• Journal of Microbiology and Biotechnology
• /
• v.8 no.6
• /
• pp.714-718
• /
• 1998

Various mutants either lacking or having decreased levels of light-harvesting complexes and reaction center complex were obtained with a high frequency by an increased formation of poly-3-hydroxybutyrate (PHB) in Rhodobacter sphaeroides. One of the photosynthesis-defective mutants, PY-17, which was devoid of any of the light-harvesting complexes (B800-850, B875) as well as the reaction center complex, was analyzed further. The mutant showed substantial transcription of the puhA, pufKBALMX, and pucBAC operons coding for the structural proteins of the photosynthetic complexes although each of the activities was lower than that of the wild type. Translation of the pufKBALMX and pucBAC operons were also active in the mutant although with activities different from the corresponding one of the wild type. From these results the mutation appears to exert its effect at the post-translational level of the photosynthetic complex assembly. Complementation of the photosynthesis-defective phenotype of the mutant was achieved with an about 12-kb DNA region containing the puhA gene. The relationship between the formation of PHB and photosynthetic complexes is discussed.

• Clean Technology
• /
• v.17 no.3
• /
• pp.280-282
• /
• 2011

Capture and conversion of abundant solar energy using biotechnology will be essential for the development of sustainable and future energy. Photosynthesis is used for the production of biofuels such as biohydrogen. In this study, lightharvesting xanthorhodopsin consisting of retinal and salinixanthin was isolated from a photosynthetic microorganism Salinibacter ruber by aqueous two phase extraction. To stabilize the light-harvesting machine, artificial xanthorhodopsin-liposome system was reconstructed to have photoelectron absorption activity.

• Journal of Ginseng Research
• /
• v.32 no.4
• /
• pp.347-356
• /
• 2008

Forest-grown American ginseng (Panax quinquefolius L.) is exposed to daily and seasonal light variations. Our goal was to determine the effect of understory light changes on the maximum quantum yield of photosystem II, expressed as $F_v/F_m$, and photosynthetic pigment composition of two-year-old plants. Understory light photon flux density and sunfleck durations were characterized using hemispherical canopy photography. Our results showed that understory light significantly affected the $F_v/F_m$ of American ginseng, especially during the initial development of the plants when light levels were the highest, averaging 28 mol $m^{-2}d^{-1}$. Associated with low $F_v/F_m$ during its initial development, American ginseng had the lowest levels of epoxidation state of the xanthophyll cycle of the season, suggesting an active dissipation of excess light energy absorbed by the chlorophyll pigments. As photon flux density decreased after the deployment of the forest canopy to less than 10 mol $m^{-2}d^{-1}$, chlorophyll a/b decreased suggesting a greater investment in light harvesting pigments to reaction centers in order to absorb the fleeting light energy.

• Journal of Microbiology and Biotechnology
• /
• v.14 no.3
• /
• pp.442-449
• /
• 2004

Improving the light utilization efficiency of photosynthetic cells in photobioreactors (PBRs) is a major topic in algal biotechnology. Accordingly, in the current study we investigated the effect and suitability of photosynthetic pigment reduction for improving light utilization efficiency. The light-harvesting complex II (LH-II) genes of Rhodobacter sphaeroides were removed to construct a mutant strain with less pigment content. The mutant strain exhibited a slower growth rate than the wild-type under a low light intensity, while the mutant grew faster under a high light intensity. In addition, the specific absorption coefficient was lower in the mutant due to its reduced pigment content, thus it seemed that light penetrated deeper into its culture broth. However, the distance (light penetration depth) from the surface of the PBR to the compensation point did not increase, due to an increase in the compensation irradiance of the mutant strain. Experimental data showed that a reduced photosynthetic pigment content, which lessened the photoinhibition under high-intensity light, helped the volumetric productivity of photosynthetic microorganisms.

• Journal of Microbiology and Biotechnology
• /
• v.15 no.5
• /
• pp.1094-1099
• /
• 2005

Photosynthetic dinoflagellates contain a water-soluble, light-harvesting antenna called the peridinin-chlorophyll-protein (PCP) complex, which has an apoprotein with no sequence similarity to other known proteins. There are two forms of PCP apoproteins; the 15-kDa short form and the 32- to 35­kDa long form. The present study describes the PCP protein and its cDNA from Alexandrium tamarense. A cDNA library was constructed from mRNA isolated from A. tamarense. The complete PCP cDNA was generated by reverse-transcription coupled to polymerase chain reaction (RT-PCR), together with rapid-amplification of cDNA ends (RACE). The A. tamarense PCP cDNA encoded a 55-amino acid signal peptide and a 313-amino acid mature protein with a calculated mass of 32 kDa, which corresponded to that of the long form of PCP. Phylogenetic analysis indicated that the sequence of A. tamarense PCP did not cluster with the short-form PCPs, to which it was only about $55\%$ identical, but which were $79-83\%$ identical to other long-form PCPs. The deduced amino acid sequence of A. tamarense PCP contains an internal duplication, which suggests the possibility that long-form PCPs arose by gene duplication or by the fusion of genes encoding the short form. The abundance of PCP mRNA changed substantially in response to different light conditions, indicating the possible existence of a photo-acclimation response in A. tamarense.

• Korean Journal of Medicinal Crop Science
• /
• v.9 no.4
• /
• pp.265-268
• /
• 2001

This experiment was conducted to investigate the effects of temperature, light, seed harvesting time, storage temperature, and period on its germination of Astragalus membranaceus. Optimum germination temperature was ${20{\sim}25^{\circ}C}$ and it was found to be light insensitive seed. The germination rates were not significantly different between 1-year and 2-year old plants, and seed harvesting times. Seeds stored at such cold temperatures as ${-4^{\circ}C\;and\;-20^{\circ}C}$ for 15 months showed over 80% in germination rate at the 6th day after placement. On the other hand, low germination rate of 60% at the 11th day was observed from the seeds stored at $4^{\circ}$ and room temperature.

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2011.10a
• /
• pp.13.1-13.1
• /
• 2011

Photoelectrochemical solar cells such as dye-sensitized cells (DSSCs), which exhibit high performance and are cost-effective, provide an alternative to conventional p-n junction photovoltaic devices. However, the efficiency of such cells plateaus at 11~12%, in contrast to their theoretical value of 33%. The majority of research has focused on improving energy conversion efficiency of DSSC by controlling nanostructure and exploiting new materials in photoelectrode consisting of semiconducting oxide nanoparticles and a transparent conducting oxide electrode (TCO) [1-5]. In this presentation, we introduce inverse opal-based scattering layers containing highly crystalline anatase nanoparticles and their feasibility for use as bi-functional light scattering layer is discussed in terms of optical reflectance and charge generation properties as a function of optical wavelength. A new ITO nanowire-based photoelecrode is also introduced and its unique charge collection property is presented, demonstrating potential use for highly efficient charge collection in DSSC.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2006.08a
• /
• pp.980-983
• /
• 2006

New blue light emitting branched molecules were synthesized by reacting 3,5-bis-(3,5-bis-benzyloxy)- benzoic moiety or 3,5-bis-(3,5-bis-benzyloxy-benzyloxy)- benzoic moiety with biscarbazolyl vinyl biphenyl moiety by dicyclohexylcarbodiimide (DCC) catalyzed esterification. Similar synthetic strategy was also applied to prepare a red light emitting dendrimer. In this paper, we described two blue emitting dendrimers for investigating the effect of the dendronized structures on photoluminescence (PL) and electroluminescence (EL). EL properties of the dendrimers were investigated using heterostructured samples in detalil.

• Journal of the Korean Society of Tobacco Science
• /
• v.21 no.2
• /
• pp.152-159
• /
• 1999

A CAB cDNA clone(pKGCAB) encoding the light harvesting chlorophyll a/b binding protein of the semi-shade plant, Korean ginseng(Panax ginseng C. A. Meyer) was isolated by the one-way path random sequencing of ginseng cDNA library clones and transgenic tobacco plants(Nicotiana tabacum NC82) were produced by the transformation of this ginseng CAB gene in use of Agrobacterium tumefaciens LBA4404. The CAB gene showed type 1 structure of LHCP-II, 84% similarity in nucleotide sequence and 92% in amino acid sequence to that of Nicotiana tabacum CAB40, respectively. Seed germination and initial growth of the transgenic tobacco plants transformed with the cDNA fragment were accelerated under low light intensity compared with those of normal tobacco plant, that may result from the higher light sensitivity of the transgenic plants than that of the normal.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.280-280
• /
• 2013

In green plants, energy generation is accomplished through light-harvesting photosystem, which utilize abundant visible light and multi-stepwise redox reaction to oxidize water and reduce NADP+, transferring electrons efficiently with active cofactors1. Inspired by natural photosynthesis, artificial solar water-splitting devices are being designed variously. However, the several approaches involving immobilization2, conjugation3, and surface modification4 still have limitations. We have made artificial photosynthesis templates by self-assembling tyrosine-based peptide to mimick photosystem II. Porphyrin sensitizer absorbing blue light strongly was conjugated with the templates and they were hybridized with cobalt oxide through the reduction of cobalt ions in an aqueous solution. The formation of hybrid templates was characterized using TEM, and their water oxidation performance was measured by fluorescence oxygen probe. Our results suggest that the bio-templated assembly of functional compounds has a great potential for artificial photosynthesis.