Illuminating developmental biology through photochemistry.

Developmental biology has been continually shaped by technological advances, evolving from a descriptive science into one immersed in molecular and cellular mechanisms. Most recently, genome sequencing and 'omics' profiling have provided developmental biologists with a wealth of genetic and biochemical information; however, fully translating this knowledge into functional understanding will require new experimental capabilities. Photoactivatable probes have emerged as particularly valuable tools for investigating developmental mechanisms, as they can enable rapid, specific manipulations of DNA, RNA, proteins, and cells with spatiotemporal precision. In this Perspective, we describe optochemical and optogenetic systems that have been applied in multicellular organisms, insights gained through the use of these probes, and their current limitations. We also suggest how chemical biologists can expand the reach of photoactivatable technologies and bring new depth to our understanding of organismal development.

Photocontrolled Living Polymerization Systems with Reversible Deactivations through Electron and Energy Transfer.

Recently, visible-light-regulated polymerization has been gaining popularity, as it opens a range of new opportunities for the synthesis of functional polymers and materials. Here, the most recent developments in this field are summarized, which is the use of photocatalysts and catalyst-free approaches to mediate polymerization upon photoexcitation. These catalysts can transfer an electron or energy to activate an initiator. The recent achievements in light-regulated atom-transfer radical polymerization, reversible addition-fragmentation chain-transfer polymerization, ring-opening metathesis polymerization, cobalt-mediated radical polymerization, iodine-mediated radical polymerization, and living cationic polymerization are reviewed. Recent development in these fields have solved important challenges in polymer chemistry, such as the development of oxygen-tolerant polymerization, polymerization mediated by near-infrared, metal-free polymerization, and spatial-, temporal-, and sequence-controlled polymerization. Some applications of these techniques will be discussed, such as adapting the current photocatalytic systems to synthesize heterogeneous photocatalysts that act as recyclable photocatalysts and novel light-mediated approaches for surface functionalization of hybrid materials and living cells. Finally, the existing challenges in polymer chemistry that could be overcome by further development of light-mediated polymerization techniques are highlighted along with the future directions of this field.

N-Heterocyclic carbene metal complexes: photoluminescence and applications.

This review covers the advances made in the synthesis of luminescent transition metal complexes containing N-heterocyclic carbene (NHC) ligands. The presence of a high field strength ligand such as an NHC in the complexes gives rise to high energy emissions, and consequently, to the desired blue colour needed for OLED applications. Furthermore, the great versatility of NHC ligands for structural modifications, together with the use of other ancillary ligands in the complex, provides numerous possibilities for the synthesis of phosphorescent materials, with emission colours over the entire visible spectra and potential future applications in fields such as photochemical water-splitting, chemosensors, dye-sensitised solar cells, oxygen sensors, and medicine.

Nano-/microstructure improved photocatalytic activities of semiconductors.

Photocatalysis has emerged as a promising technique owing to its valuable applications in environmental purification. With the demand of building effective photocatalyst materials, semiconductor investigation experienced a developing process from simple chemical modification to complicated morphology design. In this review, the general relationship between morphology structures and photocatalytic properties is mainly discussed. Various nano-/microsized structures from zero- to three-dimensional are discussed, and the photocatalytic efficiency correspon- ding to the structures is analysed. The results showed that simple structures can be easily obtained and can facilitate chemical modification, whereas one- or three-dimensional structures can provide structure-enhanced properties such as surface area increase, multiple reflections of UV light, etc. Those principles of structure-related photocatalytic properties will afford basic ideology in designing new photocatalytic materials with more effective catalytic properties.

Ultrasound and photochemical procedures for nanocatalysts preparation: application in photocatalytic biomass valorization.

Nano-photocatalysis is becoming increasingly important due to its multiple applications and multidisciplinary aspects. Applications such as water/air purification, solar energy storage, chemicals production and optoelectronics are some of the most promising. In recent years, the development of novel environmental friendly and cost efficient methods for materials preparation that could replace the old ones is on demand. Unconventional and "soft" techniques such as sonication and photochemistry offer huge possibilities for the synthesis of a broad spectrum of nanostructured materials (e.g., nano-photocatalysts). In the present study, I focus on ultrasound and photochemical procedures for the preparation of nanostructured photocatalysts (e.g., supported metals, metal oxides) and their application in food organic wastes valorization.

Photodynamic therapy for photochemists.

Photodynamic therapy (PDT) is an evolving technique for localized control of diseased tissue with light after prior administration of a photosensitizing agent and in the presence of oxygen. The biological effect is quite different from surgery, radiotherapy and chemotherapy. With no temperature change during treatment, connective tissues like collagen are largely unaffected, so maintaining the mechanical integrity of hollow organs. PDT is of particular value for pre-cancer and early cancers of the skin (not melanomas) and mouth as the cosmetic and functional results are so good. Another key indication is for small areas of cancer that are unsuitable for or have persisted or recurred after conventional management. It can be applied in areas already exposed to the maximum safe dose of radiotherapy. Outside cancer, in ophthalmology, it is established for age-related macular degeneration, and has considerable potential in arterial disease for preventing restenosis after balloon angioplasty and in the treatment of infectious diseases, where the responsible organisms are accessible to both the photosensitizer and light. New developments on the horizon include techniques for increasing the selectivity for cancers, such as coupling photosensitizers to antibodies, and for stimulating immunological responses, but many further pre-clinical and clinical studies are needed to establish PDT's role in routine clinical practice.

Light-directed nanosynthesis: near-field optical approaches to integration of the top-down and bottom-up fabrication paradigms.

The integration of top-down (lithographic) and bottom-up (synthetic chemical) methodologies remains a major goal in nanoscience. At larger length scales, light-directed chemical synthesis, first reported two decades ago, provides a model for this integration, by combining the spatial selectivity of photolithography with the synthetic utility of photochemistry. This review describes attempts to realise a similar integration at the nanoscale, by employing near-field optical probes to initiate selective chemical transformations in regions a few tens of nm in size. A combination of near-field exposure and an ultra-thin resist yields exceptional performance: in self-assembled monolayers, an ultimate resolution of 9 nm (ca. λ/30) has been achieved. A wide range of methodologies, based on monolayers of thiols, silanes and phosphonic acids, and thin films of nanoparticles and polymers, have been developed for use on metal and oxide surfaces, enabling the fabrication of metal nanowires, nanostructured polymers and nanopatterned oligonucleotides and proteins. Recently parallel lithography approaches have demonstrated the capacity to pattern macroscopic areas, and the ability to function under fluid, suggesting exciting possibilities for surface chemistry at the nanoscale.

Using light to control signaling cascades in live neurons.

Understanding the complexity of neuronal biology requires the manipulation of cellular processes with high specificity and spatio-temporal precision. The recent development of synthetic photo-activatable proteins designed using the light-oxygen-voltage and phytochrome domains provides a new set of tools for genetically targeted optical control of cell signaling. Their modular design, functional diversity, precisely controlled activity and in vivo applicability offer many advantages for investigating neuronal function. Although designing these proteins is still a considerable challenge, future advances in rational protein design and a deeper understanding of their photoactivation mechanisms will allow the development of the next generation of optogenetic techniques.

Photochemistry of dihydrobiopterin in aqueous solution.

Dihydrobiopterin (H(2)Bip) and its oxidized analogue, biopterin (Bip), accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder in which the protection against UV radiation fails. The photochemistry of H(2)Bip was studied in neutral aqueous solutions upon UV-A irradiation (320-400 nm) at room temperature. The photochemical reactions were followed by UV/vis spectrophotometry, HPLC and enzymatic methods for hydrogen peroxide (H(2)O(2)) determination. Photoproducts were analyzed by means of electrospray ionization mass spectrometry. Under anaerobic conditions, excitation of H(2)Bip leads to the formation of at least two isomeric dimers with molecular masses equal to exactly twice the molecular mass of the reactant. This reaction takes place from the singlet excited state of the reactant. To the best of our knowledge, this is the first time that the photodimerization of a dihydropterin is reported. In the presence of air, the dimers are again the main photoproducts at the beginning of the reaction, but a small proportion of the reactant is converted into Bip. As the reaction proceeds and enough Bip accumulates in the solution, a photosensitized process starts, where Bip photoinduces the oxidation of H(2)Bip to Bip, and H(2)O(2) is formed. As a consequence, the rates of H(2)Bip consumption and Bip formation increase as a function of irradiation time, resulting in an autocatalytic photochemical process. In this process, Bip in its triplet excited state reacts with the ground state of H(2)Bip. The mechanisms involved are analyzed and the biological implications of the results are discussed.

Chemistry as a prism: a review of light-emitting materials having tunable emission wavelengths.

Photoluminescent materials have been extensively applied in various fields of science because of their numerous advantages, such as excellent sensitivity, good specificity, a large linear range of analysis, ease of handling, and so on. Many strategies have been used to understand and manipulate the photophysical properties of photoluminescent materials. This Focus Review describes recent progress focused on tuning the photophysical properties, especially the emission wavelengths of pi-conjugated oligomers, photoluminescent organometallic complexes, and fluorescent organic dyes by chemical modification.

Atomic force microscopy studies of native photosynthetic membranes.

In addition to providing the earliest surface images of a native photosynthetic membrane at submolecular resolution, examination of the intracytoplasmic membrane (ICM) of purple bacteria by atomic force microscopy (AFM) has revealed a wide diversity of species-dependent arrangements of closely packed light-harvesting (LH) antennae, capable of fulfilling the basic requirements for efficient collection, transmission, and trapping of radiant energy. A highly organized architecture was observed with fused preparations of the pseudocrystalline ICM of Blastochloris viridis, consiting of hexagonally packed monomeric reaction center light-harvesting 1 (RC-LH1) core complexes. Among strains which also form a peripheral LH2 antenna, images of ICM patches from Rhodobacter sphaeroides exhibited well-ordered, interconnected networks of dimeric RC-LH1 core complexes intercalated by rows of LH2, coexisting with LH2-only domains. Other peripheral antenna-containing species, notably Rhodospirillum photometricum and Rhodopseudomonas palustris, showed a less regular organization, with mixed regions of LH2 and RC-LH1 cores, intermingled with large, paracrystalline domains. The ATP synthase and cytochrome bc(1) complex were not observed in any of these topographs and are thought to be localized in the adjacent cytoplasmic membrane or in inaccessible ICM regions separated from the flat regions imaged by AFM. The AFM images have served as a basis for atomic-resolution modeling of the ICM vesicle surface, as well as forces driving segregation of photosynthetic complexes into distinct domains. Docking of atomic-resolution molecular structures into AFM topographs of Rsp. photometricum membranes generated precise in situ structural models of the core complex surrounded by LH2 rings and a region of tightly packed LH2 complexes. A similar approach has generated a model of the highly curved LH2-only membranes of Rba. sphaeroides which predicts that sufficient space exists between LH2 complexes for quinones to diffuse freely. Measurement of the intercomplex distances between adjacent LH2 rings of Phaeospirillum molischianum has permitted the first calculation of the separation of bacteriochlorophyll a molecules in the native ICM. A recent AFM analysis of the organization of green plant photosystem II (PSII) in grana thylakoids revealed the protruding oxygen-evolving complex, crowded together in parallel alignment at three distinct levels of stacked membranes over the lumenal surface. The results also confirmed that PSII-LHCII supercomplexes are displaced relative to one another in opposing grana membranes.

Design, synthesis and properties of highly functional nanostructured photocatalysts.

Semiconductor photocatalysts with potential applications in splitting of water, degradation of toxic contaminant, and solar cells are very important research topics in recent years. In this short review, recent progresses of the synthesis and photocatalytic properties of highly functional nanostructured photocatalysts are briefly summarized. The patents for fabricating semiconductor photocatalysts are introduced in the first part. In the second part, the patents to improve photocatalytic activities of nano/microstructured photocatalysts from soft chemical method and other routes are introduced. Finally, current and future developments on highly functional photocatalysts are reviewed.

Fundamentos del láser y su aplicación en la urología / The basics of laser and its application in urology

El láser, dispositivo de amplificación de luz por emisión estimulada de radiación, se trata de un dispositivo capaz de transformar otras energías en radiación electromagnética emitiendo haces de luz de distintas longitudes de onda. Se trata de aparatos que amplifican la luz y producen haces de luz coherentes cuya frecuencia va desde el infrarrojo hasta los rayos X. La emisión estimulada, proceso en que se basa el Láser, fue descrita por A. Einstein en 1917, pero no es hasta la década de los 60, cuando se observó el primer proceso láser en un cristal de rubí. Según el medio que emplean, los láseres suelen denominarse de estado sólido, de gas, semiconductores o líquidos. Los posibles usos del láser son casi ilimitados, convirtiéndose en una herramienta muy valiosa dentro de las Ciencias biomedicas, gracias a los diversos efectos (fotovaporización, fotodisrupción, fotocoagulación o fotoestimulación) que provoca al interactuar con los tejidos. Por este motivo, hoy día, el uso de láseres en el campo de la Urología nos ofrece un amplio abanico de posibilidades, que van desde la cirugía desobstructiva como la fragmentación de un cálculo o la resección y ablación del tejido prostático hasta la cirugía reconstructiva como es la soldadura de tejidos en la vasovasostomía o la reparación de una estenosis uretral (AU)

A laser, light amplification by stimulated emission of radiation, is a device able to transform other energies into electromagnetic radiation with emission of light beams of different wavelengths. They amplify the light and produce coherent light beams, the frequency of which varies from infrared to X ray. Stimulated emission, the process laser is based on, was described by A. Einstein in 1917, but it was not until the decade of the '60s when the first laser process was observed in a ruby crystal. Depending on the environment they use, lasers may be named as solid-state, gas, semiconductors or liquid. The possibility of uses for laser is almost unlimited, becoming a very valuable tool in biomedical sciences thanks to the various effects they produce when interacting with tissues (photovaporization, photodisruption, photocoagulation or photostimulation). For this reason, today, the use of lasers in the field of urology offers a wide range of possibilities, going from surgery for the treatment of obstruction, such as the fragmentation of a urinary stone or resection/ablation of prostatic tissue, to reconstructive surgery, such as tissue welding in vasovasostomy or urethral stenosis repair (AU)

Expert assessments of future photovoltaic technologies.

Subjective probabilistic judgments about future module prices of 26 current and emerging photovoltaic (PV) technologies were obtained from 18 PV technology experts. Fourteen experts provided detailed assessments, including likely future efficiencies and prices under four policy scenarios. While there is considerable dispersion among the judgments, the results suggest a high likelihood that some PV technology will achieve a price of $1.20/Wp by 2030. Only 7 of 18 experts assess a better-than-even chance that any PV technology will achieve $0.30/Wp by 2030; 10 of 18 experts give this assessment by 2050. Given these odds, and the wide dispersion in results, we conclude that PV may have difficulty becoming economically competitive with other options for large-scale, low-carbon bulk electricity in the next 40 years. If $0.30/Wp is not reached, then PV will likely continue to expand in markets other than bulk power. In assessing different policy mechanisms, a majority of experts judged that R&D would most increase efficiency, while deployment incentives would most decrease price. This implies a possible disconnect between research and policy goals. Governments should be cautious about large subsidies for deployment of present PV technology while continuing to invest in R&D to lower cost and reduce uncertainty.

Casting a new light on azide photochemistry: photolytic production of cyclic-N3.

The first postulated structure of the N(3) moiety appeared in a scientific journal in 1890 and was reported as a cyclic triangle with one N,N double bond and two N,N single bonds. Only in the last several years has our understanding of azides advanced to the point that we can now claim to know how to synthesize this prototypical bonding motif. This article examines the experiments and theory that were essential in reaching this point and suggests future directions of research on cyclic-N(3).

Photovoltaic and photoelectrochemical conversion of solar energy.

The Sun provides approximately 100,000 terawatts to the Earth which is about 10000 times more than the present rate of the world's present energy consumption. Photovoltaic cells are being increasingly used to tap into this huge resource and will play a key role in future sustainable energy systems. So far, solid-state junction devices, usually made of silicon, crystalline or amorphous, and profiting from the experience and material availability resulting from the semiconductor industry, have dominated photovoltaic solar energy converters. These systems have by now attained a mature state serving a rapidly growing market, expected to rise to 300 GW by 2030. However, the cost of photovoltaic electricity production is still too high to be competitive with nuclear or fossil energy. Thin film photovoltaic cells made of CuInSe or CdTe are being increasingly employed along with amorphous silicon. The recently discovered cells based on mesoscopic inorganic or organic semiconductors commonly referred to as 'bulk' junctions due to their three-dimensional structure are very attractive alternatives which offer the prospect of very low cost fabrication. The prototype of this family of devices is the dye-sensitized solar cell (DSC), which accomplishes the optical absorption and the charge separation processes by the association of a sensitizer as light-absorbing material with a wide band gap semiconductor of mesoporous or nanocrystalline morphology. Research is booming also in the area of third generation photovoltaic cells where multi-junction devices and a recent breakthrough concerning multiple carrier generation in quantum dot absorbers offer promising perspectives.