Certified reference material for quantification of polycyclic aromatic hydrocarbons in sediment from the National Metrology Institute of Japan

The National Metrology Institute of Japan has issued a certified reference material (CRM) of freshwater lake sediment for polycyclic aromatic hydrocarbon (PAHs) analyses. The certification used three extraction techniques: pressurized liquid extraction (PLE) with toluene, PLE with dichloromethane/ethyl acetate (1:1 by volume), and alkaline extraction (1 M KOH in methanol) in combination with microwave-assisted extraction. Both gas chromatography/mass spectrometry (GC/MS) and liquid chromatography/dopant-assisted atmospheric pressure photoionization/MS (LC/DA-APPI/MS) analyses were used. Certified values are provided for 18 PAHs at 1–25 μg kg⁻¹ except for perylene (2.08 × 10³ μg kg⁻¹), and information values are provided for two. Since the values of PAHs in the CRM are much lower than those in other CRMs and are comparable to those found at sites with little human influence, the CRM is suitable for PAH monitoring in sediment and soil samples.     

In vitro degradation of biodegradable polymer-coated magnesium under cell culture condition

Magnesium (Mg) coated with four kinds of polymers, poly (l-lactic acid) (PLLA)-high molecular weight (HMW), PLLA-low molecular weight (LMW), poly (?-caprolactone) (PCL)-HMW and PCL-LMW, and uncoated Mg were immersed under cell culture condition to study the degradation/corrosion behavior of the polymer-coated Mg. The releases of Mg²⁺ are measured during the immersion. Surface morphology and chemical composition are observed and identified by SEM and EDX. The tomography is obtained by X-ray CT observation and degradation rate is calculated by image analysis after 10-day immersion. All kinds of polymer-coated Mg showed significantly low release of Mg²⁺ (p < 0.05) in the whole immersion process comparing to that of uncoated Mg. In SEM and EDX results show, a corrosion layer can be observed on both polymer-coated and uncoated Mg after immersion. There is no obvious difference on the morphology and chemical composition of the corrosion layer between polymer-coated and uncoated Mg, indicating the corrosion/degradation process and corrosion product of Mg substrate are not changed by the polymer films under the present condition compared with uncoated Mg. Concerning the tomography and degradation rate of 10-day immersion, it can be found that the polymer-coated Mg shows a significantly low corrosion rate (p < 0.05) compared with that of uncoated Mg. PLLA coated Mg shows relatively uniform corrosion than PCL coated Mg and uncoated Mg. The largest pitting corrosion depth of PCL-LMW is about 3 times as large as the PLLA-LMW, which might be attributed to the difference of polymer microstructure. It is suggested that PLLA coating might be a suitable option for retarding the loss of mechanical properties of Mg substrate.     

A white-light interferometer using a lamp source and heterodyne detection with acousto-optic modulators

A heterodyne technique for white-light interferometer with a lamp source, which uses two acousto-optic modulators, is developed for high-sensitivity detection of weak light. By using converging input beams input into a Michelson interferometer with spherical mirrors, the spectral dependence of the modulators is canceled, and the white-light heterodyne interference fringes are generated at 200 kHz. Using a tandem interferometer, the object surface which has a low surface reflectivity of less than 10⁻⁴ was detected with a good signal-to-noise ratio.     

cis,cis‐Ceratospong­amide N,N‐di­methyl­acet­amide hemisolvate in the presence of twinning

Ceratospong­amide (CS) is a potent inhibitor of secreted phospho­lipase A₂, and cis,cis and trans,trans isomers, related with respect to the two proline amide bonds, are known. Crystals of cis,cis‐CS were grown from N,N‐di­methyl­acet­amide solution, giving the title compound, the cyclic ester of isoleucyl­oxazolinyl­phenyl­alanyl­prolyl­thia­zolyl­phenyl­alanyl­pro­line [cyclo(‐Ile–Oxz–Phe–Pro–Thz–Phe–Pro‐)] N,N‐di­methyl­acet­amide hemisolvate, C₄₁H₄₉N₇O₆S·0.5C₄H₉NO. The structure is the third example of cis,cis‐CS to be investigated and comprises twinned crystals, in which the a and b axes are interchanged. The ratio of co‐existing twin crystals is approximately 50%. The peptide has a `saddle‐like' structure and is very similar to previously reported structures of cis,cis‐CS, which implies that the structure of cis,cis‐CS is very stable in spite of differences in crystallization conditions.     

cyclo(‐Cha–Oxz–d‐Val–Thz–Ile–Oxz–d‐Val–Thz‐) N,N‐di­methyl­acetamide dihydrate: a square form of cyclo­hexyl­alanine‐incorporated ascidiacycl­amide having the strongest cytotoxicity

The title compound, 1‐cyclo­hexyl­methyl‐1‐de(1‐methyl­propyl)­asci­dia­cycl­amide N,N‐di­methyl­acet­amide di­hy­drate, C₃₉H₅₆N₈O₆S₂·C₄H₉NO·2H₂O, a cyclo­hexyl­alanine‐incorporated ascidiacycl­amide analogue ([Cha]ASC), shows a square form similar to natural ASC. On the other hand, CD (circular dichroism) spectra showed [Cha]ASC to have a folded structure in solution, making it the second known analogue to show a discrepancy between its crystal and solution structures. Moreover, the cytotoxicity of [Cha]ASC (ED₅₀ = 5.6 µg ml⁻¹) was approximately two times stronger than that of natural ASC or a related phenyl­alanine‐incorporated analogue, viz. cyclo(‐Phe–Oxz–d ‐Val–Thz–Ile–Oxz–d ‐Val–Thz‐) ([Phe]ASC), and was confirmed to be associated with the square form. However, [Phe]ASC was previously shown to be folded in the crystal structure, which suggests that the difference between the aromatic and aliphatic rings affects the molecular folding of the ASC mol­ecule.     

Noncovalent Modification of Cycloparaphenylene by Catenane Formation Using an Active Metal Template Strategy**

The active metal template (AMT) strategy is a powerful tool for the formation of mechanically interlocked molecules (MIMs) such as rotaxanes and catenanes, allowing the synthesis of a variety of MIMs, including π-conjugated and multicomponent macrocycles. Cycloparaphenylene (CPP) is an emerging molecule characterized by its cyclic π-conjugated structure and unique properties. Therefore, diverse modifications of CPPs are necessary for its wide application. However, most CPP modifications require early stage functionalization and the direct modification of CPPs is very limited. Herein, we report the synthesis of a catenane consisting of [9]CPP and a 2,2′-bipyridine macrocycle as a new CPP analogue that contains a reliable synthetic scaffold enabling diverse and concise post-modification. Following the AMT strategy, the [9]CPP-bipyridine catenane was successfully synthesized through Ni-mediated aryl-aryl coupling. Catalytic C−H borylation/cross-coupling and metal complexation of the bipyridine macrocycle moiety, an effective post-functionalization method, were also demonstrated with the [9]CPP-bipyridine catenane. Single-crystal X-ray structural analysis revealed that the [9]CPP-bipyridine catenane forms a tridentated complex with an Ag ion inside the CPP ring. This interaction significantly enhances the phosphorescence lifetime through improved intermolecular interactions.     

Photo- and protonation-induced changes in structures and physical properties of azo-conjugated metal complex systems

Novel photo- and proton-coupled behavior of azo-conjugated metal complexes is described. The trans-to-cis isomerization of azoferrocene proceeds not only by the photoexcitation of the π-π* transition band but also by photoexcitation of the MLCT (d-π* transition) band, by a protonation-deprotonation cycle (proton-coupled isomerization), and by an oxidation-reduction cycle (redox isomerization). A platinum tolylazophenylenedithiolato complex shows reversible trans-to-cis photoisomerization, protochromism, and novel proton-coupled cis-to-trans isomerization.