LbL Fabricated Poly(Styrene Sulfonate)/TiO2 Multilayer Thin Films for Environmental Applications

Fabrication of multilayer ultrathin composite films composed of nanosized titanium dioxide particles (P25, Degussa) and polyelectrolytes (PELs), such as poly(allyl amine hydrochloride) (PAH) and poly(styrene sulfonate sodium salt) (PSS), on glass substrates using the layer-by-layer (LbL) assembly technique and its potentia application for the photodegradation of rhodamine B under ultraviolet (UV) irradiation has been reported. The polyelectrolytes and TiO2 were deposited on glass substrates at pH 2.5 and the growth of the multilayers was studied using UV/vis speccrophotometer. Thicknes measurements of the films showed a linear increase in film thickness with increase in number of bilayers. The surface microstructure of the thin films was characterized by field emission scanning electron microscope. The ability of the catalysts immobilized by this technique was compared with TiO2 films prepared by drop casting and spin coating methods. Comparison has been made in terms of film stability and photodegradation of rhodamine B. Process variables such as the effect of surface area of the multilayers, umber of bilayers, and initial dye concentration on photodegradation of rhodamine B were studied. Degradation efficiency increased with increase in number of catalysts (total surface area) and bilayers. Kinetics analysis indicated that the photodegradation rates follow first order kinetics. Under maximum loading of TiO2, with five catalyst slides having 20 bilayers of polyelectrolyte/TiO2 on each, 100 mL of 10 mg/L dye solution could be degraded completely in 4 h. The same slides could be reused with the same efficiency for several cycles. This study demonstrates that nanoparticles can be used in wastewater treatment using a simple immobilization technique. This makes the process an attractive option for scale up.

Crystal Structures of a New Polymorphic Form of Gabapentin Monohydrate and the E and Z Isomers of 4-Tertiarybutylgabapentin

Gabapentin, a widely used antiepileptic drug, crystallizes in multiple polymorphic forms. A new crystal form of gabapentin monohydrate in the space group Pbca is reported and the packing arrangement compared with that of a previously reported polymorph in the space group P2(1)/c [Ibers, J.A. (2001) Acta Crystallogr; C57:641]. Gabapentin polymorphs can also occur from a selection of one of the two distinct chair forms of the 1,1-disubstituted cyclohexane. Crystal structures of the E and Z isomers of 4-tert-butylgabapentin provide models for analyzing anticipated packing modes in the conformational isomers of gabapentin. The E isomer crystallized in the space group Pca2(1), while the Z isomer crystallized in the space group P2(1)/c. The crystal structure of E-4-tert-butylgabapentin provides the only example of a structure in a non-centrosymmetric space group. Crystal structures of the hydrochloride and hydrobromide salts of 4-tert-butyl derivatives are reported. The results suggest that for gabapentin, a large 'polymorph-space' may be anticipated, in view of the multiple conformational states that are accessible to the molecule.

Influence of the hydrogen bond on the N-H stretching frequencies in amino-acids

The spectra of glycine, its addition compounds and other amino-acids exhibit Raman lines in the region from 3250 cm.−1 to 2500 cm.−1 It has been shown that these lines cannot be assigned to N-H...O stretching vibrations, where the N atom has the covalency of three, but to N+-H...O stretching vibration where the N atom has the covalency of four. Using the data obtained with triglycine sulphate which has the largest number of N+-H...O bonds and whose H bond lengths are known, the correlation curve giving the relation between the N+-H...O stretching frequencies and the corresponding H bond lengths has been drawn. Using this correlation curve, the N+-H...O stretching frequencies appearing inα-glycine,γ-glycine, diglycine hydrochloride, diglycine hydrobromide,l-asparagine monohydrate anddl-alanine have been satisfactorily accounted for on the basis of the known hydrogen bond lengths in these substances.

Reversible polyelectrolyte capsules as carriers for protein delivery

A reversible drug delivery system based on spontaneous deposition of a model protein into preformed microcapsules has been demonstrated for protein delivery applications. Layer-by-Layer assembly of poly(allylamine hydrochloride) (PAH) and poly(methacrylic acid) (PMA) onto polystyrene sulfonate (PSS) doped CaCO3 particles, followed by core removal yielded intact hollow microcapsules having a unique property to induce spontaneous deposition of bovine serum albumin (BSA) at pH below its isoelectric point of 4.8, where it was positively charged. These capsules showed reversible pH dependent open and closed states to fluorescence labeled dextran (FITC-Dextran) and BSA (FITC-BSA). The loading capacity of BSA increased from 9.1 x 10(7) to 2.03 x 10(8) molecules per capsule with decrease in pH from 4.5 to 3.The loading of BSA-FITC was observed by confocal laser scanning microscopy (CLSM), which showed homogeneous distribution of protein inside the capsule. Efficient loading of BSA was further confirmed by atomic force microscopy (AFM) and scanning electron microscopy (SEM).The interior capsule concentration was as high as 209 times the feeding concentration when the feeding concentration was increased from 1 to 10 mg/ml. The deposition was initially controlled by spontaneous loading mechanism at lower BSA concentration followed by diffusion controlled loading at higher concentration; which decreased the loading efficiency from 35% to 7%. Circular dichroism (CD) measurements and Fourier transform infrared spectroscopy (FTIR) confirmed that there was no significant change in conformation of released BSA in comparison with native BSA. The release was initially burst in the first 0.5 h and sustained up to 5 h. The hollow capsules were found to be biocompatible with mouse embryonic fibroblast (MEF) cells during in vitro cell culture studies. Thus these pH sensitive polyelectrolyte microcapsules may offer a promising delivery system for water soluble proteins and peptides. (C) 2010 Elsevier B.V. All rights reserved.

2,1,3-Bentsoksadiatsolirakenteiset molekyylit antibakteerisina ja antiparasiittisina yhdisteinä

Aikaisemman tutkimuksen perusteella tiedettiin tiettyjen 2,1,3-bentsoksadiatsolirakenteisten molekyylien olevan aktiivisia Chlamydia pneumoniae –bakteeria vastaan. Tutkimusta lähdettiin jatkamaan ja 2,1,3-bentsoksadiatsolimolekyylien rakenne-aktiivisuusuhteista haluttiin saada lisätietoa. Tarkoituksena oli kehittää 2,1,3-bentsoksadiatsolimolekyyleille ja sen avulla muodostaa molekyylikirjasto. Syntetisoidut molekyylit haluttiin testata sekä Chlamydia pneumoniae -bakteeria että Leishmania donovani –parasiittia vastaan. Chlamydia pneumoniae –bakteeri aiheuttaa akuutteja ylä- ja alahengitystieinfektiota, kuten keuhkoputkentulehdusta. Akuutissa tulehduksessa oireet vaihtelevat huomattavasti. Chlamydia pneumoniae –bakteerilla on myös taipumus aiheuttaa kroonisia tulehduksia. Nämä ovat useissa tutkimuksissa yhdistetty kansantaloudellisesti merkittäviin sairauksiin, kuten ateroskleroosiin ja astmaan. Leishmanioosi on toiseksi yleisin loissairaus ihmisellä malarian jälkeen. Leishmania donovani –parasiitti voi aiheuttaa tappavaa viskeraalista leishmanioosia. Vuodessa leishmanioosiin kuolee yli 50 000 ihmistä. Viime vuosina leishmanioosin lääkehoidossa on esiintynyt monenlaisia ongelmia. Osat lääkkeistä ovat menettäneet tehonsa ja osalla esiintyy vakavia haittavaikutuksia. 2,1,3-Bentsoksadiatsolirakenteisille yhdisteille saatiin kehitettyä toimiva synteesireitti. Lähtöaineena käytettiin 4-amino-2-nitrobentsoehappoa, josta saatiin hapettavalla renkaansulkeutumisreaktiolla 2,1,3-bentsoksadiatsoli-5-karboksyylihappoa. Karboksyylihaposta syntetisoitiin amidi-välituotteen kautta 2,1,3-bentsoksadiatsoli-5-karbonitriiliä. Hydroksyyliamiini hydrokloridin avulla 2,1,3-bentsoksadiatsoli-5-karbonitriilistä muodostettiin vastaavaa karboksimidamidia, joka oli synteesireitin yhteinen välituote kaikille molekyyleille. Viimeisessä vaiheessa N´-hydroksidi-2,1,3-bentsoksadiatsoli-5-karboksimidamidin annettiin reagoida joko fenyyli-isosyanaatin tai fenyyli-isotiosyanaatin kanssa, jolloin saatiin lopputuotetta. Synteesireitin kehittäminen osoittautui haastavaksi ja loppujen lopuksi saatiin ainoastaan kolme lopputuotetta syntetisoitua. Yksi lopputuotteista testattiin C. pneumoniae –bakteeria vastaan Åbo akademissa Turussa. Testattavaa yhdiste ei sisältänyt 2,1,3-bentsoksadiatsoliarengasta ja bioaktiivisuuskokeen tulos oli odotusten mukainen. Yhdiste ei ollut aktiivinen C. pneumoniae –bakteeria vastaan alhaisilla konsentraatioilla ja tuloksesta voitiin todeta 2,1,3-bentsoksadiatsolirengaan olevan tärkeä aktiivisuuden kannalta. Kaksi lopputuotetta saatiin testaukseen Leishamania donovani –parasiittia vastaan Israeliin. Ainoastaan toinen molekyyleistä sisälsi 2,1,3-bentsoksadiatsolirakenteen. Bioaktiivisuuskokeiden tulokset olivat erittäin rohkaisevia. Yhdisteet olivat aktiivisia parasiittia vastaan jo alhaisilla konsentraatioilla. Kuitenkin 2,1,3-bentsoksadiatsolirakenteinen molekyyli oli aktiivisempi, joten tämäkin aktiivisuuskokeen perusteella huomattiin rengasrakenteen olevan tärkeä aktiivisuuden kannalta.

Preparation, characterization, spectral and thermal analyses of (N2H5)2MCl4·2H2O (M = Fe, Co, Ni and Cu); crystal structure of the iron complex

Hydrazinium metal chlorides, (N2H5)2MCl4·2H2O (where M = Fe, Co, Ni and Cu), have been prepared from the aqueous solutions of the respective metal chlorides and hydrazine hydrochloride (N2H4·HCl or N2H4·2HCl) and investigated by spectral and thermal analyses. The crystal structure of the iron complex has been determined by direct methods and refined by full-matrix least-squares to an R of 0.023 and Rw of 0.031 for 1495 independent reflections. The structure shows ferrous ion in an octahedral environment bonded by two hydrazinium cations, two chloride anions and two water molecules. In the complex cation [Fe(N2H5)2(H2O)2Cl2]2+, the coordinated groups are in trans positions.

Dopamine receptors in human foetal brains:Characterization, regulation and ontogeny of [3H]spiperone binding sites in striatum

Eighteen corpora striata from normal human foetal brains ranging in gestational age from 16 to 40 weeks and five from post natal brains ranging from 23 days to 42 years were analysed for the ontogeny of dopamine receptors using [3H]spiperone as the ligand and 10 mM dopamine hydrochloride was used in blanks. Spiperone binding sites were characterized in a 40-week-old foetal brain to be dopamine receptors by the following criteria: (1) It was localized in a crude mitochondrial pellet that included synaptosomes; (2) binding was saturable at 0.8 nM concentration; (3) dopaminergic antagonists spiperone, haloperidol, pimozide, trifluperazine and chlorpromazine competed for the binding with IC50 values in the range of 0.3–14 nM while agonists—apomorphine and dopamine gave IC50 values of 2.5 and 10 μM, respectively suggesting a D2 type receptor.Epinephrine and norepinephrine inhibited the binding much less efficiently while mianserin at 10 μM and serotonin at 1 mM concentration did not inhibit the binding. Bimolecular association and dissociation rate constants for the reversible binding were 5.7 × 108 M−1 min−1 and 5.0 × 10−2 min−1, respectively. Equilibrium dissociation constant was 87 pM and the KD obtained by saturation binding was 73 pM.During the foetal age 16 to 40 weeks, the receptor concentration remained in the range of 38–60 fmol/mg protein or 570–1080 fmol/g striatum but it increased two-fold postnatally reaching a maximum at 5 years Significantly, at lower foetal ages (16–24 weeks) the [3H]spiperone binding sites exhibited a heterogeneity with a high (KD, 13–85 pM) and a low (KD, 1.2–4.6 nM) affinity component, the former accounting for 13–24% of the total binding sites. This heterogeneity persisted even when sulpiride was used as a displacer. The number of high affinity sites increased from 16 weeks to 24 weeks and after 28 weeks of gestation, all the binding sites showed only a single high affinity.GTP decreased the agonist affinity as observed by dopamine competition of [3H]spiperone binding in 20-week-old foetal striata and at all subsequent ages. GTP increased IC50 values of dopamine 2 to 4.5 fold and Hill coefficients were also increased becoming closer to one suggesting that the dopamine receptor was susceptible to regulation from foetal life onwards.

Reaction of spironaphthalenones with hydroxylamine: Part I. A reinvestigation of the mechanism

Spironaphthalenones 1b–g on reaction with hydroxylamine hydrochloride gave the expected pyrrolotropones 2b–g. Furanotropone 6, postulated as an intermediate in the formation of pyrrolotropones, remained unchanged on reaction with hydroxylamine hydrochloride in ethanol. Reaction of unsymmetrical spironaphthalenones 1h–o with NH2OH.HCl gave the rearranged pyrrolotropones 2h–o.

Reaction of spironaphthalenones with hydroxylamine: Part II. Structure of product in the reaction of 1′-substituted spironaphthalenone.

Reaction of 1′-aryl substituted spironaphthalenones 1a–d with hydroxylamine hydrochloride in ethanol gave substituted cinnamic ester derivatives 4a–d. Similarly, reaction of spironaphthalenone 1a with different alcohols gave the corresponding esters 4i–m. Reaction of unsymmetrical spironaphthalenones 1e–h with hydroxylamine hydrochloride in presence of ethanol gave the respective esters 4e–h. All the esters were characterised by their spectral data.

Polyelectrolyte microcapsules for sustained delivery of water-soluble drugs

Polyelectrolyte capsules composed of weak polyelectrolytes are introduced as a simple and efficient system for spontaneous encapsulation of low molecular weight water-soluble drugs. Polyelectrolyte capsules were prepared by layer-by-layer (LbL) assembling of weak polyelectrolytes, poly(allylamine hydrochloride) (PAH) and poly (methacrylic acid) (PMA) on polystyrene sulfonate (PSS) doped CaCO3 particles followed by core removal with ethylene-diaminetetraacetic add (EDTA). The loading process was observed by confocal laser scanning microscopy (CLSM) using tetramethylrhodamineisothiocyanate labeled dextran (TRITC-dextran) as a fluorescent probe. The intensity of fluorescent probe inside the capsule decreased with increase in cross-linking time. Ciprofloxacin hydrochloride (a model water-soluble drug) was spontaneously deposited into PAH/PMA capsules and their morphological changes were investigated by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The quantitative study of drug loading was also elucidated which showed that drug loading increased with initial drug concentration, but decreased with increase in pH. The loaded drug was released in a sustained manner for 6 h, which could be further extended by cross-linking the capsule wall. The released drug showed significant antibacterial activity against E. coli. These findings indicate that such capsules can be potential carriers for water-soluble drugs in sustained/controlled drug delivery applications. (C) 2010 Elsevier B.V. All rights reserved.

Photocatalytic Inactivation of Escherichia coli with LbL Fabricated Immobilized TiO2 Thin Films

Photocatalysis using semiconductor catalyst such as TiO2, in presence of UV light, is a promising technique for the inactivation of various microorganisms present in water. In the current study, the photocatalytic inactivation of Escherichia coli bacteria was studied with commercial Degussa Aeroxide TiO2 P25 (Aeroxide) and combustion synthesized TiO2 (CS TiO2) catalysts immobilized on glass slides in presence of UV irradiation. Thin films of the catalyst and polyelectrolytes, poly(allyl amine hydrochloride) and poly(styrene sulfonate sodium salt), were deposited on glass slides by layer by layer (LbL) deposition method and characterized by SEM and AFM imaging. The effect of various parameters, namely, catalyst concentration, surface area and number of bilayers, on inactivation was studied. Maximum inactivation of 8-log reduction in the viable count was observed with 1.227 mg/cm(2) of catalyst loaded slides. With this loading, complete inactivation was observed within 90 min and 75 min of irradiation, for Aeroxide and CS TiO2, respectively. Further increase in the catalyst concentration or increasing number of bilayers had no significant effect on inactivation. The effect of surface area on the inactivation was studied by increasing the number of slides and the inactivation was observed to increase with increasing surface area. It was also observed that the immobilized catalyst slides can be used for several cycles leading to an economic process. The study shows potential application of TiO2, for the inactivation of bacteria, in its fixed form by a simple immobilization technique.

Effect of blocking oestrogen synthesis with a new generation aromatase inhibitor CGS 16949A on follicular maturation induced by pregnant mare serum gonadotrophin in the immature rat

While the endocrine role of oestrogen is well established, its function in follicular maturation as an autocrine or paracrine regulator is less well understood. This study was designed to delineate the requirement of oestrogen for follicular development in immature rats. Exogenous gonadotrophin (25 IU pregnant mare serum gonadotrophin (PMSG) per rat) was administered to 21- to 23-day old female rats to induce follicular growth and development. In the experimental animals, synthesis of oestrogen was blocked by implanting an Alzet pump containing the aromatase inhibitor (AI) CGS 16949A (fadrozole hydrochloride; 50 mu g/rat per day). The treatment resulted in blockade of the PMSG induced increase in both serum and intrafollicular oestrogen (>95%), thus leading to an inhibition in uterine weight increment. Compared with the controls, ovarian weight increased markedly in both the PMSG (295%)- and PMSG+AI (216%)-primed animals. There was no significant difference in either the proliferative capabilities of the ovarian granulosa cells or their responsiveness to human chorionic gonadotrophin (hCG; 200 pg/ml) and ovine FSH (20 ng/ml) between the PMSG- and PMSG+AI-treated groups. Histological examination of the ovary, however, indicated a decrease in the number of healthy antral follicles in the Al-treated group compared with the PMSG-primed animals but both the groups showed a percentage increase over the controls (PMSG, 225; PMSG+AI, 158). The responsiveness of the animals to an ovulatory dose of hCG was drastically reduced (>80% inhibition of ovulation) in the oestrogen-deprived animals; this could be overriden by exogenous administration of oestrogen. In conclusion, although blocking oestrogen synthesis in the PMSG-primed rat does not seem to alter the functional properties of the isolated granulosa cells in vitro there appears to be an effect on the number of follicles which complete maturation and are able to ovulate in vivo.

A facile route to synthesize silver nanoparticles in polyelectrolyte capsules

We are reporting a novel green approach to incorporate silver nanoparticles (NPs) selectively in the polyelectrolyte capsule shell for remote opening of polyelectrolyte capsules. This approach involves in situ reduction of silver nitrate to silver NPs using PEG as a reducing agent (polyol reduction method). These nanostructured capsules were prepared via layer by layer (LbL) assembly of poly(allylamine hydrochloride) (PAH) and dextran sulfate (DS) on silica template followed by the synthesis of silver NPs and subsequently the dissolution of the silica core. The size of silver nanoparticles synthesized was 60 +/- 20 nm which increased to 100 +/- 20 nm when the concentration of AgNO3 increased from 25 mM to 50 mM. The incorporated silver NPs induced rupture and deformation of the capsules under laser irradiation. This method has advantages over other conventional methods involving chemical agents that are associated with cytotoxicity in biological applications such as drug delivery and catalysis. (C) 2011 Elsevier B.V. All rights reserved.

The Folding Mechanism of Barstar: Evidence for Multiple Pathways and Multiple Intermediates

The mechanism of folding of the small protein barstar in the pre-transition zone at pH 7, 25 degrees C has been characterized using rapid mixing techniques. Earlier studies had established the validity of the three-state U-S reversible arrow U-F reversible arrow N mechanism for folding and unfolding in the presence of guanidine hydrochloride (GdnHCl) at concentrations greater than 2.0 M, where U-S and U-F are the slow-refolding and fast-refolding unfolded forms, respectively, and N is the fully folded form. It is now shown that early intermediates, I-S1 and I-S2 as well as a late native-like intermediate, I-N, are present on the folding pathways of U-S, and an early intermediate I-F1 on the folding pathway of U-F, when bars tar is refolded in concentrations of GdnHCl below 2.0 M. The rates of formation and disappearance of I-N, and the rates of formation of N at three different concentrations of GdnHCl in the pre-transition zone have been measured. The data indicate that in 1.5 M GdnHCl, I-N is not fully populated on the U-S --> I-S1 --> I-N --> N pathway because the rate of its formation is so slow that the U-S reversible arrow U-F reversible arrow N pathway can effectively compete with that pathway. In 1.0 M GdnHCl, the U-S --> I-S1 --> I-N transition is so fast that I-N is fully populated. In 0.6 M GdnHCl, I-N appears not to be fully populated because an alternative folding pathway, U-S --> I-S2 --> N, becomes available for the folding of U-S, in addition to the U-S --> I-S1 --> I-N --> N pathway Measurement of the binding of the hydrophobic dye 1-anilino-8-naphthalenesulphonate (ANS) during folding indicates that ANS binds to two distinct intermediates, I-M1 and I-M2, that form within 2 ms on the U-S --> I-M1 --> I-S1 --> I-N --> N and U-S --> I-M2 --> I-S2 --> N pathways. There is no evidence for the accumulation of intermediates that can bind ANS on the folding pathway of U-F.

Denaturant mediated unfolding of both native and molten globule states of maltose binding protein are accompanied by large [Delta]Cp's

Maltose binding protein (MBP) is a large, monomeric two domain protein containing 370 amino acids. In the absence of denaturant at neutral pH, the protein is in the native state, while at pH 3.0 it forms a molten globule. The molten globule lacks a tertiary circular dichroism signal but has secondary structure similar to that of the native state. The molten globule binds 8-anilino-1-naphthalene sulfonate (ANS). The unfolding thermodynamics of MBP at both pHs were measured by carrying out a series of isothermal urea melts at temperatures ranging from 274–329 K. At 298 K, values of [Delta]G°, [Delta]Cp, and Cm were 3.1 ± 0.2 kcal mol−1, 5.9 ± 0.8 kcal mol−1 K−1 (15.9 cal (mol-residue)−1 K−1), and 0.8 M, respectively, at pH 3.0 and 14.5 ± 0.4 kcal mol−1, 8.3 ± 0.7 kcal mol−1 K−1 (22.4 kcal (mol-residue)−1 K−1), and 3.3 M, respectively, at pH 7.1. Guanidine hydrochloride denaturation at pH 7.1 gave values of [Delta]G° and [Delta]Cp similar to those obtained with urea. The m values for denaturation are strongly temperature dependent, in contrast to what has been previously observed for small globular proteins. The value of [Delta]Cp per mol-residue for the molten globule is comparable to corresponding values of [Delta]Cp for the unfolding of typical globular proteins and suggests that it is a highly ordered structure, unlike molten globules of many small proteins. The value of [Delta]Cp per mol-residue for the unfolding of the native state is among the highest currently known for any protein.