A alga vermelha Gracilaria tenuistipitata tem sido utilizada como matéria prima para a produção de ágar e também como modelo para estudos fisiológicos e moleculares. Este trabalho analisou estratégias de fotoproteção contra a radiação UV dessa macroalga por meio de abordagens fisiológicas e moleculares, considerando a previsão de incremento de radiação UVB nas zonas tropicais do planeta nos próximos anos. Além disso, a interação entre a radiação UV e o suprimento de N foi também investigada. Essa interação estimulou a síntese de aminoácidos tipo micosporinas (MAAs) e outros compostos nitrogenados, o que proporciona proteção contra danos no aparato fotossintetizante. O envolvimento de um fotorreceptor para radiação UVA que regule a síntese de MAAs, com o efeito adicional de um segundo fotorreceptor, para radiação UVB é sugerido. Houve uma dependência da dose de radiação UV para aumento de MAAs. O aumento da intensidade da radiação UV causou efeitos negativos nos parâmetros da fotossíntese. Outra abordagem mostrou que a ausência de UVA causou danos ao DNA, com a presença de dímeros de ciclobutano pirimidina após 48 h de exposição à radiação PAR+UVB. Este estudo alerta para a importância da qualidade da radiação de UV e seu efeito biológico efetivo para danos no DNA e na fotoinibição. Fotoliases podem ter sido ativadas para evitar danos no DNA sob tratamentos com a presença de radiação UVA, tal como o sistema de enzimas antioxidantes, os quais desempenharam um papel secundário na fotoproteção da alga. A composição de carotenoides de G. tenuistipitata foi pouco afetada pelos tratamentos com N e UV. Este é o primeiro trabalho a mostrar a presença de anteraxantina em G. tenuistipitata, e se sugere a existência de um ciclo de xantofilas parcial composto por anteraxantina e zeaxantina. Um aspecto adicional foi o papel fotoprotetor de ficoeritrina, observado quando G. tenuistipitata foi tratada na presença de N, com PAR, UVA e UVB. Finalmente, a produtividade de MAAs por G. tenuistipitata foi estimulada sob tratamentos com radiação PAR+UV e suprimento de N, e se propõe que seja realizada uma aplicação em larga escala dessa alga vermelha para uso dessas substâncias como filtros de UV e antioxidantes. Desta forma, G. tenuistipitata foi capaz de lidar com a radiação UV, principalmente quando suprida com N e UVA, obtendo uma fotoproteção eficaz. Uma vez que se espera um aumento do índice de UV na superfície terrestre nos próximos anos, é possível que os organismos em ambientes oligotróficos sofram maiores impactos negativos causados por esta radiação / The red alga Gracilaria tenuistipitata has been used for the production of agar, as well as a model to physiological and molecular studies. This study analysed the photoprotective strategies of this macroalga against UV radiation through physiological and molecular approaches, considering the UV increase in tropical zones predicted by physical models. The interactive role of nitrogen supply and UV radiation was also investigated. The synthesis of mycosporine-like amino acids (MAAs) and other nitrogenous compounds was stimulated by both UVR and nitrogen, providing photoprotection against damages to photosynthetic apparatus. The involvement of a UVA-photoreceptor in the photocontrol of accumulation of MAAs and an additional effect with further activation of a second UVB-photoreceptor were suggested. There was a dependence of UV radiation dosis on MAAs accumulation. The increase of the UV irradiance caused a negative effect on the photosynthetic activity. The absence of UVA radiation caused DNA damage, with presence of cyclobutane-pirimidin dimmers after 48 h of exposure to PAR+UVB. This study shows the importance of light quality in the UV range and the biological effective irradiances to confer DNA damage and photoinhibition. Photolyases could be activated to avoid DNA damages under UVA treatments, as well as the antioxidant system, which had a possible secondary role on the photoprotection mechanisms. Carotenoid composition of G. tenuistipitata was slightly affected by UV and N treatments. This is the first study to show anteraxanthin in G. tenuistipitata, and the existence of a partial xanthophyll cycle is proposed, based on antheraxanthin and zeaxanthin. A further aspect observed was a photoprotective role of phycoerithrin in G. tenuistipitata, under the presence of UVA and UVB plus N supplement. Finally, MAAs productivity of G. tenuistipitata was stimulated under PAR+UV radiation and N supply, and we propose a large-scale application of this red alga for the use of these substances as photoprotector by both UV-screen and antioxidant capacities. Therefore, G. tenuistipitata was able to acclimate to UV radiation, under N-supply and UVA radiation i. e. efficient photoprotection and, considering the foreseen UV increment in the next years, its possible that oligotrophic organisms will suffer more with the negative effects of this radiation

Protein-DNA crosslinking is an important method to study protein-DNA interactions. Crosslinking by short pulsed UV lasers is a potentially powerful tool that results in efficient crosslinking, apparently by a two photon process. However, the major problem in using UV laser crosslinking is that the conditions which lead to high crosslinking efficiency also result in high DNA damage. Previously, it has been shown that a combination of femtosecond laser pulses at two different wavelengths, in the UV (266 nm) and the visible range (400 nm), increases the effective crosslinking yield (i.e. higher crosslinking yields with reduced DNA damage). This new strategy has the advantage that the intensity of the UV pulse for the first excitation step can be kept low, leading to lower UV-induced DNA damage and the second pulse at a visible wavelength can provide enough energy for the UV excited bases to cross their ionization threshold without damaging the DNA. The objective of this thesis project was to develop a novel UV laser cross-linking technique that would permit higher effective crosslinking yields with the commonly used pulses in the nanosecond (ns) range. To serve this purpose we tried to extend the two-wavelength femto second laser irradiation approach to longer duration pulses. We chose MBP-PIF3 protein and its target G-box DNA motif as a model system. Before ultraviolet irradiation of the protein-DNA complexes in vitro, the specific binding interaction of purified MBP-PIF3 protein with the G-box DNA motif was studied by Electrophoretic Mobility Shift Assay (EMSA). We irradiated the PIF3/DNA complexes with different laser systems (i.e. Nd:YAG and Dye lasers) and their combinations. We were expecting to see that the combination of UV laser pulses (260nm) with longer wavelength dye laser pulses (480nm) will produce higher effective crosslink yields relative to the yield from the UV pulses alone.

SODIS (Solar Water Disinfection) é uma tecnologia simples para tratamento de água no pontode- uso, sendo uma alternativa importante para disponibilizar água em situações de emergência ou onde não há acesso à água potável. A ação concomitante entre a temperatura e a radiação ultra violeta do sol provoca a morte dos microorganismos presentes na água. Este estudo avaliou a eficiência de inativação de coliformes totais e Escherichia coli pela técnica SODIS para as águas de chuva (coletada em telhado), de poço freático e de manancial superficial (reservatório), sob as condições climáticas de verão de Porto Alegre, RS. Foram ainda, realizados ensaios para verificar se ocorreu o recrescimento dos microorganismos após 24 e 48 horas do término da exposição ao sol. Também foram determinadas as constantes de decaimento das bactérias utilizando a Lei de Chick para representar o declínio dos microorganismos. Os ensaios de SODIS foram realizados em batelada, utilizando garrafas PET transparentes de 1,5 L, expostas ao sol por um período de 6 h. O mesmo número de garrafas era mantido à sombra pelo mesmo período, como controle. As temperaturas do ar e da água e a radiação ultravioleta foram monitoradas ao longo dos ensaios. Os valores médios de remoção de concentrações de E. coli no SODIS nas amostras das águas analisadas variaram entre 98,8 a maior do que 99,99%; para coliformes totais as reduções médias nas amostras variaram entre 90,00 – 99,99%. Não houve recrescimento de microorganismos após 24 e 48 horas seguindo-se ao término da exposição solar. As constantes de decaimento para coliformes totais e E. coli foram, respectivamente, 0,2979 h-1 e 0,9397 h-1, confirmando as observações de que E. coli é mais sensível a desinfecção. Os coeficientes de determinação para a equação da Lei de Chick foram de 0,938 (E. coli) e 0,877 (coliformes totais). Os resultados da pesquisa indicam que as águas de chuva e de poço freático tratadas com SODIS atingiram os padrões microbiológicos recomendados pela Organização Mundial da Saúde, o que não ocorreu com as amostras de água do reservatório superficial estudado. / SODIS (Solar Water Disinfection) is a simple techhnology for point-of-use drinking water treatment, and can be used during emergencies or in sites without running water. The joint action of high temperature and ultraviolet radiation causes the die-off of microrganisms. This study evaluated the removal of total coliforms and Escherichia coli using SODIS to disinfect water from rain (collected in roofs), from well and from surface water (reservoir) under the climate conditions of Porto Alegre, RS. Essays were also conducted to see if bacteria regrowth occurred after 24 and 48 h after the end of the SODIS test. In addition, bacterial decay coefficients were calculated using the Chick´s Law as model. SODIS essays were performed in batch reactors using 1.5 L transparent PET bottles exposed to the sunlight for 6 h.The same number of bottles were kept in the shadow, as a control. Air and water temperatures and ultraviolet radiation were monitored hourly. E. coli mean removals in samples from the three sources of water varied between 98,8% to greater than 99,99%. The mean reductions for total coliforms varied between 90.0% to 99.99%. Microorganism regrowth was not observed after 24 and 48 h. Decay coefficients for coliforms and E. coli were, respectively, 0.2979 h-1 e 0.9397 h-1, confirming the observation that E. coli is more sensitive than total coliforms to SODIS. Coefficients of determination for Chick´s Law equation were 0.938 (E. coli) and 0.877 (total coliform). The results from this research indicate that water from rain and well , but not reservoir, achieved the World´s Health Organization drinking water guidelines for drinking water with low risk of disease acquisition.

Este trabalho teve como objetivo o estudo de desempenho e a avaliação de custos econômicos do processo de desinfecção por radiação UV para efluente de lagoas de estabilização facultativas pós- tratado em alagado construído e para outros efluentes com características similares. O trabalho experimental consistiu de ensaios de desinfecção utilizando reator de desinfecção por radiação UV em batelada. Na pesquisa foram avaliadas as principais variáveis que interferem no rendimento e nos custos dos processos, de forma a adequar o par CT (concentração de desinfetante e tempo de contato) atendendo ao padrão ambiental microbiológico de 1.000 coliformes termotolerantes/100 mL, definido para corpos aquáticos enquadrados na classe 2 estabelecida pela Resolução 357/2005 CONAMA, uma vez que a maioria dos corpos receptores do Brasil estão enquadrados nessa classe. A avaliação econômica definiu custos unitários de implantação e de operação e manutenção do processo de desinfecção UV para um período de 20 anos, considerando valores pontuais e anuais de forma a se verificar o custo total a valor presente. Os dados obtidos indicaram que o efluente final das unidades de tratamento avaliadas apresentaram valores de turbidez, absorvância a 254 nm e ferro total superiores aos usuais recomendados para desinfecção UV, no entanto, não comprometendo a desinfecção. Por outro lado, a concentração de SS foi baixa e com diâmetro de partículas de pequenas dimensões. As várias combinações testadas (doses x altura de lâmina líquida- ALL) sugerem, para atendimento ao padrão microbiológico, doses de 8 Wh/\'M POT.3\' e ALL de 6 cm. A concentração remanescente dos indicadores microbiológicos testados mostrou ordem decrescente de inativação de Clostridium perfringens para coliformes totais e Escherichia coli. A análise da fotorreativação e da ausência de luz no recrescimento dos microrganismos indicadores (coliformes totais e Esherichia coli) foi mais perceptível na ausência de luz. Os custos de implantação das unidades de desinfecção UV projetadas nesta pesquisa foram significativamente menores que os dos modelos industriais comparados. Os custos de operação e manutenção para a desinfecção com radiação UV também foram baixos e equivalem a outros desinfetantes. Os custos médios globais obtidos variam de 14,3 a 20,5 R$/habitante, para garantir a desinfecção do esgoto por radiação UV durante 20 anos. / This work studied UV disinfection process performance and economic costs for facultative stabilization ponds effluent pos treated in constructed wetland and another effluents with similar characteristic. The experimental work consisted of batch disinfection tests using UV reactor, evaluating variables that may affect performance and process costs in order to adjust CT (disinfectant concentration and contact time) according to microbiological environmental standard of 1000/100 mL, set for class 2 water bodies established by 357/2005 CONAMA Resolution. Economic evaluation defined unit costs of deployment and operation and maintenance of the UV disinfection process for 20 years, considering point estimates and annual reports, in order to check total cost to present value. The final effluent from treatment units evaluated had values of turbidity, 254 nm absorbance and total iron above usual recommended for UV disinfection, however, not compromising disinfection process. On the other hand, SS concentration was low and particle size was of small diameter. Various combinations of dose x water height tested suggest, to attend microbiological standards, doses 8 wh/m³ and 6 cm water height. The remaining concentration of microbiological indicators showed descending order of inactivation from Clostridium perfringens to total coliforms and Escherichia coli. Photoreactivation and light absence regrowth of total coliforms and Esherichia coli was more noticeable in darkness. Building costs of UV disinfection units designed were significantly lower than those of industrial models compared. Operation and maintenance costs for UV radiation disinfection were also low and equivalent with other disinfectants. Average total costs obtained vary from R$ 14.3 to R$ 20.5/capita, to ensure UV radiation disinfection life time of 20 years.

A radiação solar, composta por radiação ultravioleta (UV), visível (Vis) e infravermelho, é responsável por acelerar os processos de alteração de cor e do conteúdo proteico da fibra capilar. Visando contornar este problema, este trabalho propõe a incorporação do flavonoide quercetina, de reconhecida atividade antioxidante, em uma nanoemulsão catiônica de aplicação capilar. Para tanto, foram desenvolvidas formulações contendo quercetina a 0,5% (p/p) pelo método de baixa energia sub-PIT. A formulação de menor índice de polidispersão (IPD) foi selecionada e submetida à Avaliação de Estabilidade Normal. Neste ensaio, a nanoemulsão foi armazenada em diferentes condições de temperatura por 90 dias, sendo analisados: características organolépticas, valor de pH, atividade antioxidante, conteúdo de quercetina, diâmetro médio de gotícula e potencial zeta. A fotoestabilidade da nanoemulsão envolveu a determinação do perfil de absorção e da sua atividade antioxidante após períodos de exposição à radiação UV/Vis. Posteriormente, a nanoemulsão foi caracterizada quanto aos seguintes parâmetros: eficiência de encapsulamento, perfil reológico, morfologia das gotículas por Microscopia Eletrônica de Transmissão Criogênica e Microscopia de Força Atômica (AFM). A possível interação entre a quercetina e os demais tensoativos presentes na nanoemulsão foi avaliada por Microscopia Confocal de Fluorescência e Análise térmica. A segurança da nanoemulsão foi determinada pelo método in vitro HET-CAM e por biocompatibilidade cutânea, em voluntários. A eficácia da nanoemulsão catiônica na fotoproteção das características da fibra capilar descolorida tratada com tintura cores loiro (12.0) ou ruivo (6.66) foi determinada avaliando-se os parâmetros cor, tração à ruptura, penteabilidade, fricção, perda proteica, morfologia das cutículas e nível de melanina radical por Espectroscopia de Ressonância Paramagnética Eletrônica (EPR), sendo calculado o Fator de Proteção Radicalar (FPR). As mechas de cabelo tingidas foram expostas à radiação UV/Vis artificial (500 W/m2) por até 180 h, sendo os parâmetros analisados antes e após o período de exposição. A nanoemulsão selecionada pelo reduzido IPD apresentava diâmetro médio de gotícula e potencial zeta iguais a 24,97±0,30 nm e 19,6±2,19 mV, respectivamente. Na Avaliação de Estabilidade Normal, a nanoemulsão armazenada a 45,0±2,0° C apresentou alterações significativas de todos os parâmetros avaliados, exceto potencial zeta, sendo que a elevação do diâmetro médio de gotícula acarretou em perda da transparência. A oxidação da quercetina e a instabilidade do tipo Ostwald ripening (ω3) foram as responsáveis pelas modificações observadas. No armazenamento a 5,0±2,0° C, a nanoemulsão manteve todos os parâmetros inalterados, mas a 25±2,0° C houve elevação discreta do diâmetro médio de gotícula, sem perda da funcionalidade. A nanoemulsão apresentou elevada fotoestabilidade, sem alteração da atividade antioxidante após exposição ao UV/Vis. A caracterização da nanoemulsão mostrou que a eficiência de encapsulamento foi de 99,8%, no mínimo, a formulação apresentou típico comportamento newtoniano e as gotículas apresentavam formato esférico. As imagens obtidas por Microscopia Confocal de Fluorescência e o ensaio de Análise térmica mostraram que a quercetina se encontra dentro das gotícula atuando, também, como co-tensoativo, por interagir com os tensoativos, além de exercer sua função antioxidante. A nanoemulsão foi classificada como levemente irritante (método HET-CAM), sendo esse baixo potencial de irritação corroborado pelo teste de biocompatibilidade cutânea. Na avaliação de eficácia, observou-se que a nanoemulsão protegeu a cor total (dE*) do cabelo tingido de loiro em 54%, e elevou a alteração da cor do cabelo tingido de ruivo em 47% (t = 180 h) em comparação à mecha controle. Além disso, a nanoemulsão melhorou a penteabilidade e reduziu os coeficientes de fricção. A radiação UV/Vis provocou elevada perda proteica e redução da espessura das cutículas em aproximadamente 50%. Concluiu-se, pelos resultados obtidos, que as moléculas que compoem a tintura capilar, principalmente os pigmentos mais escuros, atuaram como filtros solares, pois elas protegeram as estruturas proteicas da fibra. A nanoemulsão apresentou FPR igual a 3,31 e 4,14, para as mechas tingidas de loiro e ruivo, respectivamente. O FPR indica a capacidade de uma formulação em reduzir o nível de radicais livres formados por indução da radiação UV/Vis, um dos fatores que induzem alterações na fibra capilar tingida. Assim, considerando que a radiação UV/Vis atua tanto por mecanismos diretos quanto indiretos, e que alterações significativas de cor foram observadas mesmo quando o nível de radicais livres foi reduzido pela ação da quercetina, deve ser incorporada à formulação fotoprotetora capilar filtros solares associados a antioxidantes nanoestruturados. Tais filtros devem ficar aderidos à cutícula, de modo a protegê-la da degradação proteica e reduzir a entrada de radiação para o interior da fibra capilar, local onde os antioxidantes nanoestruturados devem atuar como uma segunda linha de defesa. / The solar radiation, comprising ultraviolet (UV), visible (VIS) and infrared, is responsible for accelerating color and protein content changes in the hair fiber. In order to avoid this problem, this work proposes the incorporation of the flavonoid quercetin, a recognized antioxidant molecule, in a cationic nanoemulsion for hair application. For this, formulations containing quercetin 0.5% (w/w) were developed by the low-energy sub-PIT method. The formulation with a lower polydispersity index (PDI), which had HLB value (Hydrophilic-Lipophilic Balance) equal to 12.5 was selected and subjected to the Normal Stability Test. In this assay, the nanoemulsion was stored under different temperature conditions for 90 days, and the following parameters were analyzed: organoleptic properties, pH, antioxidant activity, quercetin content, average droplet diameter and zeta potential. The photostability of the nanoemulsion involved the determination of the absorption profile and its antioxidant activity after periods of exposure to UV/Vis radiation. Subsequently, the nanoemulsion was characterized according to the following parameters: encapsulation efficiency, rheological profile, morphology of the droplets by Cryogenic Transmission Electron Microscopy and Atomic Force Microscopy (AFM). The possible interaction between quercetin and other surfactants present in the nanoemulsion was evaluated by Confocal Fluorescence Microscopy and thermal analysis. The safety of the nanoemulsion was assessed by the in vitro HET-CAM method and by cutaneous biocompatibility in volunteers. The photoprotection effectiveness of the bioactive cationic nanoemulsion was evaluated in blond (color 12.0) and auburn (color 6.66) dyed hair fibers by assessing the parameters: color, tensile break, combing, friction, protein loss, morphology of cuticles and level of melanin radical by Electron Paramagnetic Resonance Spectroscopy (EPR). The Radical Hair Protection Factor (RHF) was calculated. Dyed hair tresses were exposed to UV/Vis artificial radiation (500 W/m2) for 180 h. The parameters were analyzed before and after the exposure period. The nanoemulsion selected due to its reduced PDI had an average droplet diameter and zeta potential equal to 24.97±0.30 nm and 19.6±2.19 mV, respectively. In the Normal Stability Test, the nanoemulsion stored at 45.0 ± 2.0º C showed significant changes in all parameters except zeta potential, and the increase in the average droplet diameter resulted in the loss of transparency. Oxidation of quercetin and Ostwald ripening instability (ω3) were responsible for the changes. At 5.0 ± 2.0º C, the nanoemulsion kept all parameters unchanged, but at 25.0±2.0º C there was a slight increase in the average droplet diameter without loss of functionality. The nanoemulsion showed high photostability since antioxidant activity was not altered after UV/Vis exposure. The characterization of the nanoemulsion showed that the encapsulation efficiency was 99.8% at least, the formulation showed typical Newtonian behavior and droplets were spherical. The images obtained by Confocal Fluorescence Microscopy and thermal analysis showed that quercetin was within the droplet acting, also, as a cosurfactant, due to the interaction with the surfactants. The nanoemulsion was classified as slightly irritating (HET-CAM method), and this low irritation potential was supported by the cutaneous biocompatibility assay. The photoprotective effectiveness evaluation showed that the nanoemulsion protected the total color (dE*) of blond dyed hair in 54%, but raised the color change of auburn dyed hair in 47% (t = 180 h). In addition, the nanoemulsion improved combability and reduced coefficients of friction. UV/Vis radiation caused high protein loss and reduced cuticle thickness by approximately 50%. It was concluded that the molecules that compose hair dye, especially the darker pigments, acted as sun filters because they protected the protein structures of the hair fiber. The nanoemulsion showed RHF equal to 3.31 and 4.14 for blond and auburn dyed hair, respectively. The RHF indicates the ability of a formulation to reduce the level of free radicals formed by UV/Vis induction, one of the factors that induce changes in the dyed hair fibers. Thus, considering that the UV/Vis radiation acts by direct and indirect mechanisms and that significant changes in color were observed even when the level of free radicals has been reduced by the quercetin, chemical filters should be incorporated into hair formulations associated with nanostructured antioxidants in order to fully protect hair fiber. Such filters must be attached to the cuticle, protecting it from protein degradation and reducing the radiation input into the hair fiber, where the nanostructured antioxidants must act as a second line of defense.

Excess exposure to solar ultraviolet radiation (UVR) is the only readily modifiable skin cancer risk factor, and childhood exposure is implicated in melanoma aetiology. To assist the design and evaluation of child sun protection interventions in the school and community context, this first comprehensive study used electronic monitors to record time-stamped, second-by-second UVR exposure of 325 children (from 28 randomly selected New Zealand primary schools) who kept a diary record of concurrent activities and sun-protective practices and completed a sun-related knowledge, attitudes and usual behaviours questionnaire. School principals and Health promoters (HPs) were interviewed about school and community sun protection efforts. Using the Haddon matrix and Ottawa Charter of Health Promotion to guide research, four potential domains of influence were identified: the physical and social environments, protective products, and host (child). Two key outcomes identified were child UVR exposure and sun-protective practices. A path model was developed where potential influences on these outcomes included school, community, host factors (demographics, skin type, sun-related attitudes, and sun-related knowledge), and pattern of concurrent outdoor activity. Seven specific hypotheses were defined to investigate the effects of host, school and community factors on UVR exposure, sun-protective practices, and sun-related knowledge, attitudes and behaviours. To test for the effects of host factors, day of the week and activity on UVR exposure and sun-protective practices, linear mixed models containing these factors and interactions between Year level-sex, activity-Year level and activity-sex, accounting for clustering within schools and allowing for repeated measures, were applied. Logistic regression with a random school effect was used to assess differences in scored student questionnaire items. Structural equation modelling was implemented to consider associations between sun-related knowledge, attitudes and behaviours, and other explanatory factors for variations in UVR exposure and sun-protective practices. Three of the seven specific hypotheses were supported. There were statistically significant differences in UVR exposure by sex, skin type, day of the week and activity, and sex-activity and Year level-activity interactions. Passive pursuits were associated with the highest UVR exposure rates compared to outdoor active, travel and unclassified pursuits. There were statistically significant differences in sun-protective practices by sex, ethnicity and skin type, and sex-activity and Year level-activity interactions. Girls tended to have higher sun protection scores than boys, but were more likely to sunbathe and use sunscreen. Children identifying with Pacific Island ethnicities had higher scores than children with other ethnicities, and children with Fitzpatrick skin types I and II had higher scores than children with skin types III, IV and V. School and community factors were not associated with UVR exposure, sun-protective practices, sun-related knowledge, attitudes and behaviours, but school and HPs� scores were relatively high, reflecting the significant time and effort spent promoting youth sun protection. Trends for Year level indicated that whereas child sun-related knowledge increased with Year level, attitudes and behaviours supportive of sun protection declined. When considering sun-related knowledge, attitudes and behaviours simultaneously, knowledge was only significantly associated with behaviours when mediated by attitudes. The study findings have implications for child sun protection interventions.

<p>Ultraviolet radiation (UVR) is a major risk factor for development of skin cancer. UVR-induced DNA damage and a dysfunctional p53 protein are important steps in the development of squamous cell carcinoman in human skin (SCC). The aim of the present investigation was to analyze incidence trends of SCC in Sweden, quantify the risk of second primary cancer after SCC and further analyze the effects of UVR and p53 protein in human skin <i>in vivo</i> and <i>in vitro</i>. The effect of photoprotection by sunscreens was also evaluated. </p><p>We found that the age-standardized incidence rate of SCC in Sweden increased substantially in both men and women during the period 1961-1995, especially in men and at chronically sun-exposed skin sites. Patients with SCC are also at increased risk of developing new primary cancers, especially in the skin, squamous cell epithelium, hematopoietic tissues and respiratory organs. In experimental studies <i>in vivo</i> and <i>in vitro</i> in human skin we observed that repair of UV-induced DNA damage appears to be more efficient in chronically sun-exposed skin despite a less uniform p53 response. Non-sun- exposed skin is more homogeneous with respect to the epidermal p53 response. Keratinocytes in skin exposed frequently to the sun may be prone to react more easily to cytotoxic stress. Two different modalities of photoprotection significantly reduced the amount of DNA damage and the number of p53-positive cells. In addition, we demonstrated that a well-defined system for <i>in vitro</i> culture of explanted skin provides an excellent alternative to <i>in vivo</i> experiments. </p><p>In conclusion, this study has increased our knowledge of SCC epidemiology in Sweden and of the effects of artificial and solar UVR and sunscreens on chronically sun-exposed and non-sun-exposed sites, respectively, of human skin.</p>

In this dissertation, I present electronic spectroscopy of a few biologically relevant species and their complexes with solvent molecules in the gas phase using a variety of techniques, including resonantly enhanced multiphoton ionization (REMPI), laser induced fluorescence (LIF), and zero kinetic energy (ZEKE) photoelectron spectroscopy. My work on several methylated uracils and thymines and thymine-water complexes alludes to a new interpretation with regard to the origin of the photostability of our genetic code. I believe that it is the water solvent that stabilizes the photophysical and photochemical behavior of these bases under UV irradiation. For systems that demonstrate vibrational resolution in the first electronically excited state (S₁) and the cationic state, I performed vibrational analysis of both states with the aid of ab initio and density functional calculations. These observations are explained in terms of the structural changes from the ground state to S₁ and further to the cation. To bridge results from the gas phase to the solution phase, I also report studies of supersonically cooled water complexes of the three isomers of aminobenzoic acid. Density functional theory calculations are carried out to identify structural minima of water complexes in the ground state. The solvation mechanism is investigated based on vibrational analysis of the S₁ state of the neutral complex and the shift of ionization thresholds with increasing water content. / Graduation date: 2005

Graduation date: 1995

Graduation date: 1994