Membrane effects of lysozyme amyloid fibrils

The influence of mature lysozyme fibrils on the structural and physical properties of model membranes composed of phosphatidylcholine (PC) and its mixtures with cardiolipin (CL) (10 mol%) and cholesterol (Chol) (30 mol%) was studied using fluorescent probes DPH, pyrene, Laurdan and MBA. Analysis of pyrene fluorescence spectra along with the measurements of DPH fluorescence anisotropy revealed that the structure of hydrocarbon chains region of lipid bilayer is not affected by the fibrillar aggregates of lysozyme. In contrast, probing the membrane effects by Laurdan and MBA showed the rise of both the generalized polarization of Laurdan and the MBA fluorescence anisotropy, suggesting that amyloid protein induces reduction of bilayer hydration and increase of lipid packing in the interfacial region of model membranes.     

Mitochondria express α7 nicotinic acetylcholine receptors to regulate Ca2+ accumulation and cytochrome c release: study on isolated mitochondria

Nicotinic acetylcholine receptors (nAChRs) are ligand-gated ion channels that mediate synaptic transmission in the muscle and autonomic ganglia and regulate transmitter release in the brain. The nAChRs composed of α7 subunits are also expressed in non-excitable cells to regulate cell survival and proliferation. Up to now, functional α7 nAChRs were found exclusively on the cell plasma membrane. Here we show that they are expressed in mitochondria and regulate early pro-apoptotic events like cytochrome c release. The binding of α7-specific antibody with mouse liver mitochondria was revealed by electron microscopy. Outer membranes of mitochondria from the wild-type and β2-/- but not α7-/- mice bound α7 nAChR-specific antibody and toxins: FITC-labeled α-cobratoxin or Alexa 555-labeled α-bungarotoxin. α7 nAChR agonists (1 μM acetylcholine, 10 μM choline or 30 nM PNU-282987) impaired intramitochondrial Ca(2+) accumulation and significantly decreased cytochrome c release stimulated with either 90 μM CaCl(2) or 0.5 mM H(2)O(2). α7-specific antagonist methyllicaconitine (50 nM) did not affect Ca(2+) accumulation in mitochondria but attenuated the effects of agonists on cytochrome c release. Inhibitor of voltage-dependent anion channel (VDAC) 4,4'-diisothio-cyano-2,2'-stilbene disulfonic acid (0.5 μM) decreased cytochrome c release stimulated with apoptogens similarly to α7 nAChR agonists, and VDAC was co-captured with the α7 nAChR from mitochondria outer membrane preparation in both direct and reverse sandwich ELISA. It is concluded that α7 nAChRs are expressed in mitochondria outer membrane to regulate the VDAC-mediated Ca(2+) transport and mitochondrial permeability transition.     

Thyroid doses in Ukraine due to 131I intake after the Chornobyl accident. Report II: dose estimates for the Ukrainian population

This paper describes the revision of the thyroid dosimetry system in Ukraine using new, recently available data on (i) revised ¹³¹I thyroid activities derived from direct thyroid measurements done in May and June 1986 in 146,425 individuals; (ii) revised estimates of ¹³¹I ground deposition density in each Ukrainian settlement; and (iii) estimates of age- and gender-specific thyroid masses for the Ukrainian population. The revised dosimetry system estimates the thyroid doses for the residents of the settlements divided into three levels depending on the availability of measurements of ¹³¹I thyroid activity among their residents. Thyroid doses due to ¹³¹I intake were estimated in this study for different age and gender groups of residents of 30,353 settlements in 24 oblasts of Ukraine, Autonomous Republic Krym, and cities of Kyiv and Sevastopol. Among them, dose estimates for 835 settlements were based on ¹³¹I thyroid activities measured in more than ten residents (the first level), for 690 settlements based on such measurements done in neighboring settlements (the second level), and for 28,828 settlements based on a purely empirical relationship between the thyroid doses due to ¹³¹I intake and the cumulative ¹³¹I ground deposition densities in settlements (the third level). The arithmetic mean of the thyroid doses due to ¹³¹I intake among 146,425 measured individuals was 0.23 Gy (median of 0.094 Gy); about 99.8% of them received doses less than 5 Gy. The highest oblast-average population-weighted thyroid doses were estimated for residents of Chernihiv (0.15 Gy for arithmetic mean and 0.060 Gy for geometric mean), Kyiv (0.13 and 0.051 Gy) and Zhytomyr (0.12 and 0.049 Gy) Oblasts followed by Rivne (0.10 and 0.039 Gy) and Cherkasy (0.088 and 0.032 Gy) Oblasts, and Kyiv City (0.076 and 0.031 Gy). The geometric mean of thyroid doses estimated in this study for the entire Ukraine essentially did not change in comparison with a previous estimate, 0.020 vs. 0.021 Gy, respectively. The ratio of geometric mean of oblast-specific thyroid doses estimated in the present study to previously calculated doses varied from 0.51 to 3.9. The highest increase in thyroid doses was found in areas remote from the Chornobyl nuclear power plant with a low level of radioactive contamination: by 3.9 times for Zakarpatska Oblast, 3.5 times for Luhansk Oblasts and 2.9 times for Ivano-Frankivsk Oblast. The developed thyroid dosimetry system is being used to revise the thyroid doses due to ¹³¹I intake for the individuals of post-Chornobyl radiation epidemiological studies: the Ukrainian-American cohort of individuals exposed during childhood and adolescence, the Ukrainian in utero cohort, and the Chornobyl Tissue Bank.

     

Structure–Activity Relationship Prediction-Based Synthesis and Cytotoxicity Evaluation against the HEp-2 Laryngeal Carcinoma Cell of Isoflavone–Cytisine Mannich Bases

QSAR analysis of previously synthesized and nature-inspired virtual isoflavone-cytisine hybrids against the HEp-2 laryngeal carcinoma cell lines was performed using the OCHEM web platform. The validation of the models using an external test set proved that the models can be used to predict the activity of newly designed compounds such as 8-cytisinylmethyl derivatives of 5,7- and 6,7-dihydroxyisoflavones. The synthetic procedure for selective aminomethylation of 5,7-dihydroxyisoflavones with cytisine was developed. In vitro testing identified compound 7 f with cisplatin-level cytotoxicity against HEp-2 cell lines and compound 10 which was twice active than cisplatin after 72 h of incubation.     

Extra-cellular chromate-reducing activity of the yeast cultures

This paper reports on the experimental data supporting an essential role of extra-cellular reduction in chromate detoxification by baker’s and non-conventional yeasts. A decrease of chromate content in the yeast culture coincides with an increase of Cr(III) content in extra-cellular liquid. At these conditions, cell-bound chromium level was insignificant and a dominant part of extra-cellular Cr(III) species was detected in the reaction with chromazurol S only after mineralization of the cell-free samples. This phenomenon of chromium “disappearance” can be explained by the formation of Cr(III) stable complexes with extra-cellular yeast-secreted components which are “inaccessible” in the reaction with chromazurol S without mineralization. It was shown that increasing sucrose concentration in a growth medium resulted in an increase of chromate reduction. A strong inhibition of chromate reduction by 0.25 mM sodium azide, a respiration inhibitor and a protonophore, testifies that extra-cellular chromate detoxification depends on energetic status of the yeast cells. It was shown that Cr(III)-biochelates produced in extra-cellular medium are of a different chemical nature and can be separated into at least two components by ion-exchange chromatography on anionit Dowex 1x10. A total yield of the isolated Cr(III)-biocomplexes is approximately 65 % (from initial level of chromate) with a relative molar ratio 8:5.     

Influence of the KBr matrix on the luminescence properties of CdTe quantum dots

The investigation of the luminescence properties of CdTe/KBr composites with encapsulated quantum dots (QDs) of different sizes was performed and the influence of the KBr matrix on the luminescence properties of CdTe QDs was studied. Encapsulation of nanoparticles by a solid matrix caused a bathochromic shift in the luminescence peak and the shift value was the larger the smaller the size of the quantum dots. Interband quantum transition theory was used to explain the influence of the matrix on the luminescence properties of the capsulated CdTe QDs. Theoretical calculations showed that the observed QD luminescence peak corresponded to a 1 s–1 s electronic transition, and its low‐energy shift after the transfer of QDs from dielectric water to the KBr matrix was due to a corresponding decrease in the depths of electrons and holes potential wells.     

Indospicine combined with arginine deprivation triggers cancer cell death via caspase-dependent apoptosis

Arginine-deprivation therapy is a rapidly developing metabolic anticancer approach. To overcome the resistance of some cancer cells to this monotherapy, rationally designed combination modalities are needed. In this report, we evaluated for the first time indospicine, an arginine analogue of Indigofera plant genus origin, as potential enhancer compound for the metabolic therapy that utilizes recombinant human arginase I. We demonstrate that indospicine at low micromolar concentrations is selectively toxic for human colorectal cancer cells only in the absence of arginine. In arginine-deprived cancer cells indospicine deregulates some prosurvival pathways (PI3K-Akt and MAPK) and activates mammalian target of rapamycin, exacerbates endoplasmic reticulum stress and triggers caspase-dependent apoptosis, which is reversed by the exposure to translation inhibitors. Simultaneously, indospicine is not degraded by recombinant human arginase I and does not inhibit this arginine-degrading enzyme at its effective dose. The obtained results emphasize the potential of arginine structural analogues as efficient components for combinatorial metabolic targeting of malignant cells.     

Isolation and characterization of mutated alcohol oxidases from the yeast <Emphasis Type="Italic">Hansenula polymorpha</Emphasis> with decreased affinity toward substrates and their use as selective elements of an amperometric biosensor

Background  

Accurate, rapid, and economic on-line analysis of ethanol is very desirable. However, available biosensors achieve saturation at very low ethanol concentrations and thus demand the time and labour consuming procedure of sample dilution.