Lessons Learned from the Pandemic in the UAE: Children COVID-19 Vaccine Hesitancy and Its Impact on the Choice of Distance versus Face-to-Face Learning Modalities: An In-Depth Analysis of a National Study.

This study addresses the crucial aspect of childhood COVID-19 vaccination and its impact on parental decisions concerning learning modalities during the pandemic. This study aimed to gauge parental hesitancy towards vaccinating their children and its influence on choosing between distance and face-to-face learning options. Following STROBE guidelines for cross-sectional studies, this study surveyed 1973 parents in the United Arab Emirates using Google Forms during the COVID-19 pandemic. The results revealed that while more than half of the parents (51.6%) were willing to vaccinate their children if the COVID-19 vaccine was accessible and affordable, a significant majority (91.2%) expressed concerns about the rapid vaccine development process, which was the primary reason for vaccine rejection. Interestingly, a sizable portion (55.3%) had experienced online learning in the previous academic term, and, of those, 59.6% believed it negatively influenced their children's academic performance. Consequently, 66.4% expressed intent to shift their children back to face-to-face learning once feasible. Significantly, parents with medical backgrounds were more inclined (91.6%) to opt for face-to-face schooling compared to those without such backgrounds. Logistic regression analysis indicated associations between sociodemographic characteristics, educational level and background, and the decision to return children to face-to-face learning. Interestingly, when it comes to vaccine hesitancy, a noteworthy connection exists between the parents' reluctance to vaccinate their children and their preference for distance learning. In fact, parents who responded negatively to vaccinating their children against COVID-19, if the vaccine was available, showed a clear preference for the distance learning modality (p-value < 0.0001). This study underscores the complex interplay of factors and community perspectives shaping parental acceptance of childhood COVID-19 vaccination. The development pace of vaccines significantly influences parents' attitudes and beliefs about vaccination programs. Parents' medical backgrounds exhibit a clear correlation with their perceptions of sending children back to school safely. This highlights the potential impact of parental medical knowledge on decision making, emphasizing the need to consider parents' professional backgrounds when devising education- and vaccination-related policies.

First report of molecular identification of Phytophthora infestans causing potato late blight in Yemen.

Late blight, caused by Phytophthora infestans, is one of the most destructive potato diseases in the world. In Yemen, identification of P. infestans still depends on a visual survey and external examination of late blight symptoms. The objective of this study was to isolate and identify P. infestans by using advanced methods. We collected 71 disease samples and isolated the pathogen using the tuber slice method. To identify an isolated pathogen, we performed morphological characterization and gene sequence analysis of the coding genes for internal transcribed spacers. We used Koch's hypotheses to confirm the previous results. In our study. The morphological characters of the mycelium pattern of P. infestans isolates in Yemen were profusely branching, fluffy, and white. The sporangia showed remarkable limoniform papillate sporangial shape. with average length and width of 30.6 and 28.6 µm, respectively. The sequences analysis showed high homology with a degree of identity ranging from 98 to 100% to the database sequences on GenBank. Pathogenicity tests showed that the P. infestans was the causal agent. To our knowledge, this is the first study of the isolation and characterization of P. infestans in Yemen.

Assessment of solar e-cookers social acceptance in Gaza Strip.

This study aims to assess the social acceptance of using solar energy based cooking appliances in Gaza Strip. A study sample that consists of 2400 employees from three local universities in Gaza strip is targeted in study. Meanwhile, 347 participations have participated in the study. This gives the conclusions of the study a margin of error of 5% and a confidence level of 95%. Different attributes are used to measure the social acceptance of the respondents of solar energy cooking systems including knowledge of using solar cooking appliances, financial situation, educational level, age, career and gender. According to the results, 94.55% of the participants believe that the best usage of solar energy is for lighting. Meanwhile, only 37.7% of the participants have supported the usage of solar energy for cooking. It is also concluded that there are no statistical significant differences in using solar energy for cooking associated with gender and job status. Meanwhile, it is found that there is statistical significance of using solar energy for cooking associated with education and age. This shows a clear behavioral barrier for the usage of solar energy cooking systems in Gaza Strip. According to this research it is concluded that end-users with middle income put quality of life first before the technology cost (affordable costs). This conclusion is regardless the educational level of the respondents. Moreover, it is found that Funding schemes and loans are key issues in spreading the e-cooking. Finally it is concluded that noticed support of using solar energy in Gaza according to this research is directly associated with energy poverty status in Gaza. Meanwhile, the idea of using green alternative energy is very acceptable in Gaza but there is a clear lack of awareness of technologies aspects and characteristics.

The rise of telepharmacy services during the COVID-19 pandemic: A comprehensive assessment of services in the United Arab Emirates.

Objective: The study aimed to explore changes in community pharmacies' processes in response to the pandemic in the United Arab Emirates (UAE) and factors affecting the adoption of these changes. Method: A cross-sectional study was conducted using a self-administered questionnaire that was distributed to licensed community pharmacists in the UAE. The survey used to collect information on the type of telepharmacy services and related topics such as constraints and supports. The evaluation of services was done for three periods: before, during and after lockdown. Results: The number of completed surveys was 391. The majority of the participants were under 35 years old (79.5%), female (65.0%), with a bachelor's degree (82.6%), and working in a pharmacy group (70.6%). Pharmacies provided the services by phone (95.6%) and/or messaging applications (80.0%) such as WhatsApp and Messenger. The community pharmacies provided a variety of services using telepharmacy tools such as managing of mild diseases, dispensing and delivering prescribed and OTC medications, general health information, and services for patients with chronic disease. The main factors that had significant effects on several telepharmacy services were pharmacies' type (group/chain vs. individual) and the number of pharmacists in the pharmacy (p < 0.05). Lack of time, training and financial support were the main barriers associated with telepharmacy services among individual pharmacies. Conclusion: Telepharmacy supported the work of community pharmacies during the COVID-19 pandemic by facilitating the provision of pharmaceutical services. Although the occurrence of several financial and technical problems, it appeared less frequently in pharmacy chains with a large number of pharmacists.

The rise of telepharmacy services during the COVID-19 pandemic: A comprehensive assessment of services in the United Arab Emirates

Objective: The study aimed to explore changes in community pharmacies’ processes in response to the pandemic in the United Arab Emirates (UAE) and factors affecting the adoption of these changes. Method: A cross-sectional study was conducted using a self-administered questionnaire that was distributed to licensed community pharmacists in the UAE. The survey used to collect information on the type of telepharmacy services and related topics such as constraints and supports. The evaluation of services was done for three periods: before, during and after lockdown. Results: The number of completed surveys was 391. The majority of the participants were under 35 years old (79.5%), female (65.0%), with a bachelor’s degree (82.6%), and working in a pharmacy group (70.6%). Pharmacies provided the services by phone (95.6%) and/or messaging applications (80.0%) such as WhatsApp and Messenger. The community pharmacies provided a variety of services using telepharmacy tools such as managing of mild diseases, dispensing and delivering prescribed and OTC medications, general health information, and services for patients with chronic disease. The main factors that had significant effects on several telepharmacy services were pharmacies’ type (group/chain vs. individual) and the number of pharmacists in the pharmacy (p < 0.05). Lack of time, training and financial support were the main barriers associated with telepharmacy services among individual pharmacies.Conclusion: Telepharmacy supported the work of community pharmacies during the COVID-19 pandemic by facilitating the provision of pharmaceutical services. Although the occurrence of several financial and technical problems, it appeared less frequently in pharmacy chains with a large number of pharmacists. (AU)

Standalone hybrid PV/wind/diesel-electric generator system for a COVID-19 quarantine center.

This work is motivated by the need in overcoming the electricity crisis in Gaza, which is initiated due to political reasons and the spread of COVID-19. Building quarantine centers is one of the most important means used in combating the COVID-19, but connecting these centers to the electricity distribution network at the appropriate time is not always possible and increases the burden on the local utility company. This article proposed a hybrid off-grid energy system (HES) to effectively energize the quarantine COVID-19 center in Gaza economically and environmentally. To achieve this aim, the estimated load profile of the quarantine center is fed to the HOMER-Pro program. In addition, the various systems components are introduced to the program, then modeled, and optimized. The developed approach was tested using a real case study considering realistic input data. HOMER-Pro program is used to simulate and optimize the system design. The results revealed the potential of the HES to provide environment-friendly, cost-effective, and affordable electricity for the studied quarantine center, as compared to just the diesel generators system. For the considered case study, it is found that the PV-wind-diesel generators HES can cover the connected load with the lowest cost ($ 0.348/kWh) in comparison to other possible HES structures. Taking into consideration the price of harmful emissions, the wining system shows a reduction of 54.89% of the cost of energy (CoE) compared to other systems. For the considered case study, it is found that a combination of 150 kW PV, 200 kW wind, and two diesel generators with capacities of 500 and 250 kW can hold 100% of the electrical load required to keep the quarantine COVID-19 center in operation. The initial capital cost of this HES is $510,576 where the share of wind energy, solar PV, inverter, and diesel-electric generators are $320,000, $83,076, $25,000, and $82,500, respectively. The replacemen cost ($55,918) is due to diesel generators. The total operation and maintainance cost (O&M) is $268,737, that is, 25.6% for wind turbines, 1.2% for inverters, and 70.7% for diesel electric generators. The PV/wind/diesel generators HES generate 1,659,038 kWh of electricity. The total energy requirement of 1,442,553 kWh, which means a surplus of 212,553 kWh of energy/year. The total energy (kWh) is an integration of energy sources which are 427,276 (25.8%), 274,500 (16.5%), and 857,263 (57.7%), due to wind, solar and diesel generators respectively. The cost of yearly consumed fuel is $437,828.769. The payback period for the winning system is 1.8 years. Finally, it is proved that the developed approach gives a reasonable solution to the decision-makers to find a fast, economic and reliable solution to energize the quarantine centers.

Cambodia malaria indicator survey 2020: Implications for malaria elimination.

BACKGROUND: Cambodia has made significant progress in controlling malaria in the past decade. It now aims to eliminate malaria from the country by 2025. It launched the Malaria Elimination Action Framework (MEAF 2016-2020) in 2015 with strong political commitment targeting appropriate interventions on high-risk populations, particularly mobile and migrant groups. METHODS: In 2020, the household-level Cambodia Malaria Survey 2020 (CMS 2020) was conducted with the objective to assess the performance of malaria control activities using the indicators outlined in MEAF 2016-2020. The survey used a cross-sectional probability proportional to size approach drawing 4,000 households from 100 villages across the malaria-endemic districts of the country. RESULTS: A total of 3,996 households with 17,415 inhabitants were interviewed. Of the surveyed households, 98.4% owned a long-lasting insecticide-treated bednet or hammock (LLIN/LLIHN). However, only 79.5% of these reported sleeping under a net the previous night, with only 45.7% sleeping under an insecticide treated net (ITN). Given that forest visitors are at the highest risk of getting malaria, the survey also targeted this group. Of the forest visitor respondents, 89.3% brought an ITN along and 88.9% reported to have used a net during their forest stay. About 10.8% of forest goers had received a forest kit for malaria prevention from mobile malaria workers the last time they went to the forest. Knowledge about mosquito repellents was high among forest goers (62.5%) but the actual use thereof during the last visit to the forest was low (22%). While awareness about malaria prevention with LLINs remained high among most respondents, knowledge about malaria diagnosis and treatment was not universal. Source of malaria knowledge and its treatment was usually from a household member, followed by a village malaria worker or a primary health care center staff. Of those who had fever during the previous two weeks, 93.6% sought advice or treatment outside the home, and the most commonly reported source for advice or treatment was private providers (39.4%) followed by health center/district hospital (31.3%). CONCLUSIONS: ITN distribution and other malaria prevention interventions have largely benefited the high-risk groups including the forest visitors. Comparing the CMS 2020 results with the 2017 CMS results, it is clear that forest visitors' use of LLIN/LLIHN has improved considerably. However, more needs to be done to ensure forest visitors be protected either through using LLINs or repellents while working and staying in the forest areas. Also, given that sleeping under LLINs has decreased over the past several years among the at-risk populations, the programme will have to develop strategies to ensure that the communities do not lower their guard against malaria as cases further dwindle in malaria prone areas. Heightened awareness amongst the general population will be critical for eliminating malaria in Cambodia without any possibility of malaria re-emergence or re-establishment.

Effect of magnetic field on the growth of the cultured Entamoeba histolytica isolated from patients in Palestine.

Static magnetic field (SMF) is generated in vicinity of moving charge or current passing through conductor. In this study, we aimed to investigate the effect of SMF on the growth of the cultured Entamoeba histolytica (E. histolytica) trophozoites. Different SMF strengths with maximum value equals 30 mT (mT) was applied on the E.histolytica for different periods of times: 0 h, 24 h, 48 h, and 72 h. A modified diphasic liver infusion agar medium was used for culturing E. histolytica in vitro. The results showed the successful stabilization of culture of E. histolytica trophozoites. If we kept the sample for longer time, e. g. 14 days, the growth rate decreases to zero. When applying 10 mT and 15 mT SMF on the sample, it is found that the cultivated E. histolytica trophozoites dies after 4 and 2 days respectively. The experiments suggested that the SMF inhibited the growth and the propagation of E. histolytica cells. In addition, it completely killed all the cells in a short time interval which depend on the SMF strength. It is concluded that the SMFs inhibits the growth of E. histolytica and change the morphology of these cells. Thus, we recommend to use SMF as treatment to mitigate the growth of E. histolytica.

Perception of adults toward electronic cigarettes: a cross-sectional study from Jordan.

INTRODUCTION: The rate of Jordanian tobacco smokers has been reported to be one of the highest rates in the world. The electronic cigarette (E-cig) has become an option, or an alternative, to tobacco cigarette smoking. This study was aimed to measure the perception of Jordanian adults toward E-cig use. METHODS: A cross-sectional study design was used. A self-administered survey was developed and validated to solicit anonymous responses from the study participants. A convenience sample (n = 984) was recruited electronically through social media platforms. Descriptive statistics and correlation analyses were completed using the Statistical Package for the Social Sciences (SPSS). RESULTS: More than half of the participants (53%) were females, and almost all participants had heard about E-cig (99.2%), mainly from their friends (40%) and social media (34.5%). About half of the participants were nonsmokers and around one-third of them (33.1%) were current E-cig users. The majority of the participating E-cig users had replaced tobacco with E-cig (56.4%)/All the E-cig users reported positive beliefs toward the E-cig as a safer alternative for tobacco smoking. About 45% of participants believed that the E-cig is helpful in tobacco smoking cessation, but should be highly regulated. CONCLUSION: This study illustrated a significant prevalence of E-cig usage among Jordanian adults. E-cig users perceived E-cig as a safer and cheaper alternative to tobacco smoking and that it helps in tobacco smoking cessation. However, health awareness campaigns are needed for the entire Jordanian community about E-cig use, related emerging health findings, and how to promote tobacco smoking cessation.

Knowledge and awareness about human papillomavirus infection and its vaccination among women in Arab communities.

Cervical cancer (CC) is one of the most common types of cancer that affect females worldwide with hundreds of thousands of women dying annually due to this disease, mainly in developing countries. Infection with human papillomavirus (HPV) is the main risk factor for this cancer. There are no public awareness and national immunization programs in most Arab countries. This study aimed to investigate the knowledge and awareness about the HPV vaccine among females in four Arab countries and their acceptance to receive the vaccine. A cross-sectional study was conducted in several Arab countries: Jordan, Qatar, the United Arab Emirates (UAE), and Iraq. Respondents that fulfilled the desired criteria and were willing to participate in the study were asked to fill out the survey. Knowledge and awareness were assessed using 13 questions. Ethical approvals were given from the four countries. A total of 3658 individuals participated in the study; however, 2804 responses were included in the analysis and more than one third of participants (n = 1007) were aged between 18 and 25 years old. This study revealed poor awareness and knowledge of the participants about HPV and its vaccine among all four countries' participants with relatively better knowledge among participants from the UAE. Participants who are younger (18-25 years old), have a postgraduate education, have an education or career related to the medical field, or had a Pap smear in the last three years tend to have higher knowledge about the HPV vaccine compared to others. Poor knowledge and awareness findings in this study were expected, considering the lack of public education campaigns regarding the HPV virus coupled with the absence of the HPV vaccination from the national immunization schedule in three participating countries (Jordan, Qatar, and Iraq). It is recommended that there is a need to provide national educational campaigns about the HPV vaccine to the public in all Arab populations.

COVID-19 Death and BCG Vaccination Programs Worldwide.

Several clinical trials are being conducted worldwide to investigate the protective effect of the bacillus Calmette-Guérin (BCG) vaccine against death in healthcare providers who are working directly with coronavirus disease 2019 (COVID-19) patients. Clinical studies suggested that certain live vaccines, particularly the BCG vaccine, could reduce the mortality due to other diseases caused by non-targeted pathogens, most probably through the nonspecific effects (heterologous effects). By the end of May 2020, the available information on the COVID-19 pandemic indicated the great effect of the BCG vaccine in reducing the number of COVID-19 death cases. The occurrence of death due to COVID-19 was found to be 21-fold lower in countries with a national BCG vaccination policy than in countries without such a policy, based on the medians of COVID-19 death case per 1 million of the population in these two groups of countries (p<0.001, MannWhitney test). Therefore, it can be concluded that the early establishment of a BCG vaccination policy in any country is a key element in reducing the number of COVID-19 and tuberculosis death cases.

COVID-19 Death and BCG Vaccination Programs Worldwide / 결핵및호흡기질환

Several clinical trials are being conducted worldwide to investigate the protective effect of the bacillus Calmette-Guérin (BCG) vaccine against death in healthcare providers who are working directly with coronavirus disease 2019 (COVID-19) patients. Clinical studies suggested that certain live vaccines, particularly the BCG vaccine, could reduce the mortality due to other diseases caused by non-targeted pathogens, most probably through the nonspecific effects (heterologous effects). By the end of May 2020, the available information on the COVID-19 pandemic indicated the great effect of the BCG vaccine in reducing the number of COVID-19 death cases. The occurrence of death due to COVID-19 was found to be 21-fold lower in countries with a national BCG vaccination policy than in countries without such a policy, based on the medians of COVID-19 death case per 1 million of the population in these two groups of countries (p<0.001, MannWhitney test). Therefore, it can be concluded that the early establishment of a BCG vaccination policy in any country is a key element in reducing the number of COVID-19 and tuberculosis death cases.

Argan Oil Element Content is a Powerful Marker of the Quality of the Fruit Used for its Preparation.

Argan oil is prepared by cold pressing argan kernels collected from fully ripe fruit. Argan oil market price is particularly elevated. Consequently, efficient methods to ascertain its authenticity and quality are looked for by industrials as well as individual consumers. Argan oil element profile has already been shown to be sufficiently singular to be used to certify its authenticity. Quantification of eleven elements (Ca, P, Mg, Mn, K, Cu, Fe, Cd, Cr, Zn, and Sn) indicated a 55 to 60% increase in global metal content in argan oil prepared from fully ripe fruit, compared to argan oil prepared from unripe fruit. Individual variations are herein reported and our study demonstrates that argan oil element profile allows to certify the degree of maturity of the argan fruit at its harvest time and hence to guarantee the respect of one essential parameter necessary to get an argan oil of high nutritional quality.

On-line thickness measurement for two-layer systems on polymer electronic devices.

During the manufacturing of printed electronic circuits, different layers of coatings are applied successively on a substrate. The correct thickness of such layers is essential for guaranteeing the electronic behavior of the final product and must therefore be controlled thoroughly. This paper presents a model for measuring two-layer systems through thin film reflectometry (TFR). The model considers irregular interfaces and distortions introduced by the setup and the vertical vibration movements caused by the production process. The results show that the introduction of these latter variables is indispensable to obtain correct thickness values. The proposed approach is applied to a typical configuration of polymer electronics on transparent and non-transparent substrates. We compare our results to those obtained using a profilometer. The high degree of agreement between both measurements validates the model and suggests that the proposed measurement method can be used in industrial applications requiring fast and non-contact inspection of two-layer systems. Moreover, this approach can be used for other kinds of materials with known optical parameters.

Magnetostatic surface waves propagation at dissipative ferrite-MTMs-metal structure.

The magnetostatic surface waves (MSSW) propagation in a layered structure composed of ferrite film covered by air and on top of metamaterial (MTM) placed on metal is discussed. Dispersion equations which relate the parameters of different layers are derived and used to analyse propagation of MSSW. It is found that the MSSW excitation band depends on the thickness of the MTM layer and ferrite layer.

Self-assembly and energy transfer in artificial light-harvesting complexes of bacteriochlorophyll c with astaxanthin.

Chlorosomes, the light-harvesting antennae of green photosynthetic bacteria, are based on large aggregates of bacteriochlorophyll molecules. Aggregates with similar properties to those in chlorosomes can also be prepared in vitro. Several agents were shown to induce aggregation of bacteriochlorophyll c in aqueous environments, including certain lipids, carotenes, and quinones. A key distinguishing feature of bacteriochlorophyll c aggregates, both in vitro and in chlorosomes, is a large (>60 nm) red shift of their Q(y) absorption band compared with that of the monomers. In this study, we investigate the self-assembly of bacteriochlorophyll c with the xanthophyll astaxanthin, which leads to the formation of a new type of complexes. Our results indicate that, due to its specific structure, astaxanthin molecules competes with bacteriochlorophylls for the bonds involved in the aggregation, thus preventing the formation of any significant red shift compared with pure bacteriochlorophyll c in aqueous buffer. A strong interaction between both the types of pigments in the developed assemblies, is manifested by a rather efficient (~40%) excitation energy transfer from astaxanthin to bacteriochlorophyll c, as revealed by fluorescence excitation spectroscopy. Results of transient absorption spectroscopy show that the energy transfer is very fast (<500 fs) and proceeds through the S(2) state of astaxanthin.

Analytical solution of four-mode coupling in shear strain loaded fiber Bragg grating sensors.

The polarization-dependent reflection spectra of fiber Bragg grating (FBG) sensors in polarization-maintaining fibers are influenced by shear strain. This influence can be evaluated from a tensorial coupled-mode theory approach. Yet, this approach requires the numerical integration of the four coupled-mode equations. We present an easy to handle, completely analytical treatment of the polarization-dependent reflection spectra of FBGs. We derive the required equations and compare the results to the numerical integration of the four tensorial coupled mode equations.

Increasing AIDS case reports in the South: U.S. trends from 1981-2004.

This study compares the trends in AIDS case reports in Southern states and in other regions and estimates the factors associated with the trends. Data from the HIV/AIDS Surveillance Reports 1999 and 2004 of the Centers for Disease Control and Prevention were used to calculate the proportion of the total cumulative cases (1981-2004) that occurred in the five most recent years (2000-2004). A linear regression model was fitted to estimate the factors associated with the highest recent growth rate for AIDS cases by state. Results revealed that Southern states (including the District of Columbia) are more likely to have a disproportionate proportion of total AIDS cases reported within the past five years (25.5% in 16 states and the District) compared to the rest of the U.S. (mean = 19.3% in 34 states and Puerto Rico and the U.S. Virgin Islands; p < 0.001). Being a southern state (4.3% higher in proportion; 95% CI, 1.3%-7.3%) and higher representation of black race (0.1%, 95% CI, 0.02%-0.2%) were factor independently associated with higher recent growth rate for a state. AIDS case rates suggest recent worrisome trends in the South. Those states and territories that are in the South and that have higher proportions of African-Americans have a higher proportion of recent AIDS case reports than elsewhere, suggesting the need for a special geographic focus to encourage prevention, HIV testing, and access to care.

The influence of human serum albumin on the photogeneration of singlet oxygen by meso-tetra(4-sulfonatophenyl)porphyrin. An infrared phosphorescence study.

meso-Tetra(4-sulfonatophenyl)porphyrin (TPPS4) is a water soluble photosensitizer, which is currently clinically tested as a PDT drug. In our contribution, we present IR spectral- and time-resolved phosphorescence data reflecting the influence of human serum albumin (HSA) on singlet oxygen photogeneration by TPPS4. IR emission of TPPS4 was studied in samples containing various concentrations of HSA in phosphate buffer. The observed changes in spectral and temporal behaviour of TPPS4 and singlet oxygen phosphorescence caused by the addition of HSA are equivalent to the effect of nitrogen purging of HSA-free solutions of TPPS4. The main feature induced by addition of HSA appears to be the occurrence of a long-lived (tens of microseconds) photosensitizer phosphorescence at 900 nm besides ordinary short-lived (approximately 2 micros) one at 820 nm. It is accompanied by presence of a long-lived component of singlet oxygen emission with lifetime roughly corresponding to that of the long photosensitizer phosphorescence component. Moreover, the quantum yield of singlet oxygen phosphorescence decreases with increasing HSA concentration, while total quantum yield of TPPS4 phosphorescence rises. These facts are explained by a shielding effect of HSA on bound molecules of TPPS4 against quenching by oxygen which is analogous to oxygen removal by nitrogen purging.

Hole burning study of excited state structure and energy transfer dynamics of bacteriochlorophyll c in chlorosomes of green sulphur photosynthetic bacteria.

Results of low temperature fluorescence and spectral hole burning experiments with whole cells and isolated chlorosomes of the green sulfur bacterium Chlorobium limicola containing BChl c are reported. At least two spectral forms of BChl c (short-wavelength and long-wavelength absorbing BChl c) were identified in the second derivative fluorescence spectra. The widths of persistent holes burned in the fluorescence spectrum of BChl c are determined by excited state lifetimes due to fast energy transfer. Different excited state lifetimes for both BChl c forms were observed. A site distribution function of the lowest excited state of chlorosomal BChl c was revealed. The excited state lifetimes are strongly influenced by redox conditions of the solution. At anaerobic conditions the lifetime of 5.3 ps corresponds to the rate of energy transfer between BChl c clusters. This time shortens to 2.6 ps at aerobic conditions. The shortening may be caused by introducing a quencher. Spectral bands observed in the fluorescence of isolated chlorosomes were attributed to monomeric and lower state aggregates of BChl c. These forms are not functionally connected with the chlorosome.