Polyelectrolyte complexes. VI. Polycation structure,polyanion molar mass,and polyion concentration effects on complex nanoparticles based on poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate)

The formation and characterization of some interpolyelectrolyte complex (IPEC) nanoparticles based on poly(sodium 2‐acrylamido‐2‐methylpropanesulfonate) (NaPAMPS), as a function of the polycation structure, polyanion molar mass, and polyion concentration, were followed in this work. Poly(diallyldimethylammonium chloride) and two polycations (PCs) containing (N,N‐dimethyl‐2‐hydroxypropyleneammonium chloride) units in the backbone (PCA₅ and PCA₅D₁) were used as starting polyions. The complex stoichiometry, (n^?/n⁺)_iso, was pointed out by optical density at 500 nm (OD₅₀₀), polyelectrolyte titration, and dynamic light scattering. IPEC nanoparticle sizes were influenced by the polycation structure and polyanion molar mass only before the complex stoichiometry, which was higher for the more hydrophilic polycations (PCA₅ and PCA₅D₁) and for a higher NaPAMPS molar mass, and were almost independent of these factors after that, at a flow rate of the added polyion of about 0.28 mL × (mL PC)^?1 × h^?1. The IPEC nanoparticle sizes remained almost constant for more than 2 weeks, both before and after the complex stoichiometry, at low concentrations of polyions. NIPECs as stable colloidal dispersions with positive charges in excess were prepared at a ratio between charges (n^?/n⁺) of 0.7, and their storage colloidal stability, as a function of the polycation structure and polyion concentration (from 0.8 to ca. 7.8 mmol/L), was demonstrated. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2495–2505, 2004     

Reactivity of DNA guanyl radicals with phenolate anions

Guanine bases are the most easily oxidized sites in DNA. Electron-deficient guanine species are major intermediates produced in DNA by the direct effect of ionizing radiation (ionization of the DNA itself) because of preferential hole migration within DNA to guanine bases. By using thiocyanate ions to modify the indirect effect (ionization of the solvent), we are able to produce these single-electron-oxidized guanine radical species in dilute aqueous solutions of plasmid DNA where the direct effect is negligible. The guanyl radical species produce stable modified guanine products. They can be detected in the plasmid by converting them to strand breaks after incubation with a DNA repair enzyme. If a phenol is present during irradiation, the yield of modified guanines is decreased. The mechanism is reduction of the guanine radical species by the phenol. It is possible to derive a rate constant for the reaction of the phenol with the guanyl radical. The pH dependence shows that phenolate anions are more reactive than their conjugate acids, although the difference for guanyl radicals is smaller than with other single-electron-oxidizing agents. At physiological pH values, the reduction of a guanyl radical entails the transfer of a proton in addition to the electron. The relatively small dependence of the rate constant on the driving force implies that the electron cannot be transferred before the proton. These results emphasize the potential importance of acidic tyrosine residues and the intimate involvement of protons in DNA repair.     

A computer program for searching the best model for describing different experimental systems

An algorithm for searching the best polynomial analytical function for describing different experimental systems is presented. It is based

1. (1)on the generation of all possible analytical functions of a given order, with a given number of terms and with a given number of independent variables, and

2. (2)on the calculation of the parameters of all selected functions using the linear regression method.

To show the ability of the program two different examples are given:

1. (1) searching the best univariate polynomial model, and

2. (2) modelling of the stability of a two-component mixture as a function of three factors.

Field alpha-spectroscopy of radon (<Superscript>222</Superscript>Rn) and actinon (<Superscript>219</Superscript>Rn) progeny in soil gas: Locating a radon source

Summary The activities of²¹⁸Po,²¹⁴Po and²¹¹Bi were determined in samples obtained of soil/gas. Sampling work was taken in Jáchymov (Czech Republic) at the outcrop of the Geister-vein,by electrostatic precipitation from filtered soil gas on stainless steel disks.The samples were measured in a field laboratory using a semi-conductor alpha-spectrometer.The activities of²¹⁸Po,²¹⁴Po and²¹¹Bi were calculated.Samples taken from active dump material (near-by radon source) exhibited a high²¹¹Bi/²¹⁴Po ratio, while those of the vein outcrop (a relatively deeper source) had a low ratio.A mathematical model was employed to determine the radon age calculated from the actinon/radon input ratio.This varied in a range of 5.6 to -7.7 seconds.Negative age values are probably caused by the preference for actinon, which rapidly comes into equilibrium with the source of this gas.     

Die Reduktion von Ammoniumpolyuranat zu Urandioxid

Zusammenfassung Es werden die Resultate des isothermen Zerfalles und der Reduktion vonstandardisiertem Ammoniumpolyuranat im Bereich von 285 bis 463° C (in Wasserstoff) wiedergegeben. Der Zerfall zu UO₃ wurde schon bei einer Temp. unter 290° C festgestellt, diese Phase blieb jedoch darauf stabil bis 320° C. Zwischen 320° C und 380° C verläuft die Reduktion zu U₃O₈, über 380° C aber zu UO₂. Die Aktivierungsenergien bei der Reduktion von UO₃ zu U₃O₈ und von U₃O₈ zu UO₂ wurden berechnet, und zwar 32,2 kcal/g-mol und 41,7 kcal/g-mol. Die Ergebnisse können mit den Literaturangaben für die Reduktion der einzelnen Phasen UO₃ und U₃O₈ verglichen werden. Die beobachteten Unterschiede weisen auf den Einfluß der Aktivität der Präparate hin.

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The isothermal decomposition and reduction of ammonium polyuranate (ADU) was investigated in the temperature interval 285–463° C in hydrogen. The formation of UO₃ was noticed below 290° C and this product was stable up to 320° C. U₃O₈ was stable from this temperature on up to 380° C, where the reduction to UO₂ was observed. The activation energies 32,2 Kcal/mole and 41.7 Kcal/mole were calculated for the reduction of UO₃ to U₃O₈ and for the reduction of U₃O₈ to UO₂, respectively. The results are comparable with the published data on reduction of separate phases UO₃ and U₃O₈. Some differences noticed show the influence of the activities of the products.

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Mit 4 Abbildungen     

Determination of metal concentration in fat supplements for swine nutrition by atomic absorption spectroscopy

The presence of some essential and toxic metals in fat supplements for swine diet was investigated. Collected samples represented a relevant production of the Italian industry. In particular, some samples were enriched with antioxidants or waste cooking oils. The method for the determination of Ca, Cu, Cd, Fe, Mg, Mn, Ni, Pb, and Zn in fat samples was developed by means of a certified reference material (CRM 186) and a representative fatty sample (RFS). All samples were digested in closed vessels in a microwave oven and then analyzed by flame atomic absorption or graphite furnace atomic absorption spectrometry. The entire analytical method provided a satisfactory repeatability and reproducibility confirmed by agreement between the experimental recovery data obtained for the CRM 186 sample and, with the method of standard additions, for the RFS material. The samples generally showed a small amount of metals compared with the recommended daily intake for the essential elements. On the other hand, some samples contained a significant concentration, from an analytical point of view, of Cd, Ni, and Pb. Principal component analysis (PCA) was applied to inspect the experimental data obtained from samples analysis. Basically no differences were detected in terms of metal concentration among the fat supplements analyzed.     

Nucleic acid analysis using an expanded genetic alphabet to quench fluorescence

Organic chemistry has made possible the synthesis of molecules that expand on Nature's genetic alphabet. Using the previously described nonstandard DNA base pair constructed from isoguanine and 5-methylisocytosine, we report a highly specific and sensitive method that allows for the fast and specific quantitation of genetic sequences in a closed tube format. During PCR amplification, enzymatic site-specific incorporation of a quencher covalently linked to isoguanine allows for the simultaneous detection and identification of multiple targets. The specificity of method is then established by analysis of thermal denaturation or melting of the amplicons. The appropriate functions of all reactions are further verified by incorporation of an independent target into the reaction mixture. We report that the method is sensitive down to the single copy level, and specificity is demonstrated by multiplexed end-point genotypic analysis of four targets simultaneously using four separate fluorescent reporters. The method is general enough for quantitative and qualitative analysis of both RNA and DNA using previously developed primer sets. Though the method described employs the commonly used PCR, the enzymatic incorporation of reporter groups into DNA site-specifically should find broad utility throughout molecular biology.     

Styrene copolymers as pollutant adsorbents : Safe sampling volume determination

The determination of safe sampling volumes of benzene and acetone on air samplers filled with Porapak Q, Chromosorb 101, 102 and 103 is described. Two direct methods are employed; one method is based on frontal chromatography, while the second one is a concentration method followed by thermal desorption. The results are compared to those determined by the indirect pulse chromatographic method. The safe sampling volumes determined by the direct methods were in accordance. The indirect method gives slightly different values; however, this procedure is carried out at "infinite dilution". The effect of the pollutant concentration on the safe sampling volumes was also examined. The values decrease with increasing pollutant concentration.     

K18- and CAG-hACE2 Transgenic Mouse Models and SARS-CoV-2: Implications for Neurodegeneration Research

COVID-19, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a global pandemic that might lead to very serious consequences. Notably, mental status change, brain confusion, and smell and taste disorders along with neurological complaints have been reported in patients infected with SARS-CoV-2. Furthermore, human brain tissue autopsies from COVID-19 patients show the presence of SARS-CoV-2 neuroinvasion, which correlates with the manifestation of meningitis, encephalitis, leukocyte infiltration, and neuronal damage. The olfactory mucosa has been suggested as a way of entry into the brain. SARS-CoV-2 infection is also known to provoke a hyper-inflammatory reaction with an exponential increase in the production of pro-inflammatory cytokines leading to systemic responses, even in the absence of direct infection of brain cells. Angiotensin-converting enzyme 2 (ACE2), the entry receptor of SARS-CoV-2, has been extensively demonstrated to be present in the periphery, neurons, and glial cells in different brain regions. To dissect the details of neurological complications and develop therapies helping COVID-19 survivors regain pre-infection quality of life, the development of robust clinical models is highly warranted. Several human angiotensin-converting enzyme 2 (hACE2) transgenic mouse models have been developed and used for antiviral drug screening and vaccine development, as well as for better understanding of the molecular pathogenetic mechanisms of SARS-CoV-2 infection. In this review, we summarize recent results from the studies involving two such mouse models, namely K18- and CAG-hACE2 transgenics, to evaluate the direct and indirect impact of SARS-CoV-2 infection on the central nervous system.     

Casorati Inequalities for Statistical Submanifolds in Kenmotsu Statistical Manifolds of Constant ϕ-Sectional Curvature with Semi-Symmetric Metric Connection

In this paper, we prove some inequalities between intrinsic and extrinsic curvature invariants, namely the normalized δ-Casorati curvatures and the scalar curvature of statistical submanifolds in Kenmotsu statistical manifolds of constant ϕ-sectional curvature that are endowed with semi-symmetric metric connection. Furthermore, we investigate the equality cases of these inequalities. We also describe an illustrative example.