Ultrafast structural dynamics of water induced by dissipation of vibrational energy

In the liquid phase, water molecules form a disordered fluctuating network of intermolecular hydrogen bonds. Using both inter- and intramolecular vibrations as structural probes in ultrafast infrared spectroscopy, we demonstrate a two-stage structural response of this network to energy disposal: vibrational energy from individually excited water molecules is transferred to intermolecular modes, resulting in a sub-100 fs nuclear rearrangement that leaves the local hydrogen bonds weakened but unbroken. Subsequent energy delocalization over many molecules occurs on an approximately 1 ps time scale and is connected with the breaking of hydrogen bonds, resulting in a macroscopically heated liquid.     

Sodium and potassium benzeneazophosphonate complexes with crown ethers: Solid-state microwave synthesis, characterization and biological activity

The eco-friendly synthesis, spectroscopic (IR, MS, ¹H and ¹³C NMR) study and biological (cytostatic, antiviral) activity of sodium and potassium benzeneazophosphonate complexes, obtained by reaction in the solid state under microwave irradiation of the alkali salts of ethyl [α-(4-benzeneazoanilino)-N-benzyl]phosphonic acid and [α-(4-benzeneazoanilino)-N-4-methoxybenzyl]phosphonic acid with crown ethers containing 18-membered (dibenzo-18-crown-6 and bis(4′-di-tert-butylbenzo)-18-crown-6), 24-membered (dibenzo-24-crown-8) and 30-membered (dibenzo-30-crown-10) macrocyclic rings, have been described. The simple work-up solvent free reaction is an efficient green procedure for the formation of mononuclear crown ether complexes in which the sodium/potassium ion is bound to oxygen atoms of the macrocycle and the phosphonic acid oxygen. The free crown ethers, alkali benzeneazophosphonate salts and their complexes were evaluated for their cytostatic activity in vitro against murine leukemia L1210, murine mammary carcinoma FM3A and human T-lymphocyte CEM and MT-4 cell lines, as well as for their antiviral activity against a wide variety of DNA and RNA viruses. The investigated compounds showed no specific antiviral activity, whereas all the free crown ethers and their complexes demonstrated cytostatic activity, which was especially pronounced in the case of bis(4′-di-tert-butylbenzo)-18-crown-6 and its complexes.     

Influence of promoters on the performance of Au/MnOx and Pt/SnOx/SiO2 low-temperature CO oxidation catalysts

The influence of promoters on Pt/SnO_x/SiO₂ and Au/MnO_x low-temperature CO oxidation catalysts has been investigated under stoichiometric reaction conditions with no CO₂ added to the feed gas. The performance of Pt/SnO_x/SiO₂ catalysts is improved significantly by the addition of 1 wt.% Fe but reduced by the addition of 5 wt.%Fe, 1 wt.% Sb, 5 wt.% Sb, 1 wt.% As, 5 wt.%As and 1.8 wt.% P. The performance of Au/MnO_x is improved significantly by the addition of 1 at.% Ce but reduced by the addition of 1 at.% Co. For the catalysts and conditions examined, the Au/MnO_x catalysts are superior to the Pt/SnO_x/SiO₂ catalysts with respect to both activity and decay characteristics.     

Association of bound states of the coulomb potential with resonances of the coulomb potential perturbed by a barrier

In the present article we show how the bound states of the Coulomb potential may be associated with resonances that occur when this potential is perturbed by a barrier potential. The main idea is to trace the bound states on successive switching on of the barrier perturbation. It is found that those bound states that are localized inside the barrier are highly sensitive to variation with respect to the barrier height, whereas those that are localized outside are less sensitive. However, there are certain intervals for the barrier height when the role of being “a state localized inside the barrier” is shifted from one bound state to another. The result can be pictured as a “relay race,” where the “deliveries of the baton” are carried out over corresponding avoided crossings. The baton is ultimately handed over to a shape-type resonance state.     

Effects of Polydispersity on the Phase Behavior of Additive Hard Spheres in Solution

The ability to separate enzymes, nucleic acids, cells, and viruses is an important asset in life sciences. This can be realised by using their spontaneous asymmetric partitioning over two macromolecular aqueous phases in equilibrium with one another. Such phases can already form while mixing two different types of macromolecules in water. We investigate the effect of polydispersity of the macromolecules on the two-phase formation. We study theoretically the phase behavior of a model polydisperse system: an asymmetric binary mixture of hard spheres, of which the smaller component is monodisperse and the larger component is polydisperse. The interactions are modelled in terms of the second virial coefficient and are assumed to be additive hard sphere interactions. The polydisperse component is subdivided into sub-components and has an average size ten times the size of the monodisperse component. We calculate the theoretical liquid–liquid phase separation boundary (the binodal), the critical point, and the spinodal. We vary the distribution of the polydisperse component in terms of skewness, modality, polydispersity, and number of sub-components. We compare the phase behavior of the polydisperse mixtures with their concomittant monodisperse mixtures. We find that the largest species in the larger (polydisperse) component causes the largest shift in the position of the phase boundary, critical point, and spinodal compared to the binary monodisperse binary mixtures. The polydisperse component also shows fractionation. The smaller species of the polydisperse component favor the phase enriched in the smaller component. This phase also has a higher-volume fraction compared to the monodisperse mixture.     

A Lock-and-Kill Anticancer Photoactivated Chemotherapy Agent†

Photosubstitutionally active ruthenium complexes show high potential as prodrugs for the photoactivated chemotherapy (PACT) treatment of tumors. One of the problems in PACT is that the localization of the ruthenium compound is hard to trace. Here, a ruthenium PACT prodrug, [Ru(3)(biq)(STF-31)](PF₆)₂ (where 3 = 3-(([2,2′:6′,2″-ter- pyridin]-4′-yloxy)propyl-4-(pyren-1-yl)butanoate) and biq = 2,2′-biquinoline), has been prepared, in which a pyrene tracker is attached via an ester bond. The proximity between the fluorophore and the ruthenium center leads to fluorescence quenching. Upon intracellular hydrolysis of the ester linkage, however, the fluorescence of the pyrene moiety is recovered, thus demonstrating prodrug cellular uptake. Further light irradiation of this molecule liberates by photosubstitution STF-31, a known cytotoxic nicotinamide phosphoribosyltransferase (NAMPT) inhibitor, as well as singlet oxygen via excitation of the free pyrene chromophore. The dark and light cytotoxicity of the prodrug, embedded in liposomes, as well as the appearance of blue emission upon uptake, were evaluated in A375 human skin melanoma cells. The cytotoxicity of the liposome-embedded prodrug was indeed increased by light irradiation. This work realizes an in vitro proof-of-concept of the lock-and-kill principle, which may ultimately be used to design strategies aimed at knowing where and when light irradiation should be realized in vivo.     

Four levels of pattern recognition

Problems of pattern recognition in chemistry and other subjects can be divided conveniently into four different types depending on the level of scope of the problem.(1) Classification into one of a number of defined classes. As an example blood samples taken from persons known to be either controls or welders are considered. The problem is whether trace element concentrations in these samples contain information on whether or not a person is a welder.(2) Level 1 plus the possibility that an object is an outlier, i.e. does not belong to any of the defined classes. As an example, the üse of ¹³C-n.m.r. data to decide whether 2-substituted norbornanes have the exo or endo structure is discussed. (2A) Level 2, asymmetric. This situation occurs when one class does not have a systematic structure, but another class is homogeneous and can be described by a level 2 model. This occurs in the classification of materials or compounds as good or bad, active or inactive, and in binary classifications. As an example the use of trace element data to classify steel samples as having good or poor properties of strength is discussed.(3) Level 2 plus the ability to relate the variables measured to external properties of continuous character. As an example, the classification of a series of chemical compounds as β -receptor blockers, β -receptor stimulants, or neither, on the basis of their structural variables is discussed. In addition, relations between these structural variables and the measured biological activity are sought within each of the two classes.(4) Level 3 with the difference that several external property variables in the objects are measured. It may be desirable to use variables of the objects both for classification and for relations to several property variables: such examples are numerous in analytical chemistry.     

Synthesis of imidazoles as novel emivirine and S‐DABO analogues

5‐Alkyl‐4‐benzyl‐1,3‐dihydroimidazol‐2‐ones ( 3a‐d ) and 5‐alkyl‐4‐benzyl‐1,3‐dihydroimidazole‐2‐thiones (7a‐d) were prepared via Dakin West reaction on DL‐phenylalanine with the appropriate aliphatic acid anhydrides followed by hydrolysis and reaction with potassium cyanate or potassium thiocyanate. Compounds 3a‐d were alkylated with ethoxymethyl chloride to give the alkylated imidazoles 5a‐d which were considered analogues of Emivirine with deletion of carbonyl group at the 4‐position. Alkylation of 7a‐d afforded the corresponding S‐alkylated derivatives 8a‐p which in a similar way were considered analogues of S‐DABO. However all the imidazole derivatives were devoid of activity against HIV.     

Pandemic-Driven Development of a Medical-Grade,Economic and Decentralized Applicable Polyolefin Filament for Additive Fused Filament Fabrication

A polyolefin with certified biocompatibility according to USP class VI was used by our group as feedstock for filament-based 3D printing to meet the highest medical standards in order to print personal protective equipment for our university hospital during the ongoing pandemic. Besides the chemical resistance and durability, as well as the ability to withstand steam sterilization, this polypropylene (PP) copolymer is characterized by its high purity, as achieved by highly efficient and selective catalytic polymerization. As the PP copolymer is suited to be printed with all common printers in fused filament fabrication (FFF), it offers an eco-friendly cost–benefit ratio, even for large-scale production. In addition, a digital workflow was established focusing on common desktop FFF printers in the medical sector. It comprises the simulation-based optimization of personalized print objects, considering the inherent material properties such as warping tendency, through to validation of the process chain by 3D scanning, sterilization, and biocompatibility analysis of the printed part. This combination of digital data processing and 3D printing with a sustainable and medically certified material showed great promise in establishing decentralized additive manufacturing in everyday hospital life to meet peaks in demand, supply bottlenecks, and enhanced personalized patient treatment.