Level Of Mono Research Articles

Conformational properties of inulin, levan and arabinan studied by molecular dynamics simulations

Inulin, levan and arabinan are the polysaccharides that consist of exclusively furanose units. To date, their conformational features studied at the molecular scale have remained largely unexplained. To tackle this issue, we have performed a series of explicit-solvent molecular dynamics simulations, carried out within the furanose-dedicated force field. None of the polysaccharides exhibits a single, dominating structure type. Instead, they create a large number of separated conformational states originating from the intensive rotation around the φ and ω glycosidic angles. 21-helices are the preferential conformational forms for all compounds but they appear only locally, at the length of several consecutive residues. The flexibility of all three furanose-based polysaccharides is much greater in relation to the (1–4)-linked pyranose polysaccharides and is comparable to that of (1–6)-linked pyranoses. The dynamic geometries of both furanose rings and glycosidic linkages are nearly unchanged independently if considering them at the level of mono-, di- or polysaccharides.

Water deficit stress affects photosynthesis and the sugar profile in source and sink tissues of groundnut ( Arachis hypogaea L.) and impacts kernel quality

Water deficit stress conditions disturb photosynthetic activity of plants and thereby affect further growth and the mobilization of assimilates towards sink tissues. The influence of mid-season drought on sugar metabolism in both source and sink tissues and its sustained effect on kernel quality across three different habit groups of groundnut was investigated. The experiment was conducted in Kharif 2012 and water deficit stress was created by withholding irrigation for 40 days between 30−70 days after sowing under rain-out shelter to simulate mid-season drought condition. Imposition of water deficit stress reduced net photosynthesis rate, which significantly altered the sugar profiles in leaf. The content of glucose, fructose and sucrose decreased in the leaf tissue, whereas the content of sugar alcohol (inositol and mannitol) and trehalose increased. The sugar profile of the sink tissue (kernel) was also altered under stress but changes were slightly different. The sugar alcohol and oligosaccharides (RFOs) showed significant increase, but the level of mono- and di-saccharides did not show significant change. The results suggest different drought tolerance strategies in source and sink tissues. The kernel quality was also affected under stress with lower oil and higher protein content. The content of oleic acid was reduced, while linoleic acid increased resulting in a decrease of the O/L ratio and oil stability. Alteration of quality traits was least in Spanish genotypes, suggesting a relatively better tolerance of this group for water deficit stress.

Abstract A46: LSD1 globally mediates epigenetic modifications on androgen receptor-dependent enhancers

Abstract Androgen receptor (AR) belongs to nuclear receptor superfamily and plays pivotal roles in development of prostate and prostate cancer. The lignded AR binds to AR responsive elements (ARE) on the enhancers and mediates the transcription activity. AR binding on chromatin appears to depend on the binding of pioneer factor FOXA1, which recognizes the active sites marked with high level of mono- or di-methylation of Histon 3 lysine 4 (H3K4me1-2) and then make the site accessible for AR binding. However, the in depth mechanism how FOXA1 opens the enhancer and whether this results in further chromatin modification remains unclear. Through ChIP-seq studies coupled with gene expression array, we have found LSD1 (lysine specific demethylase 1) together with its binding partner CoRest were recruited by FOXA1 to the AR-dependent enhancer and its histone demethylation functions were then activated by liganded AR. This results in the loss of methylation marks and activation of gene transcription but not affecting AR binding or AR-mediated nucleosome dynamics. In contrast to this activator function, LSD1 can also formed corepressor complex to suppress the transcription of a subset of genes. This comprehensive study clearly suggested distinct roles of LSD1 as a coactivator versus a corepressor in different protein complexes therefore to mediate different cell functions. Citation Format: Changmeng Cai, Housheng Hansen He, Myles Brown, Steven P. Balk. LSD1 globally mediates epigenetic modifications on androgen receptor-dependent enhancers. [abstract]. In: Proceedings of the AACR Special Conference on Chromatin and Epigenetics in Cancer; Jun 19-22, 2013; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2013;73(13 Suppl):Abstract nr A46.

Epigenetic chromatin modifications in the cortical spreading depression

Preconditioning with Cortical Spreading Depression induces a sort of tolerance to a subsequent episode of ischemia. The mechanism of this tolerance is not clear. We studied if such treatment induces epigenetic chromatin modifications on the hemispheres of rats preconditioned by Cortical Spreading Depression. The contralateral hemispheres were used as control. We determined the level of H3K4 and H3K9 methylation and the mRNA amounts for the two well known H3K4 methyltransferases (MLL and SET7) in rats 24°h after the Cortical Spreading Depression induction. Western blotting experiments have been performed using three different types of primary antibodies against mono-, di- and tri-methyl H3K4 and primary antibody anti-dimethyl H3K9. In the same samples we checked if the H3 histones were replaced by the H3.3 histone variants that could be an additional marker of chromatin modifications. The level of mono- and di-methyl H3K4 was significantly lower in samples of the treated hemispheres than those of the contralateral hemispheres (40% and about 60%, respectively) while the level of tri-methylation remained unchanged. The level of di-methyl H3K9 was almost 60% higher in the treated hemispheres than the contralateral hemispheres. The treatment for Cortical Spreading Depression affected also the level of expression of H3K4 histone methyltransferase MLL and SET7 that decreased in the treated hemispheres in comparison to the control hemispheres (80% and 40%, respectively). The treatment for Cortical Spreading Depression instead had no effects on the overall amounts of mRNA for H3 and H3.3 histones. In conclusion epigenetic chromatin modifications are evident in rats 24°h after the Cortical Spreading Depression induction.

The Archaeal Histone-Fold Protein HMf Organizes DNA into Bona Fide Chromatin Fibers

Background: The discovery of histone-like proteins in Archaea urged studies into the possible organization of archaeal genomes in chromatin. Despite recent advances, a variety of structural questions remain unanswered. Results: We have used the atomic force microscope (AFM) with traditional nuclease digestion assays to compare the structure of nucleoprotein complexes reconstituted from tandemly repeated eukaryal nucleosome-positioning sequences and histone octamers, H3/H4 tetramers, and the histone-fold archaeal protein HMf. The data unequivocally show that HMf reconstitutes are indeed organized as chromatin fibers, morphologically indistinguishable from their eukaryal counterparts. The nuclease digestion patterns revealed a clear pattern of protection at regular intervals, again similar to the patterns observed with eukaryal chromatin fibers. In addition, we studied HMf reconstitutes on mononucleosome-sized DNA fragments and observed a great degree of similarity in the internal organization of these particles and those organized by H3/H4 tetramers. A difference in stability was observed at the level of mono-, di-, and triparticles between the HMf particles and canonical octamer-containing nucleosomes. Conclusions: The in vitro reconstituted HMf-nucleoprotein complexes can be considered as bona fide chromatin structures. The differences in stability at the monoparticle level should be due to structural differences between HMf and core histone H3/H4 tetramers, i.e., to the complete absence in HMf of histone tails beyond the histone fold. We speculate that the existence of core histone tails in eukaryotes may provide a greater stability to nucleosomal particles and also provide the additional ability of chromatin structure to regulate DNA function in eukaryotic cells by posttranslational histone tail modifications.

Remobilization of fructans in Phippsia algida during rapid inflorescence development

Plants of Phippsia algida (Sol.) R. Br. were cultivated in short days (SD; 8 h summer daylight) and in long days (LD; 8 h summer daylight + 16 h low irradiance extension of 5 μmol m−2 s−1) at 9, 15, and 21°C. In this plant, inflorescence primordia are initiated in both LD and SD, but LD are required for heading and inflorescence development (Heide, O.M.; Physiol. Plant. 85: 606–610. 1992). Total dry matter production was slightly increased by LD over SD at 9°C, while it was little affected by daylength at 15 and 21°C. Phippsia algida contained mainly fructans with a low degree of polymerization, largely of the kestose series. After 29 to 42 days (depending on the temperatature) of photoperiodic treatment, fructans constituted 15–20 percent of dry mass of SD‐grown plants compared with only 2–3 percent of dry mass for LD‐grown flowering plants. There was no difference due to photoperiod in levels of mono‐ and disaccharides. Shifting the SD‐grown plants to LD conditions resulted in rapid inflorescence development, accompanied by a parallel rapid decrease in the fructan level, while the level of mono‐ and disaccharides remained constant. The results show that fructans are important as storage carbohydrates in the late snow‐bed species P. algida that normally requires several growing seasons for completing its life cycle. Exhaustion of this storage pool during the extremely fast flower and fruit development constitutes an essential part of the plants adaption to a very short growing season.

Perioperative exposure to plasticizers in patients undergoing cardiopulmonary bypass

Di(2-ethylhexyl)phthalate and its principal metabolite, mono(2-ethylhexyl)phthalate, are contaminants of blood that are extracted on contact with polyvinylchloride surfaces, such as blood collection bags and tubing used in cardiopulmonary bypass. In this study, levels of the two plasticizers were measured in patients who underwent coronary artery bypass grafting, orthotopic transplantation, implantation of the Jarvik 7-70 total artificial heart during bridge-to-transplant procedures, and in infants who underwent corrective operations for congenital defects. In all adult patients the levels of di(2-ethylhexyl)phthalate increased tenfold by the end of cardiopulmonary bypass, whereas the levels of mono(2-ethylhexyl)phthalate increased ninefold. In infants, levels of di(2-ethylhexyl)phthalate rose seven times by the end of bypass and mono(2-ethylhexyl)phthalate rose significantly as well. In most of the patients having coronary bypass, the two plasticizers declined to preoperative levels within 24 hours. However, in some of the patients having orthotopic transplantation and in those in whom the Jarvik 7-70 total artificial heart was used as a bridge to transplant, the levels were still detectable 120 hours postoperatively. Circulating levels of mono(2-ethylhexyl)phthalate are only 20- to 35-fold lower in patients undergoing cardiac operations than the level of mono(2-ethylhexyl)phthalate causing a 50% reduction in developed contractile force and arrhythmias in an in vitro human atrial trabecular preparation. This study shows that patients with multisystem failure and infants may be at risk for this acute exposure to mono(2-ethylhexyl)phthalate.