Metal- and ligand-directed one-pot syntheses,crystal structures,and properties of novel oxo-centered tetra- and hexametallic clusters

Starting from closely related metal-ligand combinations, completely different oligomeric metal clusters are synthesized. Whereas, picoline-tetrazolylamide HL(1) (1) and zinc or nickel acetate afforded [2x2] grids [M(4)(L(1))(8)] (2), slightly different N-(2-methylthiazole-5-yl)-thiazole-2-carboxamide HL(2) (5 a) and nickel acetate yielded the monometallic complex [Ni(L(2))(2)(OH(2))(2)] (6). In contrast, reaction of 5 a with zinc acetate produced the tetrametallic zinc cluster [Zn(4)O(L(2))(4)(OAc)(2)] (7). Even more surprising, when 3-methyl-substituted HL(3) (5 b) instead of 2-methyl-substituted HL(2) (5 a) was allowed to react under identical conditions with zinc acetate, the cluster [Zn(4)O(L(3))(4)Cl(2)] (8) crystallized from dichloromethane. Clusters 7 and 8 are isostructural. As for 7, in 8 two of the edges of the tetrahedron of zinc ions are doubly bridged, two are singly bridged, and the other two are nonbridged. On the other hand, when iron(II) acetate under aerobic conditions was allowed to react with 5 a, the unprecedented complex [[Fe(3)O(L(2))(2)(OAc)(4)](2)O] (9) was isolated. Cluster 9 is composed of two trimetallic, triangular mu(3)-O(2-)-centered [Fe(3)O(L(2))(2)(OAc)(4)](+) modules, linked by an almost linear mu(2)-O(2-) bridge. The M?ssbauer spectrum together with cyclic voltammetric and square-wave voltammetric measurements of 9 are reported, and 6-9 were characterized unequivocally by single-crystal X-ray structure analyses.     

Micromechanical Properties of Microstructured Elastomeric Hydrogels

Local, micromechanical environment is known to influence cellular function in heterogeneous hydrogels, and knowledge gained in micromechanics will facilitate the improved design of biomaterials for tissue regeneration. In this study, a system comprising microstructured resilin‐like polypeptide (RLP)–poly(ethylene glycol) (PEG) hydrogels is utilized. The micromechanical properties of RLP‐PEG hydrogels are evaluated with oscillatory shear rheometry, compression dynamic mechanic analysis, small‐strain microindentation, and large‐strain indentation and puncture over a range of different deformation length scales. The measured elastic moduli are consistent with volume averaging models, indicating that volume fraction, not domain size, plays a dominant role in determining the low strain mechanical response. Large‐strain indentation under a confocal microscope enables the visualization of the microstructured hydrogel micromechanical deformation, emphasizing the translation, rotation, and deformation of RLP‐rich domains. The fracture initiation energy results demonstrate that failure of the composite hydrogels is controlled by the RLP‐rich phase, and their independence with domain size suggested that failure initiation is controlled by multiple domains within the strained volume. This approach and findings provide new quantitative insight into the micromechanical response of soft hydrogel composites and highlight the opportunities in employing these methods to understand the physical origins of mechanical properties of soft synthetic and biological materials.     

An efficient solution for resolving iTRAQ and TMT channel cross‐talk

Isobaric tagging reagents such as isobaric tag for relative and absolute quantitation (iTRAQ) and tandem mass tag (TMT) typically have isotopic impurities that cause significant cross‐talk between channels. Here, we present an efficient solution to compensate for channel cross‐talk using linear algebra and find that it is between 20× and 120× faster than previous methods. We also find that the effects of channel cross‐talk are as important to manage as the effects of ratio compression because of precursor impurities, and we have released an open‐source tool to perform both types of calculations.     

Carnitine in Pregnancy

Summary. By the 12^th week of gestation, mean whole blood and plasma carnitine levels are already significantly (p<0.01) lower than those of controls, with a further significant (p<0.01) decrease up to parturition. Diminished carnitine levels may cause a downregulation of carnitine palmitoyltransferase1 (CPT1), both the liver isoform (CPT1A) and muscle isoform (CPT1B), carnitine palmitoyltransferase2 (CPT2), and carnitine acetyltransferase (CRAT) in white blood cells of pregnant women, as determined by real time PCR using the LightCyclerSYBR Green technology.L-Carnitine-L-tartrate supplementation of 2 g/d resulted in an up to 10-fold increase of the relative mRNA abundances of CPT1B, CPT2, and OCTN2 and a 5-fold increase of CPT1A, and CRAT.There is a relationship between the relative mRNA levels of CPT1A and CPT1B and the FFA plasma levels. The substitution of 2 g L-carnitine-L-tartrate/d resulted in significant (p<0.001) lower FFA levels compared to untreated controls and the groups substituted with 0.5 and 1 g L-carnitine/d although plasma carnitine levels were not significantly increased. The most substantial effect was the reduced portion of acylcarnitines on total carnitine in those women receiving 2 g L-carnitine-L-tartrate.Carnitine substitution resulted in an enhanced excretion of both, free carnitine and acylcarnitines, whereas acetylcarnitine accounts for 50–65% of total acylcarnitines.The results of the present study provide evidence that L-carnitine supplementation in pregnancy in sufficient doses avoids a striking increase of plasma FFAs, which are thought to be the main cause of insulin resistance and consequently gestational diabetes mellitus (GDM).     

Notizen zur Synthese sulfonierter Derivate von 5,6,7,8-Tetrahydro-1-naphthylamin und 5,6,7,8-Tetrahydro-2-naphthylamin

Notes on the Synthesis of Sulfonated Derivatives of 5,6,7,8-Tetrahydro-1-naphthylamine and 5,6,7,8-Tetrahydro-2-naphthylamine Sulfonation of 5,6,7,8-tetrahydro-1-naphthylamine ( 1 ) with sulfuric acid gave a mixture of 1-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 2 ), 4-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 13 ) and 4-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 3 ). The same reaction with 5,6,7,8-tetrahydro-2-naphthylamine ( 20 ) yielded 3-amino-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 21 ); formation of 2-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 16 ) or of 3-amino-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 24 ) was not observed. Treatment of 4-bromo-5,6,7,8-tetrahydro-1-naphthylamine ( 4 ) or of its 4-chloro analogue 5 with amidosulfuric acid gave 1-amino-4-bromo-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 9 ) and its 4-chloro analogue 10 , respectively, which were dehalogenated to 2 . Preparations of 13 and 24 were achieved by sulfonation of 5-nitro-1,2,3,4-tetrahydronaphthalene ( 14 ) and 6-nitro-1,2,3,4-tetrahydronaphthalene ( 22 ) to 4-nitro-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 15 ) and 3-nitro-5,6,7,8-tetrahydronaphthalene-1-sulfonic acid ( 23 ), respectively, followed by Béchamp reductions. The sulfonic acid 13 was also obtained by hydrogenolysis of 4-amino-1-bromo-5,6,7,8-tetrahydronaphthalene-2-sulfonic acid ( 11 ) or of its 1-chloro analogue 12 ; compounds 11 and 12 were synthesized from N-(4-bromo-5,6,7,8-tetrahydro-1-naphthyl)acetamide ( 7 ) and from its 4-chloro analogue 8 , respectively, by sulfonation with oleum and subsequent hydrolysis. By ‘baking’ the hydrogensulfate salt of 1 or 20 compounds 3 and 21 were obtained, respectively. Synthesis of 16 was achieved by sulfur dioxide treatment of the diazonium chloride derived from 2-nitro-5,6,7,8-tetrahydro-1-naphthylamine ( 17 ) giving 2-nitro-5,6,7,8-tetrahydronaphthalene-1-sulfonyl chloride ( 18 ), followed by hydrolysis of 18 to the corresponding sulfonic acid 19 and final reduction.     

Comparative properties of cellulose nano-crystals from native and mercerized cotton fibers

Stable aqueous suspensions of cellulose nano-crystals (CNCs) were fabricated from both native and mercerized cotton fibers by sulfuric acid hydrolysis, followed by high-pressure homogenization. Fourier transform infrared spectrometry and wide-angle X-ray diffraction data showed that the fibers had been transformed from cellulose I (native) to cellulose II (mercerized) crystal structure, and these polymorphs were retained in the nanocrystals, giving CNC-I and CNC-II. Transmission electron microscopy showed rod-like crystal morphology for both types of crystals under the given processing conditions with CNC-II having similar width but reduced length. Freeze-dried agglomerates of CNC-II had a much higher bulk density than that of CNC-I. Thermo-gravimetric analysis showed that CNC-II had better thermal stability. The storage moduli of CNC-II suspensions at all temperatures were substantially larger than those of CNC-I suspensions at the same concentration level. CNC-II suspensions and gels were more stable in response to temperature increases. Films of CNC and Poly(ethylene oxide) were tested. Both CNC-I/PEO and CNC-II/PEO composites showed increased tensile strength and elongation at break compared to pure PEO. However, composites with CNC-II had higher strength and elongation than composites with CNC-I.     

Collective dynamics of sub- and supercritical methanol by inelastic X-ray scattering

Inelastic X-ray scattering experiments have been performed on methanol as a function of density from ambient to the supercritical state. Positive dispersion of the sound velocity, as compared to the hydrodynamic values, is 50% in the ambient condition and decreases to zero at 0.50 g cm⁻³ over the momentum transfer Q = 1–10 nm⁻¹ with lowering density; however, it increases again with a further decrease in density down to 0.20 g cm⁻³in the supercritical state only in the Q-range above 5 nm⁻¹. These results have been interpreted as the formation of small oligomers in the low-density supercritical methanol.     

Functionalization of bolalipid nanofibers by silicification and subsequent one-dimensional fixation of gold nanoparticles

In the present work, we describe the successful stabilization of bolalipid nanofibers by sol-gel condensation (silicification) of tetraethoxysilane (TEOS) or 3-mercaptopropyltriethoxysilane (MP-TEOS), respectively, onto the nanofibers. The conditions for an effective and reproducible silicification reaction were determined, and the silicification process was pursued by transmission electron microscopy (TEM). The resulting bolalipid-silica composite nanofibers were characterized by means of differential scanning calorimetry (DSC), TEM, (13)C, and (31)P NMR spectroscopy. Finally, the novel silicified bolalipid nanofibers were used as templates for the fixation of 5 and 2 nm AuNPs, respectively, resulting in one of the rare examples of one-dimensional AuNP arrangements in aqueous suspension.     

Synthesis,Structure, and Optical Properties of Terminally Sulfur‐Functionalized Core‐Substituted Naphthalene‐Bisimide Dyes

The synthesis, characterization, and optical properties of a series of new 2,6‐disubstituted naphthalene‐bisimide dyes as molecular rods comprising terminal AcS groups is reported. The first series of dyes ( 1 – 3 ), comprising phenylhetero (Ph‐X) core substituents, cover a broad range of the VIS spectrum, ranging from yellow ( 2 ) over red ( 3 ) to blue ( 1 ). The second series of dyes contains benzylhetero (Bn‐X) core substituents ( 4 – 7 ). For the same heteroatom connecting the substituent to the naphthalene core, both series were found to display comparable colors. For the second series, the colors were blue ( 4 ), red ( 5 ), and violet ( 6, 7 ). The Ph‐X‐substituted dyes 1 – 3 are nonfluorescent, in contrast to the Bn‐X‐substituted compounds 4 – 7 . This rich variety of optical features that can be adjusted by rather small alterations of the core substituents makes these structurally very comparable molecular rods ideal candidates for optically triggered molecular‐transport investigations. Also, thanks to the terminal AcS groups, these compounds can be placed between nobel‐metal electrodes for optically triggered transport experiments.