Labelling and binding of poly-( -lysine) to functionalised gold surfaces. Combined FT-IRRAS and XPS characterisation

We compare herein the interfacial reactivity of self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA), 1-undecanethiol (UDT) and 11-mercaptoundecanol (MUD) on gold surfaces towards aqueous solutions of poly-( -lysine) (PL). Liquid-phase labelling of PL with the alkyne dicobalt hexacarbonyl cluster 1 combined with analysis of the substrates by Fourier transform infrared reflection–absorption spectroscopy (FT-IRRAS) and X-ray photoelectron spectroscopy (XPS) revealed that irreversible binding of PL occurred in all cases. However, the mechanism of binding involved differed markedly from one monolayer to the other. The main mode of interaction of PL to MUA SAM was of electrostatic nature between the terminal carboxylate of MUA and the ammonium groups of PL. For a similar number of bound thiolate molecules, the UDT adsorbed layer was found less continuous than the MUA one, allowing a higher fraction of PL to directly bind to the gold surface. As for MUD, very little thiolate molecules were adsorbed, leaving bare gold surface areas for non specific adsorption of PL.     

Inorganic Photochemistry:Past,Present, and Future

Transition metal complex, in its electronic excited state, has intriguing photophysical and photochemical properties that are substantially different from its ground state, Indeed, electronically excited metal complex can be viewed as hot chemical species that is readily synthesized by photo-excitation with UV-visible light. If the energy of excited metal complex can be properly manipulated, it may be possible to devise new catalytic system for converting light to chemical energy. In the context of energy conversion reactions and chemical sensing, it is important for biomolecular reactions at room temperature. Among the photochemical bimolecular reactions, the following three have the widest applications in photocatalysis, and these are (1) bimolecular outer-sphere electron transfer reactions, (2) bimoleculat inner-sphere atom transfer/abstract reactions, and (3) exciplex formation involving electronic excited state. The past of inorganic photochemistry has demonstrated the success of[Ru(bpy)₃]²⁺ as a powerful reagent for light-induced electron transfer reactions. Much of the current photochemistry research focus on coordinative unsaturated metal complexes, that are strongly photoluminescent and readily undergo substrate binding reactions in their excited states. In this lecture, I will review some of the past successful stories of[Ru(bpy)₃]²⁺ and discuss our current research on the luminescent metal-complexes prepared in my laboratory. I will end my lecture by proposing a clue for achieving light-induced multi-electron transfer reactions, which remains a challenge in photochemistry research.     

Orally administered bismuth drug together with N-acetyl cysteine as a broad-spectrum anti-coronavirus cocktail therapy

The emergence of SARS-CoV-2 variants of concern compromises vaccine efficacy and emphasizes the need for further development of anti-SARS-CoV-2 therapeutics, in particular orally administered take-home therapies. Cocktail therapy has shown great promise in the treatment of viral infection. Herein, we reported the potent preclinical anti-SARS-CoV-2 efficacy of a cocktail therapy consisting of clinically used drugs, e.g. colloidal bismuth subcitrate (CBS) or bismuth subsalicylate (BSS), and N-acetyl-l-cysteine (NAC). Oral administration of the cocktail reduced viral loads in the lung and ameliorated virus-induced pneumonia in a hamster infection model. The mechanistic studies showed that NAC prevented the hydrolysis of bismuth drugs at gastric pH via the formation of the stable component [Bi(NAC)₃], and optimized the pharmacokinetics profile of CBS in vivo. Combination of bismuth drugs with NAC suppressed the replication of a panel of medically important coronaviruses including Middle East respiratory syndrome-related coronavirus (MERS-CoV), Human coronavirus 229E (HCoV-229E) and SARS-CoV-2 Alpha variant (B.1.1.7) with broad-spectrum inhibitory activities towards key viral cysteine enzymes/proteases including papain-like protease (PL^pro), main protease (M^pro), helicase (Hel) and angiotensin-converting enzyme 2 (ACE2). Importantly, our study offered a potential at-home treatment for combating SARS-CoV-2 and future coronavirus infections.

A cocktail therapy comprising bismuth drugs and N-acetyl-l-cysteine is reported to suppress the replication of SARS-CoV-2 via the oral route. The broad-spectrum inhibitory activities of the combination upon key viral cysteine enzymes are verified.     

Affinity foam fractionation of Trichoderma cellulase

Cellulase could not be selectively collected from fermentation broth by simple foam fractionation, because of the presence of other more surface-active compounds. A new approach of affinity foam fractionation was investigated for improvement. A hardwood hydrolysate (containing cellulose oligomers, substrates to cellulase) and two substrate analogs, i.e., carboxymethyl cellulose (CMC) and xylan hydrolysate, were added before the foaming process. The substrates and substrate analogs were indeed found to bind the cellulase selectively and form more hydrophobic complexes that partition more readily onto bubble surfaces. In this study, the effects of the type and concentration of substrate/analog as well as the presence of cells at different growth stages were examined. The foam fractionation properties evaluated included foaming speed, foam stability, foamate volume, and enrichment of filter paper unit (FPU) and individual cellulase components (i.e., endoglucanases, exoglucanases, and β-glucosidases). Depending on the broth and substrate/analog employed, the foamate FPU could be more than fourfold higher than the starting broth FPU. Addition of substrate/analog also deterred the enrichment of other extracellular proteins, resulting in the desired cellulase purification in the foamate. The value of E/P (enzyme activity-FPU/g/L of proteins) in the foamate reached as high as 18, from a lactose-based fermentation broth with original E/P of 5.6. Among cellulase components, exoglucanases were enriched the most and β-glucosidases the least. The study with CMC of different molecular weights (MW) and degrees of substitution (DS) indicated that the CMC with low DS and high MW performed better in cellulase foam fractionation.     

Study of the interface formed between poly(2-methoxy-5-(2′-ethyl-hexyloxyl)-p-phenylene vinylene) and indium tin oxide in top emission organic light emitting diodes

X-ray photoelectron spectroscopy (XPS) technique have been used to investigate the interface formed between poly(2-methoxy-5-(2′-ethyl-hexyloxyl)-p-phenylene vinylene) (MEH-PPV) and indium tin oxide (ITO) layer in top emission organic light emitting diodes. A weak but noticeable diffusion of indium into the polymer film was observed. Interactions between the diffused metallic atoms with the polymer resulted in the formation of carbon-metal complexes at the interface region. Compared to the ITO/MEH-PPV interface, the penetration of indium into the polymer layer was less important and may be explained by the surface morphology of the polymer film. It was however, a probable factor for fast degradation of devices using this structure.     

Multicriteria–multistage planning for the optimal path selection using hybrid genetic algorithms

The problem of the competence set expansion involves determining the optimal expansion path under the minimum cost and time. As we know, the conventional competence set model only considers the problems of the static situation and the single objective. However, the dynamic situation and the multicriteria should also be simultaneously considered in practice. In this paper, a multicriteria and multistage competence set model is proposed. In order to efficiently obtain an optimal expansion path, hybrid genetic algorithms (HGA) are employed. In addition, a numerical example is used to demonstrate the proposed method. On the basis of the numerical results, we can conclude that the proposed method can provide a sound competence set model by simultaneously considering the multicriteria and multistage situations.     

Superconductivity and the Anomalous Meissner Effect in La3CaBa3Cu7O15,5 + x Oxide

A superconducting oxide with a stoichiometry La₃CaBa₃Cu₇O_15.5+x, in which x = 0.75, was prepared. It had a tetragonal triple-perovskite structure with lattice parameters a = 3.879 Å and c = 11.637 Å. According to resistivity measurements, a sharp superconducting transition, ΔT_c(10-90%) = 1.5 K, and T_c(zero) = 80 K were observed. When it was measured at a small magnetic field (10-20 gauss) with field cooling, the sintered pellet showed a positive magnetic susceptibility, but the powdered sample exhibited (he diamagnetism of a typical superconductor. However, no peculiar shielding effect was found in both the sintered and powdered samples.     

Modeling of electron tunneling times in asymmetric double quantum wells

A scattering process modeled by an imaginary potential V _I in the wide well of an asymmetric double quantum well structure (DQWS) is used to model the electron tunneling from the narrow well. Taking V _I –5 meV, the ground resonant level lifetimes of the narrow well in the DQWS are in quantitative agreement with the experimental resonance and non-resonance tunneling times. The corresponding scattering time 66 fs is much faster than the intersubband scattering time of LO-photon emission.     

Metalloporphyrin-mediated asymmetric nitrogen-atom transfer to hydrocarbons: aziridination of alkenes and amidation of saturated C-H bonds catalyzed by chiral ruthenium and manganese porphyrins

Chiral metalloporphyrins [Mn(Por*)(OH)(MeOH)] (1) and [Ru(Por*)(CO)(EtOH)] (2) catalyze asymmetric aziridination of aromatic alkenes and asymmetric amidation of benzylic hydrocarbons to give moderate enantiomeric excesses. The mass balance in these nitrogen-atom-transfer processes has been examined. With PhI=NTs as the nitrogen source, the aziridination of styrenes, trans-stilbene, 2-vinylnaphthalene, indene, and 2,2-dimethylchromene catalyzed by complex 1 or 2 resulted in up to 99 % substrate conversions and up to 94 % aziridine selectivities, whereas the amidation of ethylbenzenes, indan, tetralin, 1-, and 2-ethylnaphthalene catalyzed by complex 2 led to substrate conversions of up to 32 % and amide selectivities of up to 91 %. Complex 1 or 2 can also catalyze the asymmetric amidation of 4-methoxyethylbenzene, tetralin, and 2-ethylnaphthalene with "PhI(OAc)(2) + NH(2)SO(2)Me", affording the N-substituted methanesulfonamides in up to 56 % ee with substrate conversions of up to 34 % and amide selectivities of up to 92 %. Extension of the "complex 1 + PhI=NTs" or "complex 1 + PhI(OAc)(2) + NH(2)R (R=Ts, Ns)" amidation protocol to a steroid resulted in diastereoselective amidation of cholesteryl acetate at the allylic C-H bonds at C-7 with substrate conversions of up to 49 % and amide selectivities of up to 90 % (alpha:beta ratio: up to 4.2:1). An aziridination- and amidation-active chiral bis(tosylimido)ruthenium(VI) porphyrin, [Ru(Por*)(NTs)(2)] (3), and a ruthenium porphyrin aziridine adduct, [Ru(Por*)(CO)(TsAz)] (4, TsAz=N-tosyl-2- (4-chlorophenyl)aziridine), have been isolated from the reaction of 2 with PhI=NTs and N-tosyl-2-(4-chlorophenyl)aziridine, respectively. The imidoruthenium porphyrin 3 could be an active species in the aziridination or amidation catalyzed by complex 2 described above. The second-order rate constants for the reactions of 3 with styrenes, 2-vinylnaphthalene, indene, ethylbenzenes, and 2-ethylnaphthalene range from 3.7-42.5x10(-3) dm(3) mol(-1) s(-1). An X-ray structure determination of complex 4 reveals an O- rather than N-coordination of the aziridine axial ligand. The fact that the N-tosylaziridine in 4 does not adopt an N-coordination mode disfavors a concerted pathway in the aziridination by a tosylimido ruthenium porphyrin active species.     

Structural and spectroscopic studies on Pt.Pt and pi-pi interactions in luminescent multinuclear cyclometalated platinum(II) homologues tethered by oligophosphine auxiliaries

The synthesis and structural, spectroscopic, and electrochemical properties of a series of trinuclear tridentate cyclometalated platinum(II) complexes tethered by bis(diphenylphosphinomethyl)phenylphosphine (dpmp) have been studied and compared with their mono- and binuclear homologues and a propeller-like congener. The X-ray crystal structures of several derivatives show the presence of a variety of intramolecular Pt.Pt, pi-pi, and C-H...O(crown ether) and intermolecular pi-pi interactions. The trinuclear complexes display strong absorption in the 400-600 nm region and show intense red to near-infrared phosphorescence with microsecond lifetimes in fluid and glassy solutions and in the solid state. These emissions are generally assigned as (3)MMLCT [dsigma-->pi(CNN)] in nature. The close similarities between the emission energies in acetonitrile solution and in the solid state at 298 K indicate that comparable Pt.Pt and pi-pi configurations are maintained in both media, and hence a relationship between the photophysical behavior of these lumophores and their solid-state structural features is proposed. The tendencies of the absorption and emission energies to red-shift from mono- to linearly tethered bi- and trinuclear Pt(II) species are evident. A light-emitting electrochemical cell using a trinuclear Pt(II) derivative as emitter has been demonstrated.