Study of three-dimensionally ordered structures of intact mitochondria by small-angle neutron scattering

The ultrastructure of cristae of intact mitochondria, in which the activity of the oxidative phosphorylation system was retained, was investigated by small-angle neutron scattering. Osmotic swelling of organelles was found to cause ultrastructural rearrangements of the inner mitochondrial membrane in rat liver and heart mitochondria. This process was accompanied by the appearance of diffraction peaks indicative of the formation of ordered structures. The lamellar packing of the membranes in heart mitochondria, which is observed under normal conditions, was found to undergo a transition to a nonlamellar hexagonal packing, whose scattering curve shows two peaks with the scattering vectors characterized by a spacing ratio of 1:√3. The electron-microscopy results confirm the possibility of the formation of a hexagonal packing of the inner membrane in heart mitochondria.     

C(sp2)‐Coupled Nitronyl Nitroxide and Iminonitroxide Diradicals

Spin‐labelled compounds are widely used in chemistry, physics, biology and the materials sciences but the synthesis of stable high‐spin organic molecules is still a challenge. We succeeded in synthesising heteroatom analogues of the 1,1,2,3,3‐pentamethylenepropane (PMP) diradicals with two nitronyl nitroxide ( DR¹ ) and with two iminonitroxide ( DR² ) fragments linked through the C(sp²) atom of the nitrone group. According to magnetic susceptibility measurements, EPR data and ab initio calculations at the (8,6)CASSCF and (8,6)NEVPT2 levels, DR¹ and DR² have singlet ground states. The singlet–triplet energy splitting (2J) is low (J/k=?7.4 for DR¹ and ?6.0 K for DR² ), which comes from the disjoint nature of these diradicals. The reaction of [Cu(hfac)₂] with DR¹ gives rise to different heterospin complexes in which the diradical acts as a rigid ligand, retaining its initial conformation. For the [{Cu(hfac)₂}₂( DR¹ )(H₂O)] complex, sufficiently strong ferromagnetic interactions (J₁/k=42.7 and J₂/k=14.1 K) between two coordinating Cu^II ions and DR¹ were revealed. In [{Cu(hfac)₂}₂( DR¹ )(H₂O)][Cu(hfac)₂(H₂O)], the very strong and antiferromagnetic (J/k=?416.1 K) exchange interaction between one of the coordinating Cu^II ions and DR¹ is caused by the very short equatorial Cu?O bond length (1.962 Å).     

High‐Resolution 3D Proton MRI of Hyperpolarized Gas Enabled by Parahydrogen and Rh/TiO2 Heterogeneous Catalyst

Several supported metal catalysts were synthesized, characterized, and tested in heterogeneous hydrogenation of propene with parahydrogen to maximize nuclear spin hyperpolarization of propane gas using parahydrogen induced polarization (PHIP). The Rh/TiO₂ catalyst with a metal particle size of 1.6 nm was found to be the most active and effective in the pairwise hydrogen addition and robust, demonstrating reproducible results with multiple hydrogenation experiments and stability for ≥1.5 years. 3D ¹H magnetic resonance imaging (MRI) of 1 % hyperpolarized flowing gas with microscale spatial resolution (625×625×625 μm³) and large imaging matrix (128×128×32) was demonstrated by using a preclinical 4.7 T scanner and 17.4 s imaging scan time.     

Reactions of silamorpholinones and acylsilamorpholines with electrophilic reagents. X-ray structure of products including a pentacoordinated silicon compound

Reactions of 2-sila-5-morpholinones, 4-acyl-2-silamorpholines and 4-acyl-2,6-disilamorpholines with electrophilic reagents generally lead to the opening of the sila- or disilacycle by cleavage of the Si–O bond with subsequent rearrangement to form five-membered chelate derivatives where the amide oxygen atoms coordinate with the silicon to form pentacoordinate silicon species. Multinuclear NMR spectroscopy and X-ray diffraction studies were used for structural investigation of the products. 4-Acyl-2,6-disilamorpholines initially form adducts with strong acids where the amide oxygen is protonated by the acid as demonstrated by X-ray crystallography.     

The size of particle aggregates produced by flocculation with PNIPAM, as a function of temperature

This work investigates the effect of temperature on the size of alumina aggregates formed by flocculation with temperature responsive Poly(N-Isopropylacrylamide)(PNIPAM). The results are discussed in terms of the effects of temperature on particle collision, particle adhesion and aggregate breakage. It was found that the size of alumina aggregates increases with increasing solution temperature. Particle/particle collision and aggregate breakage are largely unaffected by increasing solution temperature and therefore could not account for the change in aggregate size. The dominant factor in aggregate growth with increasing temperature was found to be the increase in the force of adhesion between alumina particles. The appearance of the adhesive force is triggered by the increase in temperature above the lower critical solution temperature of PNIPAM.     

Plasmonic nanopowders for photothermal therapy of tumors

We describe a novel strategy for the fabrication of plasmonic nanopowders (dried gold nanoparticles) by using wet chemical nanoparticle synthesis, PEG-SH functionalization, and a standard freeze-drying technique. Our strategy is illustrated by successful fabrication of different plasmonic nanopowders, including gold nanorods, gold-silver nanocages, and gold nanospheres. Importantly, the dried nanoparticles can be stored for a long time under usual conditions and then can easily be dissolved in water at a desired concentration without such hard manipulations as sonication or heating. Redispersed samples maintain the plasmonic properties of parent colloids and do not form aggregates. These properties make pegylated freeze-dried gold nanoparticles attractive candidates for plasmonic photothermal therapy in clinical settings. In this work, redispersed gold nanorods were intravenously administered to mice bearing Ehrlich carcinoma tumors at doses of 2 and 8 mg (Au)/kg (animal). Particle biodistribution was measured by atomic absorption spectroscopy, and tumor hyperthermia effects were studied under laser NIR irradiation. Significant tumor damage was observed only at the higher dose of the nanorods.     

Regioselective Heteroannelation in 4-Cyanomethyl-3,5-pyridinedicarbonitriles. Synthesis of 6-Alkoxy-3-dialkylamino-1,8-diamino-2,7-naphthyridine-4-carbonitriles

 The title naphthyridines were found to be the sole products obtained after treatment of 2-amino-4-cyanomethyl-6-dialkylamino-3,5-pyridinedicarbonitriles with alkoxides. The starting pyridine derivatives were prepared by amination of the readily available 2-amino-6-chloro-4-cyanomethyl-3,5-pyridinedicarbonitrile in quantitative yields.     

Reactivity of cationic methyl rhodium(III) complexes cis-[Rh(β-diket)(PPh3)2(CH3)(CH3CN)][BPh4] toward ligands of different character: pyridine, carbon monoxide, and triphenylphosphine

Cationic methyl complex of rhodium(III), cis-[Rh(Acac)(PPh₃)₂(CH₃)(Py)][BPh₄] (1) as a single isomer with Py in the trans to PPh₃ position, is formed upon the reaction of cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] with pyridine in methylene chloride solution.Complex 1 was characterized by elemental analysis and by ³¹P{¹H} and ¹H NMR spectra.Cationic pentacoordinate acetyl complexes, trans-[Rh(Acac)(PPh₃)₂(COCH₃)][BPh₄] (2) and trans-[Rh(BA)(PPh₃)₂(COCH₃)][BPh₄] (3), are prepared by action of carbon monoxide on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄], respectively, in methylene chloride solutions.Complexes 2 and 3 were characterized by elemental analysis and by IR, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR. According to NMR data, 2 and 3 in solution are non-fluxional trigonal bipyramids with β-diketonate and acetyl ligands in the equatorial plane and axial phosphines.In solutions, 2 and 3 gradually isomerize into octahedral methyl carbonyl complexes trans-[Rh(Acac)(PPh₃)₂(CO)(CH₃)][BPh₄] (4) and trans-[Rh(BA)(PPh₃)₂(CO)(CH₃)][BPh₄] (5), respectively.Complexes 4 and 5 were characterized by IR, ³¹P{¹H}, ¹³C{¹H} and ¹H NMR, without isolation.Upon the action of PPh₃ on cis-[Rh(Acac)(PPh₃)₂(CH₃)(CH₃CN)][BPh₄] and cis-[Rh(BA)(PPh₃)₂(CH₃)(CH₃CN)] [BPh₄], reductive elimination of the methyl ligand as a phosphonium salt, [CH₃PPh₃][BPh₄], occurs to give square planar rhodium(I) complexes [Rh(Acac)(PPh₃)₂] and[Rh(BA)(PPh₃)₂], respectively. The reaction products were identified in the reaction mixtures by ³¹P{¹H} and ¹H NMR.