Combinatorial diversity of fission yeast SCF ubiquitin ligases by homo- and heterooligomeric assemblies of the F-box proteins Pop1p and Pop2p

Background  

SCF ubiquitin ligases share the core subunits cullin 1, SKP1, and HRT1/RBX1/ROC1, which associate with different F-box proteins. F-box proteins bind substrates following their phosphorylation upon stimulation of various signaling pathways. Ubiquitin-mediated destruction of the fission yeast cyclin-dependent kinase inhibitor Rum1p depends on two heterooligomerizing F-box proteins, Pop1p and Pop2p. Both proteins interact with the cullin Pcu1p when overexpressed, but it is unknown whether this reflects their co-assembly into bona fide SCF complexes.     

A New Synthetic Route to Unsymmetrical 1,2-Bis(phosphanyl)ethanes and 1,2-Arsanyl(phosphanyl)ethanes with and without a Stereogenic Center

A one-pot reaction affords unsymmetrical 1,2-bis(phosphanyl)ethanes 2 and 1,2-arsanyl(phosphanyl)ethanes 3 from the cyclic sulfate 1 in high yield. Similarly, chiral 1,2-bis(phosphanyl)ethanes and 1,3-bis(phosphanyl)propanes could be obtained in enantiomerically pure form. R, R'=alkyl, phenyl.     

Stereochemische untersuchungen an C-10-disubstituierten C-9-hydroxyphäophorbiden der a-reihe

The diastereomeric 9-hydroxy pheophorbides 3a, b-1, 2 and 4a, b-1, 2 were prepared by reduction of the 10-alkoxy pheophorbides 1a, b and 2a, b with NaBH₄. Their absolute configuration at C-10 was determined by NMR- and ORD/CD-measurements as well as chemical correlation, the configuration at C-9 by IR- and mainly NMR-spectroscopy. For this purpose, the NMR-spectra of the 9-hydroxy pheophorbides 3a, b-1, 2 had completely to be assigned with the aid of the selectively deuterated alcohols 5a, b-1, 2. The configuration at C-10 is stable under the conditions of the alkaline reduction while C-9 partially epimerizes. The acidic alcoholysis of 3a, b-1, 2, however, proceeds by equilibration at C-10 and almost complete retention at C-9. The H-bonds between the 9-OH group and the C-10 substituents (-COOCH₃, -OCH₃ were investigated by NMR and IR spectroscopy.     

Molecular distillation

Molecular distillation was studied for the separation of tocopherols from soya sludge, both experimentally and by simulation, under different operating conditions, with good agreement. Evaporator temperatures varied from 100°C to 160°C and feed flow rates ranged from 0.1 to 0.8 kg/h. The process pressure was maintained at 10⁻⁶ bar, the feed temperature at 50°C, the condenser temperature at 60°C, and the stirring at 350 rpm. For each process condition, samples of both streams (distillate and residue) were collected and stored at −18°C before tocopherols analyses. Owing to the differences between molecular weights and vapor pressures of free fatty acids and tocopherols, tocopherols preferentially remained in the residue at evaporator temperatures of 100°C and 120°C, whereas for higher temperatures (140°C and 160°C) and lower feed flow rate, tocopherols tended to migrate to the distillate stream.     

Beiträge zur Chemie von Phosphorverbindungen mit Adamantanstruktur. XI. Über Darstellung und Eigenschaften von Phosphoroxidsulfiden der allgemeinen Formel P4O10−nSn (n = 2−9)

Contributions to the Chemistry of Phosphorus Compounds with Adamantane-like Structure. XI. Preparation and Properties of Phosphorus Oxide Sulfides of the General Formula P₄S_10?n S_n (n = 2?9) The reaction of P₄O₁₀ with P₄S₁₀ yields a mixture of phosphorus oxide sulfides of the general formula P₄O_10?nS_n. Depending on the molar ratio P₄O₁₀: P₄S₁₀ in the starting product different amounts of the individual phosphorus oxide sulfides occuring in this reorganization product are formed. Besides the well-known P₄O₆S₄ the compounds P₄O₇S₃, P₄O₅S₅, P₄O₄S₆, P₄O₃S₇, P₄O₂S₈, and P₄OS₉ occuring for the first time were obtained by fractional distillation or crystallization. The compound P₄O₈S₂ was identified by N.M.R. spectroscopy.     

Analysis of post-translational modification and characterization of the domain structure of dynamin A from Dictyostelium discoideum

The post-translational modifications of the 96 kDa protein dynamin A from Dictyostelium discoideum were analyzed using Q-TOF mass spectrometry. The accurate molecular mass of the intact protein revealed a covalent modification causing an additional mass of 42 Da. The modification could be identified as N-terminal acetylation by tandem mass spectrometry. Extracted ion chromatograms for the a(1) and b(1) ion of the tryptic T1 peptide were used to detect the acetylated peptide within 54 nanoelectrospray ionization tandem mass spectra. Owing to the accurate molecular mass of the intact protein, additional covalent modifications could be excluded. In addition to the covalent modification, the domain structure of dynamin A was determined by applying a combination of limited proteolysis, sodium dodecylsulfate polyacrylamide gel electrophoresis, automated tandem mass spectrometry and protein database searching.     

A π-acceptor series for phosphines from51V N.M.R. data on [η5-CpV(CO)3L] complexes

Summary Qualitative molecular orbital considerations of the complexes [⁵-CPV(CO)₃ L] (L = substituted phosphane, SbPh₃, AsPh₃, CN^–) suggest that s' V chemical shift parameters () obtained for these compounds should correlate with the -acceptor abilities of L. Based on observed r-values, the ligands are arranged in sequence of their -acceptor ability, which lies in the order P(OR)₃ > CN^– > PR'₃3 SbPh₃ PPhF₂ > P(i-Bu)₃ P(NR ₂ )₃ > PPh₃ > AsPh₃ Nuclear spin-spin coupling constants J (⁵¹V-³¹ P), line widths H and i.r. data in the (CO) region are also presented.P(OR)₃ = P(OEt)₃, 4-Ethyl-l-phospha-2,6,7-trioxabicyclo[2.2.2]-octane; R = Me, n-Pr; R = Me, Et.