Conformational studies of [Abu(3, 11)]-SFTI-1, an analogue of the trypsin inhibitor isolated from sunflower seeds.

With only 14 amino acid residues, the trypsin inhibitor SFTI-1 is the smallest naturally occurring serine proteinase inhibitor. It consists of two cyclic fragments (with head-to-tail cyclization and a disulfide bridge). In our previous paper, we showed that the removal of the disulfide bridge produced 2.4-fold lower activity. Here, we present the total conformational analysis of the [Abu(3, 11)]-SFTI-1 analog by means of 2D NMR spectroscopy in conjunction with theoretical methods. The peptide was synthesized by Fmoc SPPS. It was cyclized with PyBop and DIPEA in DMF. The NMR studies were performed in DMSO-d(6) at 303 K. Conformations of the peptide studied were calculated by the following three approaches: distance geometry (DG), molecular dynamics (MD) and determination of the statistical weights of conformations. The first two algorithms use a CHARMM force field, whereas the last uses an ECEPP/3 force field. Our calculations resulted in three sets of conformers with 7, 9 and 6 representatives, respectively. All our results were compared with published ones. It was found that the peptide has an ill-defined structure. Despite its conformational flexibility, the binding loop (3-11 fragment) displayed geometry similar to the corresponding fragments of the other SFTI-1 analogs and to the inhibitor itself. Furthermore, the peptide bond between the Ile7 and Pro8 residues adopts cis geometry, which is essential for inhibitory activity. Copyright (c) 2008 European Peptide Society and John Wiley & Sons, Ltd.     

Selenium-induced protection of photosynthesis activity in rape (<Emphasis Type="Italic">Brassica napus</Emphasis>) seedlings subjected to cadmium stress. Fluorescence and EPR measurements

Fluorescence and electron paramagnetic resonance measurements were used to study selenium influence on photosystem activity in rape seedlings affected by Cd stress. Water cultures containing Hoagland nutrients were supplemented with 400 μM of CdCl₂, 2 μM of Na₂SeO₄ and a mixture of both CdCl₂ and Na₂SeO₄. The seedlings were cultured till the first leaf reached about 1 cm in length. Cadmium-induced changes in the activity of both photosystems were partly diminished by Se presence in the nutrient medium. Electron microscopy photographs confirmed less degradation in chloroplasts of plants cultured on media containing Se. It is suggested that sucrose groups of starch, which is deposited in greater amounts in Cd-stressed plants, may act as traps for free radicals produced under those conditions.     

Oncogenic translation directs spliceosome dynamics revealing an integral role for SF3A3 in breast cancer

1. Download : Download high-res image (214KB)
2. Download : Download full-size image

     

Design and in Vitro Characterization of Tricyclic Benzodiazepine Derivatives as Potent and Selective Antileukemic Agents

Currently available chemotherapeutic treatments for blood cancers (leukemia) usually have strong side effects. More selective, efficient, and less toxic anticancer agents are needed. We synthesized seven, new, optically pure (12aS)-1,3,4,12a-tetrahydropyrazino[2,1-c][1,4],12(2H,11H)-dione derivatives and examined their cytotoxicity towards eight cancer cell lines, including urinary bladder (TCC-SUP, UM-UC-3, KU-19-9), colon (LoVo), and breast (MCF-7, MDA-MB-231) cancer representatives, as well as two leukemic cell lines (MV-4-11, CCRF-CEM) and normal murine fibroblasts (Balb/3T3) as reference cell line. Three of the seven newly-obtained compounds ((12aS)-8-bromo-2-(3-phenylbenzoyl)-1,3,4,12a-tetrahydropyrazino[2,1-c][1,4],12(2H,11H)-dione, (12aS)-8,9-dimethoxy-2-(4-phenylbenzoyl)-1,3,4,12a-tetrahydropyrazino[2,1-c][1,4],12(2H,11H)-dione and (12aS)-8-nitro-2-(4-phenylbenzoyl)-1,3,4,12a-tetrahydropyrazino[2,1-c][1,4],12(2H,11H)-dione, showed enhanced activity and selectivity toward the leukemic MV-4-11 cell lines when compared to our previously reported compounds, with IC₅₀ values in the range of 2.9–5.6 μM. Additionally, (12aS)-9-nitro-2-(4-phenylbenzoyl)-1,3,4,12a-tetrahydropyrazino[2,1-c][1,4],12(2H,11H)-dione exhibited a strong cytotoxic effect against the leukemic CCRF-CEM (IC₅₀=6.1 μM) and MV-4-11 (IC₅₀=11.0 μM) cell lines, a moderate cytotoxic effect toward other tumor lines (IC₅₀=31.8–55.0 μM) and very weak cytotoxic effect toward the Balb/3T3 reference cell lines. Selected compounds were further evaluated for their potential to induce apoptotic cell death in MV-4-11 cells by measuring caspase-3 activity. We also established the crystal structure of three products and investigated the effect of 22 derivatives of 1,3,4,12a-tetrahydropyrazino[2,1-c][1,4],12(2H,11H)-dione on the activity of the cancer-associated enzyme autotaxin. All compounds proved to be weak inhibitors of autotaxin, although some (R) and (S) enantiomers had K_i values of 10–19 μM. The obtained results showed that the tested compounds exhibited a selective antileukemic effect, which appeared not to be related directly to autotaxin. Molecular targets responsible for this effect remain to be identified. The newly obtained compounds can be used in the search for new, selective anticancer therapies.     

RNA polymerase activity in isolated Triticum aestivum embryos during germination

A gradual decrease in the total activity of DNA-dependent RNA polymerase in isolated wheat embryos began 6 hr after germination and continued for up to 48 hr. DEAE-cellulose column chromatography indicated the presence of two RNA polymerase fractions (major and minor) in the resting embryos, only one of which (major) could be detected in the embryos germinated for 48 hr. The major RNA polymerase fraction was tentatively identified as nucleoplasmic (RNA polymerase II).     

Angiotensin II--derived peptides devoid of phenylalanine in position 8 have full psychotropic activity of the parent hormone.

In this work we compared in rats the influence of heptapeptide 1-7-angiotensin II, hexapeptide 2-7-angiotensin II, pentapeptide 3-7-angiotensin II and angiotensin II on motility, stereotypy, learning of conditioned avoidance responses and recall of passive avoidance behaviour allowing to avoid aversive stimulation. The 4 peptides administered 15 min before the experiment, tended to increase the number of crossings, rearings and bar approaches in open field, significantly accelerated acquisition of conditioned avoidance responses and improved recall of the passive avoidance. All the peptides applied immediately before the experiment intensified stereotypy evoked by apomorphine in the dose 1 mg/kg and amphetamine in the dose 6.5 mg/kg given intraperitoneally. These results show full psychotropic activity of the examined fragments of angiotensin II, comparable with the activity of the parent octapeptide. Our previous hypothesis that the Val-Tyr-Ile-His-Pro fragment of angiotensin II is responsible for the psychotropic activity evoked by angiotensins in rats is thus confirmed.