Video rate depth-resolved two-dimensional imaging through turbid media by femtosecond parametric amplification

We report two-dimensional imaging through a liquid scattering medium by noncollinear femtosecond parametric amplification in a reflection configuration. The experiment presented permits direct observation at video rate of two-dimensional images with 24-mum depth resolution and 90-mum transverse resolution for an area with a 2.5-mm diameter on the object. These resolutions are achievable through a turbid phantom with a depth near 12 scattering mean free paths in double pass.     

Anthecularin: a novel sesquiterpene lactone from Anthemis auriculata with antiprotozoal activity

Anthecularin (1), a minor sesquiterpene lactone with a novel ring system was isolated from Greek Anthemis auriculata (Asteraceae). Its structure was elucidated by means of NMR, HRMS, and X-ray crystallography. Anthecularin showed antitrypanosomal (IC50=10.1 microg/mL) and antiplasmodial activity (IC50=23.3 microg/mL) and inhibited two key enzymes of the plasmodial type II fatty acid biosynthesis pathway, PfFabI and PfFabG (IC50 values=14 and 28.3 microg/mL, respectively). A probable biogenesis of 1 is also proposed and discussed.     

Potent Inhibitors of Malarial Aspartic Proteases,the Plasmepsins,by Hydroformylation of Substituted 7‐Azanorbornenes

The increasing prevalence of multidrug‐resistant strains of the malarial parasite Plasmodium falciparum requires the urgent development of new therapeutic agents with novel modes of action. The vacuolar malarial aspartic proteases plasmepsin (PM) I, II, and IV are involved in hemoglobin degradation and play a central role in the growth and maturation of the parasite in the human host. We report the structure‐based design, synthesis, and in vitro evaluation of a new generation of PM inhibitors featuring a highly decorated 7‐azabicyclo[2.2.1]heptane core. While this protonated central core addresses the catalytic Asp dyad, three substituents bind to the flap, the S1/S3, and the S1′ pockets of the enzymes. A hydroformylation reaction is the key synthetic step for the introduction of the new vector reaching into the S1′ pocket. The configuration of the racemic ligands was confirmed by extensive NMR and X‐ray crystallographic analysis. In vitro biological assays revealed high potency of the new inhibitors against the three plasmepsins (IC₅₀ values down to 6 nM ) and good selectivity towards the closely related human cathepsins D and E. The occupancy of the S1′ pocket makes an essential contribution to the gain in binding affinity and selectivity, which is particularly large in the case of the PM IV enzyme. Designing non‐peptidic ligands for PM II is a valid route to generate compounds that inhibit the entire family of vacuolar plasmepsins.     

Dynamics of polyelectrolyte transport through a protein channel as a function of applied voltage

We study the transport of dextran sulfate through a protein channel as a function of applied voltage. Below 60 mV, the chain's entrance to the pore is hindered by an entropic barrier; above 60 mV, the strong local electric field forces the chain entrance. The effective charge of the polyelectrolyte inside the pore is reduced. We observe two types of blockades which have durations that decrease when the applied voltage increases. The shortest is a straddling time between the polyelectrolyte and the pore; the longest is the translocation time. The translocation time obeys an exponential dependence upon applied voltage.     

New Optically Active 2H‐Azirin‐3‐amines as Synthons for Enantiomerically Pure 2,2‐Disubstituted Glycines: Synthesis of Synthons for Tyr(2Me) and Dopa(2Me), and Their Incorporation into Dipeptides

The synthesis of novel unsymmetrically 2,2‐disubstituted 2H‐azirin‐3‐amines with chiral auxiliary amino groups is described. Chromatographic separation of the mixture of diastereoisomers yielded (1′R,2S)‐ 2a , b and (1′R,2R)‐ 2a , b (c.f. Scheme 1 and Table 1), which are synthons for (S)‐ and (R)‐2‐methyltyrosine and 2‐methyl‐3′,4′‐dihydroxyphenylalanine. Another new synthon 2c , i.e., a synthon for 2‐(azidomethyl)alanine, was prepared but could not be separated into its pure diastereoisomers. The reaction of 2 with thiobenzoic acid, benzoic acid, and the amino acid Fmoc‐Val‐OH yielded the monothiodiamides 11 , the diamides 12 (cf. Scheme 3 and Table 3), and the dipeptides 13 (cf. Scheme 4 and Table 4), respectively. From 13 , each protecting group was removed selectively under standard conditions (cf. Schemes 5–7 and Tables 5–6). The configuration at C(2) of the amino acid derivatives (1R,1′R)‐ 11a , (1R,1′R)‐ 11b , (1S,1′R)‐ 12b , and (1R,1′R)‐ 12b was determined by X‐ray crystallography relative to the known configuration of the chiral auxiliary group.     

Unprecedented Route to Ordered Polyaniline: Direct Synthesis of Highly Crystalline Fibrillar Films with Strong π‐π Stacking Alignment

Films of polyaniline (PANI) featuring about 80% crystallinity and characterised with strong π‐π stacking alignment parallel to the film surface have been obtained directly after the original synthesis upon simple drying of the aqueous PANI suspension. A strong anisotropy in the growth of the nano‐sized crystals produced during the synthesis results in the formation of micrometer‐length fibrils perpendicular to the film surface in the course of water evaporation. The regular intercalation of water molecules between the PANI chains seems to be crucial for their ordering throughout the synthesis and film formation.