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PubMed1984

The endoplasmic reticulum in the cortex of developing guard cells: coordinate studies with chlorotetracycline and osmium ferricyanide.

The distribution of endoplasmic reticulum (ER) was investigated in young guard cells of Vicia faba and Allium cepa in order to gain more information on the control of guard cell development. Young, living guard cells of V. faba fluoresce when exposed to 25-100 microM chlorotetracycline (CTC). Intense fluorescence is restricted to the cytoplasm between the nucleus and adjacent regions of the ventral and paradermal walls. Much of the fluorescence is fibrillar in appearance and seems to arise from endomembranes, but not from particulate organelles such as mitochondria and plastids. A similar fluorescence pattern is produced by the membrane probes oxytetracycline and N-phenyl-1-napthylamine. Procaine and dibucaine render the fluorescence highly prone to photobleaching. Fluorescence appears near the ventral wall during early stages of cell development but declines when the guard cells mature. Epidermal tissue of V. faba and A. cepa was examined in the electron microscope with the aid of osmium ferricyanide staining. ER appears to be concentrated in regions of the guard cell that exhibit intense CTC fluorescence, while no other organelles (e.g., mitochondria) are similarly distributed. Much of the ER consists of a tubular network in close proximity to the plasmalemma. Our results indicate that the ER becomes asymmetrically distributed in young guard cells adjacent to those regions of the cell wall that undergo extensive thickening during cell differentiation. Furthermore, these membranes appear to sequester divalent cations such as Ca2+.

Calcium↗
PubMed1991

A monoclonal antibody to DNA modified with osmium tetroxide/2,2'-bipyridine.

A murine monoclonal antibody (IgG) has been generated that binds to DNA modified with osmium tetroxide in the presence of 2,2'-bipyridine and does not interact with unmodified DNA. Reactivity of the antibody was tested by gel retardation assay, ELISA, dot-binding assay and immunoblotting. The results obtained suggest that the antibody does not cross-react with modified or unmodified RNA or proteins. The high specificity of the binding reaction is due to the specific recognition of modified deoxythymidine residue by the monoclonal antibody. A possible way of using the antibody produced is discussed.

2,2'-Dipyridyl↗
PubMed1996

Detection of basal acetylcholine release in the microdialysis of rat frontal cortex by high-performance liquid chromatography using a horseradish peroxidase-osmium redox polymer electrode with pre-enzyme reactor.

To determine the basal acetylcholine level in the dialysate of rat frontal cortex, a horseradish peroxidase-osmium redox polymer-modified glassy carbon electrode (HRP-GCE) was employed instead of the conventional platinum electrode used in high-performance liquid chromatography-electrochemical detection (HPLC-ED). In initial experiments, an oxidizable unknown compound interfered with the detection of basal acetylcholine release on HPLC-HRP-GCE. An immobilized peroxidase-choline oxidase precolumn (pre-reactor) was included in the HPLC system, to eliminate the interference from the unknown compound. This combination could detect less than 10 fmol of standard acetylcholine and basal acetylcholine levels in the dialysate from a conventional concentric design microdialysis probe, without the use of cholinesterase inhibitor, and may facilitate physiological investigation of cholinergic neuronal activity in the central nervous system.

Acetylcholine↗
PubMed1986

The development of an 191Os----191mIr generator using an osmium chelate parent complex--I. Trans-dioxobismalonatoosmate(VI).

A 191Os----191mIr generator has been developed that has higher 191mIr yield and lower 191Os breakthrough than previous designs. These improvements have been realized through the use of the osmium chelate complex trans-dioxobismalonatoosmate(VI) as the parent species on the generator. The new generator provides an initial 191mIr yield of 40%/mL and 191Os breakthrough of 2-3 X 10(-3)% when eluted with a solution of 0.05 M malonic acid/0.10 M sodium chloride at pH 4. Other advantages of the new design include faster clearance of the 191Os breakthrough products and simpler assembly.

Angiography↗
PubMed2006

Development of a carbon nanotube paste electrode osmium polymer-mediated biosensor for determination of glucose in alcoholic beverages.

This paper describes a new amperometric biosensor for glucose monitoring. The biosensor is based on the activity of glucose dehydrogenase (GDH) and diaphorase (DI) co-immobilized with NAD(+) into a carbon nanotube paste (CNTP) electrode modified with an osmium functionalized polymer. This mediator was demonstrated to shuttle the electron transfer between the immobilized diaphorase and the CNTP electrode, thus, showing a good electrocatalytic activity towards NADH oxidation at potentials around +0.2V versus Ag|AgCl, where interfering reactions are less prone to occur. The biosensor exhibits a detection limit of 10 micromol L(-1), linearity up to 8 x 10(-4) mol L(-1), a sensitivity of 13.4 microA cm(-2)mmol(-1)L(-1), a good reproducibility (R.S.D. 2.1%, n=6) and a stability of about 1 week when stored dry at 4 degrees C. Finally, the proposed biosensor was applied for the determination of glucose in different samples of sweet wine and validated with a commercial spectrophotometric enzymatic kit.

Biosensing Techniques↗
PubMed2005

Flow injection kinetic spectrofluorimetric determination of trace amounts of osmium.

A flow injection (FI) kinetic spectrofluorimetric method is described for the determination of osmium(IV) and the possible mechanism of catalytic reaction is discussed. The method is based on the fluorescence enhancing reaction of o-vanillin furfuralhydrazone (OVFH) with potassium bromate, which is catalyzed by Os(IV) in water medium at pH 6.10 and 45 degrees C. OVFH is newly synthesized and its ionization, IR and elemental analysis are established. Under these experimental conditions, the oxidized product of OVFH has excitation and emission maxima at 337 and 490 nm, respectively. The linear range of this method is 0-600 ng ml(-1) with the R.S.D. of 1.2%. The detection limit is 1.0 ng ml(-1) of Os(IV). A high analysis rate of 24 samples h(-1) is obtained by the FI method. The proposed method is applied successfully to determine Os(IV) in synthetic mixture and mineral samples, and the results are well consistent with the standard values.

Benzaldehydes↗
PubMed1999

Synthesis and spectral characterization of a long-lifetime osmium (II) metal-ligand complex: a conjugatable red dye for applications in biophysics.

There is a need for luminescent probes, which display both long excitation and emission wavelengths and long decay times. We synthesized and characterized an osmium metal-ligand complex which displays a mean decay time of over 100 ns when bound to proteins. [Os(1,10-phenanthroline)2(5-amino-1,10-phenanthroline)[(PF6)2 can be excited at wavelengths up to 650 nm, and displays an emission maximum near 700 nm. The probe displays a modest but useful maximum fundamental anisotropy near 0.1 for 488-nm excitation, and thus convenient when using an argon ion laser. [Os(phen)2(aphen)](PF6)2 is readily activated to the isothiocyanate for coupling to proteins. When covalently linked to bovine serum albumin the intensity decay is moderately heterogeneous with a mean decay time of 145 ns. The anisotropy decay of the labeled protein displays a correlation time near 40 ns. This relatively long lifetime luminophores can be useful as a biophysical probe or in clinical applications such as fluorescence polarization immunoassays.

Biophysics↗
PubMed1989

Differential effects of excitatory amino acids on photoreceptors of the chick retina: an electron-microscopical study using the zinc-iodide-osmium technique.

Although excitotoxins derived from acidic amino acids are known to damage neurons in the inner nuclear and ganglion cell layers of the retina, little is known about their effects on photoreceptors. This study examines the acute and long-term effects of excitotoxins on photoreceptors of the chick retina. The zinc-iodide-osmium (ZIO) technique, which darkly labels a substantial subpopulation of synaptic vesicles in normal photoreceptor terminals, was used to supplement routine electron microscopy. Two-day-old chicks received a single intraocular injection of either 10, 50, or 200 nmoles kainic acid (KA), 200 nmoles N-methyl-D-aspartic acid (NMDA), or 200 nmoles quisqualic acid (QUIS), and were allowed to survive for either 6 h, 7 d, or 21 d. At 6 h, following exposure to 10, 50, and 200 nmoles KA, there was swelling and disruption of photoreceptor lamellae of the outer segments. At 7- and 21-d survival, 50 and 200 nmoles KA resulted in rounded, condensed synaptic terminals, which contained a high density of synaptic vesicles. However, there was complete loss of ZIO-positive vesicles within these photoreceptors. Outer segments were still disrupted, although small patches of lamellae were evident, suggestive of regeneration. Following exposure to QUIS, there was extensive swelling of outer segment lamellae at 6 h survival. Synaptic ribbons in terminals were also swollen. At longer survival periods, QUIS exposure resulted in a reduction of ZIO-positive vesicles, as well as swollen lamellae in outer segments. NMDA exposure, at either short or long-term survival, did not alter photoreceptor morphology, including the pattern of ZIO stain. The prolonged effects of KA, and to a lesser extent QUIS, on photoreceptors suggests that these drugs have a long-term effect on photoreceptor function. The ZIO technique provides a novel and potentially useful approach for identification of damaged photoreceptors.

Amino Acids↗
PubMed2002

DNA sensor with a dipyridophenazine complex of osmium(lI) as an electrochemical probe.

Application of a dipyrido[3,2-a:2',3'-c]phenazine (DPPZ)-type metal complex as an DNA electrochemical probe was studied. The introduction of electron-donating groups (NH2) was effective for controlling the redox potential and binding affinities of the DPPZ-type osmium complex. The [Os(DA-bpy)2DPPZ]2+ complex (DA-bpy; 4,4'-diamino-2,2'-bipyridine) had a lower half-wave potential (E 1/2) of 147 mV (vs Ag/AgCl) and higher binding affinity with DNA (binding constant, K = 3.1 x 10(7) M(-1)) than those of other complexes. With a single-stranded DNA immobilized gold electrode, the hybridization signal (deltaI) of the [Os(DA-bpy)2DPPZ]2+ complex was linear in the concentration range of 1.0 pg mL(-1) - 0.12 microg mL(-1) for the targeted DNA with a regression coefficient of 0.999. The detection limit was 0. 1 pg mL(-1). The 400-bp yAL3 gene was also detected with good sensitivity and selectivity using the [Os(DA-bpy)2DPPZ]2+ complex.

Biosensing Techniques↗
PubMed2004

Voltammetric sensor for oxidized DNA using ultrathin films of osmium and ruthenium metallopolymers.

Films containing [Os(bpy)2(PVP)10Cl]+ and [Ru(bpy)2(PVP)10Cl]+ metallopolymers were assembled layer by layer on pyrolytic graphite electrodes to make sensors that selectively detect oxidized DNA. These films showed reversible, independent electrochemistry for electroactive Os3+/Os2+ and Ru3+/Ru2+ centers, with formal potentials of 0.34 and 0.76 V vs SCE, respectively. The combination of ruthenium and osmium metallopolymers in the films provided a catalytic Os square wave voltammetry (SWV) peak that is mainly selective for 8-oxoguanine and the detection of other oxidized nucleobases from the Ru peak. The method is applicable to measurements on DNA in solution or DNA incorporated into films. Using the Os SWV peak, 1 oxidized nucleobase in 6000 was detected. The sensor is simple and inexpensive, and the approach may be useful for the detection of oxidized DNA as a clinical biomarker for oxidative stress.

Biosensing Techniques↗
PubMed2001

Synthesis, characterization, solid-state molecular structures, and deprotonation reactions of cationic alcohol complexes of osmium nitrosyl porphyrins.

New alkoxide (OEP)Os(NO)(OR) (OEP = 2,3,7,8,12,13,17,18-octaethylporphyrinato dianion; R = ethyl, isopropyl, hexyl, cyclohexyl) compounds and alcohol [(OEP)Os(NO)(HOR)]+ complexes (R = methyl, ethyl, isopropyl, hexyl, cyclohexyl) have been prepared in high yields and have been fully characterized by IR, 1H NMR, and UV-vis spectroscopy, and by elemental analyses. The (OEP)Os(NO)(OEt) compound was characterized by single-crystal X-ray crystallography. The cationic aqua and alcohol [(OEP)Os(NO)(HOR)]+ complexes (R = ethyl, isopropyl, hexyl) complexes were also characterized by single-crystal X-ray crystallography, and the latter represent the first osmium alcohol structures to be reported. The electrophilic [(OEP)Os(NO)]+ cation in the [(OEP)Os(NO)(HOR)]+ complexes renders the coordinated alcohol ligands susceptible to deprotonation by pyridine to produce the corresponding alkoxide (OEP)Os(NO)(OR) derivatives. A one-pot reaction sequence for the preparation of new (OEP)Os(NO)(OR) complexes from (OEP)Os(NO)(OEt) was developed, which was based on (i) initial protonation of the ethoxide compound to give [(OEP)Os(NO)(HOEt)]+, (ii) alcohol substitution by ROH to give [(OEP)Os(NO)(HOR)]+, and (iii) deprotonation of the latter by pyridine to give (OEP)Os(NO)(OR).

Alcohols↗
PubMed2006

Total synthesis of (+)-cis-sylvaticin: double oxidative cyclization reactions catalyzed by osmium.

The double oxidative cyclization of dienes is a viable procedure for making complex natural products containing cis-THF units. A double deprotection/double oxidative cyclization strategy using catalytic osmium tetroxide was used to construct the bisheterocyclic core of cis-sylvaticin and ultimately confirm its structure. The natural product was then prepared by a short sequence of reactions that is exceptionally concise: the final route being just 13 linear steps and 19 chemical operations in total.

Catalysis↗
PubMed2006

Potential-, pH-, and isotope-dependence of proton-coupled electron transfer of an osmium aquo complex attached to an electrode.

An osmium complex, [OsII(bpy)2(4-aminomethylpyridine)(H2O)]2+, is attached to a mixed self-assembled monolayer on a gold electrode. The complex exhibits 1-electron, 1-proton redox chemistry (OsIII(OH)/OsII(H2O)) at pHs and potentials that are experimentally accessible with gold electrodes in aqueous electrolytes. The thermodynamic behavior and kinetic behavior of the system are investigated as a function of pH in both H2O and D2O. The two formal potentials and two pKa values are relatively constant for two chain lengths in H2O and in D2O. The standard rate constants at all pHs are strongly and uniformly affected by chain length, indicating that electronic coupling is the dominant factor controlling the rate of electron transfer. In both H2O and D2O, the standard rate constant is weakly dependent on the pH, exhibiting a minimum value midway between the pKa values. The kinetic isotope effect is small; standard rate constants decrease by roughly a factor of 2 in D2O over a wide range of pHs, but not at the more acidic pHs. The Tafel plots and plots of the transfer coefficient vs overpotential are asymmetrical at all pHs. These results are interpreted in terms of a larger reorganization energy for the OsII species and a smaller reorganization energy for the OsIII species. The OsIII reorganization energy is constant at all pHs in both H2O and D2O. The pH dependence of the OsII reorganization energy accounts for some or all of the pH dependence of the standard rate constant in H2O and D2O. The data deviate substantially from predictions of the stepwise proton-coupled electron-transfer mechanism. The observation of a kinetic isotope effect supports the concerted mechanism.

Electrochemistry↗
PubMed1997

Stromal cell organisation in the mouse lymph node. A light and electron microscopic investigation using the zinc iodide-osmium technique.

The organisation of the stromal cell compartment in the mouse lymph node was studied by light and electron microscopy after tissue impregnation by the zinc iodide-osmium (ZIO) method. Fibroblastic reticular cells (FRCs) represented the main stromal cell population. These cells were located both in the cortical region and in the medulla and exhibited various configurations. In the cortex, FRCs were fusiform in shape and came into close proximity with the floor of the subcapsular sinus. In the medulla, the FRCs were shaped like irregular dendritic cells which formed a complex 3-dimensional network. The FRCs surrounded vascular structures such as capillaries and/or high endothelial venules; in these instances they were organised in a discontinuous sheath-like fashion around the vessel wall. By light and electron microscopy, FRCs have been observed to come in close spatial relationship with a number of cells in the lymph node, including sinus endothelial cells, the endothelium of high endothelial venules and capillaries, various types of lymphocytes, follicular dendritic cells and interdigitating cells. These microanatomical features are consistent with the proposal that FRCs may be involved in the communicative networks between the different lymph node compartments. In particular, the FRCs may be involved in the transport of molecules from the sinus compartment to the high endothelial venules or to the distinct cell populations in the lymphoid parenchyma.

Animals↗
PubMed1994

Distribution of DNA, nuclear micro-heterogeneities and compaction of the chromatin in rabbit epididymal spermatozoa. Ultrastructural evaluation of the Feulgen-like technique using osmium ammine.

An adaptation of the Feulgen procedure to visualise DNA at the ultrastructural level, using osmium ammine instead of Schiff reagent, was applied to ultrathin sections of rabbit epididymal spermatozoa, known to display increasing chromatin compaction as they progress through the epididymis. In contrast with the somatic cell nuclei of the epididymal epithelium, which display classical staining, the chromatin of spermatozoa is partly or fully destroyed during the hydrolysis step of the technique. The sperm chromatin resistance towards destruction is a function of the initial sperm nuclear compaction and of the duration of hydrolysis prior to Feulgen-like staining. For a given nucleus, the maximum staining intensity is only obtained after an optimal duration of hydrolysis. However, because of this duration and local differences in chromatin compaction, the total DNA of a section is never completely visualized. The most compact parts of the nuclei are not yet stained, when the less compact parts have already been destroyed. This gives rise to a sperm-specific pattern which corresponds to the enhancement of microheterogeneities present in all sperm nuclei and to the local depolymerisation of the nuclear material during hydrolysis. The depolymerised parts of nuclei sit over the sections, and they also bind uranyl acetate, ethidium bromide and anti-protamine antibodies. Therefore, in sperm nuclei, the Feulgen-like staining at the ultrastructural level does not reveal the true DNA distribution. However, the amount of staining can be quantified to evaluate sperm chromatin compaction.

Animals↗