Encuentros Latinoamericanos de Fotoquímica y Fotobiología (ELAFOT): the Latin-American Photochemical and Photobiological Community

The photochemical and photobiological researchers in Latin American meet biannually at a regional meeting known as Encuentros Latinoamericanos de Fotoquímica y Fotobiología (ELAFOT). The goals of this series of meetings are to discuss leading scientific work, to become acquainted with the latest research findings in the discipline, to exchange ideas, to initiate collaborations between groups and to strengthen the scientific interactions between young researchers and senior experts from the region and from developed countries. During 8-12 November 2004, the eighth such meeting took place in La Plata, Argentina. In this introduction we present a brief history of the ELAFOT meetings and a summary of the most recent gathering and the papers presented in this Symposium-in-Print.     

Tritium volume activity in natural waters of the NPP Temelín region

With the use of the tritium monitoring network the samples of river water, air humidity and precipitation are collected and analysed for HTO in the vicinity of Temelín nuclear power plant.     

Estudios sobre acidos hidroxámicos VII. Reconocimiento específico de ésteres fórmicos,su investigación en mezclas,especialmente con otros ésteres carboxílicos

Resumen Se propone una técnica para el reconocimiento específico de microcantidades de ésteres fórmicos, basada en su transformación en ácido formohidroxámico mediante hidroxilaminolisis en medio hidro-alcohólico amoniacal. En las condiciones elegidas no son causa de error los otros ésteres carboxílicos, ni la mayor parte de las sustancias cuyos grupos funcionales reaccionan con la hidroxilamina en medio alcalino de hidróxido o carbonato de sodio o potasio. El método permite reconocer el radical formilo procedente de ésteres fórmicos en diluciones de una parte por millón, con una sensibilidad de 5g. Los ésteres fórmicos no resultan interferidos por cantidades mil a diez mil veces superiores de otros ésteres carboxílicos.

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Summary A working technique is suggested for the specific detection of micro quantities of esters of formic acid. It is based on the conversion into formhydroxamic acid esters by means of hydroxylaminolysis in aqueous-alcoholic, ammoniacal medium. Under the chosen conditions, no interference is offered by the other carboxylic acids or by most of the compounds, whose functional groups react, in alkaline medium, with hydroxylamine, i. e., in the presence of the hydroxides or carbonates of sodium or potassium. The method permits the detection of the formyl radical, obtained from formic acid esters, in dilutions of 11000 000, with the corresponding limit of identification of 5g. It was found that the identification of formic acid ester was not disturbed by 1000 to 10000 times the quantity of the other carboxylic acid esters.

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Zusammenfassung Eine Arbeitstechnik für den spezifischen Nachweis von Mikromengen von Ameisensäureestern wird vorgeschlagen. Sie beruht auf der Umwandlung in Formhydroxamsäure mittels Hydroxylaminolyse in wäßrig-alkoholischem, ammoniakalischem Medium. Unter den gewählten Bedingungen stören weder die übrigen Carbonsäureester noch die meisten derjenigen Substanzen, deren funktionelle Gruppen mit dem Hydroxylamin in alkalischem Medium, das heißt in Gegenwart der Hydroxyde oder Carbonate des Natriums oder Kaliums, reagieren. Die Methode erlaubt den Nachweis des Formylradikals, das aus Ameisensäureestern entsteht, in Verdünnungen von 11000 000, wobei die Erfassungsgrenze 5g beträgt. Es stellte sich heraus, daß der Nachweis der Ameisensäureester durch 1000-bis 10 000mal größere Mengen der übrigen Carbonsäureester nicht gestört wird.

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Résumé Les auteurs recommandent une technique de travail pour l'identification spécifique de microquantités d'esters formiques. Elle repose sur leur transformation en acide formhydroxamique par hydroxylaminolyse en milieu hydroalcoholique ammoniacal. Dans les conditions choisies, aucune perturbation n'est apportée par la présence des autres esters carboniques ni par celle de la plupart des substances dont les groupes fonctionnels réagissent sur l'hydroxylamine en milieu alcalin, c'est-à-dire en présence d'hydroxyde ou de carbonate de sodium ou de potassium. La méthode permet l'identification du radical formyle qui se forme à partir des esters formiques à des dilutions de 11000 000 avec une limite de sensibilité de 5g. Il apparaît que cette identification des esters formiques n'est pas perturbée par la présence de quantités 1000 à 10 000 fois plus grandes des autres esters carboniques.

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Presentado en la 8as Sesiones Químicas Argentinas. La Plata, V, 1956.

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Expresamos nuestro agradecimiento al Dr.Carlos Torres, de Cadya, S. A., por los ésteres facilitados para la realizatión del trabajo.     

Sobre nuevas reacciones microquímicas de la piperacina y del licetol y su aplicación microanalitica

Resumen El A. estudia un nuevo reactivo, el iodo bismutato de potasio, que mediante su aplicación da lugar a nuevas reaociones microcristalinas, que sirven para caracterizar y diferenciar a la piperacina y del licetol. Del estudio microanalítico realizado y de las técnicas aconsejadas deduce que se puede investigar ambas sustancias en mezclas de cualquier proporción, por poseer cada complejo integrado, formas cristalinas, cromatismo y sensibilidades diferentes. Analiza Iuego, otras nuevas reacciones microquímicas que sirven también como elementos de juicio en la caracterización de las sustancias estudiadas. Se acompañan fotomicrografïas de los cristales obtenidos.

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Summary The use of potassium iodobismuthate led to new microanalytical precipitation reactions which are suited to the characterization and differentiation of piperazine and -dimethylpiperazine. The studies and proposed procedure show that both materials can be detected in any mixture no matter what their proportions since the compounds formed differ with respect to crystal form, color, and detection sensitivity. Other microchemical reactions were studied, which likewise are suitable for characterizing these compounds. Photographs of the crystals are included.

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Zusammenfassung Die Anwendung von Kaliumjodbismutat führte zu neuen mikroanalytischen Kristallfällungsreaktionen, die sich zur Charakterisierung und Unterscheidung von Piperazin und -Dimethylpiperazin eignen. Aus den durchgeführten Untersuchungen und der vorgeschlagenen Arbeitsweise geht hervor, daß beide Substanzen in beliebigen Mischungsverhältnissen nachweisbar sind, da sich die hergestellten Verbindungen hinsichtlich Kristallform, Farbe und Nachweisempfindlichkeit unterscheiden. Es wurden auch andere mikrochemische Reaktionen geprüft, die sich gleichfalls zur Charakterisierung der beiden Substanzen eignen. Abbildungen der erhaltenen Kristalle werden beigebracht.

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Résumé L'emploi de l'iodobismuthate de potassium a conduit à de nouvelles réactions microanalytiques de précipitation cristalline qui sont appropriées à la caractérisation et à la différenciation de la piperazine et de l' -diméthylpiperazine. Les recherches effectuées et l'application du mode opératoire recommandé par les auteurs montrent que les deux substances sont identifiables dans leurs mélanges quelles que soient leurs proportions relatives; leurs combinaisons avec le réactif se différencient en effet par leurs formes cristallines et leurs couleurs ainsi que par la sensibilité d'identification. Quelques autres réactions microchimiques ont été également éprouvées avec le même succès pour la caractérisation des deux substances. Les cristaux obtenus sont reproduits sur les figures de la communication.

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Al Señor Dr.Hans Lieb, Profesor de Universidad, con motivo de su 70⁰ aniversario.     

Sobre un nuevo complejo microquímico y su applicación a la investigation del cu++

Resumen El ácido salicilico disuelto a casi saturación en piridina constituye un buen reactivo para identificar al ión cúprico. El autor recurre, aparte de otros ensayos químicos, a reacciones topoquímicas a fin de establecer la naturaleza del complejo formado y concluye que el compuesto microcristalino es un cupri-salicilato-piridínico. Acompaña las fotomicrografías correspondientes y estudia la sensibilidad de la reacción que supera un limite de identification de 0,5g y una concentracion limite de 1100.000. A su vez, estudia los microcristales a la luz polarizada y determina el sistema cristalino a que pertenecen.

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Summary A practically saturated solution of salicylic acid in pyridine is a good reagent for identifying copper ions. After testing other chemical methods, the author has chosen topochemical reactions to determine the nature of the resulting complex, and concludes that the crystalline compound is a copperpyridine-salicylate. The sensitivity of the reaction was tested; the identification limit is 0.5g, and the limiting concentration is more than 1100,000, Microphotographs of the crystals are included. The crystals were studied in polarized light and their crystal system established.

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Zusammenfassung Fast bis zur Sättigung in Pyridin gelöste Salicylsäure ist ein gutes Reagens zur Identifizierung von Kupferionen. Nach anderweitigen chemischen Versuchen entscheidet sich der Verfasser für topochemische Reaktionen, um die Natur des entstandenen Komplexes festzustellen, und schließt daraus, daß es sich bei der kristallinen Verbindung um ein Kupfer-Pyridin-Salicylat handelt. Die Empfindlichkeit der Reaktion wurde geprüft: die Erfassungsgrenze beträgt 0,5g, die Grenzkonzentration von l100.000 wird übertroffen. Die in Mikrophotographien wiedergegebenen Kristalle wurden im polarisierten Licht untersucht und das zugehörige Kristallsystem ermittelt.

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Résumé L'acide salicylique en solution pyridinique presque saturée est un bon réactif d'identification des ions cuivriques. Indépendemment d'autres essais chimiques, l'auteur a recours à des réactions topochimiques pour établir la nature du complexe formé et il conclut qu'il s'agit d'un composé microcristallin cupri -salycilatopyridinique. Il présente les microphotographies correspondantes et étudie la sensibilité de la réaction qui permet de dépasser une limite d'identification de 0,5g et une concentration limite de 1/100 000. L'auteur étudie ensuite les microcristaux à la lumière polarisée et détermine le système cristallin auquel ils appartiennent.

     

Synthesis,structure, computational modeling and biological activity of two new Casiopeínas® complexes and their nanoparticles

Abstract

This study was conducted to prepare new complexes and their metal-based nanodrugs in order to reduce the growth of human carcinoma cell lines. For this purpose, an extensive study was performed. First, the mixed-chelate Cu(II) complexes Casiopeínas^® ([Cu(TTA)(phen)(C1O₄)] 1 and [Cu(TTA)(phen)(N₃)Cu(TTA)(phen)H₂O] (C1O₄)·H₂O 2 (TTA = 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione) were synthesized and characterized by X-ray, FT-IR, UV–Vis spectroscopy, conductivity measurements, diffuse reflection spectroscopy and elemental analysis studies. Complexes 1 and 2 exhibited tetragonal pyramidal geometry. In the following, nanoparticles (NPs) of complexes 3 and 4 with the average size of 81 and 33?nm, respectively, were prepared by an ultrasonic process. Scanning Electron Microscope (SEM) images of samples 3 and 4 showed that the morphologies of the obtained materials are rod and sphere, respectively. Furthermore, the cytotoxic activity of complexes and nanoparticles was investigated against MKN-45 cell lines. The cell proliferation was inhibited for all compounds and nanocompounds in a dose-dependent manner 1?>?2 > 3?>?4 on MKN-45 cells. Finally, docking calculations were performed to describe the mode of binding to DNA of these complexes. Docking simulations suggested that the compounds bind in the minor groove and preferentially bind to A-T base pair regions. Both complexes also interacted with DNA through one hydrogen-bond.     

Investigation on the self-association of an inorganic coordination compound with biological activity (Casiopeína III-ia) in aqueous solution

From studies using different experimental techniques employed to determine the presence of aggregates e.g. isothermal titration calorimetry, surface tension, electrical conductivity, UV–Vis spectrophotometry, dynamic and static light scattering, it is clearly demonstrated that the compound [Cu(4, 4′-dimethyl-2, 2′-bipyridine)(acetylacetonato)H₂O]NO₃ (Casiopeína III-ia), promising member of a family of new generation compounds for cancer treatment, is able to auto associate in aqueous media. Physicochemical properties associated with the formation of the aggregates were determined in pure water and in phosphate buffer media in order to simulate physiological conditions. From isothermal titration calorimetry and electrical conductivity measurements we calculated the dissociation constant of the aggregates, K _D . For pure water the values obtained in both techniques are 2.73 × 10^?4 and 5.93 × 10^?4 M respectively while for the buffer media we obtained 4.61 × 10^?4 and 1.57 × 10^?3 M. The enthalpy of dissociation, ?H _D , calculated from the calorimetric data shows that the presence of the phosphate ions has an energetic effect on the aggregate stability since in pure water a value of 18.79 kJ mol^?1 was obtained in comparison with the buffer media where a value 4 times bigger was found (70.48 kJ mol^?1). With the data collected from these techniques the number of monomers calculated which participate in the formation of the aggregates is around two. From our surface tension, electrical conductivity and UV–Vis spectrophotometry measurements the critical aggregate concentration, cac, was determined. For each technique specific concentration ranges were obtained but we can summarize that the cac in pure water is between 3 and 3.5 mM and for the buffer media is between 3.5 and 4 mM. Dynamic light scattering measurements provide us with the hydrodynamic diameter of the aggregates and from static light scattering measurements we determined the molecular weight of the Casiopeína III-ia aggregates to be of 1000.015 g mol^?1 which is two times the molecular weight of the Casiopeína III-ia molecule. This value is in agreement with the number of monomers which participate in the formation of the aggregates obtained from isothermal titration calorimetry and electrical conductivity data analysis.     

Surface enhanced Raman spectroscopy and cultural heritage biodeterioration: Fungi identification in earthen architecture from Paraíba Valley (São Paulo,Brazil)

In this work, Surface Enhanced Raman Spectroscopy (SERS) was employed in the taxonomic identification of fungi found in biofilms formed on earthen architecture walls (adobe, wattle and daub, and rammed earth) of historical buildings in the region known as Paraíba Valley (or São Paulo Historical Valley), which are representative of the first phase of the Brazilian coffee cycle (1820–1880). Very few studies are reported in the literature where SERS-based techniques are used in fungi identification, most of them focused on clinical diagnosis. In the present investigation, pure colonies isolated from biofilms on earthen walls previously identified by classic taxonomy and molecular biology were selected. The genera were Trichoderma, Cladosporium, Aspergillus, Neurospora, Fusarium and Penicillium. The fungi were cultured on solid potato dextrose agar, extracted with ethyl acetate and the extracts were applied on dried Au nanoparticles. The SERS spectra exhibited bands in the 600–1800 cm⁻¹ region which are characteristic of each genus, except Penicillium, as revealed by PCA statistical analysis. This work reports the use of a facile to prepare SERS-active substrate in the identification of microbial communities on earthen architecture walls and is the first step of an investigation aiming at the fast identification of fungi species from biofilms formed on earthen architecture buildings without the need of isolating the pure cultures.     

Investigation of degradation mechanisms by portable Raman spectroscopy and thermodynamic speciation: the wall painting of Santa María de Lemoniz (Basque Country, North of Spain)

To characterise the polymeric properties of processed lignins, a new method has been developed using hydrophobic interaction chromatography (HIC). This method separates the lignin polymers into fractions based on differences in hydrophobicity using low pressure liquid chromatography (LPLC). The hydrophobic column material consists of monodisperse polystyrene/divinylbenzene beads. An elution gradient was prepared monitoring the electrolyte concentration and pH. Citric acid buffer, containing ammonium sulphate that promotes adsorption to the column material, was used as mobile phase in a step-wise gradient together with ethanol (20/80% (v/v) ethanol/water, pH 12) and isopropanol (40/60% (v/v) isopropanol/water, pH 12). Depending on eluent composition, the degree of elution was 94% or higher. With the HIC method developed, lignosulphonates and kraft lignins were separated into seven distinctive peaks according to hydrophobicity.     

The effect of natural UV-B radiation on a perennial Salicornia salt-marsh in Bahía San Sebastián,Tierra del Fuego,Argentina: a 3-year field study

The Antarctic ozone hole and a general depletion of the stratospheric ozone layer cause increased levels of ultraviolet-B solar radiation (UV-B) over Tierra del Fuego, the southernmost tip of South America. For three consecutive growing seasons (1997–2000), we studied the biological impacts (morphology, physiology, demography and phenology) of natural UV-B radiation on a perennial Salicornia ambigua Michx. community in San Sebastian Bay (53° S and 68° W), Tierra del Fuego, Argentina. This is the first UV-B screening experiment on a subantarctic halophytic community. The shortwave UV-B spectrum (280 to 320 nm) was excluded by covering plots with UV-B blocking film (Mylar). These plots were compared to controls covered with UV-B transparent (Aclar) plastic screens, and unscreened plots. Shoot length in Salicornia was not affected by UV-B. Exposure to natural UV-B reduced biomass and density (by 17% and 38%, respectively). Concentration of UV-shielding pigments and cuticle thickness were both significantly higher (25–48% and 21–40%, respectively) in plants receiving ambient UV-B. The increase in cuticle thickness persisted throughout the growing season, whereas pigment concentration was higher at the beginning of the growing season. Also, the number of dead shoots was higher in plants exposed to UV-B. At the end of the growing season (March) shoot mortality was higher in plants exposed to ambient UV-B, and post-flowering senescence was 30 days earlier. Slight changes in the relative composition of Salicornia to Puccinellia were seen. The reduction observed in Salicornia shoot density under ambient UV-B was cumulative over time; 23% in the first growing-season, rising to 38% by the third growing-season. A similar incremental increase in pigment absorption at 305 nm was seen; 25% in the first and 48% in the third growing season.