Abstract. In this study, AgBr nanoparticles were prepared by controlled single jet method in the presence of gelatine and polyvinylpyrrolidone (PVP). In order to obtain better insight about the effect of PVP and its compatibility with gelatine on the formation of AgBr nanoparticles, effects of both components (gelatine, PVP) in the process of physical ripening on grain and grain size distribution were investigated. Several processing variables such as PVP/Ag weight ratio and addition time were investigated. PVP of three different molecular weights (PVP/ K 15, M w = 1.0 · 10 4 g mol

The novel calix [4]arene derivatives, 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetrakis(N-(2-(2-metoxyetoxy)ethyl)carbamoyl methoxy)calix[4]arene (1) and 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra(N,N-bis(2-(2-metoxyetoxy)ethyl)carbamoyl methoxy)calix[4]arene (2), were prepared by introducing diethylene glycol subunits at a lower calixarene rim. Complexation affinities of these compounds towards alkali and alkaline earth metal cations were studied at 25 °C in acetonitrile and methanol by means of spectrophotometric, conductometric, and potentiometric titrations. The stability constants of the corresponding complexes with 1:1 (cation:ligand) stoichiometry were determined (in some cases only estimated), and their values obtained by different methods were in good agreement. Much lower stabilities of the complexes with secondary-amide derivative (1) compared to those with tertiary-amide one (2) were observed. That was presumably mostly caused by the presence of intramolecular NH•••O=C hydrogen bonds in the former case. It was found that solvent significantly affected the stability of the complexes, whereby the prepared calixarenes showed considerably higher affinities for cations in acetonitrile than in methanol. Generally, the ligands studied showed better binding abilities for alkaline earth than for alkali metal cations. The extraction of metal picrates from water to dichloromethane by complexation of metal ions with ligands 1 and 2 was also investigated. In accordance with the complex stabilities, all cations were extracted fairly well (in some cases even excelently) with tertiary-amide derivative, whereas that was not the case in the extraction experiments with the other ligand studied.

We measured and computed the rate constants of the reaction between the α-hydroxyethyl radical (●CH(CH3)OH) and bromoacetate (BrCH2CO2–) in the non-buffered (NB), as well as in the bicarbonate (HCO3–) and...

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A series of tripeptides TrpTrpPhe (1), TrpTrpTyr (2), and TrpTrpTyr[CH2N(CH3)2] (3) were synthesized, and their photophysical properties and non-covalent binding to polynucleotides were investigated. Fluorescent Trp residues (quantum yield in aqueous solvent ΦF = 0.03–0.06), allowed for the fluorometric study of non-covalent binding to DNA and RNA. Moreover, high and similar affinities of 2×HCl and 3×HCl to all studied double stranded (ds)-polynucleotides were found (logKa = 6.0–6.8). However, the fluorescence spectral responses were strongly dependent on base pair composition: the GC-containing polynucleotides efficiently quenched Trp emission, at variance to AT- or AU-polynucleotides, which induced bisignate response. Namely, addition of AT(U) polynucleotides at excess over studied peptide induced the quenching (attributed to aggregation in the grooves of polynucleotides), whereas at excess of DNA/RNA over peptide the fluorescence increase of Trp was observed. The thermal denaturation and circular dichroism (CD) experiments supported peptides binding within the grooves of polynucleotides. The photogenerated quinone methide (QM) reacts with nucleophiles giving adducts, as demonstrated by the photomethanolysis (quantum yield ΦR = 0.11–0.13). Furthermore, we have demonstrated photoalkylation of AT oligonucleotides by QM, at variance to previous reports describing the highest reactivity of QMs with the GC reach regions of polynucleotides. Our investigations show a proof of principle that QM precursor can be imbedded into a peptide and used as a photochemical switch to enable alkylation of polynucleotides, enabling further applications in chemistry and biology.