A Review on the Mechanism of Pigment Dispersion

In the quest of ensuring successful pigment dispersion, additives are used to aid dispersion and stabilization of pigment particles through attraction forces of various chemical nature including van der waals and “liquid bridge” forces as well as anchor groups with high affinity for pigment surface. On the other hand, dispersion efficiency is significantly dependent on the effectiveness of various dispersion equipment and their energy transfer, dispersion force and effectiveness. The common denominator for all this equipment are that; dispersion is achieved by shearing forces produced by the application of high positive and negative attrition. This article reviews and explores the nature and the significance of the various methods and forces in pigment dispersion and the various stabilization mechanisms adopted in producing stably fine pigment particles, dispersion application as well as future prospects.     

Antifungal activity, toxicity and chemical composition of the essential oil of Coriandrum sativum L. fruits

The aims of this study were to test the antifungal activity, toxicity and chemical composition of essential oil from C. sativum L. fruits. The essential oil, obtained by hydro-distillation, was analyzed by gas chromatography/mass spectroscopy. Linalool was the main constituent (58.22%). The oil was considered bioactive, showing an LC?? value of 23 μg/mL in the Artemia salina lethality test. The antifungal activity was evaluated against Microsporum canis and Candida spp. by the agar-well diffusion method and the minimum inhibitory concentration (MIC) and the minimum fungicidal concentration (MFC) were established by the broth microdilution method. The essential oil induced growth inhibition zones of 28 ± 5.42 and 9.25 ± 0.5 for M. canis and Candida spp. respectively. The MICs and MFCs for M. canis strains ranged from 78 to 620 and 150 to 1,250 μg/mL, and the MICs and MFCs for Candida spp strains ranged from 310 to 620 and 620 to 1,250 μg/mL, respectively. C. sativum essential oil is active in vitro against M. canis and Candida spp. demonstrating good antifungal activity.     

Substrate scope in the direct imine acylation of ortho-substituted benzoic acid derivatives: the total synthesis (±)-cavidine

The direct imine acylation (DIA) and subsequent cyclisation of a range of imines with ortho-substituted benzoic acid derivatives is described. Variation in the coupling reagents, imine and benzoic acid were all examined. The DIA procedure was also applied in the total synthesis of (±)-cavidine.     

Combined experimental and theoretical study on redox-active d8 metal dithione-dithiolato complexes showing molecular second-order nonlinear optical activity

Synthesis, characterization, NLO properties, and theoretical studies of the mixed-ligand dithiolene complexes of the nickel triad [M(II)(Bz(2)pipdt)(mnt)] (Bz(2)pipdt = 1,4-dibenzyl-piperazine-3,2-dithione, mnt = maleonitriledithiolato, M(II) = Ni, 1, Pd, 2, Pt, 3) are reported. Molecular structural characterization of 1-3 points out that four sulfur atoms are in a slightly distorted square-planar geometry. While the M-S bond distances are only slightly different, comparison of the C-C and C-S bonds in the C(2)S(2)MS(2)C(2) core allows us to point out a significant difference between the C-C and the C-S distances in Bz(2)pipdt and mnt. These findings suggest assigning a dithiolato character to mnt (pull ligand) and a dithione one (push ligand) to Bz(2)pipdt. Cyclic voltammetry of 1-3 exhibits two reversible reduction waves and a broad irreversible oxidation wave. These complexes are characterized in the visible region by a peak of moderately strong intensity, which undergoes negative solvatochromism. The molecular quadratic optical nonlinearities were determined by the EFISH technique, which provided the following values μβ(λ) (10(-48) esu) = -1436 (1), -1450 (2), and -1950 (3) converted in μβ(0) (10(-48) esu) = -463 (1), -684 (2), and -822 (3), showing that these complexes exhibit large negative second-order polarizabilities whose values depend on the metal, being highest for the Pt compound. DFT and TD-DFT calculations on 1-3 allow us to correlate geometries and electronic structures. Moreover, the first molecular hyperpolarizabilities have been calculated, and the results obtained support that the most appealing candidate as a second-order NLO chromophore is the platinum compound. This is due to (i) the most extensive mixture of the dithione/metal/dithiolato orbitals, (ii) the influence of the electric field of the solvent on the frontier orbitals that maximizes the difference in dipole moments between the excited and the ground state, and (iii) the largest oscillator strength in the platinum case vs nickel and palladium ones.     

Liquid Chromatography-Mass Spectrometry (LC-MS) Derivatization-Based Methods for the Determination of Fatty Acids in Biological Samples

Fatty acids (FAs) play pleiotropic roles in living organisms, acting as signaling molecules and gene regulators. They are present in plants and foods and may affect human health by food ingestion. As a consequence, analytical methods for their determination in biological fluids, plants and foods have attracted high interest. Undoubtedly, mass spectrometry (MS) has become an indispensable technique for the analysis of FAs. Due to the inherent poor ionization efficiency of FAs, their chemical derivatization prior to analysis is often employed. Usually, the derivatization of the FA carboxyl group aims to charge reversal, allowing detection and quantification in positive ion mode, thus, resulting in an increase in sensitivity in determination. Another approach is the derivatization of the double bond of unsaturated FAs, which aims to identify the double bond location. The present review summarizes the various classes of reagents developed for FA derivatization and discusses their applications in the liquid chromatography-MS (LC-MS) analysis of FAs in various matrices, including plasma and feces. In addition, applications for the determination of eicosanoids and fatty acid esters of hydroxy fatty acids (FAHFAs) are discussed.     

Synthesis of N-Substituted phosphoramidic acid esters as “reverse” fosmidomycin analogues

An efficient synthetic pathway to a series of novel “reverse” fosmidomycin analogues has been developed, commencing from substituted benzylamines. In these analogues, the fosmidomycin hydroxamate moiety is reversed and the tetrahedral methylene carbon adjacent to the phosphonate moiety is replaced by a nitrogen atom bearing different benzyl groups. The resulting phosphonate esters were designed as potential antimalarial “pro-drugs”.     

Serine/threonine-protein phosphatase 1 α levels are paralleling olfactory memory formation in the CD1 mouse

Although olfactory discrimination has already been studied in several mouse strains, data on protein levels linked to olfactory memory are limited. Wild mouse strains Mus musculus musculus, Mus musculus domesticus and CD1 laboratory outbred mice were tested in a conditioned odor preference task and trained to discriminate between two odors, Rose and Lemon, by pairing one odor with a sugar reward. Six hours following the final test, mice were sacrificed and olfactory bulbs (OB) were taken for gel-based proteomics analyses and immunoblotting. OB proteins were extracted, separated by 2-DE and quantified using specific software (Proteomweaver). Odor-trained mice showed a preference for the previously rewarded odor suggesting that conditioned odor preference occurred. In CD1 mice levels, one out of 482 protein spots was significantly increased in odor-trained mice as compared with the control group; it was in-gel digested by trypsin and chymotrypsin and analyzed by tandem mass spectrometry (nano-ESI-LC-MS/MS). The spot was unambiguously identified as serine/threonine-protein phosphatase PP1-α catalytic subunit (PP-1A) and differential levels observed in gel-based proteomic studies were verified by immunoblotting. PP-1A is a key signalling element in synaptic plasticity and memory processes and is herein shown to be paralleling olfactory discrimination representing olfactory memory.     

Electrochemical Studies of an Iron Porphyrin Immobilized on Nb2O5/SiO2 and Its Application for Simultaneous Determination of Dopamine and Ascorbic Acid Using Multivariate Calibration Methodology

This paper shows an application of a first generation porphyrin, FeTPPCl 5,10,25,20‐tetraphenylporphyrin iron(III) chloride (FeTPPCl or FeTPP⁺) immobilized on a inorganic matrix, SiO₂/Nb₂O₅ (niobium oxide grafted on silica gel surface, designated as SiNb) to the preparation of a carbon paste electrode (CPE). The carbon paste modified with a FeTPP⁺ immobilized on SiO₂/Nb₂O₅ (SiNb), designated as CPE/SiNb/FeTPP, was applied for simultaneous electrochemical determination of dopamine (DA) and ascorbic acid (AA). Because of the overlapping of the voltammetric peaks of DA and AA, the multivariate calibration methodology based on partial least square regression (PLSR) was proposed. The data pre‐treatment used in this process was mean centering and to choose the principal components number a cross validation procedure was used (leave‐one‐out). Five principal components were necessary to obtain the lowest PRESS (prediction residual error sum of squares). The statistics showed that this model explains approximately 95.2% of the variance from the data set. Using this model, high correlation between actual and predicted concentrations was observed, mainly for higher dopamine (maximum relative error of 8%) and ascorbic acid (maximum relative error of 10%) concentrations. For low analytes concentrations the relative error increases to 35% for AA. Considering the similarity of the voltammetric response of the analytes, the results obtained were satisfactory and showed the promissory capability of the CPE/SiNb/FeTPP coupled multivariate calibration methods for simultaneous voltammetric analysis of DA and AA.     

Distinguishing rate-limiting electron versus H-atom transfers in Cu2O2-mediated oxidative N-dealkylations: application of inter- versus intramolecular kinetic isotope effects

Copper-dioxygen adducts are important biological oxidants. To gain a better understanding of the underlying chemistries of such species, we report on a series of Cu2II-O2 complexes, [{CuII(MePY2)R'}2(O2)](B(C6F5)4)2 (1R') (where (MePY2)R' is a 4-pyridyl substituted bis[2-(2-(4-R'-pyridyl)ethyl]methylamine; R' = H, MeO, Me2N; Zhang, C. X.; et al. J. Am. Chem. Soc. 2003, 125, 634-635), which readily oxidize exogenous substrates. In this study, we explore the mechanism by which 1R' facilitates the oxidative N-dealkylation of para-substituted N,N-dimethylanilines (R-DMA; R = MeO, Me, H, CN). In the case of 1H, the linear free-energy correlation plot (rho = -2.1) and intramolecular deuterium kinetic isotope effect (KIEintra, using p-R-(C6H4)-N(CH3)(CD3)) profile suggest that R-DMA oxidation occurs through rate-limiting electron transfer (ET). This mechanism was further enforced by comparison of KIEintra versus the intermolecular KIE (KIEinter, using p-R-(C6H4)-N(CH3)2 versus p-R-(C6H4)-N(CD3)2). It was found that KIEinter < KIEintra, suggesting an ET process. In the case of both 1MeO and 1Me2N, the KIEintra profile and linear free-energy correlation plots (rho = -0.49 and -0.99 for 1Me2N and 1MeO with especially poor fitting for the latter) are inconclusive in distinguishing between a rate-limiting ET or hydrogen atom transfer (HAT) pathway. Comparisons of KIEinter versus KIEintra demonstrate a switch in mechanism from ET to HAT for 1Me2N and 1MeO oxidation of R-DMA as R-DMA is made less reducing. In the case of 1Me2N, MeO-DMA and Me-DMA are oxidized via a rate-limiting ET (KIEinter < KIEintra), while H-DMA and CN-DMA are oxidized through a HAT pathway (KIEinter approximately KIEintra). For 1MeO, oxidation occurs through an ET pathway for MeO-, Me-, and H-DMA (KIEinter < KIEintra), while CN-DMA is oxidized though a HAT process (KIEinter approximately KIEintra). Copper complex attributes, which may contribute to the mechanistic observations, are suggested.     

Identification of nuclear proteins that interact with platinum-modified DNA by photoaffinity labeling

Interactions between cellular proteins and cisplatin-modified DNA are important in determining the anticancer activity of the drug. To develop a general approach for identifying proteins that mediate cellular responses to cisplatin, photoreactive cisplatin analogues having a tethered benzophenone moiety were prepared and used to form the major 1,2-intrastrand platinum-DNA cross-links. Upon irradiation of the platinated DNA dissolved in a HeLa nuclear extract, the appended photolabile benzophenone group generates a highly reactive species that binds irreversibly to cellular proteins that interact with the probe. Several DNA-protein cross-linked adducts were identified that may function in the cellular processing of cisplatin-DNA adducts. Of these, PARP-1 had not previously been demonstrated directly to contact Pt-DNA cross-links in human cells.