Identification of Two New Phosphorylated Polyketides from a Brazilian Streptomyces sp. Through the Use of LC–SPE/NMR

Two new polyketide phosphate monoesters, phosdiecin A ( 1 ) and phosdiecin B ( 2 ), were isolated from a culture of the marine Streptomyces sp. SS99BA‐2 using the hyphenated technology LC–SPE/NMR. The compounds showed to be new representatives of an important class of antitumor antibiotic metabolites known as fostriecins. Their structures, including relative configuration attribution, were fully elucidated through extensive analyses of NMR and MALDI‐TOF/TOF HR‐MS data. Herein, the application of this system to isolate and identify the new compounds is described.     

Analysis of dihydropyridine calcium channel blockers using negative ion photoionization mass spectrometry

The fragmentation of dihydropyridine calcium-channel antagonists are compared by electrospray ionization (ESI) and atmospheric pressure photonization (APPI). The results demonstrate that in ESI the preferred ionization process is in positive mode, with the mass spectra of [M+H]+ showing base peak ions probably formed by loss of alcohols from carboxyl groups. Conversely, in APPI, a high intense peak is observed in negative mode due to deprotonated molecule [M-H]- after two serial 1, 2-hydride shifts leading to a rearranged deprotonated molecule [M-H]-. These ions undergo another 1,2-hydride shifts to produce a nitro-phenyl product ion of m/z 122. The APPI is also used to develop a method for the quantitation of dihydropyridines (e.g., nifedipine) in human plasma.     

Topologic distance in the Lucena network

The Lucena network (LN) is the dual of a multifractal partition of the square. We analyzethe relation between the typical topologic distance l and the number ofvertices Nof the LN. The multifractal partition has one parameter ρ which controls thegeometrical asymmetry of the multifractal. In the limit of ρ → 1 the blocks of thepartition are squared, the connections amont the blocks are short range, the LN is moreregular and the relation l ∝ √N is observed. For the limit ρ → 0 the blocks arestrongly asymmetric, long range connections appear, and the topologic distance followsl ∝(log?N)^α, a weak smallworld phenomenon. For any network size we calculate analytically the size of the minimumdistance l_min (ρ → 0) and the maximaldistance l_max (ρ → 1). The distance in theweak small world regime is calculated using the number of vertices inside a radius oflength land taking into account the network average connectivity and the exponent α.     

New Families of <Emphasis Type="Italic">n</Emphasis>-Clusters Verifying the Erdős–Faber–Lovász Conjecture

Erd?s, Faber and Lovász conjectured in 1972 that the vertices of a linear hypergraph with n edges, each of size n, can be strongly colored with n colors. It was shown by Romero and Sánchez-Arroyo that an equivalent conjecture is obtained when linear hypergraphs are replaced by n-clusters. In this paper we describe new families of EFL-compliant n-clusters; that is, those for which the conjecture holds. Moreover, we describe ways to extend some n-clusters to larger ones preserving EFL-compliance. Also, our approach allowed us to provide a new upper bound for the chromatic number of n-clusters.     

Gossypitrin,A Naturally Occurring Flavonoid,Attenuates Iron-Induced Neuronal and Mitochondrial Damage

The disruption of iron homeostasis is an important factor in the loss of mitochondrial function in neural cells, leading to neurodegeneration. Here, we assessed the protective action of gossypitrin (Gos), a naturally occurring flavonoid, on iron-induced neuronal cell damage using mouse hippocampal HT-22 cells and mitochondria isolated from rat brains. Gos was able to rescue HT22 cells from the damage induced by 100 µM Fe(II)-citrate (EC₅₀ 8.6 µM). This protection was linked to the prevention of both iron-induced mitochondrial membrane potential dissipation and ATP depletion. In isolated mitochondria, Gos (50 µM) elicited an almost complete protection against iron-induced mitochondrial swelling, the loss of mitochondrial transmembrane potential and ATP depletion. Gos also prevented Fe(II)-citrate-induced mitochondrial lipid peroxidation with an IC₅₀ value (12.45 µM) that was about nine time lower than that for the tert-butylhydroperoxide-induced oxidation. Furthermore, the flavonoid was effective in inhibiting the degradation of both 15 and 1.5 mM 2-deoxyribose. It also decreased Fe(II) concentration with time, while increasing O₂ consumption rate, and impairing the reduction of Fe(III) by ascorbate. Gos–Fe(II) complexes were detected by UV-VIS and IR spectroscopies, with an apparent Gos-iron stoichiometry of 2:1. Results suggest that Gos does not generally act as a classical antioxidant, but it directly affects iron, by maintaining it in its ferric form after stimulating Fe(II) oxidation. Metal ions would therefore be unable to participate in a Fenton-type reaction and the lipid peroxidation propagation phase. Hence, Gos could be used to treat neuronal diseases associated with iron-induced oxidative stress and mitochondrial damage.     

Gamma radiation effects on mechanical properties and morphology of a polyurethane derivate from castor oil

In this study, an adhesive of a polyurethane derivate from castor oil was irradiated with gamma radiation from a ⁶⁰Co source, at doses from 0.2 to 25 kGy. This adhesive polyurethane is considered for use in hospital furniture because it does not liberate dangerous solvents. Hardness and elastic modulus were measured by instrumented indentation with a pyramidal Berkovich indenter, using loads from 0.08–40 mN with a nanoindenter XP. The instrumented indentation hardness was 110 MPa for an untreated sample, increasing to 124 MPa after irradiation with 25 kGy, at penetration depths of about 5 μm. The increases in elastic modulus induced by radiation were less pronounced. This polyurethane is naturally cross-linked and the relative modifications in the hardness are attributed to an additional cross-linking process induced by radiation. X-ray diffraction indicates a slight increase in crystallinity. The roughness measured by atomic force microscopy increases after gamma irradiation.     

The mystery of the discolored flints. New molecules turn prehistoric lithic artifacts blue

Prehistoric artifacts turning blue in the store rooms of the Natural History Museum in Verona, Italy recently raised serious issues for heritage materials conservation. Our analytical investigation showed that the unusual discoloration process of the flint tools is caused by the surface presence of at least three previously unknown pigmenting molecules of the triphenylmetane dyes class: 6-(bis(2,2,4-trimethyl-1,2-dihydroquinolin-6-yl)methylene)-2,2,4-trimethyl-2,6-dihydroquinolinium and its hydrogenated derivatives 2,2,4-trimethyl-6-((2,2,4-trimethyl-1,2,3,4-tetrahydroquinolin-6-yl)(2,2,4-trimethyl-1,2-dihydroquinolin-6-yl)methylene)-2,6-dihydroquinolinium and 6-(bis(2,2,4-trimethyl-1,2,3,4-tetrahydroquinolin-6-yl)methylene)-2,2,4-trimethyl-2,6-dihydroquinolinium. The peculiar formation of the molecules is possibly catalyzed within the silica pore surface starting from a well-known rubber stabilizer 2,2,4-trimethyl-1,2-dihydroquinoline released by the plastic pads flooring the storing cabinets. The investigated reaction and its surprising blue product represent a case study of the application of modern materials science to conservation and a serious warning towards the unpredictable challenges faced in the preservation of our cultural heritage.