Influence of gamma radiation onto polymeric matrix with papain

Papain is a proteolytic enzyme that has been widely used as debridement agent for scars and wound healing treatment. However, papain presents low stability, which limits its use to extemporaneous or short shelf-life formulations. The purpose of this study was to entrap papain into a polymeric matrix in order to obtain a drug delivery system that could be used as medical device. Since these systems must be sterile, gamma radiation is an interesting option and presents advantages in relation to conventional agents: no radioactive residues are formed; the product can be sterilized inside the final packaging and has an excellent reliability. The normative reference for the establishment of the sterilizing dose determines 25 kGy as the inactivation dose for viable microorganisms. A silicone dispersion was selected to prepare membranes containing 2% (w/w) papain. Irradiated and non-irradiated membranes were simultaneously assessed in order to verify whether gamma radiation interferes with the drug-releasing profile. Results showed that irradiation does not affect significantly papain release and its activity. Therefore papain shows radioresistance in the irradiation conditions applied. In conclusion, gamma radiation can be easily used as sterilizing agent without affecting the papain release profile and its activity onto the biocompatible device is studied.     

Forbidden Induced Subgraphs for Toughness

Let be a family of connected graphs. A graph G is said to be ‐free if G is H‐free for every graph H in . We study the relation between forbidden subgraphs in a connected graph G and the resulting toughness of G. In particular, we consider the problem of characterizing the graph families such that every large enough connected ‐free graph is t‐tough. In this article, we solve this problem for every real positive number t. © 2012 Wiley Periodicals, Inc. J. Graph Theory 73: 191–202, 2013     

Vanishing N = 20 shell gap: study of excited states in (27,28)Ne

This Letter reports on the (1)H((28)Ne, (28)Ne) and (1)H((28)Ne, (27)Ne) reactions studied at intermediate energy using a liquid hydrogen target. From the cross section populating the first 2(+) excited state of (28)Ne, and using the previously determined BE(2) value, the neutron quadrupole transition matrix element has been calculated to be M(n)=13.8 +/- 3.7 fm(2). In the neutron knockout reaction, two low-lying excited states were populated in (27)Ne. Only one of them can be interpreted by the sd shell model while the additional state may intrude from the fp shell. These experimental observations are consistent with the presence of fp shell configurations at low excitation energy in (27,28)Ne nuclei caused by a vanishing N=20 shell gap at Z=10.     

On the site-specificity of polycarbonyl complexes in Cu/zeolites: combined experimental and DFT study

The preferred Cu(+) sites and formation of mono-, di-, and tricarbonyl complexes in the Cu-FER were investigated at the periodic density functional theory level and by means of FTIR spectroscopy. The site-specificity of adsorption enthalpies of CO on Cu-FER and of vibrational frequencies of polycarbonyl complexes were investigated for various Cu(+) sites in Cu-FER. Large changes in the Cu(+) interaction with the zeolite framework were observed upon the formation of carbonyl complexes. The dicarbonyl complexes formed on Cu(+) in the main channel or on the intersection of the main and perpendicular channels are stable and both, adsorption enthalpies and CO stretching frequencies are not site-specific. The fraction of Cu(+) ions in the FER cage, that cannot form dicarbonyl can be determined from IR spectra (about 7% for the Cu-FER with Si/Al = 27.5 investigated here). The tricarbonyl complexes can be formed at the Cu(+) ions located at the 8-member ring window at the intersection of main and perpendicular channel. The stability of tricarbonyl complexes is very low (DeltaH degrees (0 K)>or=-4 kJ mol(-1)).     

1,6-Stannatropic strategy: effective generation and cyclization of 1,5-dipoles from o-stannylmethylated thioanilides or phenyl isothiocyanates

[reaction: see text] A new method for the generation of 1,5-dipoles from o-stannylmethylated thioanilides via 1,6-stannatropy under neutral conditions was developed. Cyclization of the 1,5-dipoles afforded indole derivatives effectively. The strategy has potential for application to the generation of alternative 1,5-dipoles from o-stannylmethylated aryl isothiocyanates leading to indole derivatives having a stannylthio group that was readily converted to other functional groups.     

CLV3/ESR-related (CLE) peptides as intercellular signaling molecules in plants

For many years, the plant hormones auxin, cytokinin, ethylene, gibberellin, abscisic acid, brassinosteroid, jasmonic acid, and salicylic acid have been extensively studied as key regulators of plant growth and development. However, recent biochemical and genetic analyses have revealed that secretory peptides are also responsible for intercellular signaling in plants and regulate various events including wound response, cell division control, and pollen self-incompatibility. We discovered two natural CLAVATA3 (CLV3)/ESR-related (CLE) peptides: tracheary elements differentiation inhibitory factor (TDIF) and CLV3, which are dodecapeptides with two hydroxyproline residues that regulate vascular development and meristem formation, respectively. This discovery enabled us to predict the chemical form of CLE gene products. In the Arabidopsis genome, there are 31 CLE genes that correspond to 26 CLE peptides. The application of all 26 chemically synthesized peptides to plants revealed the existence of distinctive functional groups. From these results, we discuss the functions of CLE peptides in plant development and plant-parasite interactions.     

AFM measurement of atomic-scale Si surface etching by active oxidation

Atomic-scale etching of a clean Si surface by active oxidation with oxygen molecules was examined using ex-situ atomic force microscopy (AFM). The etch rate was directly determined by measuring the etch depth with AFM. A SiO₂ anti-etching mask was used on a H-terminated Si(001)-2 × 1:H surface prepared by low pH HF treatment followed by annealing in H₂. The etch rate under active oxidation conditions was almost proportional to the O₂ pressure, which was consistent with previous reports. The etch rate exhibited a weak temperature dependence with an apparent activation energy of 0.2 eV. A distinct transition of the reaction mode from etching to oxide formation was observed in detail as an abrupt decrease of the etch rate by lowering the temperature near the boundary condition between the etching and oxide formation conditions.     

Uptake of SO2 to aqueous formaldehyde surfaces

Aqueous surfaces act as a gateway to absorption and aqueous-phase reaction of gases in the atmosphere. The composition of aerosols varies greatly and is expected to influence the structure of the interface. For example, aldehydes comprise a significant fraction of atmospheric organics and are likely to accumulate at aqueous surfaces. But it is difficult to anticipate their effect on the migration of gaseous species through the interfacial region. Surface organics may act as a barrier to absorption, or they may facilitate uptake via cooperative interactions with absorbing compounds. The surface spectroscopic studies presented here examine the nature of the vapor/water interface during uptake of SO(2) to aqueous formaldehyde solutions, elucidating the role of surface species in a multicomponent interfacial system. The results show that the product of the reaction between SO(2) and formaldehyde, hydroxymethanesulfonate, shows a surface affinity that is enhanced in the presence of SO(2).     

Copolymerization of vinyl ketones with allylbenzene in the presence of zinc chloride

Copolymerization of 3-buten-2-one (MVK) and 3-methyl-3-buten-2-one (MIPK) with allylbenzene (AB) in the presence of zinc chloride (ZnCl₂) was studied. The apparent monomer reactivity ratio decreased with an increasing concentration of ZnCl₂ added. By assuming a terpolymerization system as free vinyl ketone (M₁), vinyl ketone complexed with ZnCl₂ (M₂), and AB(M₃), the absolute monomer reactivity ratios were determined by using the least squares method: k₁₁/k₁₂ = 0.0038, k₁₁/k₁₃ = 11.77, k₂₂/k₂₁ = 1.37, and k₂₂/k₂₃ = 3.77 for the MVK-AB system, and k₁₁/k₁₂ = 0.0070, k₁₁/k₁₃ = 55.47, k₂₂/k₂₁ = 1.84, and k₂₂/k₂₃ = 11.16 for the MIPK-AB system, respectively. It is seen from these values that the complexed vinyl ketones are more reactive to both polymer radicals which have free and complexed vinyl ketone units at its terminal position than the free vinyl ketones. Q and e values for MVK and MIPK complexed with ZnCl₂ were found to be Q = 850, ^e_(MVK)2ZnCl₂ = 2.97, Q = 2.62, respectively.