovers needed to reduce the PQ pool. Potassium significantly enhanced the probability of electron transfer beyond Q_A and the recovery of electron transport flux per PSII reaction center. Electron transport from water to methyl viologen for samples rehydrated in K⁺‐free BG₁₁ medium was 54% of those with the addition of potassium. However, electron flow from water to p‐benzoquinone and from reduced 2,6‐dichlorophenol‐indophenol to methyl viologen showed little change with the addition of potassium. The fast phase and slow phase of millisecond delayed light emission and the ATP content for samples rehydrated in K⁺‐free BG₁₁ medium were, respectively, 71.6%, 50.7%, and 77.1% of those with the addition of potassium. These suggested that potassium affected electron transfer from PQ to plastocyanin through the cytochrome b₆f complex and the proton motive force across the thylakoid membranes, probably reflecting its role in charge balance during H⁺ transport by the cytochrome b₆f complex.     

滨海湿地生态系统微生物驱动的氮循环研究进展

滨海湿地生态系统介于陆地生态系统和海洋生态系统之间,其类型多种多样,环境差异极大,微生物种类丰富。近年来,随着人为氮源的大量输入,造成滨海湿地生态系统富营养化污染问题日趋严重。本文主要总结了滨海湿地生态系统微生物驱动的固氮、硝化、反硝化、厌氧氨氧化、NO_3~-还原成铵等主要氮循环过程,并综述了通过功能基因(如nifH、amoA、hzo、nirS、nirK、nrfA)检测微生物群落多样性及其环境影响因素的相关研究,旨在更好理解微生物驱动氮循环过程以去除氮,以期为减轻富营养化和危害性藻类爆发提供科学依据。     

Biodiversity and species competition regulate the resilience of microbial biofilm community

The relationship between biodiversity and ecosystem stability is poorly understood in microbial communities. Biofilm communities in small bioreactors called microbial electrolysis cells (MEC) contain moderate species numbers and easy tractable functional traits, thus providing an ideal platform for verifying ecological theories in microbial ecosystems. Here, we investigated the resilience of biofilm communities with a gradient of diversity, and explored the relationship between biodiversity and stability in response to a pH shock. The results showed that all bioreactors could recover to stable performance after pH disturbance, exhibiting a great resilience ability. A further analysis of microbial composition showed that the rebound of Geobacter and other exoelectrogens contributed to the resilient effectiveness, and that the presence of Methanobrevibacter might delay the functional recovery of biofilms. The microbial communities with higher diversity tended to be recovered faster, implying biofilms with high biodiversity showed better resilience in response to environmental disturbance. Network analysis revealed that the negative interactions between the two dominant genera of Geobacter and Methanobrevibacter increased when the recovery time became longer, implying the internal resource or spatial competition of key functional taxa might fundamentally impact the resilience performances of biofilm communities. This study provides new insights into our understanding of the relationship between diversity and ecosystem functioning.     

Discovery of piperidine-aryl urea-based stearoyl-CoA desaturase 1 inhibitors

A series of structurally novel stearoyl-CoA desaturase1 (SCD1) inhibitors has been identified via molecular scaffold manipulation. Preliminary structure–activity relationship (SAR) studies led to the discovery of potent, and orally bioavailable piperidine-aryl urea-based SCD1 inhibitors. 4-(2-Chlorophenoxy)-N-[3-(methyl carbamoyl)phenyl]piperidine-1-carboxamide 4c exhibited robust in vivo activity with dose-dependent desaturation index lowering effects.     

N-Propylnoraporphin-11-O-yl carboxylic esters as potent dopamine D(2) and serotonin 5-HT(1A) receptor dual ligands

A small series of N-propylnoraporphin-11-O-yl carboxylic esters with variant ester lengths were synthesized and their binding potencies at dopamine receptors (D(1), D(2)) and serotonin receptors (5-HT(1A), 5-HT(2A)) were evaluated. Monoesters 3a-f showed binding potency of 100 nM or less for the D(2) receptor, and potency of 10-30 nM for the 5-HT(1A) receptor. Butyryl ester 3d was found to be the best compound possessing the highest potency for both receptors, with K(i) values of 55 and 12 nM for D(2) and 5-HT(1A) receptors, respectively. There is no correlation between the binding potency and the length of the monoesters, but the diesters 9 and 10 were inactive for the D(2) receptor. The dual binding profile of these monoesters for the D(2) and 5-HT(1A) receptors may be useful for the treatment of neuropsychiatric disorders.     

Synthesis and pharmacological investigation of novel 2-aminothiazole-privileged aporphines

A series of apomorphine ((-)-1, APO)-derived analogues ((+/-)-3, (-)-4-(-)-6) were designed and synthesized by hybridizing APO with a privileged 2-aminothiazole functionality which was lent from the orally available anti-parkinsonian drug, pramipexole (2). Among these hybridized compounds, catecholic aporphine (-)-6 shows good affinity at the D(2) receptor with K(i) of 328nM, slightly less potent (3-fold), but more selective against the D(1) receptor than that of the parent compound, APO. Although possessing reduced affinity at the D(2) receptor, aporphines 15 and 18 show significant potency at both the D(1) and 5-HT(1A) receptors. The former compound is equipotent at both receptors (K(i): 116 and 151nM, respectively), while the latter is 8-fold more potent at the D(1) (K(i): 78nM) than at the 5-HT(1A) receptors (K(i): 640nM). These results indicate that the catechol fragment is critical for the D(2) receptor binding of the anti-parkinsonian drug, APO ((-)-1), but not necessary for binding at the D(1) and 5-HT(1A) receptors.     

夜间低温胁迫对两种生长光强下藤黄幼苗叶片荧光特征和活性氧代谢的影响

对两种不同生长光强下（自然光的8％和50％）西双版纳热带雨林木本植物藤黄（Garcinia han-buryi）幼苗经夜间低温（4℃）处理后荧光特性和活性氧代谢的研究结果表明,低温使藤黄叶片光合机构PSⅡ原初光能转化效率（Fv/Fm）、PSⅡ非环式电子传递的量子效率（ФPSⅡ）、非光化学猝灭系数（NPQ）下降,原初荧光（F0）上升。低温胁迫消除后,生长在50％光强下藤黄叶片的Fv/Fm和F0在3d后仍不能完全恢复,而生长在8％光强下藤黄叶片的Fv/Fm和F0基本恢复,说明低温使生长在8％光强下藤黄的光合机构PSⅡ反应中心受到可逆失活,而生长在50％光强下藤黄的光合机构受到氧化伤害。随着低温胁迫时间的延长,两种生长光强藤黄叶片活性氧保护酶（SOD,CAT,APX）的活性虽升高,但O2^-的生成速率、H2O2和MDA含量积累增加。而在恢复阶段,生长在8％光强比生长在50％光强下藤黄叶片的活性氧含量下降得快,进一步说明生长在高光强的植物比生长在低光强的植物受低温伤害大。