Modification of Polyvinyltrimethylsilane in Direct-Current Discharge

High Energy Chemistry - The modification of polyvinyltrimethylsilane under treatment by direct-current discharge at a reduced pressure has been investigated. Polymer films were placed at the anode...     

The Order of Convergence of Difference Schemes for Fractional Equations

In this paper, we continue our research on convergence of difference schemes for fractional differential equations. Using implicit difference scheme and explicit difference scheme, we have a deal with the full discretization of the solutions of fractional differential equations in time variables and get the order of convergence.     

Some Properties of Essential Spectra of a Positive Operator

Let E be a Banach lattice, T be a bounded operator on E. The Weyl essential spectrum σ_ew(T) of the operator T is a set , where is a set of all compact operators on E. In particular for a positive operator T next subsets of the spectrum

Chiroptical study and absolute configuration of securinine oxidation products

Time-dependant density functional theory–electronic circular dichroism spectra prediction was carried out to study the absolute configuration of phyllanthidine-type derivatives 5 and 6, derived from securinine (1) and its enantiomer virosecurinine (2), respectively. This method demonstrated to be very reliable in this alkaloid series. Thus, 5 and 6 shared the same stereochemistry as their parent precursors, confirming the retentive nature of the oxidation sequence. In addition, this study highlighted the key role of the methylene bridge (BC ring) in the chiroptical activity of these compounds. These results fully clarified the stereochemical relationships between the phyllanthidine and the securinine subgroups.     

Photochemical Strain-Release-Driven Cyclobutylation of C(sp3)-Centered Radicals

A new photoredox-catalyzed decarboxylative radical addition approach to functionalized cyclobutanes is described. The reaction involves an unprecedented formal Giese-type addition of C(sp³)-centered radicals to highly strained bicyclo[1.1.0]butanes. The mild photoredox conditions, which make use of a readily available and bench stable phenyl sulfonyl bicyclo[1.1.0]butane, proved to be amenable to a diverse range of α-amino and α-oxy carboxylic acids, providing a concise route to 1,3-disubstituted cyclobutanes. Furthermore, kinetic studies and DFT calculations unveiled mechanistic details on bicyclo[1.1.0]butane reactivity relative to the corresponding olefin system.     

Novel Cysteine Tags for the Sequencing of Non-Tryptic Disulfide Peptides of Anurans: ESI-MS Study of Fragmentation Efficiency

Mass spectrometry faces considerable difficulties in de novo sequencing of long non-tryptic peptides with S–S bonds. Long disulfide-containing peptides brevinins 1E and 2Ec from frog Rana ridibunda were reduced and alkylated with nine novel and three known derivatizing agents. Eight of the novel reagents are maleimide derivatives. Modified samples were subjected to MS/MS studies on FT-ICR and Orbitrap mass spectrometers using CAD/HCD or ECD/ETD techniques. Procedures, fragmentation patterns, and sequence coverage for two peptides modified with 12 tags are described. ECD/ETD and CAD fragmentation revealed complementary sequence information. Higher-energy collisionally activated dissociation (HCD) sufficiently enhanced y-ions formation for brevinin 1E, but not for brevinin 2Ec. Some novel tags [N-benzylmaleimide, N-(2,6-dimethylphenyl)maleimide] along with known N-phenylmaleimide and iodoacetic acid showed high total sequence coverage taking into account combined ETD and HCD fragmentation. Moreover, modification of long (34 residues) brevinin 2Ec with N-benzylmaleimide or N-(2,6-dimethylphenyl)maleimide yielded high sequence coverage and full C-terminal sequence determination with ECD alone.     

The irreducibility in ordered Banach algebras

Let A be an ordered Banach algebra. Put

A new method for the synthesis of aldehyde-spacered oligosaccharides by oxidation of l-tartaric acid derivative

Russian Chemical Bulletin - N-(N-[(2R,3R)-2,3-Dihydroxy-3-carboxypropionyl]glycyl)-β-d-glycopyranosylamines and N-[N-(formylcarbonyl)glycyl]-β-d-glycopyranosylamines, derivatives of...