Photochemistry and photobiology of psoralens

Targeted Covalent Modification Strategies for Drugging the Undruggable Targets

The term "undruggable" refers to proteins or other biological targets that have been historically challenging to target with conventional drugs or therapeutic strategies because of their structural, functional, or dynamic properties. Drugging such undruggable targets is essential to develop new therapies for diseases where current treatment options are limited or nonexistent. Thus, investigating methods to achieve such drugging is an important challenge in medicinal chemistry. Among the numerous methodologies for drug discovery, covalent modification of therapeutic targets has emerged as a transformative strategy. The covalent attachment of diverse functional molecules to targets provides a powerful platform for creating highly potent drugs and chemical tools as well the ability to provide valuable information on the structures and dynamics of undruggable targets. In this review, we summarize recent examples of chemical methods for the covalent modification of proteins and other biomolecules for the development of new therapeutics and to overcome drug discovery challenges and highlight how such methods contribute toward the drugging of undruggable targets. In particular, we focus on the use of covalent chemistry methods for the development of covalent drugs, target identification, drug screening, artificial modulation of post-translational modifications, cancer specific chemotherapies, and nucleic acid-based therapeutics.

A Comprehensive Review on Benzofuran Synthesis Featuring Innovative and Catalytic Strategies

Benzofurans have intrigued both pharmaceutical researchers and chemists owing to the medicinal usage of their derivatives against copious disease-causing agents (i.e., bacteria, viruses, and tumors). These heterocyclic scaffolds are pervasively encountered in a number of natural products and drugs. The ever-increasing utilization of benzofuran derivatives as pharmaceutical agents persuaded the chemists to devise novel and facile methodological approaches to assemble the biologically potent benzofuran nucleus. This review summarizes the current developments regarding the innovative synthetic routes and catalytic strategies to procure the synthesis of benzofuran heterocycles with their corresponding mechanistic details, reported by several research groups during 2021-2023.

The effect of UVA light/8-methoxypsoralen exposure used in Extracorporeal Photopheresis treatment on platelets and extracellular vesicles

Extracorporeal Photopheresis (ECP) is a leukapheresis based treatment for Cutaneous T-Cell Lymphoma, which takes advantage of the cellular lethal effects of UVA light in combination with a photoactivated drug, 8-methoxypsoralen. 25% of patients treated with ECP do not respond to treatment, however the underlying mechanisms for this lack of response remain unknown. Platelets, a rich source of extracellular vesicles (EVs) and key mediators in thromboinflammatory oncological progression, as well as leukocytes, are both processed through ECP and are subsequently transfused back into the patient, delivering potent immunomodulation. The effect of exposing platelets and their EVs directly to Ultra Violet A light (UVA)/8-methoxypsoralen is currently unknown. Platelet-rich plasma (PRP) was isolated from healthy donors and exposed to UVA light and/or 8-methoxysporalen in vitro and platelet activation and aggregation was assessed. EV size and concentration were also characterised by Nanoparticle Tracking Analysis and Flow Cytometry. We found that UVA light and 8-methoxypsoralen treatment in vitro does not induce platelet aggregation or significantly alter levels of the platelet activation markers, soluble P-selectin or platelet factor 4, with circulating levels of small and large EV size and concentration remaining constant. Therefore, utilising the combination of UVA light and 8-methoxypsoralen used in ECP in vitro does not activate platelets or alter important circulating EVs. Further studies will be needed to validate if our observations are consistent in vivo.

Psoralen inhibits hepatitis B viral replication by down-regulating the host transcriptional machinery of viral promoters

The hepatitis B virus (HBV) is a global public health challenge due to its highly contagious nature. It is estimated that almost 300 million people live with chronic HBV infection annually. Although nucleoside analogs markedly reduce the risk of liver disease progression, the analogs do not fully eradicate the virus. As such, new treatment options and drugs are urgently needed. Psoralen is a nourishing monomer of Chinese herb and is known to inhibit virus replication and inactivate viruses. In this study, we evaluated the potential of psoralen as an anti-HBV agent. Quantitative PCR and Southern blot analysis revealed that psoralen inhibited HBV replication in HepG2.2.15 ​cells in a concentration-dependent manner. Moreover, psoralen was also active against the 3TC/ETV-dual-resistant HBV mutant. Further investigations revealed that psoralen suppressed both HBV RNA transcription and core protein expression. The transcription factor FOXO1, a known target for PGC1α co-activation, binds to HBV pre-core/core promoter enhancer II region and activates HBV RNA transcription. Co-immunoprecipitation showed that psoralen suppressed the expression of FOXO1, thereby decreasing the binding of FOXO1 co-activator PGC1α to the HBV promoter. Overall, our results demonstrate that psoralen suppresses HBV RNA transcription by down-regulating the expression of FOXO1 resulting in a reduction of HBV replication.

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Psoralen is a nourishing monomer of Chinese herb that inhibits the replication of HBV.

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Psoralen decreases the expression of transcription factor FOXO1 of pre-core/core promoter.

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Psoralen suppresses HBV replication by down-regulation FOXO1 in HBV-producing cells.

Photocrosslinking of DNA using 4-methylpyranocarbazole nucleoside with thymine base selectivity

This report describes a novel photocrosslinker, 4-methylpyranocarbazole nucleoside (^MEPK), that can be induced to crosslink using visible light. Previously, we reported a visible light-responsive artificial nucleic acid, pyranocarbazole nucleoside (^PCX). ^MEPK can selectively photocrosslink to thymine bases in a complementary nucleic acid strand. It was synthesized by introducing a methyl group at the 4-position of ^PCX, and it can differentiate between thymine and cytosine. The previously reported visible light-responsive artificial nucleic acid ^PCX has a low synthetic yield. ^MEPK was synthesized by Pechmann condensation which suppressed by-product formation, making the synthesis more efficient, and resulting in a higher yield than that of ^PCX. ^MEPK is expected to have practical applications as a photocrosslinker that can be manipulated with visible light and that selectively targets thymine bases.

Apoptosis induction by extracorporeal photopheresis is enhanced by increasing the 8-methoxypsoralen concentration and by replacing plasma with saline

BACKGROUND

Extracorporeal photopheresis (ECP), an apheresis-based therapy for various immunological diseases, works mainly by inducing apoptosis in lymphocytes. Several factors influence the efficacy of ECP with the photosensitizer 8-methoxypsoralen (8-MOP) and ultraviolet light A (UVA). This study aimed to optimize treatment by varying the 8-MOP starting concentration and the cell suspension medium.

MATERIALS AND METHODS

All patients (n = 13) included in this study received photopheresis as medically indicated. Cells collected with a Spectra Optia apheresis system were suspended in plasma or physiological saline (NaCl) and incubated with 200 ng/ml versus 340 ng/ml photosensitizer before UVA irradiation (Macogenic G2 or UVA PIT system). Lymphocyte apoptosis and caspase activity were analyzed by flow cytometry and fluorimetry, and residual 8-methoxypsoralen concentrations by liquid chromatography-mass spectrometry.

RESULTS

Raising the 8-MOP starting concentration significantly increased lymphocyte apoptosis, with values of 22% versus 35% (plasma) and 28%-46% (NaCl) at 24 h post-ECP and 37% versus 86% (plasma) and 74% versus 97% (NaCl) at 48 h for 200 ng/ml versus 340 ng/ml. Pre-transfusion residual 8-MOP levels were 168 ng/ml (plasma) and 162 ng/ml (NaCl) versus 290 ng/ml (plasma) and 266 ng/ml (NaCl) for the lower versus higher dose, respectively.

DISCUSSION

Hence, 8-MOP concentration influences the efficacy of photopheresis as lymphocyte apoptosis rates were significantly higher with the higher starting concentration and with NaCl versus plasma. This indicates that increased 8-MOP starting doses and saline as additional suspension medium could help in improving ECP's efficacy.

Distribution of Holliday junctions and repair forks during Escherichia coli DNA double-strand break repair

Accurate repair of DNA double-strand breaks (DSBs) is crucial for cell survival and genome integrity. In Escherichia coli, DSBs are repaired by homologous recombination (HR), using an undamaged sister chromosome as template. The DNA intermediates of this pathway are expected to be branched molecules that may include 4-way structures termed Holliday junctions (HJs), and 3-way structures such as D-loops and repair forks. Using a tool creating a site-specific, repairable DSB on only one of a pair of replicating sister chromosomes, we have determined how these branched DNA intermediates are distributed across a DNA region that is undergoing DSB repair. In cells, where branch migration and cleavage of HJs are limited by inactivation of the RuvABC complex, HJs and repair forks are principally accumulated within a distance of 12 kb from sites of recombination initiation, known as Chi, on each side of the engineered DSB. These branched DNA structures can even be detected in the region of DNA between the Chi sites flanking the DSB, a DNA segment not expected to be engaged in recombination initiation, and potentially degraded by RecBCD nuclease action. This is observed even in the absence of the branch migration and helicase activities of RuvAB, RadA, RecG, RecQ and PriA. The detection of full-length DNA fragments containing HJs in this central region implies that DSB repair can restore the two intact chromosomes, into which HJs can relocate prior to their resolution. The distribution of recombination intermediates across the 12kb region beyond Chi is altered in xonA, recJ and recQ mutants suggesting that, in the RecBCD pathway of DSB repair, exonuclease I stimulates the formation of repair forks and that RecJQ promotes strand-invasion at a distance from the recombination initiation sites.

Photosensitization Reactions of Biomolecules: Definition, Targets and Mechanisms

Photosensitization reactions have been demonstrated to be largely responsible for the deleterious biological effects of UV and visible radiation, as well as for the curative actions of photomedicine. A large number of endogenous and exogenous photosensitizers, biological targets and mechanisms have been reported in the past few decades. Evolving from the original definitions of the type I and type II photosensitized oxidations, we now provide physicochemical frameworks, classifications and key examples of these mechanisms in order to organize, interpret and understand the vast information available in the literature and the new reports, which are in vigorous growth. This review surveys in an extended manner all identified photosensitization mechanisms of the major biomolecule groups such as nucleic acids, proteins, lipids bridging the gap with the subsequent biological processes. Also described are the effects of photosensitization in cells in which UVA and UVB irradiation triggers enzyme activation with the subsequent delayed generation of superoxide anion radical and nitric oxide. Definitions of photosensitized reactions are identified in biomolecules with key insights into cells and tissues.

Crosslinker-modified nucleic acid probes for improved target identification and biomarker detection

Understanding the intricate interaction pattern of nucleic acids with other molecules is essential to gain further insight in biological processes and disease mechanisms. To this end, a multitude of hybridization-based assays have been designed that rely on the non-covalent recognition between complementary nucleic acid sequences. However, the ephemeral nature of these interactions complicates straightforward analysis as low efficiency and specificity are rule rather than exception. By covalently locking nucleic acid interactions by means of a crosslinking agent, the overall efficiency, specificity and selectivity of hybridization-based assays could be increased. In this mini-review we highlight methodologies that exploit the use of crosslinker-modified nucleic acid probes for interstrand nucleic acid crosslinking with the objective to study, detect and identify important targets as well as nucleic acid sequences that can be considered relevant biomarkers. We emphasize on the usefulness and advantages of crosslinking agents and elaborate on the chemistry behind the crosslinking reactions they induce.

Matrix-dependent absorption of 8-methoxypsoralen in extracorporeal photopheresis

BACKGROUND

Extracorporeal photopheresis (ECP) is an effective immunomodulatory therapy for various diseases. Autologous leukocytes are collected, photoactivated with a photosensitizer (8-methoxypsoralen, 8-MOP) and UVA light, and subsequently reinfused back to the patient. Leukapheresis and UVA irradiation systems can be integrated into one device (inline) or handled by two separate devices (offline). ECP works via intercalation of 8-MOP into DNA helices and UVA-based interactions to inhibit DNA replication. 8-MOP is known to adhere to plastic materials, which might reduce its availability for intercalation. In the present study we examined the bioavailability of 8-MOP when different plastic materials and solvents are used as matrices.

METHODS

Varying amounts of shredded ethylene vinyl acetate (EVA) and polyvinylchloride (PVC) from the MacoGenic irradiation bag (EVA1), UVA PIT irradiation bag (EVA2), UVA PIT recirculation bag (PVC A) and UVA PIT tubing (PVC B) by MacoPharma and PIT Medical Systems, respectively, were incubated with 200 ng mL^-1 8-MOP dissolved in diisopropyl ether (DIPE) plus toluene 90/10 vol%, deionized water or plasma. After 2 h 8-MOP concentrations were determined by GC-MS.

RESULTS

After incubation, 8-MOP concentrations varied depending on the amount and type of plastic (PVC > EVA) and solvent (water > plasma > DIPE/toluene). Absorption to 200 mg EVA1 or EVA2 resulted in 8-MOP concentrations of 57% or 32% in water, 91% or 80% in plasma, and 93% or 92% in DIPE/toluene, while 200 mg PVC A and PVC B yielded recovery rates of 26% and 10% in water, 76% and 75% in plasma, and 55% and 30% in DIPE/toluene, respectively. Remaining 8-MOP differed significantly between container materials (EVA vs. PVC; p < 0.022) but not manufacturers (MacoPharma vs. PIT Medical Systems).

CONCLUSION

Absorption loss of 8-MOP depends on the type of plastic and solvent and is more pronounced with water than with plasma. As the DNA binding effect of 8-MOP is dose-dependent, ECP starting doses should be adjusted to ensure that a sufficient concentration of free bioavailable 8-MOP is present during UV irradiation.

Key factors affecting photoactivated fungicidal activity of sodium pheophorbide a against Pestalotiopsis neglecta

Recently, photodynamic therapy (PDT) and photoactivated pesticides have attracted considerable research attention. In the present study, we aimed to investigate the photodynamic activity of a chlorophyllous derivative, sodium pheophorbide a (SPA), and to evaluate its potential as a photoactivated fungicide. The singlet oxygen quantum yield, the photoreaction process, the anti-photobleaching ability in sterile water (H₂O), the effect of light conditions on its antifungal activity, and its stability were all investigated. SPA showed significant fungicidal activity and photostability, during which Type I and Type II photodynamic reactions occurred simultaneously on Pestalotiopsis neglecta, and the influence of Type I was slightly larger than that of Type II. In addition, light promoted the antifungal activity of SPA. In particular, the antifungal activity was enhanced with increasing light intensity, and was strongest under 8000 lx conditions. Under monochromatic light sources, antifungal activity was strongest under green light s; however, the effect of monochromatic light was not as good as that of white light. From 0 to 24 h, the antifungal effect of the SPA solution was enhanced; however, the activity of the solution began to weaken after 24 h. Furthermore, our study confirmed that the antifungal activity of SPA was stable under different temperatures, pH values, and UV irradiation durations.

In Vitro Alternatives and Phototoxicity Testing. II. Effects of Reactive Oxygen Species in In Vitro Phototoxicity Assays

The effects of reactive oxygen species (including singlet oxygen) in two in vitro phototoxicity assays — the 3T3 cell neutral red uptake phototoxicity (3T3 NRU PT) assay and the photohaemolysis assay — were assessed by using scavengers. Fifteen test substances, which had previously been shown to be phototoxic in vitro, were assessed. Eleven of these produced singlet oxygen. The major factor in the photodynamic reaction of bithionol was thought to be a Type I reaction, because bithionol did not produce singlet oxygen and did not react to histidine. Acridine was regarded as a Type II substance, because of the evident effect of histidine as a scavenger. 8-Methoxypsoralen and 5-methoxypsoralen produced singlet oxygen, but their actions were not affected by the scavengers. In this study, we confirmed that reactive oxygen species have great effects in in vitro phototoxicity, and that the 3T3 NRU PT assay can be used to detect effects which are thought to be the direct reaction of an excited photosensitiser to biological substrates (Type III reaction), for example, 8-methoxypsoralen. Therefore, we suggest that photohaemolysis and phototoxicity could be used to evaluate the photodynamic mechanisms of photosensitising chemicals.

An In Vitro Phototoxicity Assay Battery (Photohaemolysis and 3T3 NRU PT test) to Assess Phototoxic Potential of Fragrances

The purpose of this study was to compare the in vivo and in vitro phototoxicity potentials of 13 fragrances. We used the 3T3 neutral red uptake phototoxicity (3T3 NRU PT) test and the photohaemolysis test as in vitro phototoxicity assays. In the 3T3 NRU PT test, all of the fragrances were non-phototoxic. Six fragrances were phototoxic in the photohaemolysis test. Three of the six photohaemolytic fragrances were phototoxic in the guinea-pig photoirritation test. These phototoxic fragrances did not cause cellular phototoxicity, but showed a photohaemolytic reaction. The photohaemolysis test was more sensitive than the 3T3 NRU PT test for screening for the phototoxicity of fragrances. The accuracy of this in vitro phototoxicity test battery was 82%. It is thought that the major phototoxic mechanism of fragrances is cell membrane damage. We suggest that a battery composed of the 3T3 NRU PT test and the photohaemolysis test is a simple and effective model for the in vitro phototoxicity assay of fragrances.

Light-triggered release of photocaged therapeutics - Where are we now?

The current available therapeutics face several challenges such as the development of ideal drug delivery systems towards the goal of personalized treatments for patients benefit. The application of light as an exogenous activation mechanism has shown promising outcomes, owning to the spatiotemporal confinement of the treatment in the vicinity of the diseased tissue, which offers many intriguing possibilities. Engineering therapeutics with light responsive moieties have been explored to enhance the bioavailability, and drug efficacy either in vitro or in vivo. The tailor-made character turns the so-called photocaged compounds highly desirable to reduce the side effects of drugs and, therefore, have received wide research attention. Herein, we seek to highlight the potential of photocaged compounds to obtain a clear understanding of the mechanisms behind its use in therapeutic delivery. A deep overview on the progress achieved in the design, fabrication as well as current and possible future applications in therapeutics of photocaged compounds is provided, so that novel formulations for biomedical field can be designed.

Intramolecularly Protein-Crosslinked DNA Gels: New Biohybrid Nanomaterials with Controllable Size and Catalytic Activity

DNA micro- and nanogels-small-sized hydrogels made of a crosslinked DNA backbone-constitute new promising materials, but their functions have mainly been limited to those brought by DNA. Here a new way is described to prepare sub-micrometer-sized DNA gels of controllable crosslinking density that are able to embed novel functions, such as an enzymatic activity. It consists of using proteins, instead of traditional base-pairing assembly or covalent approaches, to form crosslinks inside individual DNA molecules, resulting in structures referred to as intramolecularly protein-crosslinked DNA gels (IPDGs). It is first shown that the addition of streptavidin to biotinylated T4DNA results in the successful formation of thermally stable IPDGs with a controllable crosslinking density, forming structures ranging from elongated to raspberry-shaped and pearl-necklace-like morphologies. Using reversible DNA condensation strategies, this paper shows that the gels can be reversibly actuated at a low crosslinking density, or further stabilized when they are highly crosslinked. Finally, by using streptavidin-protein conjugates, IPDGs with various enzymes are successfully functionalized. It is demonstrated that the enzymes keep their catalytic activity upon their incorporation into the gels, opening perspectives ranging from biotechnologies (e.g., enzyme manipulation) to nanomedicine (e.g., vectorization).

A method for the quantification of 8-methoxypsoralen by mass spectrometry for offline extracorporeal photopheresis

An LC-MS/MS assay for analysis of 8-methoxypsoralene was developed as assay to monitor extracorporeal photopheresis. This allows quantification of 8-MOP adhering to plastic surface and of the UV light-dependent decay constant.

Small-molecule inhibitors of Ataxia Telangiectasia and Rad3 related kinase (ATR) sensitize lymphoma cells to UVA radiation

BACKGROUND

Psoralen plus ultraviolet A (PUVA) photochemotherapy is a combination treatment used for inflammatory and neoplastic skin diseases such as mycosis fungoides (MF), the most common type of cutaneous T-cell lymphoma (CTCL). However, 30% of MF patients do not respond sufficiently to PUVA and require more aggressive therapies.

OBJECTIVE

The aim of this project was to investigate whether inhibition of Ataxia Telangiectasia and Rad3 related kinase (ATR) may enhance efficacy of phototherapy.

METHODS

CTCL cell lines (MyLa2000, SeAx and Mac2a) served as in vitro cell models. ATR and Chk1 were inhibited by small molecule antagonists VE-821, VE-822 or Chir-124, or by small interfering RNAs (siRNAs). Cell cycle and viability were assessed by flow cytometry.

RESULTS

Small molecule inhibitors of ATR and Chk1 potently sensitized all cell lines to PUVA and, importantly, also to UVA, which by itself did not cause apoptotic response. VE-821/2 blocked ATR pathway activation and released the cells from the G2/M block caused by UVA and PUVA, but did not affect apoptosis caused by other chemotherapeutics (etoposide, gemcitabine, doxorubicine) or by hydrogen peroxide. Knockdown of ATR and Chk1 with siRNA also blocked the ATR pathway and released the cells from G2/M block but did not sensitize the cells to UVA as observed with the small molecule inhibitors. The latter suggested that the synergism between VE-821/2 or Chir-124 and UVA was not solely caused by specific blocking of ATR kinase but also ATR-independent photosensitization. This hypothesis was further verified by administrating VE-821/2 or Chir-124 before and after UVA irradiation, as well as comparing their activity with other ATR and Chk1 inhibitors (AZD6738 and MK8776). We found that only VE-821/2 and Chir-124 kinase inhibitors had synergistic effect with UVA, and only if applied before treatment with UVA.

CONCLUSION

Small molecule ATR and Chk1 inhibitors potently sensitize lymphoma cells to UVA radiation and induce a prominent apoptotic response. Interestingly, this effect is due to the dual (kinase inhibiting and photosensitizing) mode of action of these compounds.

R. C, Chand K, Santos MA, Keri RS. Benzofuran: an emerging scaffold for antimicrobial agents

The present article systematically gives a comprehensive review of current development of benzofuran-based compounds as antimicrobial agents and the perspectives that they hold for future research.

Synthesis, reactions and biological activities of furochromones: a review

Furochromone derivatives are important synthetic targets which showed a myriad of interesting biological activities. Ammi visnaga (Umbelliferae) is the most famous source of these derivatives, which has been used in folk medicine for millennia targeting different ailments. Since the isolation of furochromone derivatives, different synthetic methodologies were developed for their preparation. Despite the recent interesting findings on this class of compounds, the chemical literatures lack a comprehensive summary on the synthetic methodologies and biological activities of furochromone derivatives. This review highlights recent advances in furochromones chemistry by discussing different synthetic procedures developed for the preparation of naturally occurring derivatives as well as other unique derivatives which showed promising biological activities. It also sheds light on the most common reactions of furochromone derivatives and the utilization of these derivatives as the blocks for many biologically active compounds.

Biological quality control for extracorporeal photochemotherapy: Assessing mononuclear cell apoptosis levels in ECP bags of chronic GvHD patients

Extracorporeal photochemotherapy (ECP) is a treatment approved by the FDA for cutaneous T-cell lymphoma, and it is currently used off-label for graft-versus-host disease (GvHD) and other conditions. In agreement with good practices for the therapeutic use of human cells, quality control has to be performed to validate the ECP procedure with the off-line technique. Since no gold-standard biological test is available, we assessed the apoptosis generated in the ECP bag using a flow cytometric analysis. Thirty-one ECP procedures performed on 13 patients with chronic GvHD were studied by monitoring the induction of mononuclear cell (MNC) apoptosis using annexin V/propidium iodide double staining; residual lymphocyte proliferation to standard mitogens was also measured in 17 of the procedures. The kinetics of apoptosis was analyzed at different times in MNCs untreated or treated with 8-methoxy-psoralen plus ultraviolet A; the variation (ΔAPOPTOSIS ) after 24 h revealed the efficacy of the treatment. In 88.6% of the 31 ECP procedures, ΔAPOPTOSIS was >15% (the "alerting" threshold for ΔAPOPTOSIS was set at 15% on the basis of our data); in the remainder (19.4%), the increment in apoptosis was lower. In four procedures, the proliferation assay was useful for assessing the effect of ECP on the apheretic bag. In conclusion, both flow cytometric assays enabled a biologically significant result to be obtained. In our opinion, the apoptosis test-being faster and easier than the proliferation test-could be a reliable way to validate ECP procedures.

Theoretical and experimental study of a novel psolaren derivate: (E)-9-(3,4-dimethylpent-2-enyloxy)-7H-furo[3,2-g]chromen-7-one

A new psolaren derivate, (E)-9-(3,4-dimethylpent-2-enyloxy)-7H-furo[3,2-g]chromen-7-one, has been isolated and characterized by experimental and theoretical methodologies. The solid state molecular structure has been determined by X-ray diffraction methods. The substance crystallizes in the monoclinic P21/c space group with a=4.2389(5), b=26.090(3), c=12.482(1)Å, β=96.990(9)°, and Z=4 molecules per unit cell. The crystal structure shows the molecule fused phenyl and hetero-cycle rings to be coplanar with each other. Ab initio(MP2) and DFT methods have been used to predict the molecular structure in the isolated molecule approximation and the results compared with the experimental data. The MP2/6-311G(d,p) calculations are in good agreement with the X-ray results. The calculated HOMO-LUMO energy gap shows that the intra-molecular charge transfer could easily occur, a prediction closely related to the observed bioactivity of this new compound. In addition, the infrared absorption and Raman dispersion spectra were recorded and an assignment of the observed spectral features to molecular vibrations was made. The vibrational study was assisted by quantum chemistry calculations at the MP2 and DFT level, which provided theoretical mode frequencies. The study was completed by natural bond orbital (NBO) analysis.

Zinc-gold cooperative catalysis for the direct alkynylation of benzofurans

The direct alkynylation of benzofurans was achieved for the first time using the hypervalent iodine reagent 1-[(triisopropylsilyl)ethynyl]-1,2-benziodoxol-3(1H)-one (TIPS-EBX) based on the cooperative effect between a gold catalyst and a zinc Lewis acid. High selectivity was observed for C2-alkynylation of benzofurans substituted with alkyl, aryl, halogen and ether groups. The reaction was also successful in the case of the more complex drug 8-methoxypsoralen (8-MOP).

The RecQ helicase RECQL5 participates in psoralen-induced interstrand cross-link repair

Interstrand cross-links (ICLs) are very severe lesions as they are absolute blocks of replication and transcription. This property of interstrand cross-linking agents has been exploited clinically for the treatment of cancers and other diseases. ICLs are repaired in human cells by specialized DNA repair pathways including components of the nucleotide excision repair pathway, double-strand break repair pathway and the Fanconi anemia pathway. In this report, we identify the role of RECQL5, a member of the RecQ family of helicases, in the repair of ICLs. Using laser-directed confocal microscopy, we demonstrate that RECQL5 is recruited to ICLs formed by trioxalen (a psoralen-derived compound) and ultraviolet irradiation A. Using single-cell gel electrophoresis and proliferation assays, we identify the role of RECQL5 in the repair of ICL lesions. The domain of RECQL5 that recruits to the site of ICL was mapped to the KIX region between amino acids 500 and 650. Inhibition of transcription and of topoisomerases did not affect recruitment, which was inhibited by DNA-intercalating agents, suggesting that the DNA structure itself may be responsible for the recruitment of RECQL5 to the sites of ICLs.

O death where is thy sting? Immunologic tolerance to apoptotic self

In higher organisms, innate scavenging cells maintain physiologic homeostasis by removal of the billions of apoptotic cells generated on a daily basis. Apoptotic cell removal requires efficient recognition and uptake by professional and non-professional phagocytic cells, which are governed by an array of soluble and apoptotic cell-integral signals resulting in immunologically silent clearance. While apoptosis is associated with profound suppression of adaptive and innate inflammatory immunity, we have only begun to scratch the surface in understanding how immunologic tolerance to apoptotic self manifest at either the molecular or cellular level. In the last 10 years, data has emerged implicating professional phagocytes, most notably stromal macrophages and CD8α(+)CD103(+) dendritic cells, as critical in initiation of the regulatory cascade that will ultimately lead to long-term whole-animal immune tolerance. Importantly, recent work by our lab and others has shown that alterations in apoptotic cell perception by the innate immune system either by removal of critical phagocytic sentinels in secondary lymphoid organs or blockage of immunosuppressive pathways leads to pronounced inflammation with a breakdown of tolerance towards self. This challenges the paradigm that apoptotic cells are inherently immunosuppressive, suggesting that apoptotic cell tolerance is a "context-dependent" event.

Antidepressant effect of 5-methoxypsoralen: The melatonin synchronizer hypothesis

5-methoxypsoralen (5-MOP) stimulates pineal melatonin secretion, and a decrease in dark phase melatonin levels has been described in major depression. As exogenous melatonin has shown synchronizer properties, authors hypothesized that giving 5-MOP would have antidepressant properties. Twenty-six inpatients meeting the criteria of major depressive disorders were enrolled in a four-week, double blind trial of 5-MOP versus amitriptyline. Clinical improvement was identical in both treatment groups but biological changes were different in each group: 5-MOP patients showed an early nocturnal surge of melatonin levels that was maintained at the fourth treatment week, while melatonin levels remained unchanged in patients treated with amitriptyline.