Quantitative analysis of relative protein contents by Western blotting: comparison of three members of the dystrophin-glycoprotein complex in slow and fast rat skeletal muscle

We have developed a method for accurate quantitative analysis and statistical comparison of the relative contents of the dystrophin-glycoprotein complex (DGC) in skeletal muscle. This method was applied to compare DGC contents in slow (soleus) and in fast (extensor digitorum longus, EDL) rat skeletal muscles. The quantitative analysis combines a modified bicinchoninic acid (BCA) assay with Western blotting and enhanced chemiluminescence (ECL). This combination allows the use of high levels of detergents and reducing reagents essential for extracting DGC. In addition, the evaluation of the total amount of proteins in each sample makes it possible to have a reference and to accurately compare relative protein levels without using a specific standard. With a large gradient gel, we could concomitantly compare two groups (n = 9) and quantify all protein contents differing highly in their molecular masses (from 35 kDa to 427 kDa). Each experiment was triplicated and normalized; the two muscles were compared using the Mann-Whitney test (P<0.001) to establish their protein content. The DGC relative levels for the slow muscle soleus and the fast muscle EDL differed significantly: dystrophin, beta-dystroglycan, and gamma-sarcoglycan levels were 130%, 110% and 120% higher in the soleus, respectively. The differences observed in the expression level of cytoskeletal associated protein (dystrophin) and transmembranous anchorage components may correspond to a physiological response of the muscle fibers to duration, magnitude, and frequency of the imposed mechanical loading.     

LBGK method coupled to time splitting technique for solving reaction-diffusion processes in complex systems

A new approach to numerically solve a reaction-diffusion system is given, specifically developed for complex systems including many reacting/diffusing species with broad ranges of rate constants and diffusion coefficients, as well as complicated geometry of reacting interfaces. The approach combines a Lattice Boltzmann (LB) method with a splitting time technique. In the present work, the proposed approach is tested by focusing on the typical reaction process between a metal ion M and a ligand L, to form a complex ML with M being consumed at an electrode. The aim of the paper is to systematically study the convergence conditions of the associated numerical scheme. We find that the combination of LB with the time splitting method allows us to solve the problem for any value of association and dissociation rate constant of the reaction process. Also, the method can be extended to a mixture of ligands. We stress two main points: (1) the LB approach is particularly convenient for the flux computation of M and (2) the splitting time procedure is very well suited for reaction processes involving association-dissociation rate constants varying on many orders of magnitude.     

Halogenation in Fungi: What Do We Know and What Remains to Be Discovered?

In nature, living organisms produce a wide variety of specialized metabolites to perform many biological functions. Among these specialized metabolites, some carry halogen atoms on their structure, which can modify their chemical characteristics. Research into this type of molecule has focused on how organisms incorporate these atoms into specialized metabolites. Several families of enzymes have been described gathering metalloenzymes, flavoproteins, or S-adenosyl-L-methionine (SAM) enzymes that can incorporate these atoms into different types of chemical structures. However, even though the first halogenation enzyme was discovered in a fungus, this clade is still lagging behind other clades such as bacteria, where many enzymes have been discovered. This review will therefore focus on all halogenation enzymes that have been described in fungi and their associated metabolites by searching for proteins available in databases, but also by using all the available fungal genomes. In the second part of the review, the chemical diversity of halogenated molecules found in fungi will be discussed. This will allow the highlighting of halogenation mechanisms that are still unknown today, therefore, highlighting potentially new unknown halogenation enzymes.     

Enantioselective Total Synthesis of (+)-Nordasycarpidone, (+)-Dasycarpidone,and (+)-Uleine

The structure of uleine type alkaloids is characterized by the presence of a bridged tetracyclic hexahydro-1H-1,5-methanoazocino[4,3-b]indole ring system 1 . Various strategies have been developed to access this polycyclic structural motif. We report herein a one-step conversion of appropriately functionalized 1,3,4-trisubstituted cyclopent-1-ene to 1 by way of an integrated oxidation/reduction/cyclization (iORC) process. This domino sequence, initiated by oxidative cleavage of cyclopentene ring, generated subsequently a cyclohexenone, an indole and a 1,3-bridged piperidine ring through formation of one C−C and two C−N bonds. Compound 1 is subsequently converted to nordasycarpidone, dasycarpidone and uleine. The chirality of the molecule was introduced by enzymatic desymmetrization of commercially available meso cis-3,5-diacetoxy-1-cyclopentene.     

TiCl3-Mediated Synthesis of 2,3,3-Trisubstituted Indolenines: Total Synthesis of (+)-1,2-Dehydroaspidospermidine, (+)-Condyfoline,and (−)-Tubifoline

2,3,3-Trisubstituted indolenine constitutes an integral part of many biologically important monoterpene indole alkaloids. We report herein an unprecedented access to this skeleton by a TiCl₃-mediated reductive cyclization of tetrasubstituted alkenes bearing a 2-nitrophenyl substituent. The proof of concept is demonstrated firstly by accomplishing a concise total synthesis of (+)-1,2-dehydroaspidospermidine featuring a late-stage application of this key transformation. A sequence of reduction of nitroarene to nitrosoarene followed by 6π-electron-5-atom electrocyclization and a 1,2-alkyl shift of the resulting nitrone intermediate was proposed to account for the reaction outcome. A subsequent total synthesis of (+)-condyfoline not only illustrates the generality of the reaction, but also provides a mechanistic insight into the nature of the 1,2-alkyl shift. The exclusive formation of (+)-condyfoline indicates that the 1,2-alkyl migration follows a concerted Wagner–Meerwein pathway, rather than a stepwise retro-Mannich/Mannich reaction sequence. Conditions for almost quantitative conversion of (+)-condyfoline to (−)-tubifoline by way of a retro-Mannich/1,3-prototropy/transannular cyclization cascade are also documented.     

Complex Polypropionates from a South China Sea Photosynthetic Mollusk: Isolation and Biomimetic Synthesis Highlighting Novel Rearrangements

Placobranchus ocellatus is well known to produce diverse and complex γ‐pyrone polypropionates. In this study, the chemical investigation of P. ocellatus from the South China Sea led to the discovery and identification of ocellatusones A–D, a series of racemic non‐γ‐pyrone polyketides with novel skeletons, characterized by a bicyclo[3.2.1]octane ( 1 , 2 ), a bicyclo[3.3.1]nonane ( 3 ) or a mesitylene‐substituted dimethylfuran‐3(2H)‐one core ( 4 ). Extensive spectroscopic analysis, quantum chemical computation, chemical synthesis, and/or X‐ray diffraction analysis were used to determine the structure and absolute configuration of the new compounds, including each enantiomer of racemic compounds 1 – 4 after chiral HPLC resolution. An array of new and diversity‐generating rearrangements is proposed to explain the biosynthesis of these unusual compounds based on careful structural analysis and comparison with six known co‐occurring γ‐pyrones ( 5 – 10 ). Furthermore, the successful biomimetic semisynthesis of ocellatusone A ( 1 ) confirmed the proposed rearrangement through an unprecedented acid induced cascade reaction.     

Superacid-Mediated Late-Stage Aromatic Polydeuteration of Pharmaceuticals

The field of medicinal chemistry is currently witnessing a deuterium rush owing to the remarkable properties of this element as bioisoster of hydrogen atom. Aromatic hydrogen isotope exchange (HIE) is one of the most studied strategies nowadays as it promises to access deuterium-modified drugs directly from their non-labeled parents. While most of the recent studies focus on metal-catalyzed C−H activation strategy, the use of superacidic conditions has been largely overlooked. This study shows that the use of TfOD as reaction medium allows the late-stage polydeuteration of a broad library of pharmaceuticals bearing a wide array of functional groups, complementing existing procedures.     

Programmed Multiple C-H Bond Functionalization of the Privileged 4-hydroxyquinoline Template

The introduction of substituents on bare heterocyclic scaffolds can selectively be achieved by directed C−H functionalization. However, such methods have only occasionally been used, in an iterative manner, to decorate various positions of a medicinal scaffold to build chemical libraries. We herein report the multiple, site selective, metal-catalyzed C−H functionalization of a “programmed” 4-hydroxyquinoline. This medicinally privileged template indeed possesses multiple reactive sites for diversity-oriented functionalization, of which four were targeted. The C-2 and C-8 decorations were directed by an N-oxide, before taking benefit of an O-carbamoyl protection at C-4 to perform a Fries rearrangement and install a carboxamide at C-3. This also released the carbonyl group of 4-quinolones, the ultimate directing group to functionalize position 5. Our study highlights the power of multiple C−H functionalization to generate diversity in a biologically relevant library, after showing its strong antimalarial potential.     

One-Pot Synthesis of Metastable 2,5-Dihydrooxepines through Retro-Claisen Rearrangements: Method and Applications

A one-pot methodology to synthesize metastable bicyclic 2,5-dihydrooxepines from cyclic 1,3-diketones and 1,4-dibromo-2-butenes through the retro-Claisen rearrangement of syn-2-vinylcyclopropyl diketone intermediates is reported. DFT calculations were performed to understand the reaction selectivity and mechanisms towards [1,3]- or [3,3]-sigmatropic rearrangements, highlighting the crucial influence of the temperature. The reaction was successfully applied to a short protecting group-free total synthesis of radulanin A, a natural 2,5-dihydrobenzoxepine. Moreover, the strong herbicidal potential of this natural product is demonstrated for the first time.