Ternäre Lithium-Selten-Erd-Nitrate mit einsamen Nitrationen: Li3[M(NO3)5](NO3) (M = Gd?Lu,Y). Die Kristallstruktur von Li3Er(NO3)6

Ternary Lithium Rare Earth Nitrates with Lonesome Nitrate Ions: Li₃[M(NO₃)₅](NO₃) (M = Gd? Lu, Y). The Crystal Structure of Li₃Er(NO₃)₆ Single crystals of the ternary nitrate Li₃Er(NO₃)₆ are obtained from a solution of “Er(NO₃)₃” in the melt of LiNO₃. In Li₃Er(NO₃)₆ (monoclinic, P2₁/n, Z = 4; a = 776.0(1); b = 748.86(8); c = 2 396(1) pm; β = 90.76(3)°; R1 = 0.0490; wR2 = 0.0792), Er³⁺ is surrounded by five bidentate nitrate ligands yielding the anionic units [Er(NO₃)₅]^2?. These are arranged in the direction of the 2₁ screw axis. Two lonesome NO₃^? ions are in the middle of such a “helix” and are connected by Li⁺ with the anions [Er(NO₃)₅]^2?. The helices are moved against each other by about half of the lattice constant a and are connected by further Li⁺ ions.     

Palladium-induced cyclizations for the synthesis of cis-2,5-disubstituted-3-methylenetetrahydrofurans: studies of the C7-C22 core of amphidinolide K

[formula: see text] The diastereoselective synthesis of cis-2,5-disubstituted-3-methylenetetrahydrofurans via Pd(0)-catalyzed cyclization of 2-methylene-1,4-diols is described. Investigations into the scope of the reaction and its application toward the synthesis of amphidinolide K is reported.     

Synthesis and dispersion of Ni(OH)2 platelet-like nanoparticles in water

Synthesis of nanometric platelet-like Ni(OH)2 particles is described. The role of several experimental parameters on the particle size is investigated. A colloidal dispersion of particles is produced by adsorbing ionizable organic ligands (trisodium citrate) on the particle surface. The stability of this colloidal dispersion and the particle charge density are determined for different citrate ions concentrations.     

Carbon monoxide induced decomposition of the active site [Ni-4Fe-5S] cluster of CO dehydrogenase

During the past two years, crystal structures of Cu- and Mo-containing carbon monoxide dehydrogenases (CODHs) and Ni- and Fe-containing CODHs have been reported. The active site of CODHs from anaerobic bacteria (cluster C) is composed of Ni, Fe, and S for which crystallographic studies of the enzymes from Carboxydothermus hydrogenoformans, Rhodospirillum rubrum, and Moorella thermoaceticarevealed structural similarities in the overall protein fold but showed substantial differences in the essential Ni coordination environment. The [Ni-4Fe-5S] cluster C in the fully catalytically competent dithionite-reduced CODH II from C. hydrogenoformans (CODHII(Ch)) at 1.6 A resolution contains a characteristic mu(2)-sulfido ligand between Ni and Fe1, resulting in a square-planar ligand arrangement with four S-ligands at the Ni ion. In contrast, the [Ni-4Fe-4S] clusters C in CO-treated CODH from R. rubrum resolved at 2.8 A and in CO-treated acetyl-CoA synthase/CODH complex from M. thermoacetica at 2.2 and 1.9 A resolution, respectively, do not contain the mu(2)-sulfido ligand between Ni and Fe1 and display dissimilar geometries at the Ni ion. The [Ni-4Fe-4S] cluster is composed of a cubane [Ni-3Fe-4S] cluster linked to a mononuclear Fe site. The described coordination geometries of the Ni ion in the [Ni-4Fe-4S] cluster of R. rubrum and M. thermoacetica deviate from the square-planar ligand geometry in the [Ni-4Fe-5S] cluster C of CODHII(Ch). In addition, the latter was converted into a [Ni-4Fe-4S] cluster under specific conditions. The objective of this study was to elucidate the relationship between the structure of cluster C in CODHII(Ch) and the functionality of the protein. We have determined the CO oxidation activity of CODHII(Ch) under different conditions of crystallization, prepared crystals of the enzyme in the presence of dithiothreitol or dithionite as reducing agents under an atmosphere of N(2) or CO, and solved the corresponding structures at 1.1 to 1.6 A resolutions. Fully active CODHII(Ch) obtained after incubation of the enzyme with dithionite under N(2) revealed the [Ni-4Fe-5S] cluster. Short treatment of the enzyme with CO in the presence of dithiothreitol resulted in a catalytically competent CODHII(Ch) with a CO-reduced [Ni-4Fe-5S] cluster, but a prolonged treatment with CO caused the loss of CO-oxidizing activity and revealed a [Ni-4Fe-4S] cluster, which did not contain a mu(2)-S. These data suggest that the [Ni-4Fe-4S] cluster of CODHII(Ch) is an inactivated decomposition product originating from the [Ni-4Fe-5S] cluster.     

Automated multi-attribute method sample preparation using high-throughput buffer exchange tips

Rationale

The multi-attribute method (MAM) has become a valuable mass spectrometry (MS)-based tool that can identify and quantify the site-specific product attributes and purity information for biotherapeutics such as monoclonal antibodies (mAbs) and fusion molecules in recent years. As we expand the use of the MAM at various stages of drug development, it is critical to enhance the sample preparation throughput without additional chemical modifications and variability.

Methods

In this study, a fully automated MAM sample preparation protocol is presented, where rapid desalting in less than 15 minutes is achieved using miniaturized size-exclusion chromatography columns in pipette tips on an automated liquid handler. The peptide samples were analyzed using an electrospray ionization (ESI) orbitrap mass spectrometer coupled to an ultra-high-performance liquid chromatography (UHPLC) system with a dual column switching system.

Results

No significant change was observed in product attributes and their quantities compared with manual, low-artifact sample preparation. The sample recovery using the buffer exchange tips was greatly enhanced over the manual spin cartridges while still demonstrating excellent reproducibility for a wide variety of starting sample concentrations. Unlike a plate desalting system, the individual columns provide flexibility in the number of samples prepared at a time and sample locations within plates.

Conclusions

This automated protocol enables the preparation of up to 96 samples with less “at-bench” time than the manual preparation of a smaller batch of samples, thereby greatly facilitating support of process development and the use of the MAM in quality control.

     

Synthesis,Crystal Structure,and Spectral Properties of a Cobalt(II) Complex with N‐Salicylidene‐p‐Toluidine

The complex Co(C₁₄H₁₃NO)₂Cl₂ with the protonated N‐salicylidene‐p‐toluidine ligand was synthesized from an ethanolic solution of CoCl₂·6H₂O and N‐salicylidene‐p‐toluidine. The crystal structure was determined from X‐ray single crystal data (monoclinic, space group Cc, a = 1496.2(3) pm, b = 1257.4(4) pm, c = 1544.6(3) pm, β = 115.01(1)°, Z = 4). Co²⁺ adopts a distorted tetrahedral geometry. The UV‐Vis and IR spectra of the complex are discussed.     

稀土高氯酸盐-谷氨酸配合物[Pr2(L-α-Glu)2(ClO4)(H2O)7](ClO4)3•4H2O的低温热容和热化学研究

合成了一种稀土高氯酸盐-谷氨酸配合物. 经TG/DTG、化学和元素分析、FTIR及与相关文献对比, 确定其组成为[Pr₂(L-α-Glu)₂(ClO₄)(H₂O)₇](ClO₄)₃•4H₂O, 纯度为99.0%以上. 利用显微熔点仪分析发现其没有熔点. 在78～370 K温区, 用精密绝热量热仪测量其低温热容, 在285～306 K温区发现一明显吸热峰, 归结为固-固相变过程. 通过相变温区三次重复热容测量, 得到相变温度T_tr、相变焓Δ_trH_m和相变熵Δ_trS_m分别为(297.158±0.280) K, (12.338±0.016) kJ•mol^－1和(41.520±0.156) J•K^－1•mol^－1. 用最小二乘法将非相变温区的热容对温度进行拟合, 得到了热容随温度变化的两个多项式方程. 用此方程进行数值积分, 得到每隔5 K的舒平热容值和相对于273.15 K的热力学函数值. 根据TG/DTG结果, 推测了该配合物的热分解机理. 依据Hess定律, 选择1 mol•dm^－3盐酸为量热溶剂, 利用等温环境溶解-反应量热计, 测定了该配合物的标准摩尔生成焓为: Δ_fH_m⁰＝－(7223.1±2.4) kJ•mol^－1.     

Photometrische Bestimmung von Antimon mit Methylfluoron

Zusammenfassung Es wird eine Arbeitsvorschrift zur photometrischen Bestimmung kleiner Mengen Antimon mit Methylfluoron beschrieben. Die günstigsten Arbeitsbedingungen und die Störung durch Fremdionen werden untersucht. Das Extinktionsmaximum liegt bei 530 nm. Die photometrische Bestimmung wird bei 495 nm durchgeführt. Das Beersche Gesetz ist im Bereich von 0,2– 4 g Sb/ml erfüllt, die Bestimmungsgrenze liegt bei 0,21 g Sb/ml · cm. Der Zeitbedarf einer Einzelbestimmung beträgt 15–20 min.Für die sorgfältige Durchführung der zahlreichen Versuche sprechen wir Herrn H. Siffrin unseren Dank aus.     

A multitechnique surface analytical study of a segmented block copolymer poly(ether-urethane) modified through an H2O radio frequency glow discharge

Recent work in our laboratories has fully characterized the surface region of a segmented poly(ether-urethane) (PEU) extending from the air/polymer interfacial region through bulk depths in the micron range. This characterization utilized energy and angle dependent Electron Spectroscopy for Chemical Analysis (ESCA), Attenuated Total Reflectance–Fourier Transform Infrared Spectroscopy (ATR–FTIR), and Comprehensive Wettability Profiling (contact angle using a homologous series of liquids) as defined by Zisman. In this study this same multi-analytical-technique approach is used to elucidate changes in these PEU surfaces induced through an H₂O Radio Frequency Glow Discharge (RFGD) plasma. This investigation reports both qualitative and quantitative changes due to the modification treatments as well as the permanency of the changes effected on these surfaces through the plasma treatment. From our analyses, the amount of surface residing polyurethane (hard segment) is observed to increase due to a proposed plasma etching mechanism. Further, the addition of oxygen containing functionality is detected at the modified surfaces unique with respect to the unmodified PEU. These surface modifications which show large increases in wettability, are finally observed to be semi-permanent over a time period of 6 months.