Biphasic fluence-response curves and derived action spectra for light-induced absorbance changes in Phycomyces mycelium

The photoresponses of Phycomyces, including phototropism and photocontrol of sporangiophore development, are mediated primarily by blue and UV light. Recent results on these two responses indicated a subsidiary role for green light. We have measured in vivo light-induced absorbance changes (LIAC) in mycelial samples of a caroteneless (carB) strain to compare the effectiveness of UV, blue, and green light. In the dual-wavelength kinetic mode of the spectrophotometer, measuring wavelengths of 445 and 470 nm were chosen, because green light produces substantial absorbance changes between these two wavelengths. Fluence-response curves were measured for 13 wavelengths between 365 and 530 nm, and for variable exposure times between 0.5 and 320 s. With one exception (365 nm), the curves were biphasic. The low fluence component was generally sigmoidal with an abrupt rise. The high fluence component failed to reach saturation for the fluences tested (less than 70 μmol m⁻² s⁻¹). Using the inferred threshold fluences of these two components as criterion effects, we obtained two action spectra. For the low fluence component, the action spectrum showed major peaks at 394, 450, and 530 nm and a minor peak at 416 nm. The high fluence component action spectrum showed very little sensitivity in the blue region. The major sensitivity was in the near UV, and a relatively small peak appeared in the green part of the spectrum at 507 nm. The biphasic character of the fluence-response curves suggests that two photosystems are responsible for the absorbance changes. The low fluence photosystem is sensitive mainly to blue and UV light and may thus represent a physiological blue-light photoreceptor. The high fluence photosystem is clearly not of this type. It (and perhaps the low fluence system as well) may mediate some of the subsidiary physiological effects of green light.     

Studies on the liquid-liquid phase distribution equilibria of selenium,and its measurement in water using extraction plant with a pulsation column

Normal heptane, xylene, and a 0.01 molar solution of 4-(5-nonyl)pyridine in toluene have been investigated as extractants for selenium(IV) from nitric acid media in potassium iodide. Various parameters affecting the distribution of the element are investigated. Extraction at high aqueous to organic phase volume ratio has been studied, using a liquid-liquid extraction plant with a pulsation column. The results have been employed to measure selenium in spiked water samples.     

Instrumental Dependent Dissociations of n-Propyl/Isopropyl Phosphonate Isomers: Evaluation of Resonant and Non-Resonant Vibrational Activations

Structural elucidation and distinction of isomeric neurotoxic agents remain a challenge. Tandem mass spectrometry can be used for this purpose in particular if a “diagnostic” product ion is observed. Different vibrational activation methods were investigated to enhance formation of diagnostic ions through consecutive processes from O,O-dialkyl alkylphosphonates. Resonant and non-resonant collisional activation and infrared multiphoton dissociation (IRMPD) were used with different mass spectrometers: a hybrid quadrupole Fourier transform ion cyclotron resonance (Qh-FTICR) and a hybrid linear ion trap-Orbitrap (LTQ/Orbitrap). Double resonance (DR) experiments, in ion cyclotron resonance (ICR) cell, were used for unambiguous determination of direct intermediate yielding diagnostic ions. From protonated n-propyl and isopropyl O-O-dialkyl-phosphonates, a diagnostic m/z 83 ion characterizes the isopropyl isomer. This ion is produced through consecutive dissociation processes. Conditions to favor its formation and observation using different activation methods were investigated. It was shown that with the LTQ, consecutive experimental steps of isolation/activation with modified trapping conditions limiting the low mass cut off (LMCO) effect were required, whereas with FT-ICR by CID and IRMPD the diagnostic ion detection was provided only by one activation step. Among the different investigated activation methods it was shown that by using low-pressure conditions or using non-resonant methods, efficient and fast differentiation of isomeric neurotoxic agents was obtained. This work constitutes a unique comparison of different activation modes for distinction of isomers showing the instrumental dependence characteristic of the consecutive processes. New insights in the dissociation pathways were obtained based on double-resonance IRMPD experiments using a FT-ICR instrument with limitation at low mass values.

Ni2+ cation and imidazole as corrosion inhibitors for carbon steel in sulfuric acid solutions

Abstract  

The effect of Ni²⁺ cation, imidazole, and mixtures of them on the corrosion behavior of carbon steel in 0.5 M H₂SO₄ solution was studied by using galvanostatic polarization, potentiodynamic anodic polarization, and weight-loss techniques. Ni²⁺ cation, imidazole, and mixtures of them provide a good protection to carbon steel against pitting corrosion in chloride-containing solutions. The inhibiting solutions were analyzed by using UV–Vis spectrophotometry. The inhibition was explained on the basis of formation of a complex between the two components. The inhibition mechanism was discussed in terms of the results derived from corrosion and UV–Vis spectrophotometric measurements as well as conductometric investigations.     

T3P-Promoted Synthesis of a Series of 2-Aryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones and Their Activity against the Kinetoplastid Parasite Trypanosoma brucei

A series of fourteen 2-aryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones was prepared at room temperature by T3P-mediated cyclization of N-phenyl-C-aryl imines with thionicotinic acid, two difficult substrates. The reactions were operationally simple, did not require specialized equipment or anhydrous solvents, could be performed as either two or three component reactions, and gave moderate–good yields as high as 63%. This provides ready access to N-phenyl compounds in this family, which have been generally difficult to prepare. As part of the study, the first crystal structure of neutral thionicotinic acid is also reported, and showed the molecule to be in the form of the thione tautomer. Additionally, the synthesized compounds were tested against T. brucei, the causative agent of Human African Sleeping Sickness. Screening at 50 µM concentration showed that five of the compounds strongly inhibited growth and killed parasites.     

A facile one-pot synthesis of 6,7,8,9-tetrahydrobenzo[4,5]thieno[2,3-d]-1,2,4-triazolo[4,5-a]pyrimidin-5-ones

Abstract  

The reaction of 2-mercapto-6,7,8,9-tetrahydro-3H-benzo[4,5]thieno[2,3-d]pyrimidin-4-one or its 2-methylthio derivative with hydrazonoyl halides, in the presence of triethylamine, yielded 6,7,8,9-tetrahydrobenzo[4,5]thieno[2,3-d]-1,2,4-triazolo[4,5-a]pyrimidin-5-ones. The structure of the latter compounds was further confirmed by reaction of 2-mercapto-6,7,8,9-tetrahydro-3H-benzo[4,5]thieno[2,3-d]pyrimidin-4-one with the appropriate active chloromethylenes followed by coupling of the products with benzenediazonium chloride to afford the non-isolable azo-coupling products which converted, in situ, to 6,7,8,9-tetrahydrobenzo[4,5]thieno[2,3-d]-1,2,4-triazolo[4,5-a]pyrimidin-5-ones. The reaction mechanism was proposed and the products were screened for their biological activity. Some of the newly synthesized compounds had a moderate effect against some bacterial and fungal species.     

Isoxazolopyrimidinethione and Isoxazolopyridopyrimidinethione Derivatives: Key Intermediates for Synthesis of Novel Fused Triazoles as Potent 5α‐Reductase Inhibitors and Anti‐Prostate Cancer

The arylideneisoxazolone derivative 1 is used for preparation of two different pyrimidinethiones 3 and 5 through interaction with thiourea and thiouracil, respectively. Compounds 3 and 5 were subjected to reaction with different hydrazonyl halides in basic medium to afford different triazolopyrimidines 9a , 9b , 9c , 9d , 9e , 9f , 9g , 9h and 13a , 13b , 13c , 13d , 13e , 13f , the structures were confirmed by their spectral and elemental analysis. All the newly synthesized products were screened against 5α‐reductase. Some of the newly synthesized compounds showed potent 5α‐reductase inhibition activities with good ED₅₀.     

A convenient ultrasound-promoted synthesis of some new thiazole derivatives bearing a coumarin nucleus and their cytotoxic activity

Successful implementation of ultrasound irradiation for the rapid synthesis of a novel series of 3-[1-(4-substituted-5-(aryldiazenyl)thiazol-2-yl)hydrazono)ethyl]-2H-chromen-2-ones 5a-h, via reactions of 2-(1-(2-oxo-2H-chromen-3-yl)ethylidene) thiosemicarbazide (2) and the hydrazonoyl halides 3(4), was demonstrated. Also, a new series of 5-arylidene-2-(2-(1-(2-oxo-2H-chromen-3-yl)ethylidene)hydrazinyl)thiazol-4(5H)-ones 10a-d were synthesized from reaction of 2 with chloroacetic acid and different aldehydes. Moreover, reaction of 2-cyano-N'-(1-(2-oxo-2H-chromen-3-yl)ethylidene)-acetohydrazide (12) with substituted benzaldehydes gave the respective arylidene derivatives 13a-c under the conditions employed. The structures of the synthesized compounds were assigned based on elemental analyses and spectral data. Also, the cytototoxic activities of the thiazole derivative 5a was evaluated against HaCaT cells (human keratinocytes). It was found that compound 5a possess potent cytotoxic activity.     

Solid state studies of drugs and chemicals by dielectric and calorimetric analysis

Novel dielectric behavior of a linear increase in ionic conductivity prior to melt temperature was observed for active pharmaceutical ingredients (APIs), organic chemicals, amino acids, and carbohydrates. Though, there are solids like polyolefins and long chain organic compounds (tetracosane, pentacosane) which do not exhibit this premelt behavior (i.e., the temperature where the onset of increase in ionic conductivity to melt temperature). We have discovered novel electrical conductivity properties and other physical analytical variations which can lead to unique synthetic routes of certain chemical entities. The above-mentioned unique variations are not related to solid–solid transitions which are quite often observed in pharmaceutical crystalline solids. These new properties are related to amorphous crystalline behavior of a solid. We have also studied the effect of various experimental variables: such as amount of mass tested, applied frequency at a given electric field and heating rate, which results in varying the onset temperature of the increase in ionic conductivity. Melting of the solids was correlated using differential scanning calorimetry (DSC). Activation energies for all the solids were measured in the premelt region using an Arrhenius plot at a specific frequency since we observed changes in the conductivity with frequency. This study focused on frequencies 0.1 to 10 Hz, since the conductivity at these frequencies related to surface analysis. This new physical properties are leading to new electro synthetic procedures to modify or prepare chemicals.