Folding propensities of peptide fragments of myoglobin

Myoglobin has been studied extensively as a paradigm for protein folding. As part of an ongoing study of potential folding initiation sites in myoglobin, we have synthetized a series of peptides covering the entire sequence of sperm whale myoglobin. We report here on the conformation preferences of a series of peptides that cover the region from the A helix to the FG turn. Structural propensities were determined using circular dichroism and nuclear magnetic resonance spectroscopy in aqueous solution, trifluoroethanol, and methanol. Peptides corresponding to helical regions in the native protein, namely the B, C, D, and E helices, populate the alpha region of (phi, psi) space in water solution but show no measurable helix formation except in the presence of trifluoroethanol. The F-helix sequence has a much lower propensity to populate helical conformations even in TFE. Despite several attempts, we were not successful in synthesizing a peptide corresponding to the A-helix region that was soluble in water. A peptide termed the AB domain was constructed spanning the A- and B-helix sequences. The AB domain is not soluble in water, but shows extensive helix formation throughout the peptide when dissolved in methanol, with a break in the helix at a site close to the A-B helix junction in the intact folded myoglobin protein. With the exception of one local preference for a turn conformation stabilized by hydrophobic interactions, the peptides corresponding to turns in the folded protein do not measurably populate beta-turn conformations in water, and the addition of trifluoroethanol does not enhance the formation of either helical or turn structure. In contrast to the series of peptides described here, either studies of peptides from the GH region of myoglobin show a marked tendency to populate helical structures (H), nascent helical structures (G), or turn conformations (GH peptide) in water solution. This region, together with the A-helix and part of the B-helix, has been shown to participate in an early folding intermediate. The complete analysis of conformational properties of isolated myoglobin peptides supports the hypothesis that spontaneous secondary structure formation in local regions of the polypeptide may play an important role in the initiation of protein folding.     

The challenge of energy poverty: Brazilian case study

In recent years successive Brazilian governments have actively pursued economic and social policies aimed at reducing poverty and promoting social equality and inclusion. In the field of energy, this has meant introducing and implementing programs aimed at expanding the supply of safe and reliable energy to the poorest sectors of Brazilian society, including those living in remote rural areas. This paper draws attention on the findings of extensive field research to evaluate the impact of rural electrification on energy poverty in the context of government policies aimed at promoting energy equity. The authors re-examine the concept of an energy poverty line, seeking to fine tune its application to Brazilian social and economic realities, and then apply an analytical framework (Lorenz Curve, Gap Poverty, Gap Quadratic, Gini Coefficient and Sen Index) to evaluate the effectiveness of recent efforts in Brazil to expand access to electricity. One of the main conclusions of this study is that is that rural electrification leads to a significant reduction of the energy poverty level and a consequent improvement in energy equity.     

ISM-AC: an immune security model based on alert correlation and software-defined networking

International Journal of Information Security - Anomaly-based detection techniques have a high number of false positives, which degrades the detection performance. To address this issue, we propose...     

Suillus collinitus methanolic extract increases p53 expression and causes cell cycle arrest and apoptosis in a breast cancer cell line

In the present work, methanolic, ethanolic and boiled water extracts of Suillus collinitus were chemically characterised and submitted to an evaluation of their bioactive properties (antioxidant potential and cytotoxic activity in tumor cell lines). Phenolic acids and sugars were identified chromatographically and quantified in the methanolic and boiled water extracts, respectively. S. collinitus ethanolic extract had the highest antioxidant activity. Nevertheless, with respect to cell growth inhibition, the methanolic extract was the most potent extract, particularly in MCF-7 cells (GI(50) 25.2±0.2μg/ml). Moreover, the GI(50) concentration of this extract induced a G1 cell cycle arrest, with a concomitant decrease in the percentage of cells in the S phase. Furthermore, it caused an increase in the percentage of apoptotic cells, from 6.0±0.2% in untreated cells, to 15.3±2.0% in cells treated with the GI(50) concentration and to 16.3±2.0% in cells treated with 2×GI(50) concentration. In addition, 48h treatment with the GI(50) concentration caused a strong increase in the levels of p53, p21, and cleaved PARP, together with a decrease in Bcl-2 and XIAP. Results indicate that S. collinitus may be a promising source of bioactive compounds. Particularly, its methanolic extract appears to have a p53-mediated effect on the normal cell cycle distribution and apoptosis induction in a human breast tumor cell line.     

Chemical composition of wild edible mushrooms and antioxidant properties of their water soluble polysaccharidic and ethanolic fractions

Mushrooms have become attractive as functional foods and as a source of physiologically beneficial bioactive compounds. Herein, we describe and compare the chemical constituents (phenolic compounds, macronutrients, sugars, fatty acids, tocopherols and ascorbic acid) of four wild edible mushrooms widely appreciated in gastronomy: Armillaria mellea (Vahl) P. Kumm., Calocybe gambosa (Fr.) Donk, Clitocybe odora (Fr.) P. Kumm., Coprinus comatus (O.F. Müll.) Pers. Furthermore, the antioxidant activity of their water soluble polysaccharidic and ethanolic fractions was studied by three different in vitro assays. C. comatus revealed the highest concentrations of sugars (43.23/100 g dry weight), PUFA (77.46%), phenolic compounds (45.02 mg/kg), tocopherols (301.03 μg/100 g) and, among all of the fractions tested, its ethanolic fraction showed the highest antioxidant activity (EC₅₀ < 2.6 mg/ml). C. odora revealed one of the highest ascorbic acid (172.65 mg/100 g) contents and its water soluble polysaccharidic fraction showed the best antioxidant properties (EC₅₀ < 3.6 mg/ml) among the polysaccharidic fractions. The studied mushrooms species could potentially be used in well-balanced diets and as a source of bioactive compounds.     

Influence of aggregates grading and water/cement ratio in workability and hardened properties of mortars

Mortar is the material responsible for the distribution of stresses in masonry structures. The knowledge about the fresh and hardened properties of mortar is fundamental to ensure a good performance of masonry walls. Water/cement ratio and aggregates grading are among several variables that influence physical and mechanical behaviour of mortars. An experimental program is presented in order to evaluate the influence of aggregates grading and water/cement ratio in workability and hardened properties of mortars. Eighteen compositions of mortar are prepared using three relations cement:lime:sand, two types of sand and three water/cement ratios. Specimens are analyzed through flow table test, compressive and flexural strength tests. Results indicate that the increase of water/cement ratio reduces the values of hardened properties and increases the workability. Besides, sands grading has no influence in compressive strength. On the other hand, significant differences in deformation capacity of mortars were verified with the variation of the type of sand. Finally, some correlations are presented among hardened properties and the compressive strength.     

Experimental Investigation of Surges in a Stormwater Storage Tunnel

Below-grade storage tunnels in stormwater systems are usually designed to operate in a free-surface flow regime. However, intense rain events may trigger flow regime transition to pressurized flow, which results in operational problems. To date, little guidance is available as to the considerations necessary to properly design a system undergoing flow regime transition. In this investigation, an experimental apparatus consisting of a 14.6-m-long, 94-mm-diameter acrylic pipe was used to observe the nature of flows in such conditions. It was noticed that the air near the pipe crown may pressurize and influence the flow dynamics. Qualitative observations regarding the interactions between the air and water phases during the filling events are included in this study. Generally the surge intensity was maximized when a hydraulic bore propagating towards the surge riser just filled the pipe cross section, and it increased with the pressure head behind the pressurization front. Furthermore, the results indicate that the effects of air phase pressurization should be properly included in numerical simulations if ventilation conditions are limited.     

Uptake by rat liver and intracellular fate of plasmid DNA complexed with poly-L-lysine or poly-D-lysine

Adding normal saline (NS) separately before 99Tcm-sodium pertechnetate to MDP cold kits has been shown to reduce substantially the radiation dose to the hand. A similar dose reduction will probably prove to be valid with the preparation of most other 99Tcm-labelled radiopharmaceuticals. However, it is unknown how this altered reconstitution procedure may affect the labelling efficiency and in vitro stability of the 99Tcm-labelled radiopharmaceuticals. We have evaluated the effects on the labelling efficiency and in vitro stability of 99Tcm-labelled MDP, mertiatide and sestamibi reconstituted with three different methods: adding normal saline before 99Tcm activity (NS/Tc); adding 99Tcm activity before normal saline (Tc/NS); and the standard reconstitution method of adding both 99Tcm activity and normal saline together. The labelling efficiency and in vitro stability were evaluated by measuring the radiochemical purity of each radiopharmaceutical tested at 0, 1, 3, 6, 12 (except 99Tcm-MDP) and 24 h after reconstitution. For 99Tc-mertiatide, there was a very slight difference in the labelling efficiency, mostly due to the Tc/NS method being approximately 0.29% lower across time post-reconstitution than the standard method. For 99Tcm-labelled MDP and sestamibi, there were no differences between the three methods in terms of labelling efficiency and in vitro stability. In conclusion, both alternative methods (i.e. NS/Tc and Tc/NS) appear not to have any detrimental effect on the labelling efficiency and in vitro stability of the 99Tcm-labelled radiopharmaceuticals that we tested. However, of the two alternative kit reconstitution methods, we recommend the NS/Tc method, since it may reduce the hand radiation dose.     

The importance of coulombic end effects: experimental characterization of the effects of oligonucleotide flanking charges on the strength and salt dependence of oligocation (L8+) binding to single-stranded DNA oligomers

Binding constants Kobs, expressed per site and evaluated in the limit of zero binding density, are quantified as functions of salt (sodium acetate) concentration for the interactions of the oligopeptide ligand KWK6NH2 (designated L8+, with ZL = 8 charges) with three single-stranded DNA oligomers (ss dT-mers, with |ZD| = 15, 39, and 69 charges). These results provide the first systematic experimental information about the effect of changing |ZD| on the strength and salt dependence of oligocation-oligonucleotide binding interactions. In a comparative study of L8+ binding to poly dT and to a short dT oligomer (|ZD| = 10),. Proc. Natl. Acad. Sci. USA. 93:2511-2516) demonstrated the profound thermodynamic effects of phosphate charges that flank isolated nonspecific L8+ binding sites on DNA. Here we find that both Kobs and the magnitude of its power dependence on salt activity (|SaKobs|) increase monotonically with increasing |ZD|. The dependences of Kobs and SaKobs on |ZD| are interpreted by introducing a simple two-state thermodynamic model for Coulombic end effects, which accounts for our finding that when L8+ binds to sufficiently long dT-mers, both DeltaGobso = -RT ln Kobs and SaKobs approach the values characteristic of binding to poly-dT as linear functions of the reciprocal of the number of potential oligocation binding sites on the DNA lattice. Analysis of our L8+-dT-mer binding data in terms of this model indicates that the axial range of the Coulombic end effect for ss DNA extends over approximately 10 phosphate charges. We conclude that Coulombic interactions cause an oligocation (with ZL < |ZD|) to bind preferentially to interior rather than terminal binding sites on oligoanionic or polyanionic DNA, and we quantify the strong increase of this preference with decreasing salt concentration. Coulombic end effects must be considered when oligonucleotides are used as models for polyanionic DNA in thermodynamic studies of the binding of charged ligands, including proteins.     

Testicular suture: a significant risk factor for infertility among formerly cryptorchid men

BACKGROUND/PURPOSE: Although fertility is decreased after cryptorchidism, the importance of risk factors, including parenchymal testicular suture, is unknown. The aim of this study was to examine the relationship between parenchymal testicular suture and failure to conceive a child for 1 year or longer among formerly cryptorchid men. METHODS: Men who underwent orchidopexy between 1955 and 1972 at the Children's Hospital of Pittsburgh (n = 619) were surveyed by questionnaire and their medical records reviewed. Only the men who attempted to conceive a child (n = 387) are included. RESULTS: Logistic regression analysis determined significant risk factors for infertility. Testicular suture was strongly related to infertility (RR, 7.56; 95% CI, 1.66, 34.39) as were bilateral cryptorchidism (RR, 5.51; 95% CI, 1.58, 19.24), varicocele (RR, 4.72; 95% CI, 1.42, 15.75), hormone treatment before surgery (RR, 3.69; 95% CI, 1.22, 11.11), and partner conception problem (RR, 3.32; 95% CI, 1.11, 9.90). CONCLUSIONS: Testicular suture was a potent independent determinant of infertility among formerly cryptorchid men who have orchidopexy. Bilateral cryptorchidism, hormone treatment, varicocele, and partner conception problems also were associated with increased infertility.