Quasicrystal Ising chain and automata theory

An automatic sequence is generated by a finite machine (automaton). These sequences can be periodic or not: in the latter case however, they are not random, but rather quasicrystalline. We consider an Ising chain with variable interaction in a uniform external field, at zero temperature, and prove that, if this interaction is automatic, then the induced magnetic field is also automatic.     

HPLC/UV analysis of proteins in dairy products using a hydrophobic interaction chromatographic column.

High-performance liquid chromatography using a Chrompack P-300-RP column containing a polystyrene-divinylbenzene copolymer-based packing was examined to analyze bovine milk protein components. The separation of major raw-milk proteins could be performed rapidly and reliably with this HPLC/UV method. The determinations were performed in the linear ranges of 0.01-2.0 mg/ml for alpha-lactalbumin, 0.04-2.5 mg/ml for caseins and 0.02-2.0 mg/ml for beta-lactoglobulin. The validity of the method was verified. Since the chromatographic column enabled the quantification of only "native" milk proteins, the extent of denaturation and loss of milk proteins could be examined. Thus, evaluation of heat-induced proteins denaturation was carried out in raw milk heated for 5 min at pre-determined temperatures.     

Determination of anisotropic optical constants and surface coverage of molecular films using polarized visible ATR spectroscopy. Application to adsorbed cytochrome c films

This article describes a method to determine the anisotropic optical constants and surface coverage of molecular films using polarized attenuated total reflectance (ATR) absorbance measurements. We have extended the transfer-matrix formalism to describe birefringent and dichroic films in ATR geometries and have combined it with an iterative numerical procedure to determine the anisotropic values of both the real (n) and imaginary (k) parts of the complex refractive index of the film under investigation. Anisotropic values of the imaginary part of the refractive index (k) allow for the determination of the surface coverage and one order parameter of the film. To illustrate this approach, we have used cytochrome c (cyt c) protein films adsorbed to glass and indium tin oxide (ITO) surfaces. Experimental results show that cyt c films on these surfaces, which were formed under identical conditions, have significant differences in their surface coverages (11.2 +/- 0.4 pmol/cm(2) on glass and 21.7 +/- 0.9 pmol/cm(2) on ITO); however, their order parameters are similar (0.30 +/- 0.02 on glass and 0.36 +/- 0.04 on ITO).     

The shielding effect of glycerol against protein ionization in electrospray mass spectrometry

Most commercial recombinant proteins used as molecular biology tools, as well as many academically made preparations, are generally maintained in the presence of high glycerol concentrations after purification to maintain their biological activity. The present study shows that larger proteins containing high concentrations of glycerol are not amenable to analysis using conventional electrospray ionization mass spectrometry (ESI-MS) interfaces. In this investigation the presence of 25% (v/v) glycerol suppressed the signals of Taq DNA polymerase molecules, while 1% (v/v) glycerol suppressed the signal of horse heart myoglobin. The signal suppression was probably caused by the interaction of glycerol molecules with the proteins to create a shielding effect that prevents the ionization of the basic and/or acidic groups in the amino acid side chains. To overcome this difficulty the glycerol concentration was decreased to 5% (v/v) by dialyzing the Taq polymerase solution against water, and the cone voltage in the ESI triple-quadrupole mass spectrometer was set at 80-130 V. This permitted observation of a mass spectrum that contained ions corresponding to protonation of up to 50% of the ionizable basic groups. In the absence of glycerol up to 85% of the basic groups of Taq polymerase became ionized, as observed in the mass spectrum at relatively low cone voltages. An explanation of these and other observations is proposed, based on strong interactions between the protein molecules and glycerol. For purposes of comparison similar experiments were performed on myoglobin, a small protein with 21 basic groups, whose ionization was apparently suppressed in the presence of 1% (v/v) glycerol, since no mass spectrum could be obtained even at high cone voltages.     

Formal fusion of a pyrrole ring onto 2-pyridyl and 2-pyrimidyl cations: one-step gas-phase synthesis of indolizine and its derivatives

Two ortho-hetarynium ions, the 2-pyridyl and 2-pyrimidyl cations, react promptly with 1,3-dienes in the gas phase by annulation, formally by fusion, onto the ions of a pyrrole ring. This novel reaction proceeds through an initial polar [4 + 2+] cycloaddition across the C[triple bond]N+ bond, followed by fast ring opening, a [1,4-H] shift, and finally a recyclization that results in a contraction of a six- to a five-membered ring and dissociation by the loss of a methyl radical. For the 2-pyridyl cation, this reaction yields ionized indolizines (pyrrolo[1,2-a]pyridines), while for the 2-pyrimidyl cation, it gives ionized pyrrolo[1,2-a]pyrimidines. The annulation reaction, performed in the rf-only collision quadrupole of a pentaquadrupole (QqQqQ) mass spectrometer, occurs readily with both 1,3-butadiene and isoprene, and is thermodynamically and kinetically favored as predicted by ab initio calculations. Ortho-hetarynium ions and 1,3-dienes provide, therefore, the two building blocks for the efficient one-step gas-phase synthesis of ionized bicyclic pyrrolo[1,2-a]pyridine (indolizine) and pyrrolo[1,2-a]pyrimidine, as well as their analogues and derivatives.     

Synthesis and electrochemical studies of η-monocyclopentadienylruthenium(II) complexes with substituted thiophene nitrile ligands. Crystal structure of [Ru(η-C5H5)(dppe)(NC{SC4H2}2NO2)][PF6]

A systematic series of η⁵-monocyclopentadienylruthenium(II) complexes with substituted thiophene nitrile ligands of general formula [Ru(η⁵-C₅H₅)(P_P)(NC{SC₄H₂}_nNO₂)][PF₆] (P_P = dppe, (+)-diop; n = 1-3) has been synthesized and characterized. Spectroscopic and electrochemical data were used in order to get an insight on the molecular nonlinear optical properties of these complexes when compared to those found for the reported thiophene iron(II) and p-benzonitrile or 1,2-di-(2-thienyl)-ethene derived iron(II)/ruthenium(II) related complexes. The compound [Ru(η⁵-C₅H₅)(dppe)(NC{SC₄H₂}₂NO₂)][PF₆] was also characterized by X-ray diffraction. The solid state nonlinear optical properties of the chiral compounds were also evaluated by Kurtz powder technique with a Nd:YAG laser emitting at 1064 nm.     

Electrochemical Detection of Guanine‐methylation Using Glassy Carbon Electrode

This work presents a study of the electrochemical oxidation of 7‐methylguanine (7‐mGua) in aqueous solution at glassy carbon electrode by cyclic voltammetry, differential pulse voltammetry, square wave voltammetry and electrochemical impedance spectrometry. The anodic behaviour of 7‐mGua was compared with the electro‐oxidation of guanine and 7‐methylguanosine. The results demonstrated that the methyl and ribose groups are not electroactive but strongly influence the oxidation mechanism of these species. The oxidation of 7‐mGua occurred in a single pH‐dependent step, with the withdrawal of two electrons and two protons of C8, to form 8‐oxo‐7‐methylguanine, while the electro‐oxidation of 7‐methylguanosine also occurred in a single pH‐dependent step, however, with the withdrawal of one electron and one proton of C8 to form a hydroxylated product, since its oxidation to 8‐oxo‐7‐methylguanosine is hindered by the presence of the pendant groups. In addition, the oxidation of 7‐mGua was investigated in the presence of DNA and DNA‐bases, leading to the conclusion that the formation of 7‐mGua, from an interaction of DNA with an alkylating agent, would cause an increase on the deoxyguanosine peak current of the DNA‐biosensor, with no interference of any free DNA bases, which demonstrated that DNA‐electrochemical biosensors find application on detecting DNA methylation, opening a new avenue for applications of DNA biosensors.     

Atom-Economic Synthesis of Functionalized Octahydroacridines from Citronellal or 3-(Phenylthio)-citronellal

Here we present a simple, solvent-free, one-pot, hetero-Diels–Alder reaction of (R)-citronellal or 3-(phenylthio)-citronellal with arylamines using solid-supported catalyst (SiO₂/ZnCl₂). This general, efficient, and improved method is selective, affording preferentially new trans-fused 3-(phenylthio)-octahydroacridines (S-OHAs) in good yields. The use of microwave irradiation facilitates the procedure and accelerates the reaction.