Abstract A study of the reaction of the elemental sulfur with 2-picoline is reported. The process was carried out at the boiling point of the 2-picoline under argon. After removing unreacted solids, the reaction products were identified by means of LC. GC and GC-MS. The following products have been identified by mass spectrometry: 1,2-di/2-pyridyl/-ethane. 1,2-di/2-pyridyl/-ethene. 2-methyl-x-[/2-pyridyl/methyl]pyridines, 2-mercapto-methyl-[x/2-pyridyl/methyl]-pyridines, l-mercapto-1,2-di/2-pyridyl/-ethane, 5,6-di/2-pyridyl/-5H-cyclopenta-[b]pyridine, 5,6-di/2-pyridyl/-7H-cyclopenta[b]pyridine, 1,2,3-tri/2-pyridyl/-propane. 1,2-di/2-pyridyl/-1-[x-/2-methyl/-pyridyl]-ethane, 5,6-di/2-pyridyl/-7-[/2-pyridyl/methyl]-7H-cyclopenta[b]pyridine, 5,6-di/2-pyridyl/-5-[/2-pyridyl/-methyl]-5H-cyclopenta-[b]pyridine. Di{7-[5,6-di/2-pyridyl/-7H-cyclopenta[b]pyridyl]} sulfide and di(7-[5,6-di/2-pyridyl/-7H-cyclopentalblpyridyl]} disulfide. 相似文献
We have reported previously that low-dose UVB radiation (UVBR, 50-200 J/m2) perturbs the antigen-presenting cell (APC) function of murine Langerhans cells (LC) by interfering with yet undefined costimulatory signals. In this study, we investigated (1) the effects of UVBR on the expression of the costimulatory molecules B7-1 and B7-2 on murine LC, (2) the functional consequences of defective B7-1 and B7-2 signalling on primary and secondary T-cell responses induced by LC and (3) the mechanism by which UVBR interferes with B7-1 and B7-2 expression. Ultraviolet-B radiation dose-dependently inhibited the culture-induced upregulation of B7-1 and B7-2 on LC from both UVB-susceptible (UVBs, C57BL/6) and UVB-resistant (UVBR, Balb/c) mice and abrogated their capacity to stimulate proliferation of naive alloreactive T cells and of the KLH (keyhole limpet hemocyanin)-specific T helper (Th)1 clone HDK-1. The UVBR-induced suppression of B7-1 and B7-2 on LC and their perturbed APC function were related, because exogenous triggering of the B7/CD28 pathway with a stimulatory monoclonal antibody (mAb) for CD28 to UVB-irradiated LC partially restored T-cell proliferation. Such reconstitution was not observed when the mAb was added to killed LC, indicating that the UVBR-induced suppression of APC function was not due to lethal effects on LC. Conditioned supernatants from UVB-irradiated epidermal cells did not inhibit the functional upregulation of B7-1 and B7-2, suggesting that UVBR inhibits B7-1 and B7-2 upregulation by acting directly on LC and not by altering LC costimulatory function via release of soluble immunosuppressive factors. In conclusion, UVBR distorts the functional expression of B7-1 and B7-2 on LC from both UVBs and UVBR mice, thereby contributing to the failure of UVB-irradiated LC to stimulate resting alloreactive T cells or KLH-specific Thl cells. 相似文献
By a flexible three‐component synthesis, alkoxy‐substituted enamides are easily available from lithiated alkoxyallenes, nitriles and carboxylic acids (see scheme). The treatment of these versatile intermediates with trifluoroacetic acid provided 5‐acetyloxazoles in moderate to good yields. Different substituents are possible at C‐2 and C‐5 and the 5‐acetyl group is a suitable handle for further synthetic transformations.
In close quarters : When confined in a metal–organic framework, magnesium borohydride reacts with arenes by a hydroboration pathway (see scheme), in contrast to its reactivity under analogous homogeneous solution‐phase conditions. Framework‐imposed organization of the reactive groups is required, which is achieved by a combination of the metal coordination and two hydrogen bonds.
Here we report for the first time on phosphorylation of cotton cellulose using baker's yeast hexokinase and phosphoryl donor adenosine‐5′‐triphosphate. An enzymatic assay was adopted for determination of the degree of phosphorylation of cellulose. This functional modification of cellulose resulted in improved colorability and flame resistance.
Phosphorylated glucopyranose unit of cellulose. 相似文献
Minichromosome maintenance proteins (Mcm) 2, 3, 4, 5, 6 and 7 are related by sequence and form a variety of complexes that
unwind DNA, including Mcm4/6/7. A Mcm4/6/7 trimer forms one half of the Mcm2-7 hexameric ring and can be thought of as the
catalytic core of Mcm2-7, the replicative helicase in eukaryotic cells. Oligomeric analysis of Mcm4/6/7 suggests that it forms
a hexamer containing two Mcm4/6/7 trimers, however, under certain conditions trimeric Mcm4/6/7 has also been observed. The
functional significance of the different Mcm4/6/7 oligomeric states has not been assessed. The results of such an assessment
would have implications for studies of both Mcm4/6/7 and Mcm2-7. 相似文献
Supramolecular protein polymers consisting of cytochrome b562 monomers with heme covalently attached to the protein surface are presented by T. Hayashi and co‐workers in their Communication on page 1271 ff. Not only one‐dimensional hemoprotein fibers with submicrometer lengths have been prepared, but when a heme triad was added as a pivot molecule, two‐dimensional protein assembly networks resulted, which cover over 100 square micrometers.
In vivo microdialysis in combination with liquid chromatography/electrospray time-of-flight mass spectrometry was used to study the processing of LVV-hemorphin-7, an endogenous decapeptide with opioid activity, in rat brain and blood. A microdialysis probe (flow rate 0.4 microL/min) was used to both introduce LVV-hemorphin-7 into the striatum of the brain (1.0 pmol/microL) or the venous blood (10 pmol/microL) and to collect the metabolic products. LVV-hemorphin-7 was extracellularly metabolized in the striatum to form C-terminal fragments 2-10, 3-10, 4-10, 5-10, 6-10, 7-10, and N-terminal fragments 1-9, 1-8, 1-6. Infusion of the aminopeptidase inhibitor amastatin (1.0 pmol/microL) into the striatum, together with LVV-hemorphin-7, decreased the processing of LVV-hemorphin-7 to form C-terminal fragments 2-10, 3-10, 4-10, but increased the relative levels of fragment 5-10 and N-terminal fragments 1-9, 1-8 and 1-6. The major metabolic product from LVV-hemorphin-7 in the striatum was the C-terminal fragment 5-10, which may be processed by an endopeptidase not sensitive to amastatin. The LVV-hemorphin-7 infusion to the venous blood produced the C-terminal fragments 2-10, 3-10, 4-10, and 5-10, N-terminal fragment 1-9, and internal fragments 4-7 and 4-9. It is concluded that the combination of microdialysis and electrospray mass spectrometry provides a powerful tool for the study of extracellular metabolism and kinetic processes of complex reaction systems in vivo. 相似文献
Weaving an intricate web : A stereoselective synthesis of (?)‐agelastatin A has been developed, which requires 11 steps from commercially available starting material. The application of a Rh‐catalyzed intramolecular olefin aziridination reaction and the subsequent manipulation of the resulting tricyclic intermediate (see scheme) punctuate this study.