Topic
Protoporphyrin IX
About: Protoporphyrin IX is a research topic. Over the lifetime, 2250 publications have been published within this topic receiving 65544 citations. The topic is also known as: PpIX.
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TL;DR: Experimental evidences of the mechanisms underlying preferential production of PpIX in neoplastic tissues are summarised and morphological, environmental, enzymatic, as well as cell-specific factors will be discussed.
Abstract: Due to its capability to induce accumulation of protoporphyrin IX (PpIX) selectively in a multitude of different pathologies, 5-aminolevulinic acid (ALA) and its derivatives have attracted enormous attention in the field of photodynamic therapy (PDT) in the past two decades. The photochemical and photophysical properties of PpIX have been used for the fluorescence photodetection and photodynamic treatment of neoplasms in several medical indications in which conversion of ALA into PpIX seems to take place preferentially. Recently, this has led to the approval of this therapy for the treatment of actinic keratosis and basal cell carcinoma. When applied topically or systemically, ALA bypasses the negative feedback control that haem exerts on the enzyme ALA synthase (ALAS), which catalyses the natural production of this delta-amino acid, thereby temporarily boosting the generation of PpIX, the direct precursor of haem. Despite considerable interest in this treatment methodology, only little is known concerning the reasons for the selective accumulation of PpIX in neoplastic tissue upon ALA administration. Following an introduction into the biochemical as well as the chemical principles of haem synthesis, the present review tries to summarise experimental evidences of the mechanisms underlying preferential production of PpIX in neoplastic tissues. Thereby, morphological, environmental, enzymatic, as well as cell-specific factors will be discussed.
162 citations
TL;DR: Both dendrimer porphyrins with either 32 quaternary ammonium groups or 32 carboxylic groups had far lower dark toxicity as compared with PIX, demonstrating their highly selective photosensitizing effect in combination with a reduced systemic toxicity.
161 citations
TL;DR: An essential role for light-induced Mg-protoporphyrin IX accumulation in this chloroplast-to-nucleus signalling pathway is suggested which makes this plastidic compound accessible to the cytoplasm/nucleu where the downstream signalling pathway may be activated.
Abstract: Chlorophyll precursors Mg-protoporphyrin IX and its monomethylester are candidates for plastid-derived molecules involved in light signalling from the chloroplast to the nucleus. The pool sizes of these two Mg2+-containing porphyrins and of protoporphyrin IX transiently increased upon a shift of Chlamydomonas cultures from dark to light. This increase coincided with the accumulation of mRNAs encoded by the nuclear genes HSP70A and HSP70B. Analysis of a mutant (brs-1), previously shown to be defective in the light induction of these genes, revealed high levels of protoporphyrin IX but no light-induced increase in the levels of Mg2+-containing porphyrins. Inhibitors of cytoplasmic protein synthesis prevented both the light-induced rise in pool levels and induction of the HSP70 genes. Similarly, pre-gametes, intermediates of sexual differentiation, lacked both responses to light. The block in light induction of the HSP70 genes in inhibitor-treated cells and in pre-gametes could be circumvented by the exogenous addition of Mg-protoporphyrin IX in the dark. This suggests an essential role for light-induced Mg-protoporphyrin IX accumulation in this chloroplast-to-nucleus signalling pathway. However, accumulation of this porphyrin in the dark - presumably in the chloroplast - did not result in induction. A second crucial role for light in this signalling pathway is postulated which makes this plastidic compound accessible to the cytoplasm/nucleus where the downstream signalling pathway may be activated.
159 citations
TL;DR: The aggregation behavior of porphyrin IX in aqueous solution, as a function of pH and ionic strength, has been studied by means of UV/vis, fluorescence emission spectroscopy, and resonant light scattering (RLS) techniques as discussed by the authors.
Abstract: The aggregation behavior of protoporphyrin IX in aqueous solution, as a function of pH and ionic strength, has been studied by means of UV/vis, fluorescence emission spectroscopy, and resonant light scattering (RLS) techniques. Our experimental results agree with previous literature assignments: (i) protoporphyrin IX is a monomer in the pH range 0−3, (ii) a dimer is present for pH > 8, and (iii) higher aggregates are present in the pH range 3−7. Addition of sodium chloride up to 0.3 M to a porphyrin solution at pH 12 gives a process resembling a phase transition, whereas it has little effect on acidic or neutral solutions. The apparent split Soret band observed in the intermediate pH range has been explained using a model in which dimers of porphyrins (with a slip angle α = 38° or 52°, as derived from depolarized RLS measurements) are the basic units and they interact axially through π−π stacking and laterally by edge-to-edge hydrophobic contacts. The half neutralization of the carboxylic acid side chain...
150 citations
TL;DR: The results show that saflufenacil is a new PPO-inhibiting, peroxidizing herbicide in multiple crops, including corn.
Abstract: Saflufenacil (Kixor™) is a new herbicide of the pyrimidinedione chemical class for preplant burndown and selective preemergence dicot weed control in multiple crops, including corn. In this study, the mode of action of saflufenacil was investigated. For initial characterization, a series of biotests was used in a physionomics approach for comprehensive physiological profiling of saflufenacil effects. With the use of treated duckweed plants, metabolite profiling was performed based on quantification of metabolite changes, relative to untreated controls. Physiological and metabolite profiling suggested a mode of action similar to inhibitors of protoporphyrinogen IX oxidase (PPO) in tetrapyrrole biosynthetic pathway. Saflufenacil inhibited PPO enzyme activity in vitro with 50% inhibition of 0.4 nM for the enzymes isolated from black nightshade, velvetleaf, and corn. PPO inhibition by saflufenacil caused accumulations of protoporphyrin IX (Proto) and hydrogen peroxide (H2O2) in leaf tissue of black n...
150 citations