Antimicrobial Depsides Produced by Cladosporium uredinicola,an Endophytic Fungus Isolated from Psidium guajava Fruits

Four depsides, all of them new as natural products, were isolated from Cladosporium uredinicola solid‐media culture and identified as 3‐hydroxy‐2,5‐dimethylphenyl 2,4‐dihydroxy‐3,6‐dimethylbenzoate ( 1 ), 3‐hydroxy‐2,4,5‐trimethylphenyl 2,4‐dihydroxy‐3,6‐dimethylbenzoate ( 2 ), 3‐hydroxy‐2,5‐dimethylphenyl 3‐[(2,4‐dihydroxy‐3,6‐dimethylbenzoyl)oxy]‐6‐hydroxy‐2,4‐dimethylbenzoate ( 3 ), and 3‐hydroxy‐2,4,5‐trimethylphenyl 3‐[(2,4‐dihydroxy‐3,6‐dimethylbenzoyl)oxy]‐6‐hydroxy‐2,4‐dimethylbenzoate ( 4 ). The endophytic fungus was isolated from Psidium guajava fruits and cultivated over sterilized rice. The compounds 1 – 4 were purified by classical chromatographic procedures, and the chemical structures were identified by spectroscopic studies, mainly 1D‐ and 2D‐NMR and LC/ESI‐MS/MS. Three of the isolated depsides exhibited moderate bacteriostatic and/or bactericide effects on Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, and Bacillus subtillis.     

Unfolding the conformational behavior of peptide dendrimers: insights from molecular dynamics simulations

We present here the first comprehensive structural characterization of peptide dendrimers using molecular simulation methods. Multiple long molecular dynamics simulations are used to extensively sample the conformational preferences of five third-generation peptide dendrimers, including some known to bind aquacobalamine. We start by analyzing the compactness of the conformations thus sampled using their radius of gyration profiles. A more detailed analysis is then performed using dissimilarity measures, principal coordinate analysis, and free energy landscapes, with the aim of identifying groups of similar conformations. The results point to a high conformational flexibility of these molecules, with no clear "folded state", although two markedly distinct behaviors were found: one of the dendrimers displayed mostly compact conformations clustered into distinct basins (rough landscape), while the remaining dendrimers displayed mainly noncompact conformations with no significant clustering (downhill landscape). This study brings new insight into the conformational behavior of peptide dendrimers and may provide better routes for their functional design. In particular, we propose a yet unsynthesized peptide dendrimer that might exhibit enhanced ability to coordinate aquocobalamin.     

Infrared spectra and quantum chemical calculations of the uranium-carbon molecules UC, CUC, UCH, and U(CC)2

Laser evaporation of carbon rich uranium/carbon alloy targets into condensing argon or neon matrix samples gives weak infrared absorptions that increase on annealing, which can be assigned to new uranium carbon bearing species. New bands at 827.6 cm(-1) in solid argon or 871.7 cm(-1) in neon become doublets with mixed carbon 12 and 13 isotopes and exhibit the 1.0381 carbon isotopic frequency ratio for the UC diatomic molecule. Another new band at 891.4 cm(-1) in argon gives a three-band mixed isotopic spectrum with the 1.0366 carbon isotopic frequency ratio, which is characteristic of the anti-symmetric stretching vibration of a linear CUC molecule. No evidence was found for the lower energy cyclic U(CC) isomer. Other bands at 798.6 and 544.0 cm(-1) are identified as UCH, which has a uranium-carbon triple bond similar to that in UC. Evidence is found for bicyclic U(CC)(2) and tricyclic U(CC)(3). This work shows that U and C atoms react spontaneously to form the uranium carbide U≡C and C≡U≡C molecules with uranium-carbon triple bonds.     

Salivary peptidome in type 1 diabetes mellitus

Diabetic patients show a high susceptibility to oral diseases of inflammatory, catabolic and chronic nature with potential impact on saliva composition. In this study, our purpose was to characterize type 1 diabetes‐induced alterations in the salivary peptidome aiming to find prospective biomarkers for type 1 diabetes oral health evaluation. Peptidomic analysis of saliva from controls (n = 5) and type 1 diabetic patients (n = 5) were performed by liquid chromatography followed by mass spectrometry. The proteolytic activity and metalloproteinases expression was accessed by zymography and slot blot analysis, respectively. Data evidenced a significant increase in the percentage of peptides in diabetic patients paralleled by a higher proteolytic activity, compared with healthy individuals. The nonsalivary gland protein fragments identified in saliva were mainly derived from collagen and extracellular matrix proteins, namely collagen type I. The cleavage site frequency analysis showed significant differences between healthy and type 1 diabetic individuals, highlighting the activity of proteases such as matrix metalloproteinase‐9 and cathepsin D. Our results highlight salivary collagen fragments as potential biomarkers to follow up diabetes‐related oral damage. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation of calcium alginate nanoparticles using water-in-oil (W/O) nanoemulsions

A procedure for the preparation of calcium alginate nanoparticles in the aqueous phase of water-in-oil (W/O) nanoemulsions was developed. The emulsions were produced from mixtures of the nonionic surfactant tetraethylene glycol monododecyl ether (C(12)E(4)), decane, and aqueous solutions of up to 2 wt % sodium alginate by means of the phase inversion temperature (PIT) emulsification method. This method allows the preparation of finely dispersed emulsions without a large input of mechanical energy. With alginate concentrations of 1-2 wt % in the aqueous phase, emulsions showed good stability against Ostwald ripening and narrow, monomodal distributions of droplets with radii <100 nm. Gelation of the alginate was induced by the addition of aqueous CaCl(2) to the emulsions under stirring, and particles formed were collected using a simple procedure based on extraction of the surfactant on addition of excess oil. The final particles were characterized using cryo-transmission electron microscopy (cryo-TEM) and dynamic light scattering (DLS). They were found to be essentially spherical with a homogeneous interior, and their size was similar to that of the initial emulsion droplets. The herein presented "low-energy" method for preparation of biocompatible nanoparticles has the potential to be used in various applications, e.g., for the encapsulation of sensitive biomacromolecules.     

Accurate ab-initio-based single-sheeted DMBE potential-energy surface for ground-state N2O

A global accurate double-many-body expansion potential-energy surface is reported for the electronic ground state of N(2)O. The new form is shown to accurately mimic the ab-initio points calculated at the multireference configuration interaction level using the aug-cc-pVTZ basis set and the full-valence-complete-active-space wave function as reference. To improve the calculated raw energies, they have been extrapolated to the completed basis set limit and most importantly to the full configuration-interaction limit by correcting semiempirically the calculated dynamical correlation with the double-many-body expansion-scaled external correlation method. The topographical features of the novel potential-energy surface were examined in detail and compared with those of other potential functions available in the literature. Good agreement with the experimental data is observed.     

Supercritical extraction of lycopene from tomato industrial wastes with ethane

Supercritical fluid extraction of all-E-lycopene from tomato industrial wastes (mixture of skins and seeds) was carried out in a semi-continuous flow apparatus using ethane as supercritical solvent. The effect of pressure, temperature, feed particle size, solvent superficial velocity and matrix initial composition was evaluated. Moreover, the yield of the extraction was compared with that obtained with other supercritical solvents (supercritical CO? and a near critical mixture of ethane and propane). The recovery of all-E-lycopene increased with pressure, decreased with the increase of the particle size in the initial stages of the extraction and was not practically affected by the solvent superficial velocity. The effect of the temperature was more complex. When the temperature increased from 40 to 60 °C the recovery of all-E-lycopene increased from 80 to 90%. However, for a further increase to 80 °C, the recovery remained almost the same, indicating that some E-Z isomerization could have occurred, as well as some degradation of lycopene. The recovery of all-E-lycopene was almost the same for feed samples with different all-E-lycopene content. Furthermore, when a batch with a higher all-E-lycopene content was used, supercritical ethane and a near critical mixture of ethane and propane showed to be better solvents than supercritical CO? leading to a faster extraction with a higher recovery of the carotenoid.     

Structural and physical–chemical evaluation of Bradykinin Potentiating Peptide and its high soluble supramolecular complex

The supramolecular interactions between a Bradykinin Potentiating Peptide (BPP10c) and β-cyclodextrin (βCD) have been investigated by using several techniques. These new properties acquired by the inclusion phenomena are important in developing a strategy for pharmaceutical formulation. The BPP10c structural elucidation and its inclusion complex formed have been investigated using Nuclear Magnetic Resonance techniques. The peptide secondary structure was investigated using infrared spectroscopy in solution, Circular Dichroism and NMR. In addition, the thermodynamic parameters of the inclusion process were also evaluated using Isothermal Titration Calorimetry. The results obtained by these physical–chemical techniques suggested a 1:1 complex formed by interaction between the Tryptophan amino acid residue and the βCD cavity. The peptide secondary structure was not substantially modified for the inclusion process. In addition, the inclusion process proved to be spontaneous (ΔGº = ?2.53 kcal mol^?1), with an enthalpy reduction (ΔHº = ?3.72 kcal mol^?1) and a favored entropic variation (TΔSº = ?1.19 kcal mol^?1).     

Similarity measures between excited singlet and triplet electron densities in linear acenes: an application to singlet fission

A theoretical framework for modelling the electronic structure of absorbing molecules that may contribute to explain and even predict phenomena where a singlet exciton is converted to triplet is reported. The pathway is suggested to occur when the excited singlet and triplet electron density maps are similarly shaped at Frank Condon states. Calculations were carried for some linear acene excitons from their multielectronic wave functions and corresponding charge maps after a configuration interaction of singly excited determinants. For cases where the singlet fission effect has been reported, charge maps of certain higher energy singlet excitons show a relevant shape similarity with the corresponding lowest triplet. This method could enlighten the way for predicting transit between singlets and triplets of very big systems and also may help to explain experimental phenomena at femto and even attosecond scales.