Browsing by Author "Ho, Ming-Yang"

Now showing 1 - 4 of 4

Breaking the Red Limit: Efficient Trapping of Long-Wavelength Excitations in Chlorophyll-f-Containing Photosystem I
(Elsevier BV, 2021-01) Tros, Martijn; Mascoli, Vincenzo; Shen, Gaozhong; Ho, Ming-Yang; Bersanini, Luca; Gisriel, Christopher J.; Bryant, Donald A.; Croce, Roberta
Background: Food insecurity (FI) is an important public health issue for US veterans. For many veterans, civilian life is fraught with service-incurred health issues and socioeconomic challenges, each risk factors for FI. The FI literature on veterans is limited due to insufficient coverage of the topic’s complexity and the methods used to study it in this population. No published analysis has evaluated how FI has been examined in US veterans. Objectives: We assessed how FI has been examined in US military veterans by identifying (1) the major content areas, or domains, studied in association with FI and (2) the existing research gaps. Methods: A scoping literature review was conducted to map the main research domains of the FI literature and identify knowledge gaps. Electronic database and hand searches identified potentially relevant studies (n = 61). Data extraction, utilizing a standardized set of design parameters, was completed. Duplicate removal and application of inclusion/exclusion criteria resulted in the studies (n = 21) selected for critical review. Results: Eight research domains were determined: FI prevalence, health status, dietary practices, health care utilization, economic instability, homelessness/housing instability, food program participation, and community/emergency preparedness—the most dominant was health status and the least dominant were social determinants (ie, homelessness/housing instability, food program participation). Research on validity and usability of FI assessment methods in veterans was virtually absent. Military service factors, longitudinal effects, FI among women, intervention effectiveness, and other areas lacked sufficient inquiry. Conclusion: Research is required on lesser examined content areas and methodology to optimize surveillance and policy for veteran FI.
Extensive remodeling of the photosynthetic apparatus alters energy transfer among photosynthetic complexes when cyanobacteria acclimate to far-red light
(2020-04) Ho, Ming-Yang; Niedzwiedzki, Dariusz M.; MacGregor-Chatwin, Craig; Gerstenecker, Gary; Hunter, C. Neil; Blankenship, Robert E.; Bryant, Donald A.
Some cyanobacteria remodel their photosynthetic apparatus by a process known as Far-Red Light Photoacclimation (FaRLiP). Specific subunits of the phycobilisome (PBS), photosystem I (PSI), and photosystem II (PSII) complexes produced in visible light are replaced by paralogous subunits encoded within a conserved FaRLiP gene cluster when cells are grown in far-red light (FRL; λ = 700–800 nm). FRL-PSII complexes from the FaRLiP cyanobacterium, Synechococcus sp. PCC 7335, were purified and shown to contain Chl a, Chl d, Chl f, and pheophytin a, while FRL-PSI complexes contained only Chl a and Chl f. The spectroscopic properties of purified photosynthetic complexes from Synechococcus sp. PCC 7335 were determined individually, and energy transfer kinetics among PBS, PSII, and PSI were analyzed by time-resolved fluorescence (TRF) spectroscopy. Direct energy transfer from PSII to PSI was observed in cells (and thylakoids) grown in red light (RL), and possible routes of energy transfer in both RL- and FRL-grown cells were inferred. Three structural arrangements for RL-PSI were observed by atomic force microscopy of thylakoid membranes, but only arrays of trimeric FRL-PSI were observed in thylakoids from FRL-grown cells. Cells grown in FRL synthesized the FRL-specific complexes but also continued to synthesize some PBS and PSII complexes identical to those produced in RL. Although the light-harvesting efficiency of photosynthetic complexes produced in FRL might be lower in white light than the complexes produced in cells acclimated to white light, the FRL-complexes provide cells with the flexibility to utilize both visible and FRL to support oxygenic photosynthesis.
Harvesting far-red light: Functional integration of chlorophyll f into Photosystem I complexes of Synechococcus sp. PCC 7002
(2020-08) Tros, Martijn; Bersanini, Luca; Shen, Gaozhong; Ho, Ming-Yang; van Stokkum, Ivo H. M.; Bryant, Donald A.; Croce, Roberta
The heterologous expression of the far-red absorbing chlorophyll (Chl) f in organisms that do not synthesize this pigment has been suggested as a viable solution to expand the solar spectrum that drives oxygenic photosynthesis. In this study, we investigate the functional binding of Chl f to the Photosystem I (PSI) of the cyanobacterium Synechococcus 7002, which has been engineered to express the Chl f synthase gene. By optimizing growth light conditions, one-to-four Chl f pigments were found in the complexes. By using a range of spectroscopic techniques, isolated PSI trimeric complexes were investigated to determine how the insertion of Chl f affects excitation energy transfer and trapping efficiency. The results show that the Chls f are functionally connected to the reaction center of the PSI complex and their presence does not change the overall pigment organization of the complex. Chl f substitutes Chl a (but not the Chl a red forms) while maintaining efficient energy transfer within the PSI complex. At the same time, the introduction of Chl f extends the photosynthetically active radiation of the new hybrid PSI complexes up to 750 nm, which is advantageous in far-red light enriched environments. These conclusions provide insights to engineer the photosynthetic machinery of crops to include Chl f and therefore increase the light-harvesting capability of photosynthesis.
The structure of Photosystem I acclimated to far-red light illuminates an ecologically important acclimation process in photosynthesis
(2020-02) Gisriel, Christopher; Shen, Gaozhong; Kurashov, Vasily; Ho, Ming-Yang; Zhang, Shangji; Williams, Dewight; Golbeck, John H.; Fromme, Petra; Bryant, Donald A.
Phototrophic organisms are superbly adapted to different light environments but often must acclimate to challenging competition for visible light wavelengths in their niches. Some cyanobacteria overcome this challenge by expressing paralogous photosynthetic proteins and by synthesizing and incorporating ~8% chlorophyll f into their Photosystem I (PSI) complexes, enabling them to grow under far-red light (FRL). We solved the structure of FRL-acclimated PSI from the cyanobacterium Fischerella thermalis PCC 7521 by single-particle, cryo–electron microscopy to understand its structural and functional differences. Four binding sites occupied by chlorophyll f are proposed. Subtle structural changes enable FRL-adapted PSI to extend light utilization for oxygenic photosynthesis to nearly 800 nm. This structure provides a platform for understanding FRL-driven photosynthesis and illustrates the robustness of adaptive and acclimation mechanisms in nature.