Coexpression of CPR from Various Origins Enhances Biotransformation Activity of Human CYPs in S. pombe

Cytochrome P450 enzymes (CYPs or P450s) are the most important enzymes involved in the phase I metabolism of drugs (and other xenobiotics) in humans, and the corresponding drug metabolites are needed as reference substances for their structural confirmation and for pharmacological or toxicological characterization. We have previously shown that biotechnological synthesis of such metabolites is feasible by whole-cell biotransformation with human CYPs recombinantly expressed in the fission yeast Schizosaccharomyces pombe. It was the aim of this study to compare the activity of seven human microsomal CYPs (CYP2C9, CYP2D6, CYP3A4, CYP3A5, CYP3A7, CYP17, and CYP21) upon coexpression with NADPH-cytochrome P450 oxidoreductases (CPRs) from various origins, namely, human CPR (hCPR) and its homologues from fission yeast (ccr1) and the bishop’s weed Ammi majus (AmCPR), respectively. For this purpose, 28 recombinant strains were needed, with five of them having been constructed previously and 23 strains being newly constructed. Bioconversion experiments showed that coexpression of a CPR does not only influence the reaction rate but, in some cases, also exerts an influence on the metabolite pattern. For CYP3A enzymes, coexpression of hCPR yielded the best results, while for another two, hCPR was equally helpful as ccr1 (both CYP17 and CYP21) or AmCPR (CYP17 only), respectively. Interestingly, CYP2D6 displayed its highest activity when coexpressed with ccr1 and CYP2C9 with AmCPR. These results corroborate the view of CPR as a well-suited bio-brick in synthetic biology for the construction of artificial enzyme complexes.     

Uncommon suffix tries

Common assumptions on the source producing the words inserted in a suffix trie with n leaves lead to a height and saturation level. We provide an example of a suffix trie whose height increases faster than a power of n and another one whose saturation level is negligible with respect to . Both are built from VLMC (Variable Length Markov Chain) probabilistic sources and are easily extended to families of tries having the same properties. The first example corresponds to a “logarithmic infinite comb” and enjoys a non uniform polynomial mixing. The second one corresponds to a “factorial infinite comb” for which mixing is uniform and exponential. © 2013 Wiley Periodicals, Inc. Random Struct. Alg., 46, 117–141, 2015     

KiSThelP: A program to predict thermodynamic properties and rate constants from quantum chemistry results†

Kinetic and Statistical Thermodynamical Package (KiSThelP) is a cross‐platform free open‐source program developed to estimate molecular and reaction properties from electronic structure data. To date, three computational chemistry software formats are supported (Gaussian, GAMESS, and NWChem). Some key features are: gas‐phase molecular thermodynamic properties (offering hindered rotor treatment), thermal equilibrium constants, transition state theory rate coefficients (transition state theory (TST), variational transition state theory (VTST)) including one‐dimensional (1D) tunnelling effects (Wigner, and Eckart) and Rice‐Ramsperger‐Kassel‐Marcus (RRKM) rate constants, for elementary reactions with well‐defined barriers. KiSThelP is intended as a working tool both for the general public and also for more expert users. It provides graphical front‐end capabilities designed to facilitate calculations and interpreting results. KiSThelP enables to change input data and simulation parameters directly through the graphical user interface and to visually probe how it affects results. Users can access results in the form of graphs and tables. The graphical tool offers customizing of 2D plots, exporting images and data files. These features make this program also well‐suited to support and enhance students learning and can serve as a very attractive courseware, taking the teaching content directly from results in molecular and kinetic modelling. © 2013 Wiley Periodicals, Inc.     

Novel C1-symmetric dibenzophosphole ligands: application in hydroformylation reactions

A new family of non-symmetrical disubstituted dibenzophospholes possessing different steric and electronic effects have been synthesized and characterized. Their preliminary evaluation in rhodium-catalyzed hydroformylation reactions is presented.     

A theoretical and experimental study of the racemization process of hexaaza[5]helicenes

A dynamic ¹H NMR study, together with DFT calculations, of bis-([1,2,3]triazolo)[1,5-a:5′,1′-k][1,10]phenanthroline 2 has allowed to identify the ring and open forms of a new example of ring/chain tautomerism, as well as their interconversion barriers (ring/ring and ring/open). The barrier of the exchange process between the chain forms and the ring form was found higher than the ‘racemization’ process in the closed form, so the ring opening does not contribute to the ‘racemization’. The di-1,10-methyl and di-1,10-iodo derivatives have been prepared and their properties calculated.     

A general synthesis of diversely substituted indazoles and hetero-aromatic derivatives from o-halo-(het)arylaldehydes or -phenones

A set of variously substituted indazoles and hetero-aromatic derivatives were synthesized from o-halo-(het)arylaldehydes using a palladium catalyzed amination followed by cyclization. Starting from phenones, this process was extended to give 3-substituted indazoles. Moreover, N-1-substituted-indazoles can be reached by this strategy using an optional selective N-1-alkylation step during the process. This methodology offers a general and easy route for the synthesis of regioselectively substituted indazoles.     

Evaluation of sphingomyelin,cholester, and phosphatidylcholine-based immobilized artificial membrane liquid chromatography to predict drug penetration across the blood-brain barrier

Over the past decades, several in vitro methods have been tested for their ability to predict drug penetration across the blood-brain barrier. So far, in high-performance liquid chromatography, most attention has been paid to micellar liquid chromatography and immobilized artificial membrane (IAM) LC. IAMLC has been described as a viable approach, since the stationary phase emulates the lipid environment of a cell membrane. However, research in IAMLC has almost exclusively been limited to phosphatidylcholine (PC)-based stationary phases, even though PC is only one of the lipids present in cell membranes. In this article, sphingomyelin and cholester stationary phases have been tested for the first time towards their ability to predict drug penetration across the blood-brain barrier. Upon comparison with the PC stationary phase, the sphingomyelin- and cholester-based columns depict similar predictive performance. Combining data from the different stationary phases did not lead to improvements of the models. Figure

Schematic representation of how IAM-LC is used to predict drug penetration across the blood-brain barrier.     

Comprehensive two-dimensional liquid chromatography coupled to the ABTS radical scavenging assay: a powerful method for the analysis of phenolic antioxidants

The on-line combination of comprehensive two-dimensional liquid chromatography (LC?×?LC) with the 2,2′-azino-bis(3-ethylbenzothiazoline)-6 sulphonic acid (ABTS) radical scavenging assay was investigated as a powerful method to determine the free radical scavenging activities of individual phenolics in natural products. The combination of hydrophilic interaction chromatography (HILIC) separation according to polarity and reversed-phase liquid chromatography (RP-LC) separation according to hydrophobicity is shown to provide much higher resolving power than one-dimensional separations, which, combined with on-line ABTS detection, allows the detailed characterisation of antioxidants in complex samples. Careful optimisation of the ABTS reaction conditions was required to maintain the chromatographic separation in the antioxidant detection process. Both on-line and off-line HILIC?×?RP-LC–ABTS methods were developed, with the former offering higher throughput and the latter higher resolution. Even for the fast analyses used in the second dimension of on-line HILIC?×?RP-LC, good performance for the ABTS assay was obtained. The combination of LC?×?LC separation with an on-line radical scavenging assay increases the likelihood of identifying individual radical scavenging species compared to conventional LC–ABTS assays. The applicability of the approach was demonstrated for cocoa, red grape seed and green tea phenolics.

Disassembly Kinetics of Quinone‐Methide‐Based Self‐Immolative Spacers that Contain Aromatic Nitrogen Heterocycles

We prepared several pyridine‐ and pyrimidine‐based self‐immolative spacer groups to evaluate the significance of the resonance energy of the spacer aromatic ring on the kinetics of 1,4‐ and 1,6‐elimination reactions, which govern spacer disassembly. Subsequently, we relied on a photoactivation procedure to accurately analyze the disassembly kinetics. Beyond providing new results that are relevant for deriving quantitative structure–property relationships, herein, we demonstrate that pH value can be used as an efficient parameter to finely control the disassembly time of a self‐immolative spacer after an initial activation.     

Characterization of Food Packaging Films with Blackcurrant Fruit Waste as a Source of Antioxidant and Color Sensing Intelligent Material

Chitosan and pectin films were enriched with blackcurrant pomace powder (10 and 20% (w/w)), as bio-based material, to minimize food production losses and to increase the functional properties of produced films aimed at food coatings and wrappers. Water vapor permeability of active films increased up to 25%, moisture content for 27% in pectin-based ones, but water solubility was not significantly modified. Mechanical properties (tensile strength, elongation at break and Young’s modulus) were mainly decreased due to the residual insoluble particles present in blackcurrant waste. FTIR analysis showed no significant changes between the film samples. The degradation temperatures, determined by DSC, were reduced by 18 °C for chitosan-based samples and of 32 °C lower for the pectin-based samples with blackcurrant powder, indicating a disturbance in polymer stability. The antioxidant activity of active films was increased up to 30-fold. Lightness and redness of dry films significantly changed depending on the polymer type. Significant color changes, especially in chitosan film formulations, were observed after exposure to different pH buffers. This effect is further explored in formulations that were used as color change indicators for intelligent biopackaging.