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Evidence for the Existence of an Effective Interfacial Tension between Miscible Fluids: Isobutyric Acid-Water and 1-Butanol-Water in a Spinning-Drop …
2006
We report definitive evidence for an effective interfacial tension between two types of miscible fluids using spinning-drop tensiometry (SDT). Isobutyric acid (IBA) and water have an upper critical solution temperature (UCST) of 26.3 degrees C. We created a drop of the IBA-rich phase in the water-rich phase below the UCST and then increased the temperature above it. Long after the fluids have reached thermal equilibrium, the drop persists. By plotting the inverse of the drop radius cubed (r(-)(3)) vs the rotation rate squared (omega(2)), we confirmed that an interfacial tension exists and estimated its value. The transition between the miscible fluids remained sharp instead of becoming more…
Sintētisko kanabinoīdu un katinonu identifikācijas iespējas
2016
Vēl aizvien nelegālajā apritē parādās jaunas psihoaktīvās vielas, kuru identificēšanas iespējas ir apgrūtinātas un maz pētītas. Jaunās psihoaktīvās vielas ir potenciāls sabiedrības veselības drauds. Populārākās ir sintētiskie kanabinoīdi un sintētiskie katinoni. To iedarbība uz cilvēka organismu ir maz pētīta un neparedzama. Lai pētītu to iedarbību uz cilvēka organismu, ir nepieciešamas efektīvas un visaptverošas pētniecības metodes. Darba ir apkopoti dati par Latvijā biežāk sastopamajām jaunajām psihoaktīvajām vielām, kā arī apkopoti un analizēti dati par šo vielu noteikšanas metodēm, kā pielietojamāko metodi nosakot jauno psihoaktīvo vielu noteikšanu, var uzskatīt GH-MS/MS metodi. Atslēgv…
Novel Penicillin-Type Analogues Bearing a Variable Substituted 2-Azetidinone Ring at Position 6: Synthesis and Biological Evaluation
2015
The synthesis and the biological activity of novel semi-synthetic β-lactam compounds containing an azetidinone moiety joined to the amino-nitrogen of the (+)-6-aminopenicillanic acid (6-APA) as new antibacterial agents is reported. The synthesized compounds were screened for their in vitro antimicrobial activity against a panel of Gram positive and Gram negative pathogens and environmental bacteria. Tested compounds displayed good antimicrobial activity against all tested Gram positive bacteria and for Staphylococcus aureus and Staphylococcus epidermidis antimicrobial activity resulted higher than that of the reference antibiotic. Additionally, in vitro cytotoxic screening was also carried …
Inhibition of the mutagenicity of 2-nitrofluorene, 3-nitrofluoranthene and 1-nitropyrene by flavonoids, coumarins, quinones and other phenolic compou…
1997
When 56 flavonoids, 32 coumarins, five naphthoquinones, 12 anthraquinones and five structurally-related compounds were tested for their antimutagenic potencies with respect to mutagenicities induced by 2-nitrofluorene (2-NF), 3-nitrofluoranthene (3-NFA) and 1-nitropyrene (1-NP) in Salmonella typhimurium TA98 distinct structure-activity relationships were detected. First, the tetracyclic nitroarenes 3-NFA and 1-NP were in general more effectively antagonized by potent antimutagenic flavonoids and coumarins than the tricyclic 2-NF, while there were only minor differences with quinones. Secondly, antimutagenicity of natural compounds of plant origin correlated with the aglyconic nature 10 of a…
4-(3H)-quinazolinones N-3 substituted with a five membered heterocycle: A promising scaffold towards bioactive molecules
2020
Abstract The quinazolinone nucleus represents, among the class of fused heterocycles, a very important scaffold to obtain molecules with biological activities. A review of literature revealed how such kind of fused heterocycles, coming from natural or synthetic source, are associated with a wide range of biological activities. This review is mainly directed towards the 4-(3H)-quinazolinones N-3 substituted with a five membered heterocycle in which all the possible combinations of nitrogen, sulfur and oxygen atoms are present.
ESR, ENDOR and TRIPLE resonance studies on radical reactions of 1,4-benzoquinone and 1,4-hydroquinone in alkaline methanol and liquid ammonia
1990
The relative signs and absolute values of the hyperfine coupling constants of different methoxy-1,4-benzoquinones were measured by ESR, ENDOR and TRIPLE resonance spectroscopy. Reactions of 1,4-benzoquinone and 1,4-hydroquinone with methanol took place in alkaline methanol, giving rise to methoxy-substituted 1,4-benzoquinones. The same substitution reaction occurred in a mixture of ammonia and methanol. The reactions depended on temperature and the alkali concentration. Coupling constants were assigned by the modified additivity relationship method. An extremely small line width of 0.014 G was measured in the ESR spectrum of deuterated 2,5-dimethoxy-1,4-benzoquinone.
Base Control of Electron-Transfer Reactions of Manganese(III) Porphyrins
2000
Homogeneous electron-transfer kinetics for the reduction of four different manganese(III) porphyrins using different reductants were examined in deaerated acetonitrile, and the resulting data were evaluated in light of the Marcus theory of electron transfer to determine electron-exchange rate constants between manganese(III) and manganese(II) porphyrins. The investigated compounds are represented as (P)MnCl, where P = the dianion of dodecaphenylporphyrin (DPPX; X = H20, Cl12H8, or F20) or tetraphenylporphyrin (TPP). The electron transfer from semiquinone radical anion derivatives to (P)MnIIICl leads to formation of the corresponding MnII complex, [(P)MnIICl]−. The electron-exchange rate con…
Experimental and theoretical study of possible correlation between the electrochemistry of canthin-6-one and the anti-proliferative activity against …
2015
Abstract This work presents an approach to study the performance of novel targets able to overcome cancer stem cell chemoresistance, based on the voltammetric data for microparticulate films of natural or synthetic alkaloids from the canthin-6-one series. A comparison of this voltammetric technique with conventional solution phase electrochemistry suggests the differences in the anti-proliferative activity of canthin-6-ones could be tentatively correlated to their different capacity to generate semiquinone radical anions. These data also match theoretical calculations.
Marine inspired antiplasmodial thiazinoquinones: synthesis, computational studies and electrochemical assays
2015
In the search for new antimalarials, we used the quinone scaffold of marine secondary metabolites as a chemical starting point to synthesize new thiazinoquinone compounds. Most of synthetic derivatives have shown a significant pharmacological activity and some structural requirements, critical for both the antiplasmodial effect and cytotoxicity, have been evidenced. The redox properties of the prepared compounds have been investigated by computational studies and electrochemical assays, which indicated that a higher antiplasmodial activity of some thiazinoquinones is related to their greater ability to form the semiquinone species and strongly interact with free Fe(III)-protoporphyrin IX.
Attenuation of NF-κB Signaling Response to UVB Light during Cellular Senescence
1999
The ability of cells to adapt to environmental stresses undergoes a progressive reduction during aging. NF-kappaB-mediated signaling is a major defensive system against various environmental challenges. The aim of this study was to find out whether replicative senescence affects the response of the NF-kappaB signaling pathway to UVB light in human WI-38 and IMR-90 fibroblasts. The exposure of early passage fibroblasts to UVB light inhibited the proliferation and induced a flat phenotype similar to that observed in replicatively senescent fibroblasts not exposed to UVB light. The UVB radiation dose used (153 mJ/cm2) did not induce apoptosis in either early or late passage WI-38 fibroblasts. …