NMR spectra of oligosaccharides at ultra-high field (900 MHz) have better resolution than expected due to favourable molecular tumbling

Nuclear magnetic resonance (NMR) remains the most promising technique for acquiring atomic-resolution information in complex carbohydrates. Significant obstacles to the acquisition of such data are the poor chemical-shift dispersion and artifacts resultant from their degenerate chemical structures. The recent development of ultra-high-field NMR (at 900 MHz and beyond) gives new potential to overcome these problems, as we demonstrate on a hexasaccharide of the highly repetitive glycosaminoglycan hyaluronan. At 900 MHz, the expected increase in spectral dispersion due to higher resonance frequencies and reduction in strong coupling-associated distortions are observed. In addition, the fortuitous molecular tumbling rate of oligosaccharides results in longer T2-values that further significantly enhances resolution, an effect not available to proteins. Combined, the resolution enhancement can be as much as twofold relative to 600 MHz, allowing all 1H-resonances in the hexasaccharide to be unambiguously assigned using standard natural-abundance experiments. The use of ultra-high-field spectrometers is clearly advantageous and promises a new and exciting era in carbohydrate structural biology.     

Full assignment of the 1H and 13C spectra and revision of the O-acetylation site of the capsular polysaccharide of Streptococcus pneumoniae Type 33F, a component of the current pneumococcal polysaccharide vaccine

The structure of the capsular polysaccharide from Streptococcus pneumoniae Type 33F was originally determined by a combination of chemical methods and limited use of NMR spectroscopy [Can. J. Biochem. Cell Biol.1984, 62, 666-677]. We report full 1H and 13C assignments and confirm the structure of the saccharide repeat unit, but find that the site of O-acetylation is O-2 of the -->5)-beta-D-Galf, rather than the -->3)-beta-D-Galf residue. We find that a slightly higher percentage of the repeat units are O-acetylated: [carbohydrate: see text].     

Effects of intraperitoneally administered ubiquinone on the level of total lipid and fatty acids in rat liver

The purpose of the present study was to evaluate the effect of ubiquinone (coenzyme Q-10) on total lipid and fatty acid composition of liver tissues in rats. Twenty male wistar rats were randomly divided into two groups. The first group was used as a control. The second group received ubiquinone (8 mg/every other day) intraperitoneally. This administration was done for a period of 38 days. Body weight increases in animals fed diets for 38 days were on average 35 g in control group (C), and only 11 g in the ubiquinone group. Total lipid content of liver tissues in the ubiquinone group (UB) decreased significantly (p < 0.0001) compared to the control group (C). The ratio of 22:6 and total omega3 fatty acid in the UB increased (p < 0.01) compared to C. While the level of oleic acid (18:1), palmitoleic acid (16:1) and total monounsaturated fatty acid (MUFA) in UB significantly decreased (p < 0.01, p < 0.001, p < 0.001, respectively), the level of stearic acid (18:0) in liver tissue increased (p < 0.05) in the same group when compared to C. Stearoyl-CoA desaturase (SCD) is the rate-limiting enzyme catalyzing the synthesis of monounsaturated fatty acid mainly oleate (18:1). We speculate that ubiquinone inhibits SCD activity. SCD is an important metabolic control point in body weight regulation. Our results indicate that ubiquinone supplementation may have an inhibitory effect on obesity and it seems that the level of 22:6 in liver increased due to ubiquinone.     

Plant community complexity in the arid valley of Minjiang River, southwestern China

Biocomplexity theory is becoming increasingly important in understanding natural vegetation dynamics and interrelation among all components of the ecosystem. In this study, based on the field investigation of plant species and environmental factors (altitude, microtopography, soil water content, and soil nutrients) in an arid valley of the upper reaches of Minjiang River, Sichuan Province, southwestern China, plant community complexity and its relationship with environmental factors, community diversity, species evenness and richness were studied. Both total and structural complexities of the communities showed a “high- low-high” tendency with the increase in altitude of the area, which meant that the complexity of communities was the highest at the sites of low and high altitude, whereas it was the lowest at the sites of intermediate altitude. It was found that the total community complexity had significant quadratic correlations with soil organic matter (SOM) content, total nitrogen (N), hydrolyzable N, soil water content, and available potassium (K), whereas it had no significant correlations with soil total K, total phosphorus (P), available P, and pH value. The total community complexity positively correlated with community diversity, species evenness and species richness, whereas the structural complexity negatively correlated with the community evenness. Of the two components of the total community complexity, namely, the structural complexity and the structural diversity, the structural complexity was more sensitive than the structural diversity to the changes of species in the community, which was not only related to the community evenness but also to the community richness. The relative contribution of both the structural complexity and the structural diversity to the total complexity would be different for different study areas or ecosystems.     

Correlation between circulating biomarkers of oxidative stress of maternal and umbilical cord blood at birth

The objective of the work was to study the relationship between the oxidative state of the mother and the newborn at the moment of birth. We measured oxidative stress markers (carbonyl groups, lipid peroxides and total antioxidant capacity (TAC)) and found a good correlation between the oxidative state of the normal mother and the neonate, since a high mother oxidative stress corresponds to an even higher oxidative stress of the newborn in umbilical cord blood. We also found that smoking mothers and their newborns had a higher concentration of the carbonyl group, lipid peroxides and less TAC. Newborns from these mothers weighed significantly less than others at birth. These data suggest a need for interest in monitoring the oxidative state of mothers during the pregnancy period, especially taking into account that the oxidative level could be involved in later risks of metabolic diseases for both mother and newborn.     

刺果甘草中黄酮类化合物的提取与分析

With three different methods, the total flavonoids from the roots of cultivated Gtycyrrhiza pallidiflora Maxim. were determined and compared by ultraviolet-visible spectrophotometry. The results showed that the extract yield of total flavonoids in crude extracts was 4.54% by direct determination method, 4.27% by AI（ NO3）3 colorimetry method and 2.09% by AlCl3 colorimetry method. The content of total flavonoids in roots of cultivated G. pallidiflora was only 0.05%. The cultivated G. pallidiflora in Lanzhou is not unfit for the medicine source of flavonoids.     

不同季节新疆圆柏总黄酮含量的变化

目的:确定乌鲁木齐南山地区新疆圆柏总黄酮含量最高的时期及其季节变化。方法:采用溶剂法萃取不同季节新疆圆柏叶、果实与枝干的总黄酮,以芦丁作为标准品,用比色法进行含量测定。结果:新疆圆柏的果实中黄酮含量最高,为0.62%～1.13%,以10月份的含量最高;叶中黄酮含量变化为0.28%～0.83%,4月份最高;枝干中的黄酮含量最少,变化不明显。结论:新疆圆柏黄酮含量的季节变化与其生长习性及乌鲁木齐南山气候有关。     

Kir6.2ΔC26 Channel Traffics to Plasma Membrane by Constitutive Exocytosis

Adenosine triphosphate （ATP）-sensitive K^＊ （KATP） channels regulate many cellular functions by coupling the metabolic state of the cell to the changes in membrane potential. Truncation of C-terminal 26 amino acid residues of Kir6.2 protein （Kir6.2ΔC26） deletes its endoplasmic reticulum retention signal, allowing functional expression of Kit6.2 in the absence of sulfonylurea receptor subunit, pEGFP-Kir6.2ΔC26 and pKir6.2ΔC26-IRES2-EGFP expression plasmids were constructed and transfected into HEK293 cells. We identified that Kir6.2ΔC26 was localized on the plasma membrane and trafficked to the plasmalemma by means of constitutive exocytosis of Kir6.2ΔC26 transport vesicles, using epi-fluorescence and total intemal reflection fluorescence microscopy. Our electrophysiological data showed that Kir6.2ΔC26 alone expressed KATP currents, whereas EGFP-Kir6.2ΔC26 fusion protein displayed no KATP channel activity.     

Structure of an AAGU tetraloop and its contribution to substrate selection by yeast RNase III

RNase III enzymes are a highly conserved family of proteins that specifically cleave double-stranded RNA (dsRNA). These proteins are involved in a variety of cellular functions, including the processing of many non-coding RNAs, mRNA decay, and RNA interference. In yeast Rnt1p, a dsRNA-binding domain (dsRBD) recognizes its substrate by interacting with stems capped with conserved AGNN tetraloops. The enzyme uses the tetraloop to cut 14nt to 16nt away into the stem in a ruler-like mechanism. The solution structure of Rnt1p dsRBD complexed to one of its small nucleolar (sno) RNA substrate revealed non-sequence-specific contacts with the sugar-phosphate backbone in the minor groove of the AGNN fold and the two non-conserved tetraloop nucleotides. Recently, a new form of Rnt1p substrates lacking the conserved AGNN sequence but instead harboring an AAGU tetraloop was found at the 5' end of snoRNA 48 precursor. Here, we report the solution structure of this hairpin capped with an AAGU tetraloop. Some of the stacking interactions and the position of the turn in the sugar-phosphate backbone are similar to the one observed in the AGNN loop structure; however, the AAGU sequence adopts a different conformation. The most striking difference was found at the 3' end of the loop where Rnt1p interacts with AGNN substrates. The last nucleotide is extruded from the AAGU tetraloop structure in contrast to the compact AGNN fold. The AAGU hairpin structure suggests that Rnt1p recognizes substrates with different tetraloop structures, indicating that the structural repertoire specifically recognized by Rnt1p is larger than previously anticipated.