Respirational activity of Chlorella fusca monitored by in vivo P-31 NMR

Energy metabolism during dark respiration of the green alga Chlorella fusca was investigated by ³¹P NMR spectroscopy. The kinetics of the transition from anaerobic to aerobic conditions (and vice versa) was followed with a temporal resolution of 16 s. This transition is accompanied by a shift of the cytoplasmic pH from 6.8 to 7.4, while the vacuolar pH remains constant. Simultaneously, an increase in the concentration of nucleoside-triphosphates and a decrease in the concentration of cytoplasmic orthophosphate take place, as well as the formation of mobile polyphosphates. The concentration of ATP and P _i reach steady-state levels within 30 s. Upon the reverse transition, from aerobic to anaerobic conditions, steady-state concentrations are obtained only after 3 min.     

Predicting RNA secondary structures with pseudoknots by MCMC sampling

The most probable secondary structure of an RNA molecule, given the nucleotide sequence, can be computed efficiently if a stochastic context-free grammar (SCFG) is used as the prior distribution of the secondary structure. The structures of some RNA molecules contain so-called pseudoknots. Allowing all possible configurations of pseudoknots is not compatible with context-free grammar models and makes the search for an optimal secondary structure NP-complete. We suggest a probabilistic model for RNA secondary structures with pseudoknots and present a Markov-chain Monte-Carlo Method for sampling RNA structures according to their posterior distribution for a given sequence. We favor Bayesian sampling over optimization methods in this context, because it makes the uncertainty of RNA structure predictions assessable. We demonstrate the benefit of our method in examples with tmRNA and also with simulated data. McQFold, an implementation of our method, is freely available from http://www.cs.uni-frankfurt.de/~metzler/McQFold.     

麋鹿幼仔的活动同步性与同性聚群倾向

哺乳动物幼体从出生到性成熟这段时间存在生理和行为上的巨大变化.麋鹿幼仔出生1周内,与成鹿和其它仔鹿呈隔离状态,且藏卧于隐蔽处,母鹿哺乳是引起幼仔活动的主要因素.     

中国车前属两种植物的补记

首次报道了毛瓣车前Plantago lagocephala Bunge在中国的分布,确认了一个鲜为人知的中国特有种——苣叶车前P．perssonii Pilger,并提供了二者的详细描述。     

Cytochrome P450cin (CYP176A1) D241N: Investigating the role of the conserved acid in the active site of cytochrome P450s

P450_cin (CYP176A) is a rare bacterial P450 in that contains an asparagine (Asn242) instead of the conserved threonine that almost all other P450s possess that directs oxygen activation by the heme prosthetic group. However, P450_cin does have the neighbouring, conserved acid (Asp241) that is thought to be involved indirectly in the protonation of the dioxygen and affect the lifetime of the ferric-peroxo species produced during oxygen activation. In this study, the P450_cin D241N mutant has been produced and found to be analogous to the P450_cam D251N mutant. P450_cin catalyses the hydroxylation of cineole to give only (1R)-6β-hydroxycineole and is well coupled (NADPH consumed: product produced). The P450_cin D241N mutant also hydroxylated cineole to produce only (1R)-6β-hydroxycineole, was moderately well coupled (31 ± 3%) but a significant reduction in the rate of the reaction (2% as compared to wild type) was observed. Catalytic oxidation of a variety of substrates by D241N P450_cin were used to examine if typical reactions ascribed to the ferric-peroxo species increased as this intermediate is known to be more persistent in the P450_cam D251N mutant. However, little change was observed in the product profiles of each of these substrates between wild type and mutant enzymes and no products consistent with chemistry of the ferric-peroxo species were observed to increase.     

磷对海水胁迫下芦荟幼苗离子分布的影响

研究了磷对海水胁迫下库拉索芦荟(A loe vera)幼苗干物质积累、植株含水量、在器官和组织水平上离子分布的影响。增磷显著缓解海水胁迫对芦荟生长的抑制,明显提高海水胁迫下芦荟幼苗的干物质积累和含水量。器官离子含量和X射线微区分析结果都表明,30%浓度海水胁迫下,外源磷水平的提高能显著降低芦荟幼苗根系N a 、C l-的吸收,增强K 、C a2 向地上部的运输和分配,从而维持叶片较高的K /N a 、C a2 /N a 比率,而这很可能是增磷提高芦荟对海水胁迫抗性的主要原因之一。     

Brain kinin B1 receptor is upregulated by the oxidative stress and its activation leads to stereotypic nociceptive behavior in insulin-resistant rats

Kinin B1 receptor (B1R) is virtually absent under physiological condition, yet it is highly expressed in models of diabetes mellitus. This study aims at determining: (1) whether B1R is induced in the brain of insulin-resistant rat through the oxidative stress; (2) the consequence of B1R activation on stereotypic nocifensive behavior; (3) the role of downstream putative mediators in B1R-induced behavioral activity. Sprague-Dawley rats were fed with 10% d-glucose in their drinking water or tap water (controls) for 4 or 12 weeks, combined either with a standard chow diet or a diet enriched with α-lipoic acid (1 g/kg feed) for 4 weeks. The distribution and density of brain B1R binding sites were assessed by autoradiography. Behavioral activity evoked by i.c.v. injection of the B1R agonist Sar-[D-Phe⁸]-des-Arg⁹-BK (10 μg) was measured before and after i.c.v. treatments with selective antagonists (10 μg) for kinin B1 (R-715, SSR240612), tachykinin NK1 (RP-67580) and glutamate NMDA (DL-AP5) receptors or with the inhibitor of NOS (L-NNA). Results showed significant increases of B1R binding sites in various brain areas of glucose-fed rats that could be prevented by the diet containing α-lipoic acid. The B1R agonist elicited head scratching, grooming, sniffing, rearing, digging, licking, face washing, wet dog shake, teeth chattering and biting in glucose-fed rats, which were absent after treatment with α-lipoic acid or antagonists/inhibitors. Data suggest that kinin B1R is upregulated by the oxidative stress in the brain of insulin-resistant rats and its activation causes stereotypic nocifensive behavior through the release of substance P, glutamate and NO.     

Brain fingerprinting: a comprehensive tutorial review of detection of concealed information with event-related brain potentials

Brain fingerprinting (BF) detects concealed information stored in the brain by measuring brainwaves. A specific EEG event-related potential, a P300-MERMER, is elicited by stimuli that are significant in the present context. BF detects P300-MERMER responses to words/pictures relevant to a crime scene, terrorist training, bomb-making knowledge, etc. BF detects information by measuring cognitive information processing. BF does not detect lies, stress, or emotion. BF computes a determination of “information present” or “information absent” and a statistical confidence for each individual determination. Laboratory and field tests at the FBI, CIA, US Navy and elsewhere have resulted in 0% errors: no false positives and no false negatives. 100% of determinations made were correct. 3% of results have been “indeterminate.” BF has been applied in criminal cases and ruled admissible in court. Scientific standards for BF tests are discussed. Meeting the BF scientific standards is necessary for accuracy and validity. Alternative techniques that failed to meet the BF scientific standards produced low accuracy and susceptibility to countermeasures. BF is highly resistant to countermeasures. No one has beaten a BF test with countermeasures, despite a $100,000 reward for doing so. Principles of applying BF in the laboratory and the field are discussed.     

An Extracellular Ion Pathway Plays a Central Role in the Cooperative Gating of a K2P K+ Channel by Extracellular pH

Proton-gated TASK-3 K⁺ channel belongs to the K_2P family of proteins that underlie the K⁺ leak setting the membrane potential in all cells. TASK-3 is under cooperative gating control by extracellular [H⁺]. Use of recently solved K_2P structures allows us to explore the molecular mechanism of TASK-3 cooperative pH gating. Tunnel-like side portals define an extracellular ion pathway to the selectivity filter. We use a combination of molecular modeling and functional assays to show that pH-sensing histidine residues and K⁺ ions mutually interact electrostatically in the confines of the extracellular ion pathway. K⁺ ions modulate the pK_a of sensing histidine side chains whose charge states in turn determine the open/closed transition of the channel pore. Cooperativity, and therefore steep dependence of TASK-3 K⁺ channel activity on extracellular pH, is dependent on an effect of the permeant ion on the channel pH_o sensors.