Bicelle-based liquid crystals for NMR-measurement of dipolar couplings at acidic and basic pH values

It is demonstrated that mixtures of ditetradecyl- phosphatidylcholine or didodecyl-phoshatidylcholine and dihexyl- phosphatidylcholine in water form lyotropic liquid crystalline phases under similar conditions as previously reported for bicelles consisting of dimyristoyl-phosphatidylcholine (DMPC) and dihexanoyl- phosphatidylcholine (DHPC). The carboxy-ester bonds present in DMPC and DHPC are replaced by ether linkages in their alkyl analogs, which prevents acid- or base-catalyzed hydrolysis of these compounds. 15N-1H dipolar couplings measured for ubiquitin over the 2.3–10.4pH range indicate that this protein retains a backbone conformation which is very similar to its structure at pH 6.5 over this entire range.     

Method for the characterization of size-exclusion chromatography media for preparative purification of DNA restriction fragments

A protocol has been developed to characterize the potential of size exclusion chromatography media for the separation of DNA fragments at a preparative scale. A standard DNA mixture composed of -DNA cut with the restriction enzymes, AluI and HaeIII, was chromatographed on a column packed with the gel of interest. Fractions were collected and examined by PAGE. A digitized image of the gel was analyzed with the aid of a computer software program to determine the DNA fractionation range and selectivity curve for each chromatography gel. Four gels were characterized using this protocol. The effect of the elution buffer ionic strength on the fractionation of DNA was also investigated.The US Government right to retain a non-exclusive royalty-freelicense in and to any copyright is acknowledged.     

The influence of geometry on hydrodynamic and mass transfer characteristics in an external airlift reactor for the cultivation of filamentous fungi

The influences of geometric configuration, mycelial broth rheology and superficial gas velocity (U_sg) were investigated with respect to the following hydrodynamic parameters: gas holdup (), oxygen transfer coefficient (K_La) and mixing time (t_m). Increases in U_sg and height of gas separator (H_t) caused an increase in and K_La, and a decrease in t_m. Consequently, a diameter ratio (D_d/D_r) of 0.71 and H_t 0.20 m were found to be the best geometry and operation parameters to achieve high aeration and mixing efficiency for the high viscous broth system in the cultivation of filamentous fungi. An external airlift reactor (EALR) was developed and designed for the cultivation of filamentous fungi. The EALR with two spargers excels in reliability and high aeration and mass transfer coefficiency, resulting in a fast mycelial growth and high biomass productivity in the cultivation of the fungus Rhizopus oryzae.     

High-level expression, functional reconstitution, and quaternary structure of a prokaryotic ClC-type chloride channel.

ClC-type anion-selective channels are widespread throughout eukaryotic organisms. BLAST homology searches reveal that many microbial genomes also contain members of the ClC family. An Escherichia coli-derived ClC Cl(-) channel homologue, "EriC," the product of the yadQ gene, was overexpressed in E. coli and purified in milligram quantities in a single-step procedure. Reconstitution of purified EriC into liposomes confers on these membranes permeability to anions with selectivity similar to that observed electrophysiologically in mammalian ClC channels. Cross-linking studies argue that EriC is a homodimer in both detergent micelles and reconstituted liposomes, a conclusion corroborated by gel filtration and analytical sedimentation experiments.     

Liquid chromatography “on-flow” 1H nuclear magnetic resonance on native glycosphingolipid mixtures together with gas chromatography/mass spectrometry on the released oligosaccharides for screening and characterisation of carbohydrate-based antigens from pig lungs

Glycosphingolipids were prepared from pig lung and pooled into two fractions with (i) 3 sugar residues, and (ii) 3 sugar residues. Oligosaccharides were prepared and used for gas chromatography, gas chromatography-mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry. The glycolipid fractions i and ii were further characterised and purified using a novel method based on high performance liquid chromatography on-flow proton nuclear magnetic resonance. The LC on-flow NMR technique showed good chromatographic separation and gave NMR spectral information which could be used as guidance for pooling of the separated mixture glycolipids. Conventional ¹H NMR, thin layer immunostaining, gas chromatography, gas chromatography/mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry were used to characterise the glycolipids and to validate LC-NMR spectral data.     

Decrease of Fluorescence Intensity After the K Step in Chlorophyll a Fluorescence Induction is Suppressed by Electron Acceptors and Donors to Photosystem 2

Chlorophyll a fluorescence induction measured by a fluorometer with a high temperature stressed plant material shows a new K step which is a clear peak due to fast fluorescence rise and subsequent decrease of fluorescence intensity. We focused on an explanation of the decrease of fluorescence after the K step using artificial electron acceptors and donors to photosystem 2 (PS2). Addition of the artificial electron acceptors or donors suppressed the decrease of fluorescence after the K step. We suggest that the decrease mainly reflects (by more than 81 %) an energy loss process in the reaction centre of PS2 which is most probably a nonradiative charge recombination between P680⁺ (oxidised primary electron donor in PS2) and a negative charge stored on either Pheo⁻ or Q_A ⁻ (reduced primary electron acceptor of PS2 and reduced primary quinone electron acceptor of PS2, respectively). We suggest that the energy loss process is only possible when the inhibition of both the donor and the acceptor sides of PS2 occurs. This revised version was published online in August 2006 with corrections to the Cover Date.     

肾脏和肾神经在应激、钠盐所致高血压中的作用

本工作采用电生理、生化、放免、电镜等方法,探讨了慢性应激和盐致高血压大鼠交感神经系统和肾脏功能的改变。实验在雄性ＳＤ大鼠上进行。结果表明：（１）高盐大鼠肾血浆流量（ＲＰＦ）和尿钠排泄明显增加,而应激大鼠ＲＰＦ显著下降。（２）电镜显示高盐大鼠近曲和远曲小管上皮细胞及线粒体变大,应激则使细胞萎缩、线粒体变小。（３）高盐大鼠肾皮质ＮａＫＡＴＰ酶活性下降,应激可使其恢复。（４）频谱分析显示应激大鼠低频波动（０２～０９Ｈｚ）明显增加。（５）应激导致大鼠肾素活性（ＰＲＡ）及血管紧张素Ⅱ（ＡＮＧⅡ）水平升高,并能使高盐大鼠低ＰＲＡ和ＡＮＧⅡ水平升高。（６）大鼠去除双侧肾神经后,应激无法造成血压升高、ＲＰＦ下降和ＰＲＡ、ＡＮＧⅡ上升。上述结果提示：肾交感神经系统兴奋性增加介导的肾脏机制,可能在应激和／或盐致高血压发病过程中具有重要作用。     

提高胞外钾引起的蛙骨骼肌咖啡因挛缩增强

用蛙胫前肌小束为材料, 研究了提高胞外钾[K+]O对咖啡因挛缩的作用.[K+]O从2 mmol/L提高到10或25 mmol/L, 由3 mmol/L咖啡因引起的挛缩明显增强.以PKC/PC (PKC和PC分别为在高钾和正常钾条件下的咖啡因挛缩)表示的咖啡因挛缩增强, 依赖[K+]O和高钾作用时间.随着10 mmol/L [K+]O作用时间延长, 直至10 min, 增强逐渐增加.但是, 25 mmol/L [K+]O作用1 min时增强达到最大, 然后下降到对照.PKC/PC变化时程不能用高钾引起的去极化解释, 而与由相似[K+]O引起的胞浆自由钙变化时程相符.提示, 至少在蛙骨骼肌, 高钾引起的咖啡因挛缩增强主要是由胞浆自由钙升高引起的.     

Response of NADPH-Diaphorase-Exhibiting Neurons in the Medullar Reticular Formation to High Spinal Cord Injury

1. The effect of hemisection of the cervical spinal cord on NADPH-diaphorase staining in the reticular nuclei of the rabbit medulla was investigated using histochemical technique.2. A quantitative assessment of somal and neuropil NADPH-diaphorase staining was made by an image analyzer in a selected area of each reticular nucleus of the rabbit medulla.3. On the 7th postsurgery day, the highest up-regulation of somatic NADPH-diapho- rase staining was observed in regions regulating cardiorespiratory processes; however, the highest increase of neuropil NADPH-diaphorase staining was found in the reticular nuclei modulating the tonus of postural muscles.4. The degeneration of non-NADPH-diaphorase-stained neurons was detected throughout the reticular formation of the medulla, but the extent of neuronal death did not correlate with the up-regulation of the NADPH-diaphorase staining in the reticular nuclei of the medulla.5. The findings provide evidence that NADPH-diaphorase-exhibiting neurons are refractory to the hemisection of the cervical spinal cord and that the neuronal up-regulation of NADPH-diaphorase at the medullar level is probably not a causative factor leading to the death of the reticulospinal neurons.     

Anogenital gland secretions of Lemur catta and Propithecus verreauxi coquereli: a preliminary chemical examination

Although prosimians are greatly olfaction-oriented, little is known about the specifics of how they use scent to communicate. In this preliminary study we attempted to delineate intra- and interspecific differences among the anogenital gland secretions of two lemur species (Lemur catta and Propithecus verreauxi coquereli) using gas chromatography-mass spectrometry (GC-MS). The results indicate that the two species are discernible through scent. Furthermore, we were able to identify reproductive status using this technique. The anogenital secretions of the different sexes in L. catta, though perhaps not P. v. coquereli, are chemically distinguishable. Given this information, it appears that at least some lemur species can use scent marks to determine species, sex, and reproductive status.