Understanding fusion suppression and enhancement in the (18)O+(58,60,64)Ni systems

Realistic coupled-channel calculation results for the (18)[O] + (58,60,64)Ni systems in the bombarding energy range 34.5 <= E(Lab) <= 6-5 MeV are presented. The overall agreement with existing experimental data is quite good. Our calculations predict an unexpected fusion suppression for above-barrier energies, with an important contribution of the two neutron ((18)O, (16)O) transfer channel couplings. The sub-barrier fusion enhancement and the above barrier suppression, predicted by the calculations, are consistent with the nuclear structure of the Ni region. Comparisons with recently reported similar effects in reactions induced by the (6)He projectile are discussed. (C) 2009 Elsevier B.V. All rights reserved.

Acanthoscurrin Fragment 101-132: Total Synthesis at 60 degrees C of a Novel Difficult Sequence

Glycine-rich proteins (GRP), serve a variety of biological functions. Acanthoscurrin is an antimicrobial GRP isolated front hemocytes-of the Brazilian spider Acanthoscurria gomesiana. Aiming to contribute to the knowledge of the secondary structure and stepwise solid-phase synthesis of GRPs` glycine-rich domains, we attempted to prepare G(101)GGLGGGRGGGYG(113) GGGGYGGGYG(123)GGy(126)GGGKYK(132)-NH(2), acanthoscurrin C-terminal amidated fragment. Although a theoretical prediction did not indicate high aggregation potential for this peptide, repetitive incomplete aminoacylations were observed after incorporating Tyr(126) to the growing peptide-MBHA resin (Boc chemistry) at 60 degrees C. The problem was not solved by varying the coupling reagents or solvents, adding chaotropic salts to the reaction media or changing the resin/chemistry (Rink amide resin/Fmoc chemistry). Some improvement was mode when CLEAR amide resin (Fmoc chemistry) was 32 used, as it allowed for obtaining fragment (G(113)-K(132) NIR-FT-Raman spectra collected for samples of the growing peptide-MBHA, -Rink amide resin and -CLEAR amide resin revealed the presence of beta-sheet structures. Only the combination of CLEAR-amide resin, 60 degrees C, Fmoc-(Fmoc-Hmb)Gly-OH and LiCl (the last two used alternately) was able to inhibit the phenomenon, as proven by NIR-FT-Raman analysis of the growing peptide-resin, allowing the total synthesis of desired 132 fragment Gly(101)-K(132). In summary, this work describes a new difficult sequence, contributes to understanding stepwise solid-phase synthesis of this type of peptide and shows that, at least while protected and linked to a resin, this GRPs glycine-rich motif presents all early tendency to assume beta-sheet structures. (c) 2008 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 92: 65-75, 2009.

Microwave-assisted solid-phase peptide synthesis at 60 degrees C: alternative conditions with low enantiomerization

Several conditions have been used in the coupling reaction of stepwise SPPS at elevated temperature (SPPS-ET), but we have elected the following as our first choice: 2.5-fold molar excess of 0.04-0.08 M Boc or Fmoc-amino acid derivative, equimolar amount of DIC/HOBt (1:1)or TBTU/DIPEA(1:3), 25% DMSO/toluene, 60 degrees C, conventional heating. In this study, aimed to further examine enantiomerization under such condition and study the applicability of our protocols to microwave-SPPS, peptides containing L-Ser, L-His, L-Cys and/or L-Met were manually synthesized traditionally, at 60 degrees C using conventional heating and at 60 degrees C using microwave heating. Detailed assessment of all crude peptides (in their intact and/or fully hydrolyzed forms) revealed that, except for the microwave-assisted coupling of L-Cys, all other reactions occurred with low levels of amino acid enantiomerization (<2%). Therefore, herein we (i) provide new evidences that our protocols for SPPS at 60 degrees C using conventional heating are suitable for routine use, (ii) demonstrate their appropriateness for microwave-assisted SPPS by Boc and Fmoc chemistries, (iii) disclose advantages and limitations of the three synthetic approaches employed. Thus, this study complements our past research on SPPS-ET and suggests alternative conditions for microwave-assisted SPPS. Copyright (C) 2009 European Peptide Society and John Wiley & Sons, Ltd.

Degradation of alachlor herbicide by gamma radiation from cobalt-60 in aqueous and alcohol solution

Alachlor has been widely used in agriculture all over the world. It is suggested that it may be a carcinogen and an environmental estrogen. The aim of this work was to verify the degradation the alachlor by gamma radiation. Gamma radiation from (60)Co was used to degrade the alachlor herbicide in water and methanol solution. The alachlor in water and alcohol solution in the concentration of 100 mgL(-1) was irradiated with doses of 0.25-50 kGy, at dose rate 5-6 and 2.7 kGyh(-1). High performance liquid chromatography was used as an analytical technique to determine the degradation rate of herbicide studied.