bluuebunny/crossref_metadata_2025 huggingface dataset:
Reduction of the oxidized bacteriochlorophyll dimer in reaction centers by ferrocene is dependent upon the driving force
Authors: Kálmán László , Haffa Arlene L. M. , Williams JoAnn C. , Woodbury Neal W. , Allen James P.
Published: July 2009

The rates of electron transfer from ferrocene to the oxidized bacteriochlorophyll dimer, P , in reaction centers from the purple photosynthetic bacterium Rhodobacter sphaeroides, were measured for a series of mutants in which the P / P + midpoint potentials range from 410 to 765 mV (Lin et al. Proc. Natl. Acad. Sci. USA 1994; 91: 10265-10269). The observed rate constant for each mutant was found to be linearly dependent upon the ferrocene concentration up to 50 μM. The electron transfer is described as a second order reaction with rate constants increasing from 1.5 to 35 × 106 M -1. s -1 with increasing P / P + midpoint potential. This dependence was tested for three additional mutants, each of which exhibits a pH dependence of the P / P + midpoint potential due to an electrostatic interaction with an introduced carboxylic group (Williams et al. Biochemistry 2001; 40: 15403-15407). For these mutants, the pH dependence of the bimolecular rate constants followed a sigmoidal pattern that could be described with a Henderson-Hasselbalch equation, attributable to the change of the free energy difference for the reaction due to deprotonation of the introduced carboxylic side chains.
The photophysics of metalloporphyrins excited in their Soret and higher energy UV absorption bands
Authors: Tripathy Umakanta , Steer Ronald P.
Published: July 2009

Photophysical processes involving the higher electronic excited states of diamagnetic porphyrins and metalloporphyrins are critically reviewed. Intramolecular electronic relaxation of one-photon Soret-excited molecules in solution is now known to involve processes other than S 2 - S 1 internal conversion; dark electronic states are implicated. Sequential two-photon excitation to produce gerade excited singlet states ( S n , n > 2) results in relaxation dynamics that are quantitatively different from those resulting from one-photon excitation to ungerade states of about the same energy. Intermolecular electron and electronic energy transfer involving Soret-excited metalloporphyrins and intramolecular electron and electronic energy transfer in Soret-excited dyads and larger arrays containing porphyrins are reviewed. Metalloporphyrins containing main group metals or transition metals with filled d orbitals exhibit relaxation dynamics that differ from metalloporphyrins containing transition metals with unfilled d orbitals. Non-linear phenomena associated with multi-photon excitation of diamagnetic metalloporphyrins are also reviewed.
Free-base corroles: determination of deprotonation constants in non-aqueous media
Authors: Shen Jing , Ou Zhongping , Shao Jianguo , Gałęzowski Michał , Gryko Daniel T. , Kadish Karl M.
Published: July 2009

A series of free-base corroles with different electron-donating or electron-withdrawing substituents were reacted with piperidine, 4-aminopyridine, 2-methylimidazole, 2-aminopyridine or pyridine in PhCN and the UV-visible spectral changes monitored during conversion of ( Cor ) H 3 to [( Cor ) H 2]- as a function of the concentration and strength of the added organic base. Analysis of the UV-visible spectral changes as a function of the added base concentration enabled calculation of equilibrium constants ( logK ) for deprotonation of each corrole under the given experimental conditions. Relationships are examined between the experimentally measured logK values and previously published spectroscopic and structural properties of the compounds.
Syntheses and properties of acetylene-linked bis- and trisporphyrins toward two-photon photodynamic therapy
Authors: Inaba Yusuke , Ogawa Kazuya , Kobuke Yoshiaki
Published: July 2009

Acetylene-bridged bisporphyrins and trisporphyrins having branched bulky bis(carboxylethyl)methyl meso-substituents were synthesized. These compounds showed large effective two-photon absorption cross-section values at 890 nm measured by using a nanosecond Z-scan method. Sodium salt of hydrolyzed trisporphyrins showed broad and red-shifted Q-bands over 900 nm. Two-photon absorption cross-section values of water-soluble dimers in water were similar to, or slightly larger than, those of ester forms evaluated in toluene. Furthermore, the generation of singlet oxygen upon one-photon irradiation for dimers in water was confirmed.
Single-wall carbon nanotube porphyrin nanoconjugates
Authors: Ehli Christian , Campidelli Stéphane , Brunetti Fulvio G. , Prato Maurizio , Guldi Dirk M.
Published: July 2009

We describe the synthesis, microscopic and spectroscopic characterization of a novel donor-acceptor prototype, namely, a single wall carbon nanotube (SWNT) nanoconjugate bearing a covalently linked free base porphyrin ( H 2 P ). In the characterized SWNT- H 2 P nanoconjugate the electronic features of SWNT are largely retained, when compared to pristine SWNT. In fact, carefully controlled reaction conditions lead to a low degree of SWNT functionalization, as evidenced by the preservation of the SWNT van Hove singularities. As a consequence, the overall SWNT loading with H 2 P is so low that in the ground state, the H 2 P features are barely seen, which is different from the excited state, where features of H 2 P are clearly discernable. For example, fluorescence and transient absorption characteristics corroborate, unequivocally, the formation of the H 2 P singlet excited state, which is, however, impacted by the presence of SWNT.
Synthesis and photophysical and electrochemical properties of a binuclear Ru(bpy)3-Cu(III) corrole complex
Authors: Gao Yan , Liu Jianhui , Jiang Wenfeng , Xia Ming , Zhang Wei , Li Minna , Åkermark Björn , Sun Licheng
Published: July 2009

A novel binuclear Ru - Cu complex, composed of a copper(III)-corrole and a ruthenium(II) tris(bipyridine) moiety linked by an amide bond, has been synthesized and characterized by 1 H NMR, UV-vis and mass spectrometry. The steady-state emission and the electrochemical properties were investigated. Compared to the parent [ Ru ( bpy )3]2+, the emission of the desired complex was substantially quenched when the MLCT of [ Ru ( bpy )3]2+ was selectively photoexcited.
The voltammetric study of the reduction of tetraalkylammonium perchlorate by Fe(TPP)2−
Authors: Ryan Michael D. , DeSilva Chathra
Published: July 2009

Tetraalkylammonium ions react with Fe ( TPP )2− to form Fe ( TPP )( R )− and trialkylamine. The tetrabutylammonium cation was verified to be the source of the alkyl group in the product, Fe ( TPP )( R )−, by using (1 H 5 C 2)3(2 H 5 C 2) N − as the cation and 2 H NMR. The reaction of Fe ( TPP )2− with Bu 4 N − was monitored by cyclic voltammetry and thin layer spectroelectrochemistry. The activation parameters were measured, and were most consistent with an electron transfer (ET) mechanism. The rate of the reaction of tetramethyl and tetraethylammonium ions with Fe ( TPP )2− was also examined. The rate constant decreased significantly as the carbon chain length decreased, which was also consistent with an ET mechanism.
Photophysical, photochemical and bovine serum albumin binding studies on water-soluble gallium(III) phthalocyanine derivatives
Authors: Ogunsipe Abimbola , Nyokong Tebello , Durmuş Mahmut
Published: July 2009

Spectral, photophysical, photochemical and bovine serum albumin binding studies on some gallium(III) derivatives - {1,(4)-(tetrapyridyloxyphthalocyaninato)gallium(III), (α GaPc ); 2,(3)-(tetrapyridyloxyphthalocyaninato)gallium(III), (β GaPc ); and their quaternized derivatives: Q α GaPc and Q β GaPc )} are hereby presented. β-Substituted complexes are more fluorescent, but show lower tendencies to undergo intersystem crossing than the α-substituted, as judged by their fluorescence and triplet quantum yield values. The quaternized derivatives ( QGaPc ) are water-soluble and non-aggregated, which makes them potential photosensitizers of choice for photodynamic therapy applications; these amphiphilic compounds also bind strongly to bovine serum albumin in 1:1 stoichiometries, and with binding constants ( Kb) in the order of 106M−1.
Synthesis and photophysical studies of porphyrin-ferrocene conjugates
Authors: Mansour Hanaa , El-Khouly Mohamed E. , Shaban Shaban Y. , Ito Osamo , Jux Norbert
Published: July 2009

The porphyrin-ferrocene conjugates ( P-nFc; n = 1, 2 and 4 ), which are simple examples of a donor-acceptor charge separation system, were synthesized. Their photoindued intramolecular and intermolecular processes have been investigated by time-resolved emission and nanosecond transient absorption techniques. Upon excitation of the porphyrins ( H 2P and ZnP ) moieties, an efficient fluorescence quenching of the excited singlet porphyrin is observed. It was found that the quenching efficiency increases with increasing number of attached ferrocene moieties and solvent polarity. The main quenching pathway involves (i) electron transfer from ferrocene to the singlet excited porphyrin and (ii) the heavy-atom effect.
Supporting porphyrins on resin-beads by cyanuric chloride linker
Authors: Carofiglio Tommaso , Schiorlin Milko , Tonellato Umberto
Published: July 2009

A straightforward procedure for supporting porphyrin-derivatives onto resin beads has been developed by reacting the commercially available 4,6-dichloro-1,3,5-triazene polymer-bound, with 5-(4-aminophenyl)-10,15,20-triphenylporphyrins as free base and as Zn (II) and Co (II) complexes. The supported porphyrins have been characterized by on-resin UV-vis spectroscopy. Kinetic and Hammett LFER studies have shown that the S N Ar reaction with the triazine-bound reagent occurs at a similar rate for free and metalated complexes, with a nucleophilic strength comparable to that of the unsubstituted aniline (σ p + = 0.07-0.08).
Structure, aromaticity, and bonding in subporphyrins: theoretical study of [14]tribenzosubporphine(1.1.1)hydroxyboron(III) and [14]subporphine(1.1.1)hydroxyboron(III) complexes
Authors: Campomanes Pablo , Menéndez María I. , Sordo Tomás L.
Published: July 2009

A theoretical analysis of the structure, aromaticity, magnetic properties and bonding in TBSPBOH and SPBOH complexes was performed. Geometry optimizations were carried out in the gas-phase at the B3LYP/6-31G(d) theory level.1H and13C NMR spectra of these complexes were evaluated at the B3LYP/6-311+G(2d,p)-PCM theory level in CHCl3solution. The vector field induced by an external magnetic field was computed at the CHF/6-31G(d) theory level using the CTOCD-DZ formulation. In these cone-shaped molecules, the 14-π electron current induced in them by an external magnetic field does not follow a [14]-annulene path but the inner edge of the macrocycle. Therefore, the 14-π electron aromatic core corresponding to this induced current is constituted by the three meso C atoms, the three N atoms, and the six C atoms directly bonded to them. The involvement of the N atoms in the 14-π aromatic core implies that one of the B - N bonds is a weaker B←N dative bond whose presence is reflected in the geometry of these complexes, which display larger average B - N bond lengths than in tripyrrolylborane. Thus, according to our analysis, structure, aromaticity and bonding in these systems are closely related. The anisotropic effect is somewhat larger in SPBOH than in TBSPBOH, and the larger curvature of the former makes larger relative shielding constants possible, not only for the hydroxyl proton but also for the outer atoms.
Synthesis of some β-nitro-meso-tetraphenylporphyrin derivatives
Authors: Wyrębek Przemysław , Ostrowski Stanisław
Published: July 2009

A selective electrophilic nitration of meso-tetraarylporphyrin copper(II) and nickel(II) complexes, bearing in meso-aryl rings a variety of substituents (3- NO 2, 3- CH 3, 3- Cl , 2,3,4,5,6-pentafluoro-, and 2,6-dichloro-), is described. The reactions of the above porphyrinates, carried out in CHCl 3 at room temperature, with aqueous HNO 3 (concentration 15-50%), resulted in the formation of the respective mono-β-nitrated products, in good or very good yield (74-93%). All the synthesized compounds were demetallated in CF 3 CO 2 H/H 2 SO 4 mixture to give β-nitro-substituted porphyrin free bases – very versatile substrates for further chemical transformations.
Synthesis of methyl pyropheophorbide-a pyrazole derivatives and their in vitro cell viabilities on A549 cells
Authors: Galindev Oyunbileg , Badraa Narangerel , Shim Young Key
Published: July 2009

Porphyrins and chlorins containing acetylacetone residues on the peripheral substituents are known to readily react with hydrazine derivatives to form porphyrin and chlorin derivatives possessing a pyrazole moiety. In this study, we have carried out the synthesis of methyl pyropheophorbide-a derivatives containing a pyrazole moiety on its peripheral position. Moreover, we have examined a preliminary in vitro effect of these new derivatives on A549 cancer cell in photodynamic therapy.
Ruthenium(II) meso-tetra-(benzo-15-crown-5)-porphyrinates: synthesis and spectroscopic investigation
Authors: Enakieva Yuliya Yu. , Gorbunova Yuliya G. , Tsivadze Aslan Yu. , Stern Christine , Guilard Roger
Published: July 2009

The synthesis of novel ruthenium(II) meso-tetra-(benzo-15-crown-5)-porphyrinates, meso-[( B 15 C 5)4 Por ] Ru ( CO )( MeOH ) (1) and meso-[( B 15 C 5)4 Por ] Ru ( L )2 (2)-(4) (meso-[( B 15 C 5)4 Por ]2-= 5,10,15,20-tetrakis-(benzo-15-crown-5)-porphyrinato-dianion; L = pyridine (py), pyrazine (pyz), 4,4′-bipyridyl (4,4′-bpy)), where CO and MeOH , or two N -donor ligands are axially coordinated to the central metal, are reported. The metalation of the free ligand performed by the reaction of Ru 3( CO )12 with meso-[( B 15 C 5)4 Por ] H 2 in 1,2,4-trichlorobenzene (TCB, bp = 215°C), gives (1) in a high yield. The synthesis of (2)-(4) involves the decarbonylation of (1) with trimethylamine N -oxide (( CH 3)3 NO ) in the presence of an excess of the N -donor ligand. The coordination of the axially bonded ligands is evidenced by different spectroscopic data.
Copper-64 labeled sulfophthalocyanines for positron emission tomography (PET) imaging in tumor-bearing rats
Authors: Soucy-Faulkner Anton , Rousseau Jacques A. , Langlois Réjean , Berard Véronique , Lecomte Roger , Bénard François , van Lier Johan E.
Published: July 2009

Sulfonated metallophthalocyanines ( PcS ) are second generation photosensitizers for photodynamic therapy (PDT) of cancer. Metal-free H2PcS are readily labeled with64Cu++to yield a mixture of sulfonated [64Cu ] CuPcS suitable for biodistribution studies in tumor-bearing rats by positron emission tomography (PET). Most of the64Cu activity was sequestrated within the kidneys (20%ID/g) and liver (12%ID/g) while tumor uptake values remained low (0.2%ID/g). Dissection and counting of individual tissue samples after the 24 h scan confirmed the uptake values derived from the PET images. The procedure can be applied to series of novel PcS to evaluate structure-tumor selectivity relationships as a parameter to select potential agents for photodynamic therapy.
Seco-porphyrazines with eight (p-tolyl) and (o-tolyl) units
Authors: Gonca Ergün , Baklaci Ümmü Gülsüm , Dinçer Hatice Akin
Published: July 2009

Magnesium porphyrazinates substituted with eight (p-tolyl) and (o-tolyl) units on the peripheral positions have been synthesized for the first time by cyclotetramerization of 1,2-bis(p-tolyl)maleonitrile and 1,2-bis(o-tolyl)maleonitrile in the presence of magnesium butanolate. Their demetalation by the treatment with trifluoroacetic acid resulted in partially oxidized products, namely, octakis(p-tolyl)-2-seco-porphyrazine-2,3-dione and octakis(o-tolyl)-2-seco-porphyrazine-2,3-dione. Further reactions of these products with copper(II) acetate, zinc(II) acetate and cobalt(II) acetate have led to the metallo derivatives, [octakis(p-tolyl)-2-seco-2,3-dioxoporphyrazinato] M(II) and [octakis(o-tolyl)-2-seco-2,3-dioxoporphyrazinato] M(II) ( M = Cu , Zn , Co ). These novel compounds have been characterized by elemental analysis, together with FT-IR, 1H NMR, UV-vis and mass spectral data.
Porphyrins with metal, metalloid or phosphorus atoms directly bonded to the carbon periphery
Authors: Atefi Farzad , Arnold Dennis P.
Published: July 2009

Organometallic porphyrins with a metal, metalloid or phosphorus fragment directly attached to their carbon framework emerged for the first time in 1976, and these macrocycles have been intensively investigated in the past decade. The present review summarises for the first time all reported examples as well as applications of these systems.
Synthesis of new side-chain phthalocyanine methacrylate monomers for ophthalmosurgery in ophthalmology
Authors: Kutureva Valentina , Baziakina Natascha , Maximova Ksenia , Morozova Valentina , Schnurpfeil Günter , Wöhrle Dieter , Suvorova Olga
Published: July 2009

Convenient synthesis of new methacryloyloxy-substituted phthalocyanines for polymerization reactions, i.e. copper(II) 2,9,16,23-tetra(methacryloxyethoxycarbonyl)phthalocyanine and copper 2,9,16-tris(tert-butyl)-23-(methacryloxyethoxycarbonyl)phthalocyanine, consisting of just a few steps, has been developed. The copolymerization with a dimethacrylate derivative was investigated. The substituted phthalocyanines are interesting materials for ophthalmosurgery in ophthalmology (contact vision correction of eye lenses).
Efficient synthesis of secondary and primary dialkyl α-aminophosphonates catalyzed by tetramethyl-tetra-3,4-pyridinoporphyrazinato copper(II) methyl sulfate under solvent-free conditions
Authors: Sobhani Sara , Safaei Elham , Asadi Mozaffar , Jalili Fariba , Tashrifi Zahra
Published: July 2009

An efficient method for the synthesis of secondary and primary dialkyl α-aminophosphonates under solvent-free conditions by one-pot reaction of aldehydes/ketones, amines/ammonium acetate and trialkyl/diethyl phosphite in the presence of a low catalytic amount of [ Cu (3,4-tmtppa)]( MeSO 4)4(0.16 mol%) as a highly stable and reusable catalyst, is described. By this method, aromatic, aliphatic, cyclic and heterocyclic aldehydes, hindered and cage ketones are converted into their corresponding α-aminophosphonates in good to excellent yields.
Tumor-localizing and radiosensitizing properties of meso-tetra(4-nido-carboranylphenyl)porphyrin (H2TCP)
Authors: Soncin Marina , Friso Elisabetta , Jori Giulio , Hao Erhong , Vicente M. Graça H. , Miotto Giovanni , Colautti Paolo , Moro Davide , Esposito Juan , Rosi Giancarlo , Fabris Clara
Published: July 2009

Background and Purpose: Boron Neutron Capture Therapy (BNCT) is a binary cancer treatment that exploits the short range particles released from a nuclear fission reaction involving the non-radioactive 10 B nucleus and low-energy neutrons for the destruction of tumor cells. In this perspective, porphyrins and phthalocyanines can represent a vehicle for the transport of significant amounts of boron to the neoplastic lesion. Material and Methods: B16F1 melanotic melanoma subcutaneously transplanted in C57/BL6 mice has been used as an in vivo model. Pharmacokinetic studies were performed by intratumoral and intravenous injection of a meso-substituted porphyrin containing 36 B atoms per molecule ( H 2 TCP ) and the distribution of H 2 TCP in the tumor was assessed by fluorescence microscopy analysis. The tumor-bearing mice were exposed to the radiation field for 20 min at a reactor power of 5 kW. Results: At 0.5 h after intratumoral administration or at 24 h after intravenous injection, the amount of 10 B in the tumor was found to be about 60 ppm and about 6 ppm, respectively. In spite of the different amounts of 10 B in the tumor at the time of irradiation, a very similar delay in tumor growth (5-6 days) was induced by neutron irradiation in the two groups of injected mice with respect to control mice. Conclusions: Our results demonstrate that a suitable boron-loaded porphyrin displays a significant affinity for subcutaneous tumors, and upon activation by thermal neutrons, can promote an important response even in a fairly aggressive and generally radioresistant tumor such as melanotic melanoma.
DNA and BSA binding studies of novel tetracationic phthalocyanines
Authors: Öztürk Ramazan , Kalay Şaban , Kalkan Ayfer , Türkan Ali , Abasıyanık Mustafa F. , Bayır Zehra A. , Gül Ahmet
Published: July 2009

The novel tetracationic metallophthalocyanines having diethylmethyl aminoethylsulfanyl groups on the periphery have been synthesized and characterized. The compounds tend to form aggregates in aqueous solutions. The aggregation of ZnPc 4+ or CoPc 4+, but not that of CuPc 4+, was hindered by the addition of surfactants (Triton X-100 and Tween 20). Using absorption and fluorescence spectroscopic techniques, DNA and BSA binding properties of tetracationic ZnPc in the presence of the surfactants were also investigated.
Interaction of cationic water-soluble meso-tetrakis(4-N-methylpyridiniumyl)porphyrin (TMPyP) with ionic and nonionic micelles: aggregation and binding
Authors: Santiago Patrícia S. , Gandini Shirley C.M. , Moreira Leonardo M. , Tabak Marcel
Published: July 2009

The equilibrium of meso-tetrakis(4-N-methylpyridiniumyl)porphyrin (TMPyP) in aqueous solution in the presence of surfactants was studied by optical spectroscopic techniques and SAXS (small angle X-ray scattering). Anionic SDS (sodium dodecyl sulfate), zwitterionic HPS (N-hexadecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate) and nonionic TRITON X-100 (t-octylphenoxypolyethoxyethanol), surfactants were used. TMPyP is characterized by a protonation equilibrium with a pKa around 1.0, associated with the diacid-free base transition, and a second pKa around 12.0 related with the transition between the free base and the monoanion form. Three independent species were observed for TMPyP at pH 6.0 as a function of SDS concentration: free TMPyP, TMPyP-SDS aggregates and porphyrin monomer bound to micelles. For HPS and TRITON X-100, the equilibrium of TMPyP as a function of pH is quite similar to that obtained in pure aqueous solution: no aggregation was observed, suggesting that electrostatic contribution is the major factor in the interaction between TMPyP and surfactants. SAXS data analysis demonstrated a prolate ellipsoidal shape for SDS micelles; no significant changes in shape and size were observed for SDS-TMPyP co-micelles. Moreover, the ionization coefficient, α, decreases with the increase of the porphyrin concentration, suggesting the "screening" of the anionic charge of SDS by the cationic porphyrin. These results are consistent with optical absorption, fluorescence and RLS (resonance light scattering) spectroscopies data, allowing to conclude that neutral surfactants present a smaller interaction with the cationic porphyrin as compared with an ionic surfactant. Therefore, the interaction of TMPyP with the ionic and nonionic surfactants is predominantly due to the electrostatic contribution.
Synthesis, properties and photodynamic activities of some zinc(II) phthalocyanines against Escherichia coli and Staphylococcus aureus
Authors: Seven Ozlem , Dindar Bircan , Aydemir Sohret , Cilli Feriha
Published: July 2009

Two new zinc phthalocyanine derivatives bearing four 3,5-di-tert-butyl-4-hydroxyphenyl (ZnPc1) and 3,5-dimethylphenoxy (ZnPc2) have been synthesized and proved by elemental analyses and UV-vis, 1H NMR, FTIR and MALDI-TOF mass spectra as spectroscopic determination. Thermal stabilities of these neutral Zn -phthalocyanines were performed by thermal gravimetric analysis and, significantly, were found stable up to 373 °C for ZnPc1 and 550 °C for ZnPc2. In addition, the photostability of the sensitizers was quite successful within 240 min. Furthermore, photodynamic therapy has been investigated using these neutral phthalocyanines. Singlet oxygen generation capacities of ZnPc1 and ZnPc2 were studied using 1,3-diphenyl-iso-benzofuran (50.0 μM) as a selective singlet oxygen trap in DMSO and both of them demonstrated very high singlet oxygen generation capacity. Photodynamic therapy is of considerable interest for its potential as an antimicrobial therapy on the grounds that the photodynamic activity of these compounds was tested against a Gram-negative bacteria, Escherichia coli and a Gram-positive bacteria, Staphylococcus aureus. Suspensions of the microorganisms were irradiated for 240 min in the presence of ZnPc1 (with hydrophilic group) and ZnPc2 phthalocyanines. In order to simulate solar radiation, we used a 750 W xenon lamp. Minimum photosensitizer concentration was used as 0.1 mg.10 mL-1 in 1% dimethylsulfoxide/phosphate buffer saline solution (DMSO/PBS). Moreover, the photostability of these compounds has been investigated and the effect of the amount of DMSO tested against selected bacteria. In the dark, with and without Pcs, bacterial inactivation did not occur. Bacterial inactivation by light with ZnPc1 was observed in response to Gram-negative bacteria E. coli and Gram-positive bacteria S. aureus, whereas the photoinactivation studies with ZnPc2 have revealed that the lack of its activity is due to its poor affinity for either of the organisms. These results suggest that a neutral amphiphilic photosensitizer may be easily used in an application concerning photoinactivation of bacterial cells as well as ionic photosensitizers.
Long-lived charge-separated states of simple electron donor-acceptor dyads using porphyrins and phthalocyanines
Authors: Ohkubo Kei , Fukuzumi Shunichi
Published: July 2009

Control of electron-transfer processes is described for a number of electron donor-acceptor dyads containing porphyrins or phthalocyanines as models for the photosynthetic reaction center. The rates for intramolecular electron transfer in the dyads are controlled by the driving force and reorganization energy of electron transfer. The small reorganization energy of electron transfer reactions and large driving force of charge recombination are required to form long-lived charge-separated states. A directly linked zinc chlorin-fullerene dyad, especially, has the longest lifetime of charge-separated state at 120 s at -150 °C, which is a much longer lifetime and higher energy than those of natural photosynthetic reaction centers. On the other hand, the charge-separated states of the phthalocyanine-based donor-acceptor dyads (silicon phthalocyanine-fullerene, and zinc phthalocyanine-perylenebisimide) are short-lived since charge recombination forms the low-lying triplet excited state of the chromophore. The energy of the charge-separated state of a zinc phthalocyanine-perylenebisimide dyad is decreased by binding of metal ions to the radical anion moiety in order to be lower than the triplet excited state. This results in formation of a long-lived charge-separated state. The mechanistic viability of formation of long-lived charge-separated states is demonstrated by a variety of examples based on the Marcus theory of electron transfer.
Electronic structure of five- and six-coordinate iron(III) tetraazaporphyrin complexes: pyrrole-Cαchemical shift as a useful probe
Authors: Ikeue Takahisa , Kurahashi Satoshi , Handa Makoto , Sugimori Tamotu , Nakamura Mikio
Published: July 2009

Electronic structure of a series of five-coordinate Fe ( OArTAzP ) X ( OAr = octaaryltetraazaporphyrin , X = Cl-, Br-, I-; Ar = 4-tert-butylphenyl) have been examined on the basis of1H NMR,13C NMR, and EPR spectroscopy as well as SQUID magnetometry. These complexes adopt the intermediate-spin state as in the case of analogous complexes reported by Fitzgerald et al. (Inorg. Chem. 1992; 31: 2006-2013) and Stuzhin et al. (Inorg. Chim. Acta 1995; 236: 131-139). The13C NMR studies using13C -enriched complexes at the pyrrole α positions have revealed that the pyrrole- Cαsignals appear at extraordinary upfield positions, i.e. -130 to -250 ppm at 273 K, due to the dz2-a2 uand dπ-3 eginteractions. The Curie plots of the pyrrole- Cαsignals have further revealed that the iodide complex adopts a much purer intermediate-spin state than the bromide and chloride complexes. In contrast to the case of Fe ( OArTAzP ) X , six-coordinate [ Fe ( OArTAzP )( CN )2]-showed the pyrrole- Cαsignal at 47 ppm at 273 K, which indicates that the complex adopts the low-spin state with the ( dxy)2( dxz, dyz)3electron configuration. Thus, the13C NMR chemical shift of the pyrrole- Cαsignal turns out to be quite a good probe to elucidate the spin state and electron configuration of iron(III) tetraazaporphyrins, where the1H NMR spectroscopy is less useful because of the absence of the hydrogen atoms as well as the alkyl or aryl groups directly attached to the meso positions.
Amphiphilic galactosylated phthalocyanines
Authors: Kumru Ufuk , Ermeydan Mahmut Ali , Dumoulin Fabienne , Ahsen Vefa
Published: July 2009

Two amphiphilic Ni phthalocyanines bearing a hydrophilic galactose head facing six hydrophobic thiohexyl chains are described. The place of the glycosylation step on the overall synthetic pathway is discussed. For the first time, phthalocyanines are used as acceptors in glycosylation reactions, in excellent yields.
Topography and electrical conductivity of films of molecular complexes of zinc(II)tetra-tert-butylphthalocyanine with electron-donating ligands
Authors: Lebedeva Natalia Sh. , Malkova Elena A. , Melkonyn Shushanna R. , Fedorov Mihail I. , Maslennikov Sergey V. , Parfenyuk Elena V. , Vyugin Anatoly I.
Published: July 2009

Topography and specific electrical conductivity of films of molecular complexes of zinc(II)tetra-tert-butylphthalocyanine ( Zn (t- Bu )4 Pc ) with electron-donating ligands and films of pure α-polymorphous modification of zinc(II)tetra-tert-butylphthalocyanine have been studied. It has been found that the specific electrical conductivity increases from 30 to 3.5 × 105 times upon molecular complex formation of Zn (t- Bu )4 Pc with ligands.
Bismuth insertion in functionalized porphyrins: influence of the structure delivering substituted malonic acid groups
Authors: Balieu Sébastien , Halime Zakaria , Lachkar Mohammed , Boitrel Bernard
Published: July 2009

A comparative study of bismuth complexation by various porphyrins which differ according to the structural scaffold – either picket(s) or strap(s) – that deliver the carboxylic acid groups close to the metal, has been performed. Unlike strapped porphyrins, and although more flexible, the picket ligands do not lead to more stable bismuth complexes.
Chiral supramolecular capsule by ligand promoted self-assembly of resorcinarene-Zn porphyrin conjugate
Authors: Stefanelli Manuela , Monti Donato , Van Axel Castelli Valeria , Ercolani Gianfranco , Venanzi Mariano , Pomarico Giuseppe , Paolesse Roberto
Published: July 2009

Cavitand- Zn porphyrin conjugates self-assemble to give supramolecular (1 + 1) structures upon coordination of bifunctional ligands such as 4,4'-bipyridine and the like. The formation of the capsule depends on key structural factors, such as the size of the cavity, and the possibility of the onset of hydrogen bonds, π–π and π–cation interactions. The extension of this protocol to chiral bifunctional ligands, such as (+)-cinchonine and (−)-cinchonidine, and cinchona alkaloid derivatives, results in the achievement of supramolecular structures with chiral cavities, whose configuration is dependent on the asymmetry of the bound ditopic ligand. MM calculations, gave further insights into the plausible geometry of the structures.
Just for you
Authors: Monroe Don
Published: July 2009

Recommender systems that provide consumers with customized options have redefined e-commerce, and are spreading to other fields.
Face recognition breakthrough
Authors: Kroeker Kirk L.
Published: July 2009

By using sparse representation and compressed sensing, researchers have been able to demonstrate significant improvements in accuracy over traditional face-recognition techniques.
U.S. unveils cybersecurity plan
Authors: Goth Gregory
Published: July 2009

'Intent and timing' may help the federal cyberspace initiative work better than previous blueprints.
A blind person's interactions with technology
Authors: Shinohara Kristen , Tenenberg Josh
Published: July 2009

Meaning can be as important as usability in the design of technology.
Learning to build an IT innovation platform
Authors: Kohli Rajiv , Melville Nigel P.
Published: July 2009

Introduction

Information Technology (IT) pervades every aspect of a firm's value chain as a vast electronic network of interconnected applications and data. Managers perceive the immense
potential
of this complex infrastructure to enhance products and processes and create altogether new ones. However, some have gone a step further and determined how to harness untapped IT business value again and again to create innovative and valuable applications by reconfiguring existing systems in new ways. Creative adaptation of existing functionality (such as broadband over power lines) to enable entirely new applications (such as real-time power grid monitoring) rules the day for these forward-thinking business leaders.

What separates successful IT innovators from others? Is luck a primary driver, or are there deliberate actions that management can take to raise the odds of success? Given substantial implications for business performance, we set out to explore this question by interviewing senior IS and business executives with demonstrated track records of extracting untapped IT business value from existing IT infrastructural assets. Our objective was to uncover underlying mechanisms linking organizational actions with innovation outcomes.

What we learned is that while serendipity can sometimes play a role, developing a specialized set of competencies, which we call an
IT innovation platform
, plays a much larger and decisive role. IT capabilities drive innovation by enabling organizations to redesign business processes, craft a competitive strategy, and identify and cater to customer preferences. As we discuss below, understanding what these competencies are, how they are developed, and how they work together holistically can yield significant new sources of growth and bolster performance. While our research is exploratory in nature and requires rigorous testing, we believe that this new perspective on IT business value expands managerial understanding of how to extract ever-greater value from existing IT assets.
Ranking billions of web pages using diodes
Authors: Kaul Rohit , Yun Yeogirl , Kim Seong-Gon
Published: July 2009

Introduction

Because of the web's rapid growth and lack of central organization, Internet search engines play a vital role in assisting the users of the Web in retrieving relevant information out of the tens of billions of documents available. With millions of dollars of potential revenue at stake, commercial Web sites compete fiercely to be placed prominently within the first page returned by a search engine. As a result, search engine optimizers (SEOs) developed various forms of search engine spamming (or spamdexing) techniques to artificially inflate the rankings of Web pages. Link-based ranking algorithms, such as Google's PageRank, have been largely effective against most conventional spamming techniques.

However, PageRank has three fundamental flaws that, when exploited aggressively, can be proven to be its Achilles' heel: First, PageRank gives a minimum guaranteed score to every page on the Web; second, it rewards all incoming links as valid endorsements; and third, it imposes no penalty for making links to low-quality pages. SEOs can take advantage of these shortcomings to the extreme by employing an Artificial Web, a collection of an extremely large number of computer-generated Web pages containing many links to only a few target pages. Each page of the Artificial Web collects the minimum PageRank and feeds it back to the target pages. Although the individual endorsements are small, the flaws of PageRank make it possible for an Artificial Web to accumulate sizable PageRank values for the target pages. The SEOs can even download a substantial portion of the real Web and modify only the destinations of the hyperlinks, thus circumventing any detection algorithms based on the quality or the size of pages. As the size of an Artificial Web can be comparable to that of the real Web, SEOs can seriously compromise the objectivity of the results that PageRank provides. Although some statistical measures can be employed to identify specific attributes associated with an Artificial Web and filter them out of search results, it is far more desirable to develop a new ranking model that is free of such exploits to begin with.
An architecture for routing in the ISO connectionless internet
Authors: Zakon Stuart J.
Published: July 2009

The ISO Connectionless Internet Protocol provides a uniform network service over many types of subnetworks. The protocol has currently progressed to the status of draft international standard (DIS 8473). Ideally, the Internet protocol allows for a high degree of connectivity in a global packet-switched network. However, much work needs to be done in the area of routing before this becomes possible in practice.
Articles on computer communication from other publications
Authors: Burruss John C.
Published: July 2009

The following list of articles has been selected from "Network News," a monthly publication produced by Janet Slinn, who is a Library Systems Supervisor at Digital Equipment Corporation (1925 Andover Street, Tewksbury, MA 01876). Janet has been kind enough to send the Editor her material which is a quite extensive cross-referenced compendium of current articles in the communications area. The material in this section is a technically oriented subset of interest to CCR readers, extracted from several issues of Janet's publication.
Dust Explosion Prevention and Mitigation, Status and Developments in Basic Knowledge and in Practical Application
Authors: Eckhoff Rolf K.
Published: July 2009

Right from the early days of the process industries, continuous efforts have been made to develop and improve measures for prevention and mitigation of dust explosions in these industries. Nevertheless this hazard continues to threaten industries that manufacture, use and/or handle powders and dusts of a wide range of combustible materials. To improve methods for predicting explosion development in real industrial plant has been one major challenge. Hence, during the last years comprehensive numerical simulation codes, for addressing this problem, have been developed. Progress has also been made in other areas, for example, ignition source prevention. The importance of adopting inherently safer process design, by building on firm knowledge in powder science and technology, and of systematic education/training of personnel, is also emphasized.
Epicardial Substrate and Outcome With Epicardial Ablation of Ventricular Tachycardia in Arrhythmogenic Right Ventricular Cardiomyopathy/Dysplasia
Authors: Garcia Fermin C. , Bazan Victor , Zado Erica S. , Ren Jian-Fang , Marchlinski Francis E.
Published: July 2009

Background—

Efficacy of endocardial ventricular tachycardia (VT) ablation in arrhythmogenic right ventricular cardiomyopathy/dysplasia may be limited by epicardial VT, right ventricular thickening, or both. We sought to characterize the endocardial versus epicardial substrate, measure right ventricular free wall thickness, and determine epicardial ablation efficacy in patients with right ventricular cardiomyopathy/dysplasia.

Methods and Results—

Thirteen consecutive patients (3 female; aged 43±15 years; range, 17 to 70 years) undergoing endocardial and epicardial sinus rhythm voltage mapping and epicardial VT ablation after failed endocardial VT ablation were included. In each patient, the low bipolar voltage area (<1.0 mV for epicardium and <1.5 mV for endocardium) was more extensive on the epicardium (95±47 versus 38±32 cm
2
;
P
<0.001) and was uniformly marked by multicomponent and late electrograms. The basal right ventricular thickness assessed by electroanatomic map was >10 mm in 6 of 13 patients compared with 5 to 10 mm in 4 reference patients without structural disease. Twenty-seven VTs were targeted on the epicardium with the use of activation, entrainment, or pace mapping with focal/linear ablation and targeting of late potentials. Epicardial VTs were targeted opposite normal endocardium in 10 patients (77%) and/or opposite ineffective endocardial ablation sites in 11 patients (85%). During 18±13 months, 10 of the 13 patients (77%) had no VT, with 2 patients having only a single VT at 2 and 38 months, respectively.

Conclusions—

Patients with right ventricular cardiomyopathy/dysplasia and VT after endocardial ablation have a more extensive epicardial area of electrogram abnormalities and frequently have basal right ventricular wall thickening. Epicardial substrate and VT mapping identifies targets, and ablation results in VT control.
Effects of Dietary Sodium Reduction on Blood Pressure in Subjects With Resistant Hypertension
Authors: Pimenta Eduardo , Gaddam Krishna K. , Oparil Suzanne , Aban Inmaculada , Husain Saima , Dell'Italia Louis J. , Calhoun David A.
Published: July 2009

Observational studies indicate a significant relation between dietary sodium and level of blood pressure. However, the role of salt sensitivity in the development of resistant hypertension is unknown. The present study examined the effects of dietary salt restriction on office and 24-hour ambulatory blood pressure in subjects with resistant hypertension. Twelve subjects with resistant hypertension entered into a randomized crossover evaluation of low (50 mmol/24 hours×7 days) and high sodium diets (250 mmol/24 hours×7 days) separated by a 2-week washout period. Brain natriuretic peptide; plasma renin activity; 24-hour urinary aldosterone, sodium, and potassium; 24-hour ambulatory blood pressure monitoring; aortic pulse wave velocity; and augmentation index were compared between dietary treatment periods. At baseline, subjects were on an average of 3.4±0.5 antihypertensive medications with a mean office BP of 145.8±10.8/83.9±11.2 mm Hg. Mean urinary sodium excretion was 46.1±26.8 versus 252.2±64.6 mmol/24 hours during low- versus high-salt intake. Low- compared to high-salt diet decreased office systolic and diastolic blood pressure by 22.7 and 9.1 mm Hg, respectively. Plasma renin activity increased whereas brain natriuretic peptide and creatinine clearance decreased during low-salt intake, indicative of intravascular volume reduction. These results indicate that excessive dietary sodium ingestion contributes importantly to resistance to antihypertensive treatment. Strategies to substantially reduce dietary salt intake should be part of the overall treatment of resistant hypertension.
Effect of Modest Salt Reduction on Blood Pressure, Urinary Albumin, and Pulse Wave Velocity in White, Black, and Asian Mild Hypertensives
Authors: He Feng J. , Marciniak Maciej , Visagie Elisabeth , Markandu Nirmala D. , Anand Vidya , Dalton R. Neil , MacGregor Graham A.
Published: July 2009

A reduction in salt intake lowers blood pressure. However, most previous trials were in whites with few in blacks and Asians. Salt reduction may also reduce other cardiovascular risk factors (eg, urinary albumin excretion, arterial stiffness). However, few well-controlled trials have studied these effects. We carried out a randomized double-blind crossover trial of salt restriction with slow sodium or placebo, each for 6 weeks, in 71 whites, 69 blacks, and 29 Asians with untreated mildly raised blood pressure. From slow sodium to placebo, urinary sodium was reduced from 165±58 (±SD) to 110±49 mmol/24 hours (9.7 to 6.5 g/d salt). With this reduction in salt intake, there was a significant decrease in blood pressure from 146±13/91±8 to 141±12/88±9 mm Hg (
P
<0.001), urinary albumin from 10.2 (IQR: 6.8 to 18.9) to 9.1 (6.6 to 14.0) mg/24 hours (
P
<0.001), albumin/creatinine ratio from 0.81 (0.47 to 1.43) to 0.66 (0.44 to 1.22) mg/mmol (
P
<0.001), and carotid-femoral pulse wave velocity from 11.5±2.3 to 11.1±1.9 m/s (
P
<0.01). Subgroup analysis showed that the reductions in blood pressure and urinary albumin/creatinine ratio were significant in all groups, and the decrease in pulse wave velocity was significant in blacks only. These results demonstrate that a modest reduction in salt intake, approximately the amount of the current public health recommendations, causes significant falls in blood pressure in all 3 ethnic groups. Furthermore, it reduces urinary albumin and improves large artery compliance. Although both could be attributable to the falls in blood pressure, they may carry additional benefits on reducing cardiovascular disease above that obtained from the blood pressure falls alone.
Regional Release and Clearance of C-Type Natriuretic Peptides in the Human Circulation and Relation to Cardiac Function
Authors: Palmer Suetonia C. , Prickett Timothy C.R. , Espiner Eric A. , Yandle Timothy G. , Richards A. Mark
Published: July 2009

Production and clearance of plasma C-type natriuretic peptide (CNP) and amino terminal (NT)-proCNP immunoreactivity in the human circulation remain poorly characterized. Accordingly, we have measured arterial and venous concentrations of CNP and NT-proCNP across multiple tissue beds during cardiac catheterization in 120 subjects (age: 64.2±9.0 years; 73% men) investigated for cardiovascular disorders. The heart, head and neck, and musculoskeletal tissues made the clearest contributions to both plasma CNP and NT-proCNP (
P
<0.05). Net release of NT-proCNP was also observed from hepatic tissue (
P
<0.001). Negative arteriovenous gradients for CNP were observed across renal, hepatic, and pulmonary tissue (
P
<0.05), indicating net clearance, whereas no tissue-specific site of NT-proCNP clearance was identified. Age, mean pulmonary artery pressure, left ventricular end diastolic pressure, Brandt score of myocardial jeopardy, and troponin I were independent predictors of circulating CNP levels in multivariable analysis. Sex and kidney function were independently predictive of arterial NT-proCNP. The proportional step-up of CNP (+60%) across the heart was less than for brain natriuretic peptide (+123%) but greater than for NT–pro-brain natriuretic peptide (NT-proBNP) (+36%) and NT-proCNP (+42%;
P
<0.001 for all). We conclude that cardiac and head and neck tissue are important sources of CNP. Circulating CNP but not NT-proCNP concentrations are related to cardiac hemodynamic load and ischemic burden. Although cardiac release is most evident, multiple additional tissues release NT-proCNP immunoreactivity without evidence for an organ-specific site for NT-proCNP degradation. Taken together, differences in magnitude and direction of transorgan gradients for CNP compared with NT-proCNP suggest net generalized cosecretion with differing mechanisms of clearance.
Endogenous Interleukin-10 Inhibits Angiotensin II–Induced Vascular Dysfunction
Authors: Didion Sean P. , Kinzenbaw Dale A. , Schrader Laura I. , Chu Yi , Faraci Frank M.
Published: July 2009

Angiotensin II (Ang II) produces inflammation and endothelial dysfunction in blood vessels. We tested the hypothesis that interleukin 10 (IL-10), an antiinflammatory cytokine, protects against Ang II–induced vascular dysfunction. Responses of carotid arteries from wild-type and IL-10–deficient mice (
IL-10
−/−
) were examined in vitro after overnight incubation with vehicle or Ang II (1 nmol/L). In arteries from wild-type mice, acetylcholine (an endothelium-dependent agonist) produced relaxation that was not affected by Ang II. In contrast, relaxation to acetylcholine in arteries from
IL-10
−/−
mice was reduced by >50% by Ang II (
P
<0.05) and this effect was prevented by a scavenger of superoxide. Vascular superoxide increased ≈2-fold (
P
<0.05) after treatment with Ang II in
IL-10
−/−
mice but not in wild-type. After systemic administration of Ang II (1.4 mg/kg per day for 10 days), Ang II produced modest impairment of endothelial function in wild-type mice but marked impairment in
IL-10
−/−
mice (
P
<0.05) that was reversed by a superoxide scavenger. Increases in arterial pressure in response to Ang II were similar in wild-type and
IL-10
−/−
mice. These findings provide the first evidence that endogenous IL-10 limits Ang II-mediated oxidative stress and vascular dysfunction both in vitro and in vivo suggesting that at least some of the protective effects of IL-10 may occur within the vessel wall.