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

Karakterisasi Antosianin Buah Murbei Spesies Morus alba dan Morus cathayana di Indonesia

Buah murbei kaya antioksidan karena kandungan antosianin yang banyak. Sayangnya,  pemanfaatannya sebagai sumber antioksidan di Indonesia masih  minim. Pemanfaatan tanaman murbei hanya sebatas daun yang dijadikan pakan ternak dan teh. Penelitian ini bertujuan untuk melakukan karakterisasi antosianin buah murbei spesies Morus alba dan Morus cathayana. Karakterisasi antosianin ekstrak buah murbei Morus cathayana dan Morus alba dilakukan menggunakan pelarut 0,1% asam klorida (HCl)  dalam metanol dan dianalisis menggunakan spektrofotometer UV-tampak dan Kromatografi Cair Kinerja Tinggi (KCKT). Hasil serapan spektra UV-tampak yang diperoleh dari ekstrak kasar menunjukkan spektra serapan ekstrak buah M. cathayana memberikan nilai yang lebih tinggi ± 1,3 a.u dibandingkan serapan yang diperoleh dari ekstrak kasar buah M. alba dengan serapan ± 0,4 a.u. Nilai total antosianin yang diperoleh dari M. cathayana sebanding dengan serapan ekstrak segarnya, yaitu 40,39 ± 7,64 mg/g berat kering dibandingkan  M. alba yang memiliki nilai total antosianin 11,57 ± 3,02 mg/g berat kering. Hasil kromatogram dari KCKT menggunakan kolom XR-ODS dengan pengelusi A adalah 0,1% asam formiat dalam asetonitril dan pengelusi B adalah 0,1% asam formiat dalam air menunjukkan baik M. cathayana maupun M. alba memiliki dua pigmen antosianin dominan. Walaupun bergitu, intensitas kromatogram M. cathayana lebih tinggi dibandingkan intesitas pada M. alba. Nilai intensitas M. cathayana adalah 50 mAU untuk waktu tambat 7,86 menit dan 15 mAU untuk waktu tambat 8,38 menit. Nilai intensitas M. alba adalah 10 mAU untuk waktu tambat 7,35 menit dan 3 mAU untuk waktu tambat 7,76 menit. Dua antosianin dominan pada M. alba dan M. cathayana  diprediksi  merupakan sianidin-3-O-glukosida dan sianidin-3-O-rutinosida

Multispectral Imaging and Convolutional Neural Network for Photosynthetic Pigments Prediction

The evaluation of photosynthetic pigments composition is an essential task in agricultural studies. This is due to the fact that pigments composition could well represent the plant characteristics such as age and varieties. It could also describe the plant conditions, for example, nutrient deficiency, senescence, and responses under stress. Pigment role as light absorber makes it visually colorful. This colorful appearance provides benefits to the researcher on conducting a nondestructive analysis through a plant color digital image. In this research, a multispectral digital image was used to analyze three main photosynthetic pigments, i.e., chlorophyll, carotenoid, and anthocyanin in a plant leaf. Moreover, Convolutional Neural Network (CNN) model was developed to deliver a real-time analysis system. Input of the system is a plant leaf multispectral digital image, and the output is a content prediction of the pigments. It is proven that the CNN model could well recognize the relationship pattern between leaf digital image and pigments content. The best CNN architecture was found on ShallowNet model using Adaptive Moment Estimation (Adam) optimizer, batch size 30 and trained with 15 epoch. It performs satisfying prediction with MSE 0.0037 for in sample and 0.0060 for out sample prediction (actual data range -0.1 up to 2.2)

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

Photosynthesis provides 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-membrane redox reaction. The light harvesting proteins not only provide the scaffolding that correctly positions the bacteriochlorophyll a and carotenoid pigments for optimal energy transfer but also creates an environment that can modulate the wavelength at which different bacteriochlorophyll molecules absorb light thereby creating the energy funnel. How these proteins can modulate the absorption spectra of the bacteriochlorophylls will be discussed in this review

Low Light Adaptation: Energy Transfer Processes in Different Types of Light Harvesting Complexes from Rhodopseudomonas palustris

Energy transfer processes in photosynthetic light harvesting 2 (LH2) complexes isolated from purple bacterium Rhodopseudomonas palustris grown at different light intensities were studied by ground state and transient absorption spectroscopy. The decomposition of ground state absorption spectra shows contributions from B800 and B850 bacteriochlorophyll (BChl) a rings, the latter component splitting into a low energy and a high energy band in samples grown under low light (LL) conditions. A spectral analysis reveals strong inhomogeneity of the B850 excitons in the LL samples that is well reproduced by an exponential-type distribution. Transient spectra show a bleach of both the low energy and high energy bands, together with the respective blue-shifted exciton-to-biexciton transitions. The different spectral evolutions were analyzed by a global fitting procedure. Energy transfer from B800 to B850 occurs in a mono-exponential process and the rate of this process is only slightly reduced in LL compared to high light samples. In LL samples, spectral relaxation of the B850 exciton follows strongly nonexponential kinetics that can be described by a reduction of the bleach of the high energy excitonic component and a red-shift of the low energetic one. We explain these spectral changes by picosecond exciton relaxation caused by a small coupling parameter of the excitonic splitting of the BChl a molecules to the surrounding bath. The splitting of exciton energy into two excitonic bands in LL complex is most probably caused by heterogenous composition of LH2 apoproteins that gives some of the BChls in the B850 ring B820-like site energies, and causes a disorder in LH2 structure