Synthesis, protonation behavior, conformational analysis, and regioselective enzymatic acylation of the novel diamino analogue of (E)-5-(2-bromovinyl)-2'-deoxyuridine (BVDU)

(E)-3',5'-Diamino-5-(2-bromovinyl)-2',3',5'-trideoxyuridine (5), the diamino analogue of BVDU (1), was synthesized from BVDU. The protonation behavior of 5 has been studied by means of pH-metric measurements and NMR spectroscopy. This study allows the determination of the basicity constants and the stepwise protonation sites. Thus, the main species at physiological pH is the monoprotonated form. The conformational analysis of this nucleoside analogue was also carried out through 1H NMR spectroscopy. In addition, a convenient synthesis of N-3' and N-5' acylated derivatives was developed by regioselective enzymatic acylation. Thus, Candida antarctica lipase B (CAL-B) selectively acylated the 5'-amino group, thus furnishing nucleosides 8. On the other hand, immobilized Pseudomonas cepacia lipase (PSL-C) exhibited the opposite selectivity, conferring acylation at the 3'-amino group, thus affording derivatives 9.     

Synthesis and fluorescent properties of 6-(4-biphenylyl)-3,9-dihydro-9-oxo-5H-imidazo[1,2-a]purine analogues of acyclovir and ganciclovir

Tricyclic (T) analogues of acyclovir (ACV, 1) and ganciclovir (GCV, 2) carrying the 3,9-dihydro-9-oxo-5H-imidazo[1,2-a]purine system [i.e., 6-(4-BrPh)TACV, 5 and 6-(4-BrPh)TGCV, 6] were transformed into 6-[(4'-R2)-4-biphenylyl] derivatives of TACV (7-9) and TGCV (10-12) by Suzuki cross coupling with 4-substituted phenylboronic acids. Compound 11 (R2 = CH2OH) showed a high (approximately 1000) selectivity index against herpes simplex virus type 1 (HSV-1) together with advantageous fluorescence properties (emission in visible region, little overlap with absorption and moderate intensity).     

IGF-I and IGFBP-3 transport in the rat heart

Specific binding of IGF-binding protein (IGFBP)-3 was shown to be present in the isolated, beating rat heart. The uptake of perfused (125)I-labeled IGF-I in the beating heart was decreased to 9% by blocking IGF-I binding sites with the IGF-I analog Long R(3) (LR(3)) IGF-I. When LR(3) was perfused with complexes of (125)I-IGF-I. IGFBP-3, uptake of (125)I-IGF-I was decreased to 41%, which was significantly greater than LR(3) and (125)I-IGF-I (41 vs. 9%). These data suggest that both microvessel IGF-I and IGFBP-3 binding sites contribute to the transport of IGF-I in the perfused rat heart. This also suggests a novel and plausible mechanism whereby circulating IGFs reach sites of IGF bioactivity.     

Deleterious effects of beta-branched residues in the S1 specificity pocket of Streptomyces griseus proteinase B (SGPB): crystal structures of the turkey ovomucoid third domain variants Ile18I, Val18I, Thr18I, and Ser18I in complex with SGPB

Turkey ovomucoid third domain (OMTKY3) is a canonical inhibitor of serine proteinases. Upon complex formation, the inhibitors fully exposed P1 residue becomes fully buried in the preformed cavity of the enzyme. All 20 P1 variants of OMTKY3 have been obtained by recombinant DNA technology and their equilibrium association constants have been measured with six serine proteinases. To rationalize the trends observed in this data set, high resolution crystal structures have been determined for OMTKY3 P1 variants in complex with the bacterial serine proteinase, Streptomyces griseus proteinase B (SGPB). Four high resolution complex structures are being reported in this paper; the three beta-branched variants, Ile18I, Val18I, and Thr18I, determined to 2.1, 1.6, and 1.7 A resolution, respectively, and the structure of the Ser18I variant complex, determined to 1.9 A resolution. Models of the Cys18I, Hse18I, and Ape18I variant complexes are also discussed. The beta-branched side chains are not complementary to the shape of the S1 binding pocket in SGPB, in contrast to that of the wild-type gamma-branched P1 residue for OMTKY3, Leu18I. Chi1 angles of approximately 40 degrees are imposed on the side chains of Ile18I, Val18I, and Thr18I within the S1 pocket. Dihedral angles of +60 degrees, -60 degrees, or 180 degrees are more commonly observed but 40 degrees is not unfavorable for the beta-branched side chains. Thr18I Ogamma1 also forms a hydrogen bond with Ser195 Ogamma in this orientation. The Ser18I side chain adopts two alternate conformations within the S1 pocket of SGPB, suggesting that the side chain is not stable in either conformation.     

The Link between Inequality and Population Health in Low and Middle Income Countries: Policy Myth or Social Reality?

An influential policy idea states that reducing inequality is beneficial for improving health in the low and middle income countries (LMICs). Our study provides an empirical test of this idea: we utilized data collected by the Demographic and Health Surveys between 2000 and 2011 in as much as 52 LMICs, and we examined the relationship between household wealth inequality and two health outcomes: anemia status (of the children and their mothers) and the women'' experience of child mortality. Based on multi-level analyses, we found that higher levels of household wealth inequality related to worse health, but this effect was strongly reduced when we took into account the level of individuals'' wealth. However, even after accounting for the differences between individuals in terms of household wealth and other characteristics, in those LMICs with higher household wealth inequality more women experienced child mortality and more children were tested with anemia. This effect was partially mediated by the country''s level and coverage of the health services and infrastructure. Furthermore, we found higher inequality to be related to a larger health gap between the poor and the rich in only one of the three examined samples. We conclude that an effective way to improve the health in the LMICs is to increase the wealth among the poor, which in turn also would lead to lower overall inequality and potential investments in public health infrastructure and services.     

Imaging phosphatidylinositol 4-phosphate dynamics in living plant cells

Polyphosphoinositides represent a minor group of phospholipids, accounting for less than 1% of the total. Despite their low abundance, these molecules have been implicated in various signalling and membrane trafficking events. Phosphatidylinositol 4-phosphate (PtdIns4 P ) is the most abundant polyphosphoinositide. ³²Pi-labelling studies have shown that the turnover of PtdIns4 P is rapid, but little is known about where in the cell or plant this occurs. Here, we describe the use of a lipid biosensor that monitors PtdIns4 P dynamics in living plant cells. The biosensor consists of a fusion between a fluorescent protein and a lipid-binding domain that specifically binds PtdIns4 P , i.e. the pleckstrin homology domain of the human protein phosphatidylinositol-4-phosphate adaptor protein-1 (FAPP1). YFP–PH_FAPP1 was expressed in four plant systems: transiently in cowpea protoplasts, and stably in tobacco BY-2 cells, Medicago truncatula roots and Arabidopsis thaliana seedlings. All systems allowed YFP–PH_FAPP1 expression without detrimental effects. Two distinct fluorescence patterns were observed: labelling of motile punctate structures and the plasma membrane. Co-expression studies with organelle markers revealed strong co-labelling with the Golgi marker STtmd–CFP, but not with the endocytic/pre-vacuolar marker GFP–AtRABF2b. Co-expression with the Ptdins3 P biosensor YFP–2 × FYVE revealed totally different localization patterns. During cell division, YFP–PH_FAPP1 showed strong labelling of the cell plate, but PtdIns3 P was completely absent from the newly formed cell membrane. In root hairs of M. truncatula and A. thaliana , a clear PtdIns4 P gradient was apparent in the plasma membrane, with the highest concentration in the tip. This only occurred in growing root hairs, indicating a role for PtdIns4 P in tip growth.     

Conformational analysis of oxidized peptide fragments of the C‐terminal redox center in thioredoxin reductases by NMR spectroscopy

Vicinal disulfide rings (VDRs) occur when a disulfide bond forms between adjacent cysteine residues in a protein and results in a rare eight‐membered ring structure. This eight‐membered ring has been found to exist in four major conformations in solution, divided between cis and trans conformers. Some selenoenzymes use a special type of VDR in which selenium replaces sulfur, generating a vicinal selenosulfide ring (VSeSR). Here, we provide evidence that this substitution reduces ring strain, resulting in a strong preference for the trans conformation relative to cis in a VSeSR (cis:trans – 9:91). This was determined by using the ‘γ‐gauche effect’, which makes use of both ¹H‐NMR and two‐dimensional (2D) NMR techniques for determining the amide bond conformeric ratio. The presence of selenium in a VSeSR also lowers the dihedral strain energy (DSE) of the selenosulfide bond relative to the disulfide bond of VDRs. While cis amide geometry decreases strain on the amide bond, it increases strain on the scissile disulfide bond of the VDR found in thioredoxin reductase from Drosophila melanogaster (DmTR). We hypothesize that the cis conformation of the VDR is the catalytically competent conformer for thiol/disulfide exchange. This hypothesis was investigated by computing the DSE of VDR and VSeSR conformers, the structure of which was determined by 2D NMR spectroscopy and energy minimization. The computed values of the VDR from DmTR are 16.5 kJ/mol DSE and 14.3 kJ/mol for the C+ and T? conformers, respectively, supporting the hypothesis that the enzyme uses the C+ conformer for thiol/disulfide exchange. Copyright © 2014 European Peptide Society and John Wiley & Sons, Ltd.     

Similarity between contemporary vegetation and plant remains in the surface sediment in Mediterranean lakes

相似文献   

ATP-levels of germinating seeds in relation to vigor

Determination of seed vigor was attempted by comparing ATP-levels of deteriorating seed to germination percentage and production of dry matter. Immediately after imbibition of any seed lot investigated, a production of ATP took place. This ATP-accumulation invariably reached a plateau after 6 h of imbibition. Two well germinating seed lots of rape, one of cauliflower and one of sugar beet, were artificially aged by means of elevated storage temperature and humidity. Every second week through 16 weeks of deterioration the levels of ATP, ADP and AMP after 7 h of imbibition were compared with the germination percentage. While ADP- and AMP-contents of germinating seed displayed no change (when imbibed 7 h) during the period of artificial aging, seed deterioration was reflected in the ATP-levels long before loss of viability could be detected by the conventional germination test.
When ATP-levels per seed were related to germination percentage throughout the aging, all four seed lots displayed similar patterns although the absolute figures differed. In contrast to the conventional "per seed' basis, however, ATP per gram seed not only displayed similar deterioration patterns, but the absolute values were also of the same magnitude.