Power absorbed by a subsystem in the response theory

A macroscopic system which consists of a set of interacting subsystems in an external field is considered. A convenient formula is derived for the mean energy Q_j absorbed per unit time by a subsystem. The expression obtained for Q_j takes into account that in general the Hamiltonian H of such a system does not coincide with the sum of the Hamiltonians of the subsystems H_j; Q_j appears to be the same for various possible definitions of H_j's.     

Magnetic polaron in a ferromagnetic semiconductor. A new self-consistent finite temperature solution

A complete self-consistent finite temperature theory of magnetic polaron states with damping in a ferromagnetic semiconductor is developed using the irreducible Green function (IGF) method.     

Synthesis of trans-Non-4-EN-2-Ynoic Acid

The synthesis of the title compound has been achieved from 1 -methoxybutenyne in 77% yield in three steps. A reaction mechanism is given to explain exclusive formation of 4,5-trans-configuration.     

13C nuclear magnetic resonance spectroscopy to determine olive oil grades

¹³C nuclear magnetic resonance spectroscopy was used in a first attempt to differentiate olive oil samples by grades. High resolution ¹³C NMR Distortionless Enhancement by Polarization Transfer (DEPT) spectra of 137 olive oil samples from the four grades, extra virgin olive oils, olive oils, olive pomace oils and lampante olive oils, were measured. The data relative to the resonance intensities (variables) of the unsaturated carbons of oleate (C-9 and C-10) and linoleate (L-9, L-10 and L-12) chains attached at the 1,3- and 2-positions of triacylglycerols were analyzed by linear discriminant analysis. The 1,3- and 2- carbons of the glycerol moiety of triacylglycerols along with the C-2, C-16 and C-18 resonance intensities of saturated, oleate and linoleate chains were also analyzed by linear discriminant analysis. The three discriminanting functions, which were calculated by using a stepwise variable selection algorithm, classified in the true group by cross-validation procedure, respectively, 76.9, 70.0, 94.4 and 100% of the extra virgin, olive oil, olive pomace oil and lampante olive oil grades.     

Determination of the 1,3- and 2-positional distribution of fatty acids in olive oil triacylglycerols by 13C nuclear magnetic resonance spectroscopy

Linear models were selected from a large data set acquired for Italian olive oil samples by quantitative 13C nuclear magnetic resonance (NMR) spectroscopy with distortionless enhancement by polarization transfer (DEPT). The models were used to determine the composition of the 2 fatty acid pools esterifying the 1,3- and 2-positions of triacylglycerols. The linear models selected proved that the 1,3- and 2-distribution of saturated, oleate, and linoleate chains in olive oil triacylglycerols deviated from the random distribution pattern to an extent that depended on the concentration of the fatty acid in the whole triacylglycerol. To calculate the fatty acid composition of the 1,3- and 2-positions of olive oil triacylglycerols, the equations of the selected linear models were applied to the fatty acid percentages determined by gas chromatography. These data were compared with the values predicted by the computer method (used to determine the theoretical amounts of triacylglycerols), which is based on the 1,3-random-2-random theory of the fatty acid distribution in triacylglycerols. The biggest differences were found in the linoleate chain, which is the chain that deviated the most from a random distribution pattern. The results confirmed that the 1,3-random-2-random distribution theory provides an approximate method for determining the structure of triacylglycerols; however, the linear models calculated by the direct method that applies 13C NMR spectroscopy represent a more precise measurement of the composition of the 2 fatty acid pools esterifying the 1,3- and 2-positions of triacylglycerols.     

An assembly concept for the consecutive introduction of unsymmetrical disulfide bonds: synthesis of a releasable multidrug conjugate of folic acid

We describe the development of methodology which allows for the introduction of a second disulfide bond into a molecular framework with a pre-existing disulfide linker system. Compounds which contain an S-9-fluorenylmethyl-protected thiol and an additional disulfide linkage are deprotected in situ and trapped with an activated thiophile. This methodology allowed for the synthesis of the first molecule possessing two different biologically active agents covalently attached to a folate receptor targeting ligand unit via two disulfide-based release systems.     

C-2 Epimerization of N-Acetylglucosamine in an Oligosaccharide Derived From Heparan Sulfate

Abstract

The isolation of a heparan sulfate derived tetrasaccharide containing N-acetylmannosamine is described. The N-acetylmannosamine residue at the reducing terminus of heparin lyase derived tetrasaccharide is formed by base catalyzed C-2 epimerization of N-acetylglucosamine. This C-2 epimerization takes place under very mild conditions suggesting that this residue may be formed in small amounts under physiologic conditions.