Regiospecific Photocyclization of Mono- and Bis-Styryl-Substituted N‑Heterocycles: A Synthesis of DNA-Binding Benzo[<i>c</i>]quinolizinium Derivatives

Regiospecific C–N photocyclization of mono<i>-</i> and bis-styryl-substituted N-heterocycles was investigated. We demonstrated that the C–N regiospecificity of the photoinduced electrocyclization is a general feature of <i>ortho-</i>styryl-substituted N-heterocycles comprising one and two nitrogen atoms. This phototransformation provides a straightforward synthesis of the pharmaceutically important benzo­[<i>c</i>]­quinolizinium cation and its aza-analogues. Noticeably, bis-styryl derivatives undergo only one-fold cyclization with the second styryl fragment remaining uninvolved in the cyclization process. Photocyclization products of monostyryl derivativatives intercalate into calf thymus DNA (ct DNA), whereas photocyclization products of bis-styryl derivativatives possess a mixed binding mechanism with ct DNA. The results can be used for development of novel DNA-targeting chemotherapeutics based on benzo­[<i>c</i>]­quinolizinium derivatives

Regiospecific C–N Photocyclization of 2‑Styrylquinolines

Regiospecific C–N photocyclization of 2-styrylquinolines resulting in formation of potentially biologically active quino­[1,2-<i>a</i>]­quinolizinium derivatives was investigated. The presence of strong electron-donating groups in the phenyl ring reveals to be a crucial factor managing photocyclization effectiveness. Introduction of a crown ether moiety allows changing the photoreaction parameters by means of complexation with Mg­(ClO₄)₂

Hybrid Macrocycles for Selective Binding and Sensing of Fluoride in Aqueous Solution

Synthesis and anion binding properties of hybrid macrocycles containing ammonium and hydrogen bond donor groups are reported. Receptor properties were studied in a 10 mM MES buffer solution at pH 6.2, at which the receptors carry two positive charges at the secondary amine groups. Receptor <b>1</b> was found to bind fluoride with the highest affinity (10⁵ M^–1) and selectivity among the synthesized receptors. It was the only receptor that demonstrated fluorescence increase upon addition of fluoride. Other titration experiments with halides and oxyanions led to an anion-induced aggregation and fluorescence quenching. The mechanism of the particular turn-on fluorescence for fluoride was explained by the ability of receptor <b>1</b> to encapsulate several fluoride anions. Multiple anion coordination resulted in the protonation of the tertiary amine group and subsequent hindering of the PET process. ¹H and ¹⁹F NMR titrations, single-crystal X-ray structure of chloride complex, and DFT calculation suggest that <b>1</b> can perfectly accommodate two fluoride anions in the inner cavity but only one chloride, keeping the second chloride in the outer coordination sphere. Thus, the importance of size selectivity, which is reflected in a collective behavior of molecules in an aqueous solution, represents a new strategy for the design of highly selective probes for fluoride functioning in an aqueous solution

Combined treatment of human multiple myeloma cells with bortezomib and doxorubicin alters the interactome of 20S proteasomes

<p>The proteasome is the key player in targeted degradation of cellular proteins and serves as a therapeutic target for treating several blood malignancies. Although in general, degradation of proteins via the proteasome requires their ubiquitination, a subset of proteins can be degraded independently of their ubiquitination by direct interaction with subunits of the 20S proteasome core. Thus, investigation of the proteasome-associated proteins may help identify novel targets of proteasome degradation and provide important insights into the mechanisms of malignant cell proteostasis. Here, using biochemical purification of proteasomes from multiple myeloma (MM) cells followed by mass-spectrometry we have uncovered 77 proteins in total that specifically interacted with the 20S proteasome via its PSMA3 subunit. Our GST pull-down assays followed by western blots validated the interactions identified by mass-spectrometry. Eleven proteins were confirmed to bind PSMA3 only upon apoptotic conditions induced by a combined treatment with the proteasome inhibitor, bortezomib, and genotoxic drug, doxorubicin. Nine of these eleven proteins contained bioinformatically predicted intrinsically disordered regions thus making them susceptible to ubiquitin-independent degradation. Importantly, among those proteins five interacted with the ubiquitin binding affinity matrix suggesting that these proteins may also be ubiquitinylated and hence degraded via the ubiquitin-dependent pathway. Collectively, these PSMA3-interacting proteins represent novel potential substrates for 20S proteasomes upon apoptosis. Furthermore, these data may shed light on the molecular mechanisms of cellular response to chemotherapy.</p> <p><b>Abbreviations:</b> BD: bortezomib/doxorubicin treatment; CDK: cyclin-dependent kinases; CHCA: α-cyanohydroxycinnamic acid; IDP: intrinsically disordered proteins; IDR: intrinsically disordered regions; IPG: immobilized pI gradient; MALDI TOF/TOF: matrix-assisted laser desorption/ionization time-of-flight tandem mass-spectrometry; MM: multiple myeloma; ODC: ornithine decarboxylase; PI: proteasomal inhibitors; PSMA: alpha-type 20S proteasome subunits; PTMs: post-translational modifications; SDS-PAGE: sodium dodecylsulphate polyacrylamide gel electrophoresis; UIP: ubiquitin-independent proteasomal proteolysis.</p