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This paper is concerned with the attitude control of a three-axis-stabilized spacecraft which consists of a central rigid body and a flexible sun-tracking solar array driven by a solar array drive assembly. Based on the linearization of the dynamics of the spacecraft and the modal identities about the flexible and rigid coupling matrices, the spacecraft attitude dynamics is reduced to a formally singular system with periodically varying parameters, which is quite different from a spacecraft with fixed appendages. In the framework of the singular control theory, the regularity and impulse-freeness of the singular system is analyzed and then admissible attitude controllers are designed by Lyapunov’s method. To improve the robustness against system uncertainties, an H ∞ optimal control is designed by optimizing the H ∞ norm of the system transfer function matrix. Comparative numerical experiments are performed to verify the theoretical results.

Perchlorotrityl radicals, mono-substituted with a fluorophore using an amide linker of varying chain length, were synthesized and characterized. Electron paramagnetic resonance (EPR) spectroscopic study indicated free-electron coupling with the aromatic hydrogen nuclei and long-range coupling with the methylene hydrogens of the linker group. Reactivity of the fluorophore-conjugated trityls with superoxide radical anion showed quenching of EPR signal and enhancement of fluorescence emission spectrum. This work presents the first example of a perchlorotrityl-fluorophore conjugate that can potentially be employed as a dual probe for the detection of superoxide under oxidative stress-mediated conditions in biological systems.

Ethanol injection is widely used in liposome preparation. However, the parameters determining particle size distribution of the liposomal preparation has not been fully defined.A syringe pump-driven microfluidic injection device was used to produce liposomes under different conditions.Particle size of the liposomes was decreased with decrease in needle diameter (or increase in hydrodynamic pressure), decrease in lipid concentration in the alcohol solution, decrease in phase transition temperature (T(m)) of the lipid bilayer and the absence of cholesterol (or decrease in, membrane rigidity).The device used is simple to adopt and can be used for affordable production of liposomes with tunable particle size.

The over-expression of glutathion S-transferase Pi (GSTpi) in tumors and inhibitory effect of GSTpi to JNK are two possible causes of the development of drug-resistance in chemotherapy. This research is to develop a novel pH-controlled NO donor to inhibit GSTpi(and to activate the JNK/c-Jun pathway (omit "to induce apoptosis").Four 4-Aryl-1,3,2-oxathiazolylium-5-olate (OZO) derivatives with varying aryl para-substitutions (-H, -CF(3), -Cl, and -OCH(3)) were synthesized. Anticancer activity was determined by MTS assay. GST activity was measured with spectrophotometry using 1-chlro-2,4-dinitrobenzene (CDNB) and GSH as substrates. (omit "Apoptosis was evaluated by annexin V staining and flow cytometry"). c-Jun N-terminal kinase 1 (JNK1) association with GSTpi and activation of c-Jun were evaluated with immunoprecipitation and western blot.OZO derivatives showed anticancer effect against leukemia and breast cancer cells by MTS assay. The relative potency of their anticancer effects is OZO-HOZO-Cl, OZO-OMeOZO-CF(3). The anticancer activity of these compounds was correlated with their inhibition of GST activity in cancer cells. The immunoprecipitation result showed that the treatment of OZO-H released JNK1 from GSTpi-JNK1 complex. Consequently, the treatment of OZO-H in cancer cells induced JNK1 phophorylation and activated c-Jun in cancer cells.OZO-H is a novel GST inhibitor to release JNK1 for activation of JNK/c-Jun pathway (original is "c-Jun to trigger apoptosis in cancer cells"). It provides a new class of GST target compound for anticancer therapy.

S-Nitrosothiols (RSNOs) are important exogenous and endogenous sources of nitric oxide (NO) in biological systems. A series of 4-aryl-1,3,2-oxathiazolylium-5-olates derivatives with varying aryl para-substituents (-CF3, -H, -Cl, and -OCH3) were synthesized. These compounds were found to release NO under acidic condition (pH = 5). The decomposition pathway of the aryloxathiazolyliumolates proceeded via an acid-catalyzed ring-opening mechanism after which NO was released and an S-centered radical was generated. Electron paramagnetic resonance (EPR) spin trapping studies were performed to detect NO and the S-centered radical using the spin traps of iron(II) N-methyl-D-glucamine dithiocarbamate [(MGD)2-FeII] and 5,5-dimethyl-1-pyrroline N-oxide (DMPO). Also, EPR spin trapping and UV-vis spectrophotometry were used to analyze the effect of aryl para substitution on the NO-releasing property of aryloxathiazolyliumolates. The results showed that the presence of an electron-withdrawing substituent such as -CF3 enhanced the NO-releasing capability of the aryloxathiazolyliumolates, whereas an electron-donating substituent like methoxy (-OCH3) diminished it. Computational studies using density functional theory (DFT) at the PCM/B3LYP/6-31+G**//B3LYP/6-31G* level were used to rationalize the experimental observations. The aryloxathiazolyliumolates diminished susceptibility to reduction by ascorbate or gluthathione, and their capacity to cause vasodilation as compared to other S-nitrosothiols suggests potential application in biological systems.

Nitric oxide (NO) has been implicated in a wide variety of disease states. Both inhibitors and substrates of nitric oxide synthase (NOS) could have great therapeutic potential in the treatment of these diseases. There is considerable pharmacological interest in developing inhibitors of NOS, and hundreds of inhibitors have been identified. In contrast, the study on NOS substrates is less active. The advances in the identification, design and development of NOS substrates are discussed in this review. The focus is the chemistry and biochemistry of N-hydroxyguanidines. The crystal structures of substrates bound to NOSs and the mechanisms of NOS catalyzed NO generation from substrates are also discussed.

[reaction: see text] To achieve site specific delivery of nitric oxide (NO), a new class of glycosidase activated NO donors has been developed. Glucose, galactose, and N-acetylneuraminic acid were covalently coupled to 3-morphorlinosydnonimine (SIN-1), a mesoionic heterocyclic NO donor, via a carbamate linkage at the anomeric position. The beta-glycosides were successfully prepared for these conjugates, while the alpha-glycosidic compounds were very unstable. The new stable sugar-NO conjugates could release NO in the presence of glycosidases. Such NO prodrugs may be used as enzyme activated NO donors in biomedical research.

A new sialated diazeniumdiolate has been synthesized, and the glycosylation product was exclusively an alpha anomer. This new nitric oxide donor exhibited significantly improved stability as compared to its parent diazeniumdiolate salts, and it could be efficiently hydrolyzed by neuraminidase to release nitric oxide with a K(m) of 0.14 mM. The sialic acid-NO conjugate would be a valuable prodrug that targets NO to influenza viruses.