Studies on the different types of LH2 complexes from the purple non-sulphur photosynthetic bacterium Rhodopseudomonas palustris strain 2.1.6

Some purple bacteria species, such as Rhodopseudomonas palustris 2.1.6, produce light harvesting antenna (LH2) with unusual absorption spectra when they are grown under low-light intensities. This ability is often related to the presence of multiple genes encoding the LH2 apoproteins. This thesis describes isolation of pure stable LH2s from Rhodopseudomonas palustris 2.1.6 grown at different light intensities, determination of the polypeptide composition of high- (HL) and low-light (LL) LH2 complexes and characterisation their spectroscopic properties using various optical spectroscopies. The question of whether rings with a heterogeneous apoprotein composition exist has been addressed by single-molecule spectroscopy. For the first time, direct evidence that individual LL LH2 complexes have a heterogeneous αβ-apoprotein composition has been found. Such mixed rings feature Bchl a molecules with both B820-like and B850-like site-energies. This finding was supported by a femtosecond study on the energy transfer reactions and exciton relaxations within both HL and LL LH2 complexes. This thesis also describes attempts to crystallise the HL and LL LH2s. Even though three-dimensional crystals of both HL and LL LH2 complexes only diffracted to low resolution, it was possible to use molecular replacement to obtain structures that suggest both these types of LH2s are nonamers

STUDY ON THE STRUCTURAL BASIS OF PERIPHERAL LIGHT HARVESTING COMPLEXES (LH2) IN PURPLE NON-SULPHUR PHOTOSYNTHETIC BACTERIA

ABSTRACT Photosynthesisprovides an example of a natural process that has been optimized during evolution to harness solar energy efficiently and safely, and finally to use it to produce a carbon-based fuel. Initially, solar energy is captured by the light harvesting pigment-protein complexes. In purple bacteria these antenna complexes are constructed on a rather simple modular basis. Light absorbed by these antenna complexes is funnelled downhill to reaction centres, where light drives a trans-membraneredox reaction. The light harvesting proteins not only provide the scaffolding that correctly positions the bacteriochlorophylla and carotenoid pigments for optimal energy transfer but also creates an environment that can modulate the wavelengthat which different bacteriochlorophyllmolecules absorb light thereby creating the energy funnel. How these proteins can modulate the absorption spectra of the bacteriochlorophyllswill be discussedin this review. INTRODUCTION Keywords: photosynthesis, peripheral light harvesting complex, H-bonding, energy transfe

Reconstitution Approach to Tune Spectral Features of Light Harvesting Complexes for Improved Light Absorption and Energy Transfer

AbstractLight harvesting complexes developed by living organisms render themselves as an excellent system for understanding basic physical and chemical processes behind the conversion of sunlight energy. Although light harvesting complexes are pretty robust, biochemical reconstitution and genetic modifications have proven the flexibility to tailor their absorption spectra and energy transfer. Importantly, the refolding of the protein and the exchanging of the pigment in micellar media results in very similar pigment arrangement within the native complexes. Here, we show reconstitution approaches with different pigments that have been carried out in PCP, LHCII, and LHI complexes. Monitoring on the spectral changes and energy transfer has also been described

Telaah Literatur Potensi Lutein dari Bunga Marigold Lokal sebagai Suplemen Kesehatan

Abstract Lutein is a type of xanthophyll that accumulated predominantly in eye macula, and is distributed in several parts of the human body, such as skin and brain. Lutein accumulation in the human body is associated with the health benefits of lutein, including being an antioxidant and protecting, the eyes and skin from exposure to blue light, and playing an important role to maintain human cognitive health. Lutein cannot be synthesized by human, so consumption of lutein can be obtained from foods such as fruits and green vegetables, as well as from supplements. The purpose of writing this article was to increase awareness of the importance of adequate lutein intake early in the body, as well as increased research interest in exploring local resources as a potential source of lutein, the Mega Orange marigold from Bali as a raw material for health supplements. The potential lutein article as health supplement was prepared by reviewing articles from international journals and followed by testing the composition of carotenoids in Mega Orange marigolds and a health supplement product by HPLC analysis. Various studies and article publications regarding the health benefits of lutein have been found in the last decade. There are at least two main benefits of lutein, namely as an antioxidant and to maintain the health of organs such as the eyes, brain and skin. Meanwhile, the local marigold flower variety of Mega Orange contains carotenoids lutein and zeaxanthin up to 13.88 mg/g dry weight, and this result is in the range of lutein concentrations in marigold flowers that grow in Thailand. Mega Orange marigold is a potential source of lutein that can be used as raw materials for health supplement products. The importance of lutein intake for the human body makes the use of lutein from local marigolds in the manufacture of health supplements needs to be optimized and utilized. Abstrak Lutein termasuk jenis xantofil yang terakumulasi secara dominan pada makula, serta terdistribusi pada beberapa bagian tubuh manusia seperti kulit dan otak. Akumulasi lutein pada tubuh manusia dikaitkan dengan manfaat kesehatan lutein, diantaranya sebagai antioksidan serta melindungi mata dan kulit dari paparan sinar biru, dan memainkan peranan penting untuk menjaga kesehatan kognitif manusia. Lutein tidak dapat disintesis oleh manusia, sehingga konsumsi lutein dapat diperoleh dari makanan seperti buah dan sayuran hijau, serta dari suplemen. Tujuan penulisan artikel ini adalah untuk meningkatkan kesadaran akan pentingnya kecukupan asupan lutein sejak dini dalam tubuh, serta menambah minat penelitian akan eksplorasi sumber daya lokal yang sebagai sumber potensial lutein yaitu bunga marigold Mega Orange dari Pulau Bali sebagai bahan baku suplemen kesehatan. Artikel potensi lutein sebagai suplemen kesehatan ini disusun dengan menelaah artikel-artikel pada jurnal internasional dan diikuti dengan pengujian komposisi karotenoid pada bunga marigold Mega Orange dan satu produk suplemen kesehatan dengan analisis Kromatografi Cair Kinerja Tinggi (KCKT). Berbagai penelitian dan publikasi artikel mengenai manfaat kesehatan lutein telah banyak ditemukan dalam dekade terakhir. Setidaknya terdapat dua manfaat utama lutein, yaitu sebagai antioksidan dan untuk menjaga kesehatan organ tubuh seperti mata, kulit, dan otak. Adapun, bunga marigold lokal varietas Mega Orange mengandung karotenoid lutein dan zeaksantin hingga 13,88 mg/g berat kering, dan hasil ini berada pada rentang konsentrasi lutein dalam bunga marigold yang tumbuh di Thailand. Bunga marigold Mega Orange merupakan sumber potensial lutein yang dapat digunakan sebagai bahan baku produk suplemen kesehatan. Pentingnya asupan lutein bagi tubuh manusia menjadikan pemanfaatan lutein dari bunga marigold lokal dalam pembuatan suplemen kesehatan perlu dioptimalkan dan dimanfaatkan

Improving the Resilience of Small-Scale Food Entrepreneurs in the New Norm through Government Assistance during Covid-19 Pandemic Era

The existence of small-scale food enterprises helps a lot in increasing the country's income, as well as providing many employment opportunities to the community. This study was to examine how small-scale food entrepreneurs strive to survive in the enterprise when faced with the effects of COVID-19. Factor analysis was used to form the resilience factor and descriptive analysis was used to look demography, resilience practices, and to analyze the assistance in improving entrepreneurial resilience. This study has developed resilience factors and improved resilience. The government needs to be vigilant in providing the assistance needed by entrepreneurs to rehabilitate businesses affected by the COVID-19 pandemic. Keywords: SMEs, New Norms, Resilience eISSN: 2398-4287 © 2022. The Authors. Published for AMER ABRA cE-Bs by e-International Publishing House, Ltd., UK. This is an open access article under the CC BYNC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer–review under responsibility of AMER (Association of Malaysian Environment-Behaviour Researchers), ABRA (Association of Behavioural Researchers on Asians/Africans/Arabians) and cE-Bs (Centre for Environment-Behaviour Studies), Faculty of Architecture, Planning & Surveying, Universiti Teknologi MARA, Malaysia. DOI: https://doi.org/10.21834/ebpj.v7i20.344

Chloroplast Pigments: Structure, Function, Assembly and Characterization

Chlorophyll and carotenoid are vital components that can be found in the intrinsic part of chloroplast. Their functions include light-harvesting, energy transfer, photochemical redox reaction, as well as photoprotection. These pigments are bound non-covalently to protein to make pigment-protein supercomplex. The exact number and stoichiometry of these pigments in higher plants are varied, but their compositions include chlorophyll (Chl) a, Chl b, lutein, neoxanthin, violaxanthin, zeaxanthin and β-carotene. This chapter provides introduction to the structure and photophysical properties of these pigments, how they assemble as pigment-protein complexes and how they do their functions. Various common methods for isolation, separation and identification of chlorophylls and carotenoid are also discussed

Metal-Enhanced Fluorescence of Chlorophylls in Single Light-Harvesting Complexes

Ensemble and single-molecule spectroscopy demonstrates that both emission and absorption of peridinin−chlorophyll−protein photosynthetic antennae can be largely enhanced through plasmonic interactions. We find up to 18-fold increase of the chlorophyll fluorescence for complexes placed near a silver metal layer. This enhancement, which leaves no measurable effects on the protein structure, is observed when exciting either chlorophyll or carotenoid and is attributed predominantly to an increase of the excitation rate in the antenna. The enhancement mechanism comes from plasmon-induced amplification of electromagnetic fields inside the complex. This result is an important step toward applying plasmonic nanostructures for controlling the optical response of complex biomolecules and improving the design and functioning of artificial light-harvesting systems

Polarization control of metal-enhanced fluorescence in hybrid assemblies of photosynthetic complexes and gold nanorods

Fluorescence imaging of hybrid nanostructures composed of a bacterial light-harvesting complex LH2 and Au nanorods with controlled coupling strength is employed to study the spectral dependence of the plasmon-induced fluorescence enhancement. Perfect matching of the plasmon resonances in the nanorods with the absorption bands of the LH2 complexes facilitates a direct comparison of the enhancement factors for longitudinal and transverse plasmon frequencies of the nanorods. We find that the fluorescence enhancement due to excitation of longitudinal resonance can be up to five-fold stronger than for the transverse one. We attribute this result, which is important for designing plasmonic functional systems, to a very different distribution of the enhancement of the electric field due to the excitation of the two characteristic plasmon modes in nanorods

AKTIVITAS TERMOPROTEKSI DAN FOTOPROTEKSI EKSTRAK KASAR KAROTENOID MESOKARP KELAPA SAWIT (Elaeis guineensis Jacq.) TERHADAP KESTABILAN KLOROFIL-A)

AbstrakKelapa sawit (Elaeis guineensis Jacq.) merupakan tanaman yang mengandung karotenoid tinggi pada mesokarp yang merupakan bagian dari buah. Cahaya dan suhu dalam proses fotosintesis memberi pengaruh bagi kestabilan dan ketidakstabilan karotenoid dan klorofil. Penelitian ini bertujuan untuk mengetahui aktivitas fotostabilitas dan termostabilitas ekstrak karotenoid mesokarp terhadap klorofil-a yang diiradiasi dengan lampu volpi (intralux 4100) daylight pada intensitas cahaya 31960 lux, 47040 lux dan 76640 lux dalam seri waktu penyinaran 0, 5, 10, 15, 20, 25, dan 30 menit serta dipanaskan pada suhu 25, 50, 65, dan 90 °C dengan seri waktu pemanasan 0, 1, 2, 3, 6, 9, dan 24 jam. Pengukuran spektrum serapan tiap perlakuan diukur menggunakan Spektrofotometer UV-Tampak pada panjang gelombang 300–800 nm. Hasil penelitian menunjukkan bahwa karotenoid tidak melakukan fungsi proteksi dengan baik pada perlakuan pemanasan 65 °C dan 90 °C selama 24 jam, serta perlakuan iradiasi hingga 30 menit pada ketiga intensitas cahaya. Kesimpulan dari penelitian ini adalah klorofil-a murni lebih stabil pada perlakuan pemanasan dan iradiasi. Kemampuan proteksi karotenoid terhadap kestabilan klorofil-a yaitu pada suhu di bawah 50 °C dan pada intensitas cahaya di bawah 31960 lux.Abstract Oil palm (Elaeis guineensis Jacq.) is a plant that contains high carotenoids in its mesocarp which is part of the fruit. Light and temperature in photosynthesis may affect the stability and instability of carotenoid and chlorophyll. The aim of this research was to examine the thermostability and photostability activities of the carotenoids in mesocarp extract on chlorophyll which were irradiated by Volpi lamp (4100 intralux) daylight at light intensity of 31960 lux, 47040 lux and 76640 lux in series of time radiation 0, 5, 10, 15, 20, 25, and 30 minutes and heated at 25, 50, 65, and 90°C with series of heating time 0, 1, 2, 3, 6, 9, and 24 hours. Measurement of the absorption spectrum of each treatment was measured using a UV-Vis Spectrophotometer at a wavelength range of 300–800 nm. The results showed the protective function of carotenoids did not perform well at the heating treatments of 65°C and 90°C in 24 hours and at the irradiation for 30 minutes in all the light intensities. In conclusion, pure chlorophyll-a is more stable in heating and irradiation treatments. Carotenoid protection ability against chlorophyll-a is at temperatures below 50 °C and at a light intensity below 31960 lux

Preprocess dependence of optical properties of ensembles and single siphonaxanthin-containing major antenna from the marine green alga Codium fragile

The siphonaxanthin-siphonein-Chl-a/b-protein (SCP) is the light-harvesting complex of the marine alga Codium fragile. Its structure resembles that of the major light-harvesting complexes of higher plants, LHC II, yet it features a reversed Chl a:Chl b ratio and it accommodates other variants of carotenoids. We have recorded the fluorescence emission spectra and fluorescence lifetimes from ensembles and single SCP complexes for three different scenarios of handling the samples. While the data obtained from ensembles of SCP complexes yield equivalent results, those obtained from single SCP complexes featured significant differences as a function of the sample history. We ascribe this discrepancy to the different excitation intensities that have been used for ensemble and single complex spectroscopy, and conclude that the SCP complexes undergo an aging process during storage. This process is manifested as a lowering of energetic barriers within the protein, enabling thermal activation of conformational changes at room temperature. This in turn leads to the preferential population of a red-shifted state that features a significant decrease of the fluorescence lifetime