286 resultados para B ... n C ... f.
Resumo:
We describe the isolation and structural characterization of a family of antimicrobial peptides related to kassinatuerin-2, from the skin secretion of the African hyperoliid frog, Kassina maculata. All four peptides, designated kassinatuerin-2Ma through Md, are C-terminally-amidated 20-mers with the consensus sequence – FX1GAIAAALPHVIX2AIKNAL – where X1 = L/F/V/I and X2 = S/N. All four peptides are encoded by precursors of 69 amino acids. Synthetic replicates of all kassinatuerin-2 related peptides displayed a potent inhibitory activity against Staphylococcus aureus with a minimal inhibitory concentration of 16 µM, at which concentration, however, they effected 18% haemolysis of horse erythrocytes after 2 h. Despite obvious membranolytic properties, all peptides were ineffective at inhibiting the growth of Escherichia coli at concentrations up to 200 µM and were relatively ineffective against Candida albicans (MIC 120 µM). The kassinatuerin-2 related peptides of K. maculata skin secretion thus possess a discrete antimicrobial and weak haemolytic activity in contrast to the prototype kassinatuerin-2 from the skin secretion of Kassina senegalensis.
Resumo:
Bradykinin-related peptides (BRPs) represent one of the most widespread and closely studied families of amphibian defensive skin secretion peptides. Apart from canonical bradykinin (RPPGFSPFR) that was first reported in skin extracts of the European brown frog, Rana temporaria, many additional site-substituted, N- and/or C-terminally extended peptides have been isolated from skin extracts and secretions from representative species of the families Ranidae, Hylidae, Bombinatoridae and Leiopelmatidae. The most diverse range of BRPs has been found in ranid frog skin secretions and this probably reflects the diversity and number of species studied and their associated life histories within this taxon. Amolops (torrent or cascade frogs) is a genus within the Ranidae that has been poorly studied. Here we report the presence of two novel BRPs in the skin secretions of the Chinese Wuyi Mountain torrent frog (Amolops wuyiensis). Amolopkinins W1 and W2 are dodecapeptides differing in only one amino acid residue at position 2 (Val/Ala) that are essentially (Leu1, Thr6)-bradykinins extended at the N-terminus by either RVAL (W1) or RAAL (W2). Amolopkinins W1 and W2 are structurally similar to amolopkinin L1 from Amolops loloensis and the major BRP (Leu1, Thr6, Trp8)-bradykinin from the skin of the Japanese frog, Rana sakuraii. A. wuyiensis amolopkinins were separately encoded as single copies within discrete precursors of 61 amino acid residues as deduced from cloned skin cDNA. Synthetic replicates of both peptides were found to potently antagonize the contractile effects of canonical bradykinin on isolated rat ileum smooth muscle preparations. Amolopkinins thus appear to represent a novel sub-family of ranid frog skin secretion BRPs.
Resumo:
Amphibian defensive skin secretions are known to contain a plethora of biologically-active peptides that are often structural and functional analogues of vertebrate neuropeptides. Here we report the structures of two invertebrate neuropeptide analogues, IPPQFMRF amide (IF-8 amide) and EGDEDEFLRF amide (EF-10 amide), from the defensive skin secretions of two different species of African hyperoliid frogs, Kassina maculata and Phylictimantis verrucosus, respectively. These represent the first canonical FMRF amide-related peptides (FaRPs) from a vertebrate source. The cDNA encoding IF-8 amide was cloned from a skin secretion library and found to contain a single copy of the peptide located at the C-terminus of a 58 amino acid residue open-reading frame. These data extend the potential targets of the defensive arsenal of amphibian tegumental secretions to parasitic/predatory invertebrates and the novel peptides described may represent the first vertebrate peptidic endectocides.
Resumo:
Here we describe the structural and functional characterization of a novel myotropic peptide, sauvatide, from the skin secretion of the waxy monkey frog, Phyllomedusa sauvagei. Sauvatide is a C-terminally amidated decapeptide with the following primary structure – LRPAILVRTKamide – monoisotopic mass 1164.77 Da, which was found to contract the smooth muscle of rat urinary bladder with an EC50 of 2.2 nM. The sauvatide precursor, deduced from cloned skin cDNA, consists of 62 amino acid residues with a single copy of sauvatide located near the C-terminus. The mature peptide is generated from the precursor by cleavage at a classical –KR-cleavage site located proximal to the N-terminus and by removal of a –GKGK sequence at the C-terminus, the first glycyl residue acting as amide donor. Amphibian skin secretions thus continue to be a source of novel and potent biologically active peptides acting through functional targets in mammalian tissues.
Resumo:
Tachykinins are among the most widely-studied families of regulatory peptides characterized by a highly-conserved C-terminal -Phe-X-Gly-Leu-Met.amide motif, which also constitutes the essential bioactive core. The amphibian skin has proved to be a rich source of these peptides with physalaemin from the skin of Physalaemus fuscomaculatus representing the archetypal aromatic tachykinin (X = Tyr or Phe) and kassinin from the skin of Kassina senegalensis representing the archetypal aliphatic tachykinin in which X = Val or Ile. Despite the primary structures of both mature peptides having been known for at least 30 years, neither the structures nor organizations of their biosynthetic precursors have been reported. Here we report the structure and organization of the biosynthetic precursor of kassinin deduced from cDNA cloned from a skin secretion library. In addition, a second precursor cDNA encoding the novel kassinin analog (Thr2, Ile9)-kassinin was identified as was the predicted mature peptide in skin secretion. Both transcripts exhibited a high degree of nucleotide sequence similarity and of open-reading frame translated amino acid sequences of putative precursor proteins. The translated preprotachykinins each consisted of 80 amino acid residues encoding single copies of either kassinin or its site-substituted analog. Synthetic replicates of each kassinin were found to be active on rat urinary bladder smooth muscle at nanomolar concentrations. The structural organization of both preprotachykinins differs from that previously reported for those of Odorrana grahami skin indicating a spectrum of diversity akin to that established for amphibian skin preprobradykinins.
Resumo:
The cathodic and anodic: potential limit of eleven different ionic liquids were determined at a mercury hemisphere electrode. Ionic liquids containing the phosphonium cation (tri(n-hexyl)tetradecylphosphonium, [P-14.6,P-6.6](+)) give the largest potential window, especially When Coupled to a trifluorotris(pentafluoroethyl)- [FAP](-). or bis(trifluoromethanesulfonyl)imide, [NTf2](-), anion.
Resumo:
The solubility of manganese in mercury was determined electrochemically via amalgamation and stripping in the room temperature ionic liquid n-hexyltriethylammonium bis(trifluoromethanesulfonyl)imide, [N-6,N-2,N-2,N-2][NTf2]. A hemispherical mercury electrode was made by electrodepositing mercury onto a planar platinum microelectrode. Cyclic voltammetry of Mn2+ in [N-6,N-2,N-2,N-2][NTf2] at the mercury microhemisphere electrode was investigated at temperatures of 298, 303 and 313 K. The solubility of Mn in Hg was determined on the basis of the charge under the reduction peak (Mn2+ --> Mn-0) and the corresponding reoxidation.
Resumo:
We report the discovery of WASP-13b, a low-mass M-p = 0.46(-0.05)(+0.06) M-J transiting exoplanet with an orbital period of 4.35298 +/- 0.00004 days. The transit has a depth of 9 mmag, and although our follow-up photometry does not allow us to constrain the impact parameter well (0 <b <0.46), with radius in the range R-p similar to 1.06-1.21 R-J the location of WASP-13b in the mass-radius plane is nevertheless consistent with H/He-dominated, irradiated, low core mass and core-free theoretical models. The G1V host star is similar to the Sun in mass (M-* = 1.03(-0.09)(+0.11) M-circle dot) and metallicity ([M/H] = 0.0 +/- 0.2), but is possibly older (8.5(-4.9)(+5.5) Gyr).
Resumo:
We report the discovery of a 7.3 M-J exoplanet WASP-14b, one of the most massive transiting exoplanets observed to date. The planet orbits the 10th-magnitude F5V star USNO-B1 11118-0262485 with a period of 2.243 752 d and orbital eccentricity e = 0.09. A simultaneous fit of the transit light curve and radial velocity measurements yields a planetary mass of 7.3 +/- 0.5 M-J and a radius of 1.28 +/- 0.08 R-J. This leads to a mean density of about 4.6 g cm(-3) making it the densest transiting exoplanets yet found at an orbital period less than 3 d. We estimate this system to be at a distance of 160 +/- 20 pc. Spectral analysis of the host star reveals a temperature of 6475 +/- 100 K, log g = 4.07 cm s(-2) and v sin i = 4.9 +/- 1.0 km s(-1), and also a high lithium abundance, log N(Li) = 2.84 +/- 0.05. The stellar density, effective temperature and rotation rate suggest an age for the system of about 0.5-1.0 Gyr.
Resumo:
The primary goal of this work is to quantify any bene?ts that the use of digital manufacturing methods can offer when used upstream from production, for manufacturing process design, and tool development. Learning at this stage of product development is referred to as management learning. Animated build simulations have been used to develop build procedures and tooling for a panel assembly for the new Bombardier CRJ1000 (Canadair Regional Jet, 100 seat). When the jig format was developed, its simulated performance was compared to that of current CRJ700/900 panel builds to identify and quantify any improvements in terms of tooling cost and panel build time. When comparing like-for-like functions between existing CRJ700/900 (Canadair Regional Jet, 70/90 seat) and the
/>CRJ1000 tooling, it was predicted that the digitally assisted improvements had brought about a 4.9% reduction in jig cost. An evaluation of the build process for the CRJ1000 uplock panel predicted a 5.2% reduction in the assembly time. In addition to the improvement of existing tooling functions, new jig functionality was added so that both the drilling and riveting functions could be carried out in a single jig for the new RJ1000 panel.
Resumo:
Objectives: Cilostazol improves walking distance in peripheral arterial disease (PAD) patients. The study objectives were to assess the effects of cilostazol on walking distance, followed by the additional assessment of cilostazol on exercise-induced ischaemiaereperfusion injury in such patients.
/><br/>Methods: PAD patients were prospectively recruited to a double-blinded, placebo-controlled trial. Patients were randomised to receive either cilostazol 100 mg or placebo twice a day. The primary end-point was an improvement in walking distance. Secondary end-points included the assessment of oxygen-derived free-radical generation, antioxidant consumption and other markers of the in?ammatory cascade. Initial and absolute claudication distances (ICDs and ACDs, respectively) were measured on a treadmill. In?ammatory response was assessed before and 30 min post-exercise by measuring lipid hydroperoxide, ascorbate, atocopherol, b-carotene, P-selectin, intracellular and vascular cell-adhesion molecules (I-CAM and V-CAM), thromboxane B2 (TXB2), interleukin-6, interleukin-10, high-sensitive C-reactive protein (hsCRP), albuminecreatinine ratio (ACR) and urinary levels of p75TNF receptor. All tests were performed at baseline and 6 and 24 weeks.
/><br/>Results: One hundred and six PAD patients (of whom 73 were males) were recruited and successfully randomised from December 2004 to January 2006. Patients who received cilostazol demonstrated a more signi?cant improvement in the mean percentage change from baseline in ACD (77.2% vs. 26.6% at 6 weeks, pZ0.026 and 161.7% vs. 79.0% at 24 weeks, pZ0.048) as compared to the placebo. Cilostazol reduced lipid hydroperoxide levels compared to a placebo-related increase before and after exercise (6 weeks: pre-exercise: 11.8% vs.
Resumo:
Three experiments examined whether children and adults would use temporal information as a cue to the causal structure of a three-variable system, and also whether their judgements about the effects of interventions on the system would be affected by the temporal properties of the event sequence. Participants were shown a system in which two events B and C occurred either simultaneously (synchronous condition) or in a temporal sequence (sequential condition) following an initial event A. The causal judgements of adults and 6-7-year-olds differed between the conditions, but this was not the case for 4-year-olds' judgements. However, unlike those of adults, 6-7-year-olds' intervention judgements were not affected by condition, and causal and intervention judgements were not reliably consistent in this age group. The findings support the claim that temporal information provides an important cue to causal structure, at least in older children. However, they raise important issues about the relationship between causal and intervention judgements.