Powering the Future: Unleashing the Potential of MXene-Based Dual-Functional Photoactive Cathodes in Photo-Rechargeable Zinc-Ion Capacitor.

Dual-functional photo-rechargeable (photo-R) energy storage devices, which acquire stored energy from solar energy harvesting, are being developed to battle the current energy crisis. In this study, these findings on the photo-driven characteristics of MXene-based photocathodes in photo-R zinc-ion capacitors (ZICs) are presented. Along with the pristine Ti3 C2 Tx MXene, tellurium/Ti3 C2 Tx (Te/Ti3 C2 Tx ) hybrid nanostructure is synthesized via facile chemical vapor transport technique to examine them for photocathodes in ZICs. Interestingly, the evaluated self-powered photodetector devices using MXene-based samples revealed a pyro-phototronic behavior introduced into the samples, with higher desirability observed in Te/Ti3 C2 Tx . The photo-R ZICs results exhibited a capacitance enhancement of 50.86% for Te/Ti3 C2 Tx at two scan rates of 5 and 10 mV s-1 under illumination, compared to dark conditions. In contrast, a capacitance enhancement of 30.20% is obtained for the pristine Ti3 C2 Tx at only a 5 mV s-1 scan rate. Furthermore, both samples achieved photo-charging voltage responses of ≈960 mV, and photoconversion efficiencies of 0.01% (for Te/ Ti3 C2 Tx ) and 0.07% (for Ti3 C2 Tx ). These characteristics in MXene-based single photo-R ZICs are significant and considerable with the distinguished integrated photo-R supercapacitors with solar cells, or coupled energy-harvesting and energy-storing devices reported recently in the literature.

Observation-Based Diagnostics of Reactive Nitrogen Recycling through HONO Heterogenous Production: Divergent Implications for Ozone Production and Emission Control.

Understanding of nitrous acid (HONO) production is crucial to photochemical studies, especially in polluted environments like eastern China. In-situ measurements of gaseous and particulate compositions were conducted at a rural coastal site during the 2018 spring Ozone Photochemistry and Export from China Experiment (OPECE). This data set was applied to investigate the recycling of reactive nitrogen through daytime heterogeneous HONO production. Although HONO levels increase during agricultural burning, analysis of the observation data does not indicate more efficient HONO production by agricultural burning aerosols than other anthropogenic aerosols. Box and 1-D modeling analyses reveal the intrinsic relationships between nitrogen dioxide (NO2), particulate nitrate (pNO3), and nitric acid (HNO3), resulting in comparable agreement between observed and simulated HONO concentrations with any one of the three heterogeneous HONO production mechanisms, photosensitized NO2 conversion on aerosols, photolysis of pNO3, and conversion from HNO3. This finding underscores the uncertainties in the mechanistic understanding and quantitative parametrizations of daytime heterogeneous HONO production pathways. Furthermore, the implications for reactive nitrogen recycling, ozone (O3) production, and O3 control strategies vary greatly depending on the HONO production mechanism. On a regional scale, the conversion of HONO from pNO3 can drastically enhance O3 production, while the conversion from NO2 can reduce O3 sensitivity to NOx changes in polluted eastern China.

Photoelectrochemical sensor based on AuNPs@WO3@TpPa-1-COF for quantification of DNA methylation levels.

A "signal-off" photoelectrochemical (PEC) sensing platform has been designed for the ultrasensitive detection of DNA methylation levels and multiple methylated sites. The platform employs tungsten trioxide and TpPa-1-COF loaded by gold nanoparticle (AuNPs@WO3@TpPa-1-COF) composite material as the photoactive component and p-type reduced graphene (rGO) as an efficient quencher. The PEC signal of AuNPs@WO3@TpPa-1-COF composite is effectively quenched in the presence of p-type rGO, because p-type rGO can compete with AuNPs@WO3@TpPa-1-COF to deplete light energy and electron donors. In addition, a hybrid strand reaction (HCR) amplification strategy fixes more target DNA and then combines with rGO-modified anti-5-methylcytosine antibody to facilitate ultrasensitive DNA methylation detection. Under optimal conditions, DNA methylation can be measured within a linear concentration range of 10-14 to 10-8 M, with an exceptionally low detection limit of 0.19 fM (S/N = 3). At the same time, the platform can conduct quantitative determination of multi-site methylation, with the linear equation △I = 44.19LogA + 61.43, and the maximum number of methylation sites is 5. The sensor demonstrates high sensitivity, excellent selectivity, and satisfactory stability. Furthermore, the proposed signal-off PEC strategy was successfully employed to detect DNA methylation in spiked human serum samples, with recoveries ranging from 93.17 to 107.28% and relative standard deviation (RSD) ranging from 1.15 to 5.49%.

Red and near-infrared light-activated photoelectrochemical nanobiosensors for biomedical target detection.

Photoelectrochemical (PEC) nanobiosensors integrate molecular (bio)recognition elements with semiconductor/plasmonic photoactive nanomaterials to produce measurable signals after light-induced reactions. Recent advancements in PEC nanobiosensors, using light-matter interactions, have significantly improved sensitivity, specificity, and signal-to-noise ratio in detecting (bio)analytes. Tunable nanomaterials activated by a wide spectral radiation window coupled to electrochemical transduction platforms have further improved detection by stabilizing and amplifying electrical signals. This work reviews PEC biosensors based on nanomaterials like metal oxides, carbon nitrides, quantum dots, and transition metal chalcogenides (TMCs), showing their superior optoelectronic properties and analytical performance for the detection of clinically relevant biomarkers. Furthermore, it highlights the innovative role of red light and NIR-activated PEC nanobiosensors in enhancing charge transfer processes, protecting them from biomolecule photodamage in vitro and in vivo applications. Overall, advances in PEC detection systems have the potential to revolutionize rapid and accurate measurements in clinical diagnostic applications. Their integration into miniaturized devices also supports the development of portable, easy-to-use diagnostic tools, facilitating point-of-care (POC) testing solutions and real-time monitoring.

Confinement of a Styryl Dye into Nanoporous Aluminophosphates: Channels vs. Cavities.

Styryl dyes are generally poor fluorescent molecules inherited from their flexible molecular structures. However, their emissive properties can be boosted by restricting their molecular motions. A tight confinement into inorganic molecular sieves is a good strategy to yield highly fluorescent hybrid systems. In this work, we compare the confinement effect of two Mg-aluminophosphate zeotypes with distinct pore systems (the AEL framework, a one-dimensional channeled structure with elliptical pores of 6.5 Å × 4.0 Å, and the CHA framework, composed of large cavities of 6.7 Å × 10.0 Å connected by eight-ring narrower windows) for the encapsulation of 4-DASPI styryl dye (trans-4-[4-(Dimethylamino)styryl]-1-methylpyridinium iodide). The resultant hybrid systems display significantly improved photophysical features compared to 4-DASPI in solution as a result of tight confinement in both host inorganic frameworks. Molecular simulations reveal a tighter confinement of 4-DASPI in the elliptical channels of AEL, explaining its excellent photophysical properties. On the other hand, a singular arrangement of 4-DASPI dye is found when confined within the cavity-based CHA framework, where the 4-DASPI molecule spans along two adjacent cavities, with each aromatic ring sitting on these adjacent cavities and the polymethine chain residing within the narrower eight-ring window. However, despite the singularity of this host-guest arrangement, it provides less tight confinement for 4-DASPI than AEL, resulting in a slightly lower quantum yield.

How can heteroatoms boost the performance of photoactive nanomaterials for wastewater purification?

Photocatalysis, as an alternative for treating persistent water pollutants, holds immense promise. However, limitations hinder sustained treatment and recycling under varying light conditions. This comprehensive review delves into the novel paradigm of metal and non-metal doping to overcome these challenges. It begins by discussing the fundamental principles of photocatalysis and its inherent limitations. Understanding these constraints is crucial for developing effective strategies. Band gap narrowing by metal and non-metal doping modifies the band gap, enabling visible-light absorption. Impurity energy levels and oxygen vacancies influenced the doping energy levels and surface defects. Interfacial electron transfer and charge carrier recombination are the most important factors that impact overall efficiency. The comparative analysis of nanomaterials are reviewed on various, including nanometal oxides, nanocarbon materials, and advanced two-dimensional structures. The synthesis process are narratively presented, emphasizing production yields, selectivity, and efficiency. The review has potential applications in the environment for efficient pollutant removal and water purification, economic cost-effective and scalable production and technological advancement catalyst design, in spite of its challenges in material stability, synthesis methods and optimizing band gaps. The novelty of the review paper is on the proposal of a new paradigm of heterojunctions of doped metal and non-metal photocatalysts to promise highly efficient water treatment. This review bridges the gap between fundamental research and practical applications, offering insights into tailored nano photocatalysts.

Application of Photoactive Compounds in Cancer Theranostics: Review on Recent Trends from Photoactive Chemistry to Artificial Intelligence.

According to the World Health Organization (WHO) and the International Agency for Research on Cancer (IARC), the number of cancer cases and deaths worldwide is predicted to nearly double by 2030, reaching 21.7 million cases and 13 million fatalities. The increase in cancer mortality is due to limitations in the diagnosis and treatment options that are currently available. The close relationship between diagnostics and medicine has made it possible for cancer patients to receive precise diagnoses and individualized care. This article discusses newly developed compounds with potential for photodynamic therapy and diagnostic applications, as well as those already in use. In addition, it discusses the use of artificial intelligence in the analysis of diagnostic images obtained using, among other things, theranostic agents.

Recent Progress in Photoelectrochemical Sensing of Pesticides in Food and Environmental Samples: Photoactive Materials and Signaling Mechanisms.

Pesticides have become an integral part of modern agricultural practices, but their widespread use poses a significant threat to human health. As such, there is a pressing need to develop effective methods for detecting pesticides in food and environmental samples. Traditional chromatography methods and common rapid detection methods cannot satisfy accuracy, portability, long storage time, and solution stability at the same time. In recent years, photoelectrochemical (PEC) sensing technology has gained attention as a promising approach for detecting various pesticides due to its salient advantages, including high sensitivity, low cost, simple operation, fast response, and easy miniaturization, thus becoming a competitive candidate for real-time and on-site monitoring of pesticide levels. This review provides an overview of the recent advancements in PEC methods for pesticide detection and their applications in ensuring food and environmental safety, with a focus on the categories of photoactive materials, from single semiconductor to semiconductor-semiconductor heterojunction, and signaling mechanisms of PEC sensing platforms, including oxidation of pesticides, steric hindrance, generation/decrease in sacrificial agents, and introduction/release of photoactive materials. Additionally, this review will offer insights into future prospects and confrontations, thereby contributing novel perspectives to this evolving domain.

Rhodamine 6G/Transition Metal Dichalcogenide Hybrid Nanoscrolls for Enhanced Optoelectronic Performance.

The low light absorption efficiency has seriously hindered the application of two-dimensional transition metal dichalcogenide (TMDC) nanosheets in the field of optoelectronic devices. Various approaches have been used to improve the performance of TMDC nanosheets. Preparation of one-dimensional TMDC nanoscrolls in combination with photoactive materials has been a promising method to improve their properties recently. In this work, we report a facile method to enhance the optoelectronic performance of TMDC nanoscrolls by wrapping the photoactive organic dye rhodamine (R6G) into them. After R6G molecules were deposited on monolayer TMDC nanosheets by the solution method, the R6G/MoS2 nanoscrolls with lengths up to hundreds of microns were prepared in a short time by dropping a mixture of ammonia and ethanol solution on the R6G/MoS2 nanosheets. The as-obtained R6G/MoS2 nanoscrolls were well characterized by optical microscopy, atomic force microscopy, Raman spectroscopy, and transmission electron microscopy to prove the encapsulation of R6G. There are multiple type II heterojunction interfaces in the R6G/MoS2 nanoscrolls, which can promote the generation of photo-induced carriers and the following electron-hole separation. The separated electrons were transported rapidly along the axial direction of the R6G/MoS2 nanoscrolls, which greatly improves the efficiency of light absorption and photoresponse. Under the irradiation of an incident 405 nm laser, the photoresponsivity, carrier mobility, external quantum efficiency, and detectivity of R6G/MoS2 nanoscrolls were enhanced to 66.07 A/W, 132.93 cm2V-1s-1, 20,261%, and 1.25 × 1012 cm·Hz1/2W-1, which are four orders of magnitude higher than those of monolayer MoS2 nanosheets. Our work indicates that the R6G/TMDC hybrid nanoscrolls could be promising materials for high-performance optoelectronic devices.

Photoactive Organo-Sulfur Polymers for Hydrogen Generation.

Herein, we report the synthesis of photoactive polymeric organo-sulfur (POS) materials. These polymers absorb light in the ultraviolet/visible and near-infrared region of the solar spectrum, and upon irradiation, they reduce water to hydrogen (H2 ). The decoration of POS materials with nitrile (-CN) groups is found to be the critical factor for enhanced interactions with the co-catalyst, Ni2 P, leading to greater H2 evolution rates compared to the nitrile-free POS material.

B, P, and S heteroatom doped, bio- and hemo-compatible 2D graphitic-carbon nitride (g-C3N4) with antioxidant, light-induced antibacterial, and bioimaging endeavors.

The synthesis of two-dimensional (2D) graphiticg-C3N4and heteroatom-doped graphitic H@g-C3N4(H: B, P, or S) particles were successfully done using melamine as source compounds and boric acid, phosphorous red, and sulfur as doping agents. The band gap values of 2Dg-C3N4, B50@g-C3N4, P50@g-C3N4, and S50@g-C3N4structures were determined as 2.90, 3.03, 2.89, and 2.93 eV, respectively. The fluorescent emission wavelengths of 2Dg-C3N4, B50@g-C3N4, P50@g-C3N4, and S50@g-C3N4structures were observed at 442, 430, 441, and 442 nm, respectively upon excitation atλEx= 325 nm. There is also one additional new emission wavelength was found at 345 nm for B50@g-C3N4structure. The blood compatibility test results ofg-C3N4, B50@g-C3N4, P50@g-C3N4, and S50@g-C3N4structures revealed that all materials are blood compatible with <2% hemolysis and >90% blood clotting indices at 100µg ml-1concentration. The cell toxicity of the prepared 2D graphitic structures were also tested on L929 fibroblast cells, and even the heteroatom doped hasg-C3N4structures induce no cytotoxicity was observed with >91% cell viability even at 250µg ml-1particle concentration with the exception of P50@g-C3N4which as >75 viability. Moreover, for 2Dg-C3N4, B50@g-C3N4, and S50@g-C3N4constructs, even at 500µg ml-1concentration, >90% cell viabilities was monitored. As a diagnostic material, B50@g-C3N4was found to have significantly high penetration and distribution abilities into L929 fibroblast cells granting a great potential in fluorescence imaging and bioimaging applications. Furthermore, the elemental doping with B, P, and S ofg-C3N4were found to significantly increase the photodynamic antibacterial activity e.g. more than half of bacterial elimination by heteroatom-doped forms ofg-C3N4under UVA treatment was achieved.

Label-free "signal-off" PEC aptasensor for determination of kanamycin based on 3D nanoflower-like FeIn2S4/CdS Z-scheme heterostructures.

Highly photoactive 3D nanoflower-like FeIn2S4/CdS heterostructures were synthesized by hydrothermal treatment and low-temperature cation exchange. The FeIn2S4/CdS displayed 14.5 times signal amplification in contrast to FeIn2S4 alone. It was applied as a photoactive substrate to construct a label-free photoelectrochemical (PEC) aptasensor for ultrasensitive determination of kanamycin (KAN). Under the optimal conditions, the constructed PEC aptasensor displayed a wide linear range (5.0 × 10-4 ~ 5.0 × 101 ng mL-1) and a low detection limit (S/N = 3) of 40.01 fg mL-1. This study provides some constructive insights for preparation of advanced photoactive materials and exhibits great potential for quantitative determination of antibiotics in foods and environmental samples.

Photoactive 3D-Printed Hypertensile Metamaterials for Improving Dynamic Modeling of Stem Cells.

Current three-dimensional (3D) cell culture systems mainly rely on static cell culture and lack the ability to thoroughly manage cell intrinsic behaviors and biological characteristics, leading to unsatisfied cell activity. Herein, we have developed photoactive 3D-printed hypertensile metamaterials based dynamic cell culture system (MetaFold) for guiding cell fate. MetaFold exhibited high elasticity and photothermal conversion efficiency due to its metapattern architecture and micro/nanoscale polydopamine coating, allowing for responding to mechanical and light stimulation to construct dynamic culture conditions. In addition, MetaFold possessed excellent cell adhesion capability and could promote cell viability and function under dynamic stimulation, thereby maximizing cell activity. Importantly, MetaFold could improve the differentiation efficacy of stem cells into cardiomyocytes and even their maturation, offering high-quality precious candidates for cell therapy. Therefore, we present a dual stimuli-responsive dynamic culture system, which provides a physiologically realistic environment for cell culture and biological study.

Physical Characteristics, Blue-Green Band Emission and Photocatalytic Activity of Au-Decorated ZnO Quantum Dots-Based Thick Films Prepared Using the Doctor Blade Technique.

Nanoscale ZnO is a vital semiconductor material whose versatility can be enhanced by sensitizing it with metals, especially noble metals, such as gold (Au). ZnO quantum dots were prepared via a simple co-precipitation technique using 2-methoxy ethanol as the solvent and KOH as the pH regulator for hydrolysis. The synthesized ZnO quantum dots were deposited onto glass slides using a simple doctor blade technique. Subsequently, the films were decorated with gold nanoparticles of different sizes using a drop-casting method. The resultant films were characterized via various strategies to obtain structural, optical, morphological, and particle size information. The X-ray diffraction (XRD) reveals the formation of the hexagonal crystal structure of ZnO. Upon Au nanoparticles loading, peaks due to gold are also observed. The optical properties study shows a slight change in the band gap due to Au loading. Nanoscale sizes of particles have been confirmed through electron microscope studies. P.L. studies display blue and blue-green band emissions. The significant degradation efficiency of 90.2% methylene blue (M.B.) was attained in natural pH in 120 min using pure ZnO catalyst while one drop gold-loaded catalysts, ZnO: Au 5 nm, ZnO: Au 7 nm, ZnO: Au 10 nm and ZnO: Au 15 nm, delivered M.B. degradation efficiency of 74.5% (in 245 min), 63.8% (240 min), 49.6% (240 min) and 34.0% (170 min) in natural pH, respectively. Such films can be helpful in conventional catalysis, photocatalysis, gas sensing, biosensing, and photoactive applications.

Triphenylamine-Containing Benzoic Acids: Synthesis, Liquid Crystalline and Redox Properties.

The synthesis, characterization and liquid crystalline and electrochemical properties of novel triarylamines, in which the triphenylamine platform is non-symmetrically modified with a 4-(6-oxyhexyloxy)benzoic acid group, are reported. Compounds show columnar liquid crystalline behavior, as confirmed through the use of polarized optical microscopy, differential scanning calorimetry and X-ray diffraction. Electrochemical properties were measured using cyclic voltammperometry, obtaining low oxidation potentials and HOMO values that were optimum for consideration as organic semiconductors in hole transport layers. In addition, the photoredox activity of one of these derivatives in dichloromethane was studied under light irradiation. A photooxidation/assembly process under white light irradiation occurs without the assistance of hydrogen bonding amide functional groups.

Photoactive Yellow Protein Adsorption at Hydrated Polyethyleneimine and Poly-l-Glutamic Acid Interfaces.

Chiral and achiral vibrational sum-frequency generation (VSFG) spectroscopy was performed in the 1400-1700 and 2800-3800 cm-1 range to study the interfacial structure of photoactive yellow protein (PYP) adsorbed on polyethyleneimine (PEI) and poly-l-glutamic acid (PGA) surfaces. Nanometer-thick polyelectrolyte layers served as the substrate for PYP adsorption, with 6.5-pair layers providing the most homogeneous surfaces. When the topmost material was PGA, it acquired a random coil structure with a small number of ß2-fibrils. Upon adsorption on oppositely charged surfaces, PYP yielded similar achiral spectra. However, the VSFG signal intensity increased for PGA surfaces with a concomitant redshift of the chiral Cα-H and N-H stretching bands, suggesting increased adsorption for PGA compared to PEI. At low wavenumbers, both the backbone and the side chains of PYP induced drastic changes to all measured chiral and achiral VSFG spectra. Decreasing ambient humidity led to the loss of tertiary structure with a re-orientation of α-helixes, evidenced by a strongly blue-shifted chiral amide I band of the ß-sheet structure with a shoulder at 1654 cm-1. Our observations indicate that chiral VSFG spectroscopy is not only capable of determining the main type of secondary structure of PYP, i.e., ß-scaffold, but is also sensitive to tertiary protein structure.

Mechanochemical Mediated Coexistence of B←N Coordination and Hydrogen Bonding.

Mechanochemistry afforded a photoactive cocrystal via coexisting (B)O-H⋅⋅⋅N hydrogen bonds and B←N coordination. Specifically, solvent-free mechanochemical ball mill grinding and liquid-assisted grinding of a boronic acid and an alkene resulted in mixtures of hydrogen-bonded and coordinated complexes akin to mixtures of noncovalent complexes that can be obtained in solution in equilibria processes. The alkenes of the hydrogen-bonded assembly undergo an intermolecular [2+2] photodimerization in quantitative conversion, effectively reporting the outcome of the self-assembly processes. Our results suggest that interplay involving noncovalent bonds subjected to mechanochemical conditions can lead to functional solids where, in the current case, the structure composed of the weaker hydrogen bonding interactions predominates.

A Photoisomerizable Zinc (II) Complex Inhibits Microtubule Polymerization for Photoactive Therapy.

The photoisomerization-induced cytotoxicity in photopharmacology provides a unique pathway for phototherapy because it is independent of endogenous oxygen. In this study, we developed a biosafe photoisomerizable zinc(II) complex (Zn1), which releases its trans ligand (trans-L1) after being irradiated with blue light. This causes the complex to undergo photoisomerization and produce the toxic cis product (cis-L1) and generate singlet oxygen (1 O2 ). The resulting series of events caused impressive phototoxicity in hypoxic A431 skin cancer cells, as well as in a tumor model in vivo. Interestingly, Zn1 was able to inhibit tumor microtubule polymerization, while still showing good biocompatibility and biosafety in vivo. This photoisomerizable zinc(II) complex provides a novel strategy for addressing the oxygen-dependent limitation of traditional photodynamic therapy.

Light-Activated Assembly of DNA Origami into Dissipative Fibrils.

Hierarchical DNA nanostructures offer programmable functions at scale, but making these structures dynamic, while keeping individual components intact, is challenging. Here we show that the DNA A-motif-protonated, self-complementary poly(adenine) sequences-can propagate DNA origami into one-dimensional, micron-length fibrils. When coupled to a small molecule pH regulator, visible light can activate the hierarchical assembly of our DNA origami into dissipative fibrils. This system is recyclable and does not require DNA modification. By employing a modular and waste-free strategy to assemble and disassemble hierarchical structures built from DNA origami, we offer a facile and accessible route to developing well-defined, dynamic, and large DNA assemblies with temporal control. As a general tool, we envision that coupling the A-motif to cycles of dissipative protonation will allow the transient construction of diverse DNA nanostructures, finding broad applications in dynamic and non-equilibrium nanotechnology.

Photoactive Yellow Protein Represents a Distinct, Evolutionarily Novel Family of PAS Domains.

Photoactive yellow protein (PYP) is a model photoreceptor. It binds a p-coumaric acid as a chromophore, thus enabling blue light sensing. The first discovered single-domain PYP from Halorhodospira halophila has been studied thoroughly in terms of its structural dynamics and photochemical properties. However, the evolutionary origins and biological role of PYP homologs are not well understood. Here, we show that PYP is an evolutionarily novel domain family of the ubiquitous PAS (Per-Arnt-Sim) superfamily. It likely originated from the phylum Myxococcota and was then horizontally transferred to representatives of a few other bacterial phyla. We show that PYP is associated with signal transduction either by domain fusion or by genome context. Key cellular functions modulated by PYP-initiated signal transduction pathways likely involve gene expression, motility, and biofilm formation. We identified three clades of the PYP family, one of which is poorly understood and potentially has novel functional properties. The Tyr42, Glu46, and Cys69 residues that are involved in p-coumaric acid binding in the model PYP from H. halophila are well conserved in the PYP family. However, we also identified cases where substitutions in these residues might have led to neofunctionalization, such as the proposed transition from light to redox sensing. Overall, this study provides definition, a newly built hidden Markov model, and the current genomic landscape of the PYP family and sets the stage for the future exploration of its signaling mechanisms and functional diversity. IMPORTANCE Photoactive yellow protein is a model bacterial photoreceptor. For many years, it was considered a prototypical model of the ubiquitous PAS domain superfamily. Here, we show that, in fact, the PYP family is evolutionarily novel, restricted to a few bacterial phyla and distinct from other PAS domains. We also reveal the diversity of PYP-containing signal transduction proteins and their potential mechanisms.