The role of organisational- and country-level factors in the volume and public visibility of business and management research.

Using a multilevel modelling approach to analyse a novel dataset of academic publications at all business schools in 11 European countries, this paper finds that the influence of organisational- and country-level contextual factors on researchers varies considerably based on the type of institution and the development level of the country they are located in. At the organisational-level, we find that greater spatial connectivity-operationalised through proximity to nearby business schools, rail stations, and airports-is positively related to scientific research volume and public dissemination (news mentions). While this result is significant only for high-income countries (above EU-average 2018 GDP per capita), this is likely because the low-income countries (below EU-average 2018 GDP per capita) examined here lack a 'critical mass' of well-connected universities to generate observable agglomeration effects. At the country-level, the results indicate that in high-income countries, less prestigious schools benefit from higher rates of recent international immigration from any foreign country, providing a direct policy pathway for increasing research output for universities that aren't already well-known enough to attract the most talented researchers. In low-income countries, recent immigration rates are even stronger predictors of research performance across all levels of institutional prestige; more open immigration policies would likely benefit research performance in these countries to an even greater extent. Finally, the paper's results show that, in low-income countries, a composite measure of a country's quality of life (including self-rated life satisfaction, health, working hours, and housing overcrowding) is positively related to research outcomes through its interaction with school prestige. This suggests that the lower a country's quality of life, the more researchers are incentivised to produce higher levels of research output. While this may in part reflect the greater disparities inherent in these countries' economic systems, it is noteworthy-and perhaps concerning-that we have observed a negative correlation between country-level quality of life and research performance in low-income countries, which is particularly felt by researchers at less prestigious institutions.

Interaction of a tricationic meso-substituted porphyrin with guanine-containing polyribonucleotides of various structures.

The interaction of a tricationic water-soluble meso-(N-methylpyridinium)-substituted porphyrin, TMPyP3+, derived from classic TMPyP4, with double-stranded poly(G) ⋅ poly(C) and four-stranded poly(G) polyribonucleotides has been studied in aqueous buffered solutions, pH 6.9, of low and near-physiological ionic strengths in a wide range of molar phosphate-to-dye ratios (P/D). To clarify the binding modes of TMPyP3+ to biopolymers various spectroscopic techniques, including absorption and polarized fluorescence spectroscopy, Raman spectroscopy, and resonance light scattering, were used. As a result, two competitive binding modes were revealed. In solution of low ionic strength outside binding of the porphyrin to the polynucleotide backbone with self-stacking prevailed at low P/D ratios (P/D < 3.5). It manifested itself by the substantial quenching of porphyrin fluorescence. Also the formation of large-scale porphyrin aggregates was observed near the stoichiometric binding ratio. The spectral changes observed at P/D > 30 including emission enhancement were supposed to be caused by the embedding of partially stacked porphyrin J-dimers into the polymer groove. TMPyP3+ binding to poly(G) induced a fluorescence increase 2.5 times as large as that observed for poly(G) ⋅ poly(C). In solution of near-physiological ionic strength the efficiency of external porphyrin binding was reduced substantially due to the competitive binding of Na+ ions with the polymer backbone. The spectroscopic characteristics of porphyrin bound to polynucleotides at different conditions were compared with those for free porphyrin.

Binding of Metallated Porphyrin-Imidazophenazine Conjugate to Tetramolecular Quadruplex Formed by Poly(G): a Spectroscopic Investigation.

The binding of telomerase inhibitor ZnTMPyP(3+)-ImPzn, Zn(II) derivative of tricationic porphyrin-imidazophenazine conjugate, to tetramolecular quadruplex structure formed by poly(G) was studied in aqueous solutions at neutral pH and near physiological ionic strength using absorption and polarized fluorescent spectroscopy techniques. Three binding modes were determined from the dependences of the fluorescence intensity and polarization degree for the porphyrin and phenazine moieties of the conjugate on molar polymer-to-dye ratio (P/D). The first one is outside electrostatic binding of positively charged porphyrin fragments to anionic phosphate groups of the polymer which prevails only at very low P/D values and manifests itself by substantial fluorescence quenching. It is suggested that the formation of externally bound porphyrin dimers occurs. The other two binding modes observed at high P/D are embedding of the ZnTMPyP(3+) moiety into the groove of poly(G) quadruplex accompanied by more than 3-fold enhancement of the conjugate emission, and simultaneous intercalation of the phenazine fragment between the guanine bases accompanied by the increase of its fluorescence polarization degree up to 0.25. Thus Zn(II) conjugate seems to be promising ligand for the stabilization of G-quadruplex structures since porphyrin binding to poly(G) is strengthened by additional intercalation of phenazine moiety.

Spectroscopic Studies on Binding of Porphyrin-Phenazine Conjugate to Four-Stranded Poly(G).

Binding of a novel cationic porphyrin-imidazophenazine conjugate, TMPyP(3+)-ImPzn, to four-stranded poly(G) was investigated in aqueous solutions of neutral pH under near physiological ionic conditions using absorption, polarized fluorescent spectroscopy and fluorescence titration techniques. In absence of the polymer the conjugate folds into stable internal heterodimer with stacking between the porphyrin and phenazine chromophores. Binding of TMPyP(3+)-ImPzn to poly(G) is realized by two competing ways. At low polymer-to-dye ratio (P/D < 6) outside electrostatic binding of the cationic porphyrin moieties of the conjugate to anionic polynucleotide backbone with their self-stacking is predominant. It is accompanied by heterodimer dissociation and distancing of phenazine moieties from the polymer. This binding mode is characterized by strong quenching of the conjugate fluorescence. Increase of P/D results in the disintegration of the porphyrin stacks and redistribution of the bound conjugate molecules along the polymer chain. At P/D > 10 another binding mode becomes dominant, embedding of TMPyP(3+)-ImPzn heterodimers into poly(G) groove as a whole is occurred.

Self-assemblies of tricationic porphyrin on inorganic polyphosphate.

Self-assemblies formed by the new synthesized tricationic porphyrin derivative (TMPyP(3+)) on the polyanionic inorganic polyphosphate (PPS) in aqueous solution were studied using different spectroscopic techniques and DFT calculation method. From the fluorescence quenching of the bound TMPyP(3+) molecules and their Raman spectra we conclude that porphyrin chromophores form the stable π-π stacking-assemblies onto PPS polyanions. The transformation of the Soret band in absorption spectra at different PPS/TMPyP(3+)concentration ratios evidences that the assemblies are mixtures of J- and H-aggregates. Molecular modeling performed shows that the flexibility of PPS strand allows a realization of spiral or "face-to-face" one-dimensional structures formed by porphyrin molecules arranged in parallel and antiparallel modes. The peculiarity of PPS structure allows a formation of two porphyrin stacks on opposite sides of polymer strands that result in the appearance of higher-order aggregates. Their size was estimated from the light scattering data. Distinctions between TMPyP(3+) and TMPyP4 aggregation on PPS template are discussed.

Spectroscopic study on the effect of imidazophenazine tethered to 5'-end of pentadecathymidilate on stability of poly(dA)·(dT)15 duplex.

The effect of imidazo[4,5-d]phenazine (Pzn) attached to the 5(')-end of (dT)(15) oligonucleotide via a flexible linker on the thermal stability of poly(dA)·(dT)(15) duplex was studied in aqueous buffered solution containing 0.1 М NaCl at the equimolar ratio of adenine and thymine bases (100 µM each) using spectroscopic techniques. Duplex formation was investigated by measuring UV absorption and fluorescence melting curves for the Pzn-modified system. Tethered phenazine derivative enhances the thermostability of poly(dA)·(dT)(15) duplex increasing the helix-to-coil transition temperature by 4.5 °Ð¡ due to an intercalation of the dye chromophore between AT-base pairs. The thermodynamic parameters of the transition for non-modified and modified systems were estimated using "all-or-none" model. The modification of the (dT)(15) results in a decrease in the transition enthalpy, however, the observed gain in the Gibbs free energy of complex formation, ΔG, is provided with the corresponding decrease in entropy change. The increase of ΔG value at 37 °C in consequence of (dT)(15) modification was found to be equal to 1.3 kcal/mol per oligonucleotide strand.

Postsynthetic modification of oligonucleotides with imidazophenazine dye and its effect on duplex stability.

Carboxyalkyl derivative of the intercalating agent imidazo[4,5-b]phenazine was used for the postsynthetic oligonucleotide modification. Model pentadecathymidylate-imidazophenazine conjugate was prepared from 5'-aminoalkyl-modified (dT)(15) by using phosphonium coupling reagent BOP in the presence of 1-hydroxybenzotriazole. Spectral-fluorescent properties of the conjugate were studied. The attachment of the dye was found to increase the thermal stability of (dT)(15) duplex with poly(dA) by more than 4°C, probably by the intercalation mechanism.

Effect of Ni2+ and Cd2+ ions on thermally induced conformational transitions in poly(dA)-poly(dT) system.

Effects of Ni(2+) and Cd(2+) ions on thermally induced conformational transitions in the poly(dA)·poly(dT) polynucleotide duplex and poly(dA)·2poly(dT) triplex under near physiological ionic conditions were studied by measurement of UV absorption melting curves and static light scattering intensity. The diagrams of conformational transitions in poly(dA)-poly(dT)-Me(2+) systems were plotted. An aggregation in these polynucleotide systems arises at certain values of the metal ions concentration and the temperature after the polymer dissociation into single strands. The phenomenon is conditioned by the aggregation of poly(dA) via the interstrand cross-linking by the dication bridges. Unlike Ni(2+), Cd(2+) induces formation of very stable aggregates which did not disintegrate even upon cooling up to room temperature.

Spectroscopic detection of tetracationic porphyrin H-aggregation on polyanionic matrix of inorganic polyphosphate.

Self-assembly of tetracationic porphyrin TMPyP(4+) onto polyanionic matrix of inorganic polyphosphate (PPS) in aqueous solutions has been studied in a wide range of molar phosphate-to-dye ratios using techniques of polarized fluorescence, absorption, resonance Raman spectroscopy and static light scattering. The binding of TMPyP(4+) to PPS is characterized by the binding constant of 3 x 10(5) M(-1) and the cooperativity parameter of about 150. The fluorescence quenching of the bound TMPyP(4+) evidences the stacking of the porphyrine chromophores. Under the stoichiometric binding ratio TMPyP(4+) forms extended continuous face-to-face aggregates (so-called H-aggregates) which manifest themselves by a blue shift (12 nm) and a large hypochromisity (51%) of the Soret absorption band. Each face-to-face TMPyP(4+) stack is formed with participation of four PPS chains. Formation of such columnar aggregates is promoted by the ability of PPS chains to take a helix conformation where negative charges are arranged along two oppositely situated rows with intercharge distance of 0.36 nm which corresponds to the thickness of the porphyrin pi-electronic system. The ability of each PPS strand to be template for formation of two porphyrin stacks results in the integration of the adjacent stacks into higher-order aggregates which dimension was estimated from the fluorescence polarization data.

Fluorescent studies on cooperative binding of cationic pheophorbide-a derivative to polyphosphate.

The cooperative binding of a novel water-soluble cationic derivative of pheophorbide-a (CatPheo-a) to inorganic polyphosphate (PPS) in buffered aqueous solutions was studied by means of polarized fluorescence spectroscopy in a wide range of molar phosphate-to-dye ratios (P/D). Under low P/D values, CatPheo-a forms extended stacking associates on the PPS matrix, while under high P/D the dye binds to PPS in the dimer form. The CatPheo-a self-association is accompanied by 40-fold dye fluorescence quenching and a substantial increase in the fluorescence polarization degree. The fluorescent titration data were used for determination of cooperative binding parameters by Schwarz's method.