Fluorescence spectroscopy of small peptides interacting with microheterogeneous micelles

Many peptides containing tryptophan have therapeutic uses and can be studied by their fluorescent properties. The biological activity of these peptides involves interactions with many cellular components and micelles can function as carriers inside organisms. We report results from the interaction of small peptides containing tryptophan with several microheterogeneous systems: sodium dodecyl sulphate (SDS) micelles; sodium dodecyl sulphate-poly(ethylene oxide) (SDS-PEO) aggregates; and neutral polymeric micelles. We observed that specific parameters, such as wavelength of maximum emission and fluorescence anisotropy, could be used to ascertain the occurrence of interactions. Affinity constants were determined from changes in the intensity of emission while structural modifications in rotameric conformations were verified from time-resolved measurements. Information about the location and diffusion of peptides in the microheterogeneous systems were obtained from tryptophan emission quenching experiments using N-alkylpyridinium ions. The results show the importance of electrostatic and hydrophobic effects, and of the ionization state of charged residues, in the presence of anionic and amphiphilic SDS in the microheterogeneous systems. Conformational stability of peptides is best preserved in the interaction with the neutral polymeric micelles. (C) 2009 Elsevier B.V. All rights reserved.

Thermal analysis, nuclear magnetic resonance spectroscopy, and impedance spectroscopy of N,N-dimethyl-pyrrolidinium iodide: An ionic solid exhibiting rotator phases

N,N-dimethyl-pyrrolidinium iodide has been investigated using differential scanning calorimetry, nuclear magnetic resonance (NMR) spectroscopy, second moment calculations, and impedance spectroscopy. This pyrrolidinium salt exhibits two solid-solid phase transitions, one at 373 K having an entropy change, Delta S, of 38 J mol(-1) K-1 and one at 478 K having Delta S of 5.7 J mol(-1) K-1. The second moment calculations relate the lower temperature transition to a homogenization of the sample in terms of the mobility of the cations, while the high temperature phase transition is within the temperature region of isotropic tumbling of the cations. At higher temperatures a further decrease in the H-1 NMR linewidth is observed which is suggested to be due to diffusion of the cations. (C) 2005 American Institute of Physics.

Acute Toxic Leukoencephalopathy: Potential for Reversibility Clinically and on MRI With Diffusion-Weighted and FLAIR Imaging

OBJECTIVE. Toxic leukoencephalopathy may present acutely or subacutely with symmetrically reduced diffusion in the periventricular and supraventricular white matter, hereafter referred to as periventricular white matter. This entity may reverse both on imaging and clinically. However, a gathering together of the heterogeneous causes of this disorder as seen on MRI with diffusion-weighted imaging (DWI) and an analysis of their likelihood to reverse has not yet been performed. Our goals were to gather causes of acute or subacute toxic leukoencephalopathy that can present with reduced diffusion of periventricular white matter in order to promote recognition of this entity, to evaluate whether DWI with apparent diffusion coefficient (ADC) values can predict the extent of chronic FLAIR abnormality ( imaging reversibility), and to evaluate whether DWI can predict the clinical outcome ( clinical reversibility). MATERIALS AND METHODS. Two neuroradiologists retrospectively reviewed the MRI examinations of 39 patients with acute symptoms and reduced diffusion of periventricular white matter. The reviewers then scored the extent of abnormality on DWI and FLAIR. ADC ratios of affected white matter versus the unaffected periventricular white matter were obtained. Each patient`s clinical records were reviewed to determine the cause and clinical outcome. Histology findings were available in three patients. Correlations were calculated between the initial MRI markers and both the clinical course and the follow-up extent on FLAIR using Spearman`s correlation coefficient. RESULTS. Of the initial 39 patients, seven were excluded because of a nontoxic cause (hypoxic-ischemic encephalopathy [HIE] or congenital genetic disorders) or because of technical errors. In the remaining 32 patients, no correlation was noted between any of the initial MRI markers (percentage of ADC reduction, DWI extent, or FLAIR extent) with the clinical outcome. Three patients had histologic correlation. However, moderate correlation was seen between the extent of abnormality on initial FLAIR and the extent on follow-up FLAIR (r = 0.441, p = 0.047). Of the 13 patients who underwent repeat MRI at 21 days or longer, the reduced diffusion resolved in all but one. Significant differences were noted between ADC values in affected white matter versus unaffected periventricular white matter on initial (p < 0.0001) but not on follow-up MRI (p = 0.13), and in affected white matter on initial versus follow-up (p = 0.0014) in those individuals who underwent repeat imaging on the same magnet (n = 9), confirming resolution of the DWI abnormalities. CONCLUSION. Acute toxic leukoencephalopathy with reduced diffusion may be clinically reversible and radiologically reversible on DWI, and may also be reversible, but to a lesser degree, on FLAIR MRI. None of the imaging markers measured in this study appears to correlate with clinical outcome, which underscores the necessity for prompt recognition of this entity. Alerting the clinician to this potentially reversible syndrome can facilitate treatment and removal of the offending agent in the early stages.

Profiling the Proteome of the Venom from the Social Wasp Polybia paulista: A Clue to Understand the Envenoming Mechanism

The study reported here is a classical bottom-up proteomic approach where proteins from wasp venom were extracted and separated by 2-DE; the individual protein spots were proteolytically digested and subsequently identified by using tandem mass spectrometry and database query with the protein search engine MASCOT. Eighty-four venom proteins belonging to 12 different molecular functions were identified. These proteins were classified into three groups; the first is constituted of typical venom proteins: antigens-5, hyaluronidases, phospholipases, heat shock proteins, metalloproteinases, metalloproteinase-desintegrin like proteins, serine proteinases, proteinase inhibitors, vascular endothelial growth factor-related protein, arginine kinases, Sol i-II and -II like proteins, alpha-glucosidase, and superoxide dismutases. The second contained proteins structurally related to the muscles that involves the venom reservoir. The third group, associated with the housekeeping of cells from venom glands, was composed of enzymes, membrane proteins of different types, and transcriptional factors. The composition of P. paulista venom permits us to hypothesize about a general envenoming mechanism based on five actions: (i) diffusion of venom through the tissues and to the blood, (ii) tissue, (iii) hemolysis, (iv) inflammation, and (v) allergy-played by antigen-5, PLA1, hyaluronidase, HSP 60, HSP 90, and arginine kinases.

Targeted drug delivery to the skin and deeper tissues: Role of physiology, solute structure and disease

1. Drug delivery through the skin has been used to target the epidermis, dermis and deeper tissues and for systemic delivery, The major barrier for the transport of drugs through the skin is the stratum corneum, with most transport occurring through the intercellular region, The polarity of the intercellular region appears to be similar to butanol, with the diffusion of solutes being hindered by saturable hydrogen bonding to the polar head groups of the ceramides, fatty acids and other intercellular lipids, Accordingly, the permeability of the more lipophilic solutes is greatest from aqueous solutions, whereas polar solute permeability is favoured by hydrocarbon-based vehicles. 2. The skin is capable of metabolizing many substances and, through its microvasculature, limits the transport of most substances into regions below the dermis. 3. Although the flux of solutes through the skin should be identical for different vehicles when the solute exists as a saturated solution, the fluxes vary in accordance with the skin penetration enhancement properties of the vehicle. It is therefore desirable that the regulatory standards required for the bioequivalence of topical products include skin studies. 4. Deep tissue penetration can be related to solute protein binding, solute molecular size and dermal blood flow. 5. Iontophoresis is a promising area of skin drug delivery, especially for ionized solutes and when a rapid effect is required. 6. In general, psoriasis and other skin diseases facilitate drug delivery through the skin. 7. It is concluded that the variability in skin permeability remains an obstacle in optimizing drug delivery by this route.

Calcitonin, sodium alendronate and high intensity laser in the treatment of traumatized teeth: a preliminary study

The aim of this study was to evaluate the influence of erbium:yttrium-aluminum-garnet (Er:YAG) laser compared with traditional treatment on dentin permeability to calcitonin and sodium alendronate. Forty bovine roots were sectioned and divided into eight groups. Groups 1 and 2 (G1/G2) were immersed in saline solution; G1T/G2T were immersed in ethylene diamine tetra-acetic acid plus sodium lauryl ether sulfate (EDTA-T) and sodium hypochlorite (NaOCl); G1I/G2I were irradiated with Er:YAG laser (2.94 mu m, 6 Hz, 40.4 J/cm(2)); G1TI/G2TI were immersed in EDTA-T, NaOCl and subjected to Er:YAG irradiation. After 4 h the radioactivity of the saline solution was measured. Statistical analysis revealed a significant difference (P < 0.05) when the groups treated with EDTA-T and NaOCl followed by Er:YAG laser irradiation were compared with the groups treated with EDTA-T only and with the groups that received no treatment. Er:YAG laser associated with traditional procedures significantly increased the diffusion of calcitonin and sodium alendronate through dentin. All groups showed calcitonin and sodium alendronate diffusion.

NMR imaging of water sorption into poly(hydroxyethyl methacrylate-co-tetrahydrofurfuryl methacrylate)

The diffusion of water into a series of hydroxyethyl methacrylate, HEMA, copolymers with tetrahydrofurfuryl methacrylate, THFMA, has been studied over a range of copolymer compositions using NMR imaging analyses. For polyHEMA the diffusion was found to be consistent with a Fickian model. The mass diffusion coefficient of water in polyHEMA at 37 degreesC was determined from the profiles of the diffusion front to be 1.5 x 10(-11) m(2) s(-1), which is less than the value based upon mass uptake, 2.0 x 10(-11) m(2) s(-1). The profiles of the water diffusion front obtained from the NMR images showed that stress was induced at the interface between the rubbery and glassy regions which led to formation of small cracks in this region of the glassy matrix of polyHEMA and its copolymers with mole fractions of HEMA greater than 0.6. Water was shown to be able to enter these cracks forming water pools. For copolymers of HEMA and THFMA with mole fractions of HEMA less than 0.6 the absence of cracks was attributed to the ability of the THFMA sequences to undergo stress relaxation by creep.

The Antarctic nemertean Parborlasia corrugatus: an example of an extreme oxyconformer

The Antarctic nemertean worm, Parborlasia corrugatus, exhibits gigantism, reaching at least 100 g, yet lacks any specialised respiratory organs. The diffusion of oxygen into this worm occurs cutaneously. We examined the metabolic rate of P. corrugatus at -1degreesC in response to decreasing ambient PO2. As the PO2 of the water decreased. so did the metabolic rate of P. corrugatus, indicating that this nemertean worm is an extreme example of an oxyconformer. When the water PO2 decreased below about 120 mmHg, the normally short, round worms became elongated and extremely flattened. This behavioural mechanism would allow for an increase in surface area of the skin, thereby facilitating the diffusion of oxygen.

Of convicts and capitalists: honour and colonial commerce in 1830s Cape Town and Sydney

This comparative history examines the importance of notions of credit and honour in new definitions of masculinity that gained ground in New South Wales and the Cape Colony in the 1830s. The argument draws on an analysis of two defamation actions brought by auctioneers in this period and discusses the role of masculine occupation in colonial bourgeois identity. The diffusion of a culture of respectability through the British Empire was a global phenomenon, and a necessary precursor to the establishment of representative political institutions in the colonies by the middle of the nineteenth century.

Tracing the fate of N-15-enriched feed in an intensive shrimp system

The fate of N-15-nitrogen-enriched formulated feed fed to shrimp was traced through the food web in shallow, outdoor tank systems (1000 1) stocked with shrimp. Triplicate tanks containing shrimp water with and without sediment were used to identify the role of the natural biota in the water column and sediment in processing dietary nitrogen (N). A preliminary experiment demonstrated that N-15-nitrogen-enriched feed products could be detected in the food web. Based on this, a 15-day experiment was conducted. The ammonium (NH4+) pool in the water column became rapidly enriched (within one day) with N-15-nitrogen after shrimp were fed N-15-enriched feed. By day 15, 6% of the added N-15-nitrogen was in this fraction in the 'sediment' tanks compared with 0.4% in the 'no sediment' tanks. The particulate fraction in the water column, principally autotrophic nanoflagellates, accounted for 4-5% of the N-15-nitrogen fed to shrimp after one day. This increased to 16% in the 'no sediment' treatment, and decreased to 2% in the 'sediment' treatment by day 15. It appears that dietary N was more accessible to the phytoplankton community in the absence of sediment. The difference is possibly because a proportion of the dietary N was buried in the sediment in the 'sediment' treatment, making it unavailable to the phytoplankton. Alternatively, the dietary N was retained in the NH4+ pool in the water column since phytoplankton growth, and hence, N utilization was lower in the 'sediment' treatment. The lower growth of phytoplankton in the 'sediment' treatment appeared to be related to higher turbidity, and hence, lower light availability for growth. The percentage N-15-nitrogen detected in the sediment was only 6% despite the high capacity for sedimentation of the large biomass of plankton detritus and shrimp waste. This suggests rapid remineralization of organic waste by the microbial community in the sediment resulting in diffusion of inorganic N sources into the water column. It is likely that most of the dietary N will ultimately be removed from the tank system by water discharges. Our study showed that N-15-nitrogen derived from aquaculture feed can be processed by the microbial community in outdoor aquaculture systems and provides a method for determining the effect of dietary N on ecosystems. However, a significant amount of the dietary N was not retained by the natural biota and is likely to be present in the soluble organic fraction. (C) 2002 Elsevier Science B.V. All rights reserved.

Analysis of multicomponent adsorption kinetics on activated carbon

An integrated mathematical model for the kinetics of multicomponent adsorption on microporous carbon was developed. Transport in this bidisperse solid is represented by balance equations in the macropore and micropore phases, in which gas-phase diffusion dominates the mass transfer in the macropores, with the phenomenological diffusivities represented by the generalized Maxwell-Stefan (GMS) formulation. Viscous flow also contributes to the macropore fluxes and is included in the MS expressions. Diffusion of the adsorbed phase controls the mass transfer in the micro ore phase, p which is also described in a similar way by the MS method. The adsorption isotherms are represented by a new heterogeneous modified vacancy solution theory formulation of adsorption, which has proved to be a robust method for adsorption on activated carbons. The model is applied to the coadsorption and codesorption of C2H6 and C3H8 on Ajax and Norit carbon, as well as the displacement on Ajax carbon. The effect of the viscous flow in the macropore phase is not significant for the cases studied. The model accurately predicts the overshoot behavior and rollup of C2H6 during coadsorption. The prediction for the heavier compound C3H8 is always satisfactory, though at higher C3H8 mole fraction, the overshoot extent of C2H6 is overpredicted, possibly due to neglect of heat effects.

Consumidor de mídias móveis : a influência do perfil do adotante na relação entre valor percebido e intenção de compra

O presente estudo tem por objetivo avaliar se o perfil do adotante de inovações altera a relação entre o Valor Percebido e a Intenção de Compra de mídias móveis (smartphones, tablets, ultrabooks e leitores de e-books). Trata-se de uma pesquisa quantitativa que busca explorar a relação estrutural entre as variáveis por meio de Modelagem de Equações Estruturais (SEM – Strutural Equation Modeling). O modelo de pesquisa proposto foi desenvolvido tendo como base a Teoria da Difusão da Inovação (TDI), a Teoria Unificada de Aceitação e Uso de Tecnologia (UTAUT), o Modelo de Aceitação de Tecnologia (TAM), o Modelo Baseado em Valor (VAM), o Modelo de Aceitação de Tecnologia pelo Consumidor (CAT) e o Modelo de Influência Social (IS). Para coletar os dados foi utilizada a técnica snowball sampling ou amostragem em bola de neve, forma de amostragem não probabilística utilizada em pesquisas sociais. Foi feito um levantamento (survey), distribuindo-se questionário disponibilizado pela rede social Facebook, a partir dos contatos do autorsolicitando-se que os respondentes replicassem em suas páginas pessoais o link da pesquisa, ampliando a amostra. A coleta dos dados foi realizada nos meses de setembro e outubro de 2013, obtendo-se um total de 362 questionários respondidos. O estudo apresentou um efeito significativo da variável Valor Percebido na Intenção de Compra (estatística t = 4,506; nível de significância de 1%), além de sustentar a influência moderadora do Perfil do Adotante sobre essa relação (estatística t = 4,066; nível de significância de 1%), apresentando alto impacto sobre a Intenção de Compra (f 2 = 0,582) e relevância preditiva moderada (q2 = 0,290). Entre as variáveis antecedentes relacionadas à adoção de tecnologia, não apresentaram efeito significativo sobre o Valor Percebido: a Facilidade de Uso Percebida, a Complexidade Percebida e o Risco Percebido. O modelo contribuiu significativamente para explicar a influência dos fatores que impactam o Valor Percebido (R2 = 51,7%) o efeito do Valor Percebido na Intenção de Compra (R2 = 49,1%) de equipamentos eletrônicos portáteis. O suporte da presumidade influência moderadora do Perfil do Adotante sobre a relação Valor Percebido e Intenção de Compra indica que as organizações devem conhecer melhor os consumidores desse tipo de equipamento móveis, segmentando e desenvolvendo ações alinhadas com cada perfil de adotante.

Knowledge cities: a taxonomy for analyzing software and information service clusters

Software and information services (SIS) have become a field of increasing opportunities for international trade due to the worldwide diffusion of a combination of technological and organizational innovations. In several regions, the software industry is organized in clusters, usually referred to as "knowledge cities" because of the growing importance of knowledge-intensive services in their economy. This paper has two primary objectives. First, it raises three major questions related to the attractiveness of different cities in Argentina and Brazil for hosting software companies and to their impact on local development. Second, a new taxonomy is proposed for grouping clusters according to their dominant business segment, ownership pattern and scope of operations. The purpose of this taxonomy is to encourage further studies and provide an exploratory analytical tool for analyzing software clusters.

Importance of global co-innovation networks: A TCS case study

Today all kinds of innovations and research work is done by partnerships of competent entities each having some specialized skills. Like the development of the global economy, global innovation partnerships have grown considerably and form the basis of most of the sophisticated innovations today. To further streamline and simplify such cooperation, several innovation networks have been formed, both at local and global levels. This paper discusses the different types of innovations and how cooperation can benefit innovation in terms of pooling of resources and sharing of risks. One example of an open global co-innovation network promoted by Tata Consultancy Services, the TCS COIN is taken as a case. It enables venture capitalists, consultants, research agencies, companies and universities form nodes of the network so that each entity can play a meaningful role in the innovation network. Further, two innovation projects implemented using the COIN are discussed. Innovation Networks like these could form the basis of a unique global innovation network, which is not owned by any company and is used by innovation partners globally to collaborate and conduct research and development.

Cooperative effects in the detection of a nitroaliphatic liquid explosive and na explosive taggant in the vapor phase by calix[4]arene-based carbazole-containing conjugated polymers

Two fluorescent molecular receptor based conjugated polymers were used in the detection of a nitroaliphatic liquid explosive (nitromethane) and an explosive taggant (2,3-dimethyl-2,3-dinitrobutane) in the vapor phase. Results have shown that thin films of both polymers display remarkably high sensitivity and selectivity toward these analytes. Very fast, reproducible, and reversible responses were found. The unique behavior of these supramolecular host systems is ascribed to cooperativity effects developed between the calix[4] arene hosts and the phenylene ethynylene-carbazolylene main chains. The calix[4]-arene hosts create a plethora of host-guest binding sites along the polymer backbone, either in their bowl-shaped cavities or between the outer walls of the cavity, to direct guests to the area of the transduction centers (main chain) at which favorable photoinduced electron transfer to the guest molecules occurs and leads to the observed fluorescence quenching. The high tridimensional porous nature of the polymers imparted by the bis-calixarene moieties concomitantly allows fast diffusion of guest molecules into the polymer thin films.