High Intensity Visible Light Research Articles

Photodegradation of poly(ether-b-amide) catalyzed by bismuth radiopaque additive

Bismuth compounds (e.g., bismuth subcarbonate and bismuth oxychloride) are often used as radiopaque additives in poly(ether-b-amide) (PEBA) for medical catheter applications to enhance the visibility of the catheter tips during fluoroscopy-guided minimally invasive surgeries. However, there is an increasing number of reports on bismuth-based photocatalysts in other fields; yet the impact of bismuth additives on the shelf life of PEBA has never been studied/reported. In this work, the stability of PEBA containing bismuth subcarbonate was tested against PEBA containing other radiopaque additives, barium sulfate and tungsten, in several real-life-relevant lighting conditions. It was found bismuth-containing PEBA degraded significantly faster than these counterpart materials under light exposure conditions including indoor fluorescent light, daylight-simulating xenon light and high-flux visible blue light. The extents of photodegradation of bismuth-containing PEBA were characterized by optical imaging, tensile test, FTIR analysis, Raman imaging and ESR radical analysis. The results showed material surface cracking, material hardening, surface oxidation and radical concentration increase over the course of light exposure. Various environmental factors were studied; it was found PEBA containing bismuth not only degraded under lights containing UV light but also degraded under high intensity visible blue light. Larger doses of light exposure and higher environmental temperatures led to more material degradation. Additional shelf aging studies on light-exposed samples were performed, which showed latent aging with continued degradation shortening the shelf life after the initial light exposure, due to the formation of persistent free radicals. Finally, several design and use considerations were discussed in the context of catheter material photodegradation.

MYB24 orchestrates terpene and flavonol metabolism as light responses to anthocyanin depletion in variegated grape berries.

Variegation is a rare type of mosaicism not fully studied in plants, especially fruits. We examined red and white sections of grape (Vitis vinifera cv. 'Béquignol') variegated berries and found that accumulation of products from branches of the phenylpropanoid and isoprenoid pathways showed an opposite tendency. Light-responsive flavonol and monoterpene levels increased in anthocyanin-depleted areas in correlation with increasing MYB24 expression. Cistrome analysis suggested that MYB24 binds to the promoters of 22 terpene synthase (TPS) genes, as well as 32 photosynthesis/light-related genes, including carotenoid pathway members, the flavonol regulator HY5 HOMOLOGUE (HYH), and other radiation response genes. Indeed, TPS35, TPS09, the carotenoid isomerase gene CRTISO2, and HYH were activated in the presence of MYB24 and MYC2. We suggest that MYB24 modulates ultraviolet and high-intensity visible light stress responses that include terpene and flavonol synthesis and potentially affects carotenoids. The MYB24 regulatory network is developmentally triggered after the onset of berry ripening, while the absence of anthocyanin sunscreens accelerates its activation, likely in a dose-dependent manner due to increased radiation exposure. Anthocyanins and flavonols in variegated berry skins act as effective sunscreens but for different wavelength ranges. The expression patterns of stress marker genes in red and white sections of 'Béquignol' berries strongly suggest that MYB24 promotes light stress amelioration but only partly succeeds during late ripening.

Reproducible method for assessing the effects of blue light using in vitro human skin tissues.

High-intensity visible light (HEV), also referred to as blue light, has a wavelength of 400-500 nm and accounts for approximately one-third of the visible light. Blue light is also emitted from electronic devices and artificial indoor lighting. Studies have shown that exposure of human skin cells to light emitted from electronic devices, even as short as 1 h, can cause an increase in reactive oxygen species (ROS), apoptosis and necrosis. Despite comprising a significant portion of the light spectrum, the effects of HEV light have not been studied as extensively. This is in part due to a lack of suitable in vitro testing methods. This work was conducted in order to develop a reproducible testing method for assessing the effects of blue light on the skin. Testing was performed using a full thickness, 3D in vitro skin tissue model. Different exposure protocols were tested to (1) determine the biological effects of blue light on the skin and (2) to identify an appropriate exposure for routine testing of cosmetic materials that may protect the skin from blue light damage. Gene expression and protein biomarkers were measured using qPCR, ELISA and immunohistochemical (IHC) methods. Our work demonstrates that daily exposure to blue light produced dose-and-time-dependent changes in biomarkers associated with skin damage. Exposure to blue light for 6 h for 5 consecutive days (total intensity of 30 J/cm2 ) increased the expression of genes that regulate inflammation and oxidative stress pathways and decreased the expression of genes that maintain skin barrier and tissue integrity. Exposure to blue light significantly increased protein biomarkers associated with ageing, inflammation and tissue damage. IHC staining confirmed changes in collagen, filaggrin and NQO1 protein expression. Treatment with ascorbic acid inhibited the effects of blue light, demonstrating a role in protection from blue light. Our results showed that consistent blue light exposure produced skin damage via alterations in biological pathways that are associated with skin ageing. This work provides a new, reproducible in vitro testing method for assessing the effects of blue light on human skin using gene expression, protein ELISA and IHC staining.

UV Radiation Induces Specific Changes in the Carotenoid Profile of Arabidopsis thaliana.

UV-B and UV-A radiation are natural components of solar radiation that can cause plant stress, as well as induce a range of acclimatory responses mediated by photoreceptors. UV-mediated accumulation of flavonoids and glucosinolates is well documented, but much less is known about UV effects on carotenoid content. Carotenoids are involved in a range of plant physiological processes, including photoprotection of the photosynthetic machinery. UV-induced changes in carotenoid profile were quantified in plants (Arabidopsis thaliana) exposed for up to ten days to supplemental UV radiation under growth chamber conditions. UV induces specific changes in carotenoid profile, including increases in antheraxanthin, neoxanthin, violaxanthin and lutein contents in leaves. The extent of induction was dependent on exposure duration. No individual UV-B (UVR8) or UV-A (Cryptochrome or Phototropin) photoreceptor was found to mediate this induction. Remarkably, UV-induced accumulation of violaxanthin could not be linked to protection of the photosynthetic machinery from UV damage, questioning the functional relevance of this UV response. Here, it is argued that plants exploit UV radiation as a proxy for other stressors. Thus, it is speculated that the function of UV-induced alterations in carotenoid profile is not UV protection, but rather protection against other environmental stressors such as high intensity visible light that will normally accompany UV radiation.

Covalent functionalization of polypropylene filters with diazirine\u2013photosensitizer conjugates producing visible light driven virus inactivating materials\ufeff

The SARS-CoV-2 pandemic has highlighted the weaknesses of relying on single-use mask and respirator personal protective equipment (PPE) and the global supply chain that supports this market. There have been no major innovations in filter technology for PPE in the past two decades. Non-woven textiles used for filtering PPE are single-use products in the healthcare environment; use and protection is focused on preventing infection from airborne or aerosolized pathogens such as Influenza A virus or SARS-CoV-2. Recently, C–H bond activation under mild and controllable conditions was reported for crosslinking commodity aliphatic polymers such as polyethylene and polypropylene. Significantly, these are the same types of polymers used in PPE filtration systems. In this report, we take advantage of this C–H insertion method to covalently attach a photosensitizing zinc-porphyrin to the surface of a melt-blow non-woven textile filter material. With the photosensitizer covalently attached to the surface of the textile, illumination with visible light was expected to produce oxidizing 1O2/ROS at the surface of the material that would result in pathogen inactivation. The filter was tested for its ability to inactivate Influenza A virus, an enveloped RNA virus similar to SARS-CoV-2, over a period of four hours with illumination of high intensity visible light. The photosensitizer-functionalized polypropylene filter inactivated our model virus by 99.99% in comparison to a control.

Gelatin embedding and LED autofluorescence reduction for rodent spinal cord histology

We present two innovations in histological technique for rodent spinal cord: gelatin embedding and LED photobleaching. Gelatin embedding uses liquid gelatin solution to permeate delicate biological structures then solidify to provide mechanical support throughout dissection, vibratome sectioning, and staining. LED photobleaching uses high-intensity visible light during blocking and primary incubations to reduce autofluorescence in tissue sections before fluorescent secondaries are added. We found gelatin embedding improved mechanical stability without interfering with immunohistochemical staining. Gelatin embedding also preserved some spinal roots and provided an opportunity for dye-less and cut-less tracking of left/right orientation during free-floating staining, which is valuable for tissue samples that have no spare areas that can be marked. LED photobleaching greatly reduced autofluorescence and added essentially no extra time or labor to the process. Descriptions of the techniques and characterization data are provided.

A Comparative Clinical Study of the Self-Adhering Flowable Composite Resin Vertise Flow and the Traditional Flowable Composite Resin Premise Flowable

Background. The aim of this research was to carry out a comparative clinical study of a self-adhesive, light-curing composite material called Vertise Flow and a traditional flow material called Premise flowable used in combination with dedicated bonding systems. In order to standardize the clinical environment, the stability of oral hygiene (analyzed with the oral hygiene index and the approximal plaque index) was taken into consideration. Methods. The study involved 37 patients with 64 fillings. They were distributed into three groups: 22 fillings in Group I, 22 fillings in Group II and 20 fillings in Group III. In Group I (G I), Vertise Flow material was applied without the use of an etching agent or a bonding system; in Group II (G II), Premise flowable material was applied without the use of an etching agent, but with the use of the OptiBond All-In-One seventh-generation bonding system; in Group III (G III), Premise flowable material was applied after etching and treatment of the hard tooth tissues using a fifth-generation OptiBond Solo Plus bonding system. Then, at appropriate time intervals (0, i.e., right after filling and after 6, 12 and 24 months), the fillings were subjected to clinical evaluation, conducted according to the Ryge scale criteria with the use of registration by means of a fluorescent high-intensity visible light beam produced by a camera (Vista Proof). Results. The quality of fillings performed with the use of comparable materials was subjected to clinical evaluation using the Ryge scale of fillings after 6, 12, and 24 months; the examination showed significant differences between the tested materials. The Vertise Flow material used without an etching agent or a bonding system (G I) presented the weakest results with respect to marginal adaptation and smoothness among those evaluated in this study. The intensification of the degradation continued over time until the final clinical observation at 24 months. The results confirmed that the best quality was achieved with the Premise flowable material after etching and treatment of the hard tooth tissues using a fifth-generation OptiBond Solo Plus bonding system (G III) relative to others for all time points during the observation. Conclusions. The used preparation scheme and bonding system have an impact on the final quality of the composite filling. There is a need to carry out a qualitative clinical evaluation of dental restorative materials under uniform conditions using evaluation scales.

Polymeric Composites with Silver (I) Cyanoximates Inhibit Biofilm Formation of Gram-Positive and Gram-Negative Bacteria.

Biofilms are surface-associated microbial communities known for their increased resistance to antimicrobials and host factors. This resistance introduces a critical clinical challenge, particularly in cases associated with implants increasing the predisposition for bacterial infections. Preventing such infections requires the development of novel antimicrobials or compounds that enhance bactericidal effect of currently available antibiotics. We have synthesized and characterized twelve novel silver(I) cyanoximates designated as Ag(ACO), Ag(BCO), Ag(CCO), Ag(ECO), Ag(PiCO), Ag(PICO) (yellow and red polymorphs), Ag(BIHCO), Ag(BIMCO), Ag(BOCO), Ag(BTCO), Ag(MCO) and Ag(PiPCO). The compounds exhibit a remarkable resistance to high intensity visible light, UV radiation and heat and have poor solubility in water. All these compounds can be well incorporated into the light-curable acrylate polymeric composites that are currently used as dental fillers or adhesives of indwelling medical devices. A range of dry weight % from 0.5 to 5.0 of the compounds was tested in this study. To study the potential of these compounds in preventing planktonic and biofilm growth of bacteria, we selected two human pathogens (Gram-negative Pseudomonas aeruginosa and Gram-positive Staphylococcus aureus) and Gram-positive environmental isolate Bacillus aryabhattai. Both planktonic and biofilm growth was abolished completely in the presence of 0.5% to 5% of the compounds. The most efficient inhibition was shown by Ag(PiCO), Ag(BIHCO) and Ag(BTCO). The inhibition of biofilm growth by Ag(PiCO)-yellow was confirmed by scanning electron microscopy (SEM). Application of Ag(BTCO) and Ag(PiCO)-red in combination with tobramycin, the antibiotic commonly used to treat P. aeruginosa infections, showed a significant synergistic effect. Finally, the inhibitory effect lasted for at least 120 h in P. aeruginosa and 36 h in S. aureus and B. aryabhattai. Overall, several silver(I) cyanoximates complexes efficiently prevent biofilm development of both Gram-negative and Gram-positive bacteria and present a particularly significant potential for applications against P. aeruginosa infections.

Antimicrobial activity of a continuous visible light disinfection system.

We evaluated the ability of high-intensity visible violet light with a peak output of 405 nm to kill epidemiologically important pathogens. The high irradiant light significantly reduced both vegetative bacteria and spores at some time points over a 72-hour exposure period.

Combined Effects of Trace Metals and Light on Photosynthetic Microorganisms in Aquatic Environment

In the present review, we critically examine the state-of-the-art of the research on combined effects of trace metals and light on photosynthetic microorganisms in aquatic environment. Light of different intensity and spectral composition affects the interactions between trace metals and photosynthetic microorganisms directly, by affecting vital cellular functions and metal toxicokinetics and toxicodynamics, and indirectly, by changing ambient medium characteristics. Light radiation and in particular, the ultraviolet radiation component (UVR) alters the structure and reactivity of dissolved organic matter in natural water, which in most of the cases decreases its metal binding capacity and enhances metal bioavailability. The increase of cellular metal concentrations is generally associated with increasing light intensity, however further studies are necessary to better understand the underlying mechanisms. Studies on the combined exposures of photosynthetic microorganisms to metals and UVR reveal antagonistic, additive or synergistic interactions depending on light intensity, spectral composition or light pre-exposure history. Among the light spectrum components, most of the research was performed with UVR, while the knowledge on the role of high-intensity visible light and environmentally relevant solar light radiation is still limited. The extent of combined effects also depends on the exposure sequence and duration, as well as the species-specific sensitivity of the tested microorganisms and the activation of stress defense responses.

Fabrication of UV photodetector using needle-shaped ZnO nanostructure arrays prepared on porous silicon substrate by a facile low-temperature method

Arrays of vertically well-aligned ZnO nanoneedles were successfully grown on seeded porous silicon substrate through electric field-assisted aqueous solution method. The surface morphologies of needle-like ZnO nanostructures were studied using field-emission scanning electron microscopy and transmission electron microscopy. Meanwhile, structural and morphological analyses displayed wurtzite nanostructures with strong c-axis oriented crystal structure and preferred (0 0 2) orientation. The photoluminescence spectra revealed intensive and sharp ultraviolet light emission at 382 nm with high intensity and low broad visible light emission in a 500–700 nm wavelength range confirming high optical quality of the formed ZnO nanoneedles. The fabrication and characterization of a metal–semiconductor–metal ultraviolet photodetector based on ZnO nanoneedles were studied. Upon exposure to 325 nm light (1.6 mW/cm2) at 3 V bias voltage, the device displayed 1.98 A/W responsivity and 10.48 photosensitivity. Furthermore, the response and the recovery times measured under these conditions were 86 and 83 ms, respectively.

Photo-Oxidative Stress in Green Algae and Cyanobacteria

High intensity visible light and ultraviolet radiation (UVR) could trigger oxidative stress (OS) and pigment bleaching in photosynthetic organisms and thus might represent a serious threat for cell survival. In the present study, green alga Chlamydomonas reinhardtii and cyanobacterium Synechocystis sp. were exposed to solar simulated light with different spectral composition: (i) visible light, (ii) visible light with environmental level of UVR, (iii) visible light with enhanced ultraviolet B (UVB) radiation. Photo-induced increase of the cellular reactive oxygen species (ROS), OS, and damage, as well as the alterations of the cell autofluorescence were thoroughly examined using flow cytometry. A small percentage of the cell population was affected by visible light and light with environmental levels of UVR. Exposure to light with enhanced UVB radiation resulted in severe OS, lipid peroxidation, and membrane damage. Light with enhanced UVB also induced a shift of the photosynthetic pigment fluorescence towards low values. C. reinhardtii was more sensitive to UVB as compared with Synechocystissp.The obtained results highlight the considerable difference in the levels of OS induced by visible, UVA, and UVB radiation in both species, as well as the species-specific sensitivity to UVB radiation, which should be taken into account when assessing the impact of enhanced UVB radiation on natural phytoplankton communities.

Arc Flash Visible Light Intensity as Viewed From Human Eyes

Human eye can be damaged by the intense light from an arc flash event. Though it is certain that high intensity visible light will be emitted during an arc flash event, there is limited research that provides quantitative light intensity estimation during different arcing incidents as viewed from human eyes. To provide better understanding of the light intensity during arc flash events, this paper proposes an arc flash light intensity estimation model based on approximately 1500 measurement data from arc flash tests using ambient light sensors, which are capable of measuring the light intensity of the arc flash as perceived by the human eyes. The proposed light intensity estimation model can be used to evaluate the potential impact of an arc flash on the human eyes. In addition, the autodarkening welding lens is used in the arc flash testing to explore its effectiveness in attenuating the light intensity and mitigating the exposure to the light hazard during an arc flash event.

Rhinophototherapy in persistent allergic rhinitis

Previous published results have revealed that Rhinolight® intranasal phototherapy is safe and effective in intermittent allergic rhinitis. The present objective was to assess whether phototherapy is also safe and effective in persistent allergic rhinitis. Thirty-four patients with persistent allergic rhinitis were randomized into two groups; twenty-five subjects completed the study. The Rhinolight® group was treated with a combination of UV-B, UV-A, and high-intensity visible light, while the placebo group received low-intensity visible white light intranasal phototherapy on a total of 13 occasions in 6weeks. The assessment was based on the diary of symptoms, nasal inspiratory peak flow, quantitative smell threshold, mucociliary transport function, and ICAM-1 expression of the epithelial cells. All nasal symptom scores and nasal inspiratory peak flow measurements improved significantly in the Rhinolight® group relative to the placebo group and this finding persisted after 4weeks of follow-up. The smell and mucociliary functions did not change significantly in either group. The number of ICAM-1 positive cells decreased non-significantly in the Rhinolight® group. No severe side-effects were reported during the treatment period. These results suggest that Rhinolight® treatment is safe and effective in persistent allergic rhinitis.

A Quaternary Ammonium Disinfectant Containing Germinants Reduces Clostridium difficile Spores on Surfaces by Inducing Susceptibility to Environmental Stressors.

Exposing Clostridium difficile spores to germinants in a quaternary ammonium matrix was an effective method to reduce environmental contamination by sensitizing the spores, leaving them susceptible to ambient conditions and enhancing killing by acid, high-intensity visible light, and radiation.

The Effects of 405-nm Visible Light on the Survival of Campylobacter on Chicken Skin and Stainless Steel.

Campylobacter spp. are foodborne pathogens responsible for a significant portion of human cases of bacterial-mediated gastrointestinal disease. A primary method for the introduction of Campylobacter into the food supply is through poultry products. Reducing the number of Campylobacter on poultry products may reduce the incidence of human disease. Research has been conducted on the use of light to inactivate Campylobacter on poultry products and processing environments. More recently, the use of high intensity visible 405-nm light has been proposed for the elimination of pathogenic bacteria. This study investigated the ability of 405-nm light to reduce Campylobacter jejuni and Campylobacter coli in poultry products. Campylobacter in chicken exudate were placed onto chicken skin or food-grade stainless steel before treatment with 405-nm light. A range of 405-nm light doses were applied to cocktails of six C. jejuni or six C. coli strains in exudate at 10°C to minimize thermal effects. Little difference was observed between inactivation of C. jejuni and C. coli on poultry skin with only minor average reductions of 1.7 logs and 2.1 logs, respectively, at the maximal dose of 184-186 J/cm(2). More noticeable differences were observed when the samples were placed on stainless steel and treated with a dose of 89 J/cm(2), producing an average reduction of 3.0 logs for C. coli but only 1.1 logs for C. jejuni. The maximal dose (181-183 J/cm(2)) applied to Campylobacter on stainless steel produced significant (p ≤ 0.05) reductions for C. jejuni and C. coli of 4.9 logs and 5.1 logs, respectively. However, significant 405-nm-mediated reductions in Campylobacter numbers required exposure times to achieve necessary dose levels that might be impractical under processing conditions. In addition, the most potent exposure times likely produced secondary thermal effects by raising sample surface temperatures above 48°C.

Radiation-damage-induced phasing: a case study using UV irradiation with light-emitting diodes.

Exposure to X-rays, high-intensity visible light or ultraviolet radiation results in alterations to protein structure such as the breakage of disulfide bonds, the loss of electron density at electron-rich centres and the movement of side chains. These specific changes can be exploited in order to obtain phase information. Here, a case study using insulin to illustrate each step of the radiation-damage-induced phasing (RIP) method is presented. Unlike a traditional X-ray-induced damage step, specific damage is introduced via ultraviolet light-emitting diodes (UV-LEDs). In contrast to UV lasers, UV-LEDs have the advantages of small size, low cost and relative ease of use.

The change in antioxidant properties of dextran-coated redox active nanoparticles due to synergetic photoreduction-oxidation.

Nanoparticles have proven to be novel material with resourceful applications in the field of nanomedicine. Cerium oxide nanoparticles (CNPs) coated with dextran (Dex-CNPs) have been shown to exhibit anticancer properties which is attributed to the change in oxidation states mediated at the oxygen vacancies on the surface of CNPs. In this study, the extreme sensitivity of Dex-CNPs to visible light is demonstrated using room light with a clear indication of synergetic phenomenon of photoreduction of CNPs in the presence of dextran which undergoes simultaneous oxidation. The phenomenon was further confirmed through a systematic time-based expedited study using a high intensity visible light source. The physiochemical changes of Dex-CNPs such as dispersion stability, pH, surface chemistry, antioxidant property, cytotoxicity and the surrounding microenvironment of Dex-CNPs were significantly altered on exposure to visible light, thereby affecting the biological response. Given the significance of nanoparticles which are widely researched nanomaterials, in different fields of nanotechnology and biomedicine, this study demonstrates the significant changes in physiochemical properties of Dex-CNPs with light. The photoreduction of Dex-CNPs affects its bifunctional applications in cancer therapy and thereby this study puts forward the necessity to preserve and sustain their properties through proper storage.

Synthesis and characterization of two cyanoxime ligands, their precursors, and light insensitive antimicrobial silver(I) cyanoximates

High-yield syntheses of N-piperidine-cyanacetamide (1), N-morpholyl-cyanacetamide (4) and their oxime derivatives N-piperidine-2-cyano-2-oximino-acetamide (HPiPCO, 2) and N-morpholyc-2-cyano-2-oximino-acetamide (HMCO, 5) were developed using two-step preparations. At first, the reactions of neat cyanoacetic acid esters and the respective cyclic secondary amines such as piperideine and morpholine afforded pure cyan-acetamides, which were converted into cyanoximes at room temperature using the nitrosation reaction with gaseous CH3ONO. The synthesized compounds were investigated by means of IR, 1H, 13C and UV–Vis spectroscopy. Crystal structures of two starting substituted cyan-acetamides and two target cyanoximes were determined. Silver(I) complexes of AgL composition (L=PipCO, 3; MCO, 6) were prepared in high yield. Both metal complexes are thermally stable above 100°C, and remarkably stable to high intensity visible light. The stability of dried AgL compounds towards short wavelength UV-radiation (a frequently used germicidal light) was examined using diffusion reflectance spectroscopy. Both complexes demonstrate slow photoreduction within ∼3h, observable as a gradual color change and darkening due to the formation of fine (nano-scale) particles of metallic silver. The complex Ag(MCO), 6, is about 2.6 times less stable towards UV-radiation than its more lypophyllic analog Ag(PipCO), 3. Antimicrobial and biofilm growth inhibition properties of the prepared solid acrylate-based polymeric composites containing embedded silver(I) cyanoximates were investigated using three human pathogens: Pseudomonas aeruginosa PAO1 (wound isolate), Staphylococcus aureus NRS70 (methicillin resistant respiratory isolate), and Streptococcus mutans UA159 (cariogenic dental isolate). Studies showed that both 3 and 6 compounds completely abolished the growth of PAO1 at 0.5 weight% concentration, and the growth of UA159 and NRS70 at 1% concentration. Thus, the data demonstrate that complexes 3 and 6 inhibit both planktonic and biofilm growth of Gram-positive and Gram-negative bacterial pathogens. The demonstrated thermal stability and pronounced antimicrobial activity of both silver(I) cyanoximates indicates the strong potential for the studied complexes to be used as light insensitive antimicrobial additives to light-curable adhesives that set indwelling devices in place.

A unique regulation of the expression of the psbA, psbD, and psbE genes, encoding the D1, D2 and cytochrome b559 subunits of the Photosystem II complex in the chlorophyll d containing cyanobacterium Acaryochloris marina

Photosynthetic electron transport, chromatic photoacclimation and expression of the genes encoding the D1, D2, and cytochrome b559 subunits of the Photosystem II complex were studied in the chlorophyll d containing cyanobacterium Acaryochloris marina MBIC11017 under various environmental conditions. During oxygen deprivation and inhibition of photosynthetic electron transport by dibromothymoquinone the psbA1 gene encoding a D1′ isoform was induced. All of the three psbA and one of the three psbD (psbD2) genes, encoding two different isoforms of the D1 and the abundant isoform of the D2 proteins, respectively were induced under exposure to UV-B radiation and high intensity visible light. Under far red light the amount of Photosystem II complexes increased, and expression of the psbE2 gene encoding the alpha-subunit of cytochrome b559 was enhanced. However, the psbF and psbE1 genes encoding the beta- and another isoform of alpha-cytochrome b559, respectively remained lowly expressed under all conditions. Far red light also induced the psbD3 gene encoding a D2′ isoform whose primary structure is different from the abundant D2 isoform. psbD3 was also induced under low intensity visible light, when chromatic photoacclimation was indicated by a red-shifted absorption of chlorophyll d. Our results show that differential expression of multigene families encoding different isoforms of D1 and D2 plays an important role in the acclimation of A. marina to contrasting environmental conditions. Moreover, the disproportionate quantity of transcripts of the alpha and beta subunits of cytochrome b559 implies the existence of an alpha–alpha homodimer organization of cytochrome b559 in Photosystem II complexes.