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11.
S -nitrosothiols have many biological activities and may act as nitric oxide (NO) carriers and donors, prolonging NO half-life in vivo. In spite of their great potential as therapeutic agents, most S -nitrosothiols are too unstable to isolate. We have shown that the S -nitroso adduct of N -acetylcysteine (SNAC) can be synthesized directly in aqueous and polyethylene glycol (PEG) 400 matrix by using a reactive gaseous (NO/O2 ) mixture. Spectral monitoring of the S–N bond cleavage showed that SNAC, synthesized by this method, is relatively stable in nonbuf-fered aqueous solution at 25°C in the dark and that its stability is greatly increased in PEG matrix, resulting in a 28-fold decrease in its initial rate of thermal decomposition. Irradiation with UV light (λ= 333 nm) accelerated the rate of decomposition of SNAC to NO in both matrices, indicating that SNAC may find use for the photogeneration of NO. The quantum yield for SNAC decomposition decreased from 0.65 ± 0.15 in aqueous solution to 0.047 ± 0.005 in PEG 400 matrix. This increased stability in PEG matrix was assigned to a cage effect promoted by the PEG microenvironment that increases the rate of geminated radical pair recombination in the homolytic S–N bond cleavage process. This effect allowed for the storage of SNAC in PEG at −20°C in the dark for more than 10 weeks with negligible decomposition. Such stabilization may represent a viable option for the synthesis, storage and handling of S -nitrosothiol solutions for biomedical applications. 相似文献
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Tosylmethylisocyanide, when coordinated to osmium(II), reacts with aldehydes and ketones in the presence of sodium methoxide, to produce oxazol-2-ylidene and oxazolidin-2-ylidene complexes. 相似文献
14.
Liaoran Cao Xinyu Zhang Alix Grimley Anna R. Lomasney Michael G. Roper 《Analytical and bioanalytical chemistry》2010,398(5):1985-1991
A microfluidic device was developed to produce temporal concentration gradients of multiple analytes. Four on-chip pumps delivered
pulses of three analytes and buffer to a 14-cm channel where the pulses were mixed to homogeneity. The final concentration
of each analyte was dependent on the temporal density of the pulses from each pump. The concentration of each analyte was
varied by changing the number of pump cycles from each reservoir while maintaining the total number of pump cycles per unit
time to ensure a constant total flow rate in the device. To gauge the independent nature of each pump, sinusoidal waves of
fluorescein concentration were produced from each pump with independent frequencies and amplitudes. The resulting fluorescence
intensity was compared with a theoretical summation of the waves and the experimental data matched the theoretical waves within
1%, indicating that the pumps were operating independently and outputting the correct frequency and amplitude. The device
was used to demonstrate the role of adenosine triphosphate-sensitive K+ channels in glucose-stimulated increases in intracellular [Ca2+] in islets of Langerhans. Perfusion of single islets of Langerhans with combinations of glucose, diazoxide, and K+ resulted in intracellular Ca2+ patterns similar to what has been observed using conventional perfusion devices. The system will be useful in other studies
with islets of Langerhans, as well as other assays that require the modulation of multiple analytes in time. 相似文献
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E. J. Corey Thomas D. Roper Kazuaki Ishihara Georgios Sarakinos 《Tetrahedron letters》1993,34(52):8399-8402
A titanium complex derived from (1R, 2S)-N-(2,4,6-trimethylbenzenesulfonyl)-2-amino-1-indanol catalyzes the Diels-Alder reaction of 2-bromoacrolein and cyclopentadiene with 96.5:3.5 enantioselectivity. A new and efficient synthesis of 2-amino-1-indanol (6) contributes to the potential of this methodology. 相似文献
18.
N. Allen N. H. Furman E. Krause R. Becker P. Pfeiffer K. Schnurmann R. F. Chambers Ph. C. Scherer W. F. Hillebrand G. E. F. Lundell D. S. Reynolds W. H. Roß K. D. Jacob O. B. Winter Lillian Butler F. J. Frere G. Batchelder V. W. Meloche I. Tananaeff H. Flisik E. C. Roper E. B. R. Prideaux P. Drawe W. Rehwinkel L. Dupare P. Wenger G. Graz 《Analytical and bioanalytical chemistry》1934,96(5-6):211-223
19.
The biological events occurring in the body are complex and challenging to decode. The expression, production, secretion and interaction of proteins, peptides and small molecules often occur in a fast manner and at low concentrations. Methods used to quantify these events must be rapid, selective, sensitive and robust. In recent years, new variations of affinity methodologies have been developed to facilitate quantitation of these biomolecules. This review will focus on selected affinity techniques that have described multi-analyte measurement, high sensitivity techniques, or the application of new affinity reagents applied to conventional technologies to measure analytes involved in cell communication and biomarkers produced in specific disease states. 相似文献