Porphyrin architectures tailored for studies of molecular information storage

A molecular approach to information storage employs redox-active molecules tethered to an electroactive surface. Zinc porphyrins tethered to Au(111) or Si(100) provide a benchmark for studies of information storage. Three sets of porphyrins have been synthesized for studies of the interplay of molecular design and charge-storage properties: (1) A set of porphyrins is described for probing the effect of surface attachment atom on electron-transfer kinetics. Each porphyrin bears a meso-CH2X group for surface attachment where X = OH, SAc, or SeAc. (2) A set of porphyrins is described for studying the effect of surface-charge density in monolayers. Each porphyrin bears a benzyl alcohol for surface attachment and three nonlinking meso substituents of a controlled degree of bulkiness. (3) A set of porphyrins is described that enables investigation of on-chip patterning of the electrolyte. Each porphyrin bears a formyl group distal to the surface attachment group for subsequent derivatization with a molecular entity that comprises the electrolyte. Taken together, this collection of molecules enables a variety of studies to elucidate design issues in molecular-based information storage.     

A novel and facile one‐pot synthesis of pyridylselenium compounds through selective bromine–magnesium exchange with isopropylmagnesium halide

One‐pot synthesis of various unsymmetrical 2‐bromo‐5‐pyridylselenium compounds has been carried out under non‐cryogenic conditions by selective single bromine–magnesium exchange of 2,5‐dibromopyridine using isopropylmagnesium chloride. This exchange gives 2‐bromo‐5‐pyridylmagnesium chloride, which upon the insertion of elemental selenium followed by the treatment with alkyl halide gives the title compounds in good yield. This exchange has also been extended towards bromine–magnesium exchange of 2‐bromopyridine for the improved synthesis of 2‐pyridylselenium compounds. The molecular structure of 2‐bromo‐5‐selenopyridyltribromomethane has been examined by single crystal X‐ray diffraction. This compound crystallizes in the monoclinic space group P2₁/n. From the molecular structure it was found that intermolecular BrBr, NSe and SeBr interactions control its crystal packing. Copyright © 2005 John Wiley & Sons, Ltd.     

Spectrophotometric determination of some phenothiazine drugs using chloramine-T-iodine-starch

A simple, accurate, and sensitive spectrophotometric method for the determination of promethazine hydrochloride (PMH), prochlorperazine maleate (PCPM), trifluoperazine hydrochloride (TFPH), trimeperazine tartrate (TMT), fluphenazine dihydrochloride (FH), and trifluopromazine hydrochloride (TPH) is described. The method is based on the oxidation of the studied drugs by a known excess of chloramine-T in a hydrochloric acid medium and subsequent determination of the unreacted oxidant by interacting it with iodide in the same acid medium. Liberated iodine subsequently reacts with starch to form a stable starch-iodine complex. The reacted oxidant corresponds to the drug content. The colored complex exhibits a maximum absorption at 590 nm. The apparent molar absorptivity and Sandell sensitivity values are in the range 4.07 × 10⁴ − 1.18 × 10⁵ L/mol cm and 45.00−95.00 ng/cm², respectively. The proposed method has been applied to the assay of phenothiazine drugs in pure and dosage forms. The reliability of the analysis was established using parallel determination by the reference method. The text was submitted by the authors in English.     

Heat transfer in a visco-elastic fluid past a stretching sheet with viscous dissipation and internal heat generation

This paper deals with the study of heat transfer characteristics in the laminar boundary layer flow of a visco-elastic fluid over a linearly stretching continuous surface with variable wall temperature subjected to suction or blowing. The study considers the effects of frictional heating (viscous dissipation) and internal heat generation or absorption. An analysis has been carried out for two different cases of heating processes namely: (i) Prescribed surface temperature (PST) and (ii) Prescribed wall heat flux (PHF) to get the effect of visco-elastic parameter for various situations. Further increase of visco-elastic parameter is to decrease the skin friction on the sheet. The solutions for the temperature and the heat transfer characteristics are obtained in terms of Kummers function. Received: June 16, 2004; revised: February 8, 2005     

Effect of creatine monohydrate in improving cellular energetics and muscle strength in ambulatory Duchenne muscular dystrophy patients: a randomized,placebo-controlled P MRS study

Randomized, placebo-controlled single blinded study was carried out to evaluate the effect of oral creatine supplementation on cellular energetics, manual muscle test (MMT) score and functional status in steroid-naive, ambulatory boys suffering with Duchenne muscular dystrophy (DMD; n=33). Eighteen patients received creatine monohydrate (Cr; 5 g/day for 8 weeks), while 15 received placebo (500 mg of vitamin C). Phosphorus metabolite ratios were determined from the right calf muscle of patients using phosphorus magnetic resonance spectroscopy (³¹P MRS) both prior to (baseline) and after supplementation of Cr or placebo. In addition, metabolite ratios were determined in normal calf muscle of age and sex matched controls (n=8). Significant differences in several metabolite ratios were observed between controls and DMD patients indicating a lower energy state in these patients. Analysis using analysis of covariance adjusted for age and stature showed that the mean phosphocreatine (PCr)/inorganic phosphate (Pi) ratio in patients treated with Cr (4.7; 95% CI; 3.9–5.6) was significantly higher (P=.03) compared to the placebo group (3.3; 95% CI; 2.5–4.2). The mean percentage increase in PCr/Pi ratio was also more in patients <7 years of age compared to older patients after Cr supplementation indicating variation in therapeutic effect with the age. In the placebo group, significant reduction in PCr/Pi (P=.0009), PCr/t-ATP (P=.05) and an increase in phosphodiester (PDE)/PCr ratios was observed after supplementation. Further, in the placebo group, patients <7 years showed reduction of PCr/t-ATP and Pi/t-ATP compared to older patients (>7 years), after supplementation. These results imply that the significant difference observed in PCr/Pi ratio between the Cr and the placebo groups after supplementation may be attributed to a decrease of PCr in the placebo group and an increase in PCr in the Cr group. Changes in MMT score between the two groups was significant (P=.04); however, no change in functional scale (P=.19) was observed. Parents reported subjective improvement on Cr supplementation versus worsening in placebo (P=.02). Our results indicated that Cr was well tolerated and oral Cr significantly improved the muscle PCr/Pi ratio and preserved the muscle strength in short term. However, this study provides no evidence that creatine will prove beneficial after long-term treatment, or have any positive effect on patient lifespan.     

A novel class of banana-shaped azo compounds exhibiting antiferroelectric switching behaviour

The first banana-shaped liquid crystal materials with photo-active azo linkages are reported. The higher temperature mesophase X₁ (believed to be B₆) above the B₁ phase exhibited by these azo compounds shows antiferroelectric switching characteristics. The observation of banana phases in azo compounds assumes significance from the point of view of photochromic studies.     

Thorium(IV) and zirconium(IV) complexes of oxygen donor ligands,part 12. Thorium(IV) complexes of monoN-oxides of 2,2′-bipyridine and 1,10-phenanthroline

Summary Crystalline thorium(IV) chelates with monoN-oxides of 2,2-bipyridine (bipyNO) and 1,10-phenanthroline (phenNO), ThX₄ · 2L (X = Cl, Br, NO₃ or NCS) and ThX₄ · 3L (X = I or ClO₄, and I = bipyNO or phenNO) have been synthesised and characterized on the basis of i.r. spectra, molar conductance, molecular weights, t.g.a. and d.t.a. data. All the complexes are weakly diamagnetic and contain bipyNO and phenNO bonded to thorium(IV) through nitrogen and oxygen. The coordination number of thorium(IV) varies from six to twelve depending on the nature of the anions.Author on leave from L. R. Postgraduate College, Sahibabad (Ghaziabad) and to whom all correspondence should be directed.     

An immunomodulator from Tinospora cordifolia with antioxidant activity in cell-free systems

Several plant products are known to exhibit immense medicinal value against human diseases. Our earlier studies showed that dry stem crude extract (DSCE) ofTinospora cordifolia contained a polyclonal B cell mitogen, G1-4A. DSCE as well as G1-4A also enhanced immune response in mice. In order to explore the possibility of using G1-4A/PPI (partially purified immunomodulator) to modulate radiation induced immunosuppression, the antioxidant effect of PPI from this plant was examined against reactive oxygen and nitrogen species (ROS/RNS), generated by photosensitization/peroxynitrite. Levels of lipid peroxidation products, superoxide dismutase (SOD) and catalase in liver/spleen homogenate from mouse were monitored. Photosensitization induced significant increase in thiobarbituric acid reactive substances (TBARS) in liver. The activities of SOD and catalase were reduced considerably. PPI, present during photosensitisation, prevented lipid peroxidation and restored the activities of both the enzymes. Likewise, oxidative damage induced by peroxynitrite was inhibited by PPI. The degradation of proteins due to photosensitization as assessed by SDS-PAGE was effectively reduced by simultaneous treatment with PPI during photosensitization. Selective inhibitors of ROS like mannitol, SOD, sodium azide and antioxidants, GSH and vitamin C brought about significant inhibition of formation of TBARS suggesting possible involvement of O₂ ^•,^•OH and¹O₂. Photosensitization in deuterated buffer enhanced formation of TBARS thus indicating generation of¹O₂. Thus, the action of PPI may be against oxidative damage through Type I and II photosensitization mechanisms. Therefore, the immunomodulator fromTinospora cordifolia may also be beneficial as an antioxidant.