Rapid detection of a foreign protein in milk using IMS–SERS

A method for rapid detection of foreign protein contamination in complex food matrices is critically needed. Here we present a novel method that combines immunomagnetic separation (IMS) and surface‐enhanced Raman scattering (SERS) to detect ovalbumin (OVA), an egg white protein, added into whole milk. IMS was used to specifically capture the OVA out of the milk. Then SERS was applied to analyze the IMS eluate using silver dendrites as the substrate. Two SERS sample preparation methods, namely solution based and substrate based, were used to prepare the IMS eluate for SERS analysis. Results show both methods were able to detect 1 µg OVA in 1 ml milk (1 part per million). Based on the results of principal component analysis and partial least‐squares analysis, solution SERS was more capable of quantitative analysis, while substrate SERS was more sensitive for qualitative analysis. The total analytical time for IMS–SERS was less than 20 min, which satisfied the requirement of rapid detection in a milk processing facility. Copyright © 2011 John Wiley & Sons, Ltd.     

Deprotonated and non-deprotonated cobalt(II) complexes of the bis-amide tetradentate ligand N,N′-(dipicolyl)-1,8-naphthylene diamine. Three different modes of coordination by the ligand

The preparation and some properties of the cobalt(II) complexes Co(LH₂)Cl₂·2H₂O, Co(LH₂(NCS)₂ and CoL·H₂O (whereLH₂=N,N-(dipicolyl)-1,8-naphthylenediamine) are reported. On the basis of magnetic moments, visible reflectance and IR data, the structure is proposed to be pseudo-octahedral for Co(LH₂)Cl₂·2 H₂O, pseudo-tetrahedral for Co(LH₂)(NCS)₂ and square planar for CoL·H₂O.

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Deprotonierte und Nicht-deprotonierte Co(II)-Komplexe des vierzähnigen Bisamid-Liganden N,N-(Dipicolyl)-1,8-naphthyldiamin. Drei verschiedene Koordinationstypen

Zusammenfassung Es werden die Darstellung und einige Eigenschaften der Kobalt(II)-Komplexe Co(LH₂)Cl₂·2 H₂O, Co(LH₂)(NCS)₂ und CoL·H₂O [LH₂=N,N-(dipicolyl)-1,8-naphthylendiamin] diskutiert. Auf der Grundlage von magnetischen Momenten, von Daten der sichtbaren Reflektions-und IR-Spektren wird eine pseudooctaedrische Struktur für Co(LH₂)Cl₂·2H₂O, eine pseudotetraedrische für Co(LH₂)(NCS)₂ und eine planar-quadratische für CoL·H₂O vorgeschlagen.

     

The -theory of the computably enumerable Turing degrees is undecidable

We show the undecidability of the -theory of the partial order of computably enumerable Turing degrees.

     

Early aggregation in prion peptide nanostructures investigated by nonlinear and ultrafast time-resolved fluorescence spectroscopy

We report the characterization of early aggregates in the self-assembly of prion peptides using nonlinear and ultrafast time-resolved fluorescence spectroscopy. The dye-labeled peptide and dye/peptide guest-host systems were used to demonstrate the feasibility of the new approach. By measuring the two-photon absorption cross-section, small aggregates of the dye labeled peptide were characterized. Ultrafast time-resolved fluorescence anisotropy spectroscopy reveals the packing state (microenvironment) of the probes to be tightly associated with aggregates and associated with aggregation progression of the peptides. Fluorescence intensity decay shows a correlation with growth of aggregates having a high level of structured beta-sheet content. A new binding ligand Cascade Yellow shows promise for beta-sheet recognition of prion peptide nanostructures. These findings may have implications for in vivo studies of neurotoxic aggregates targeting with fluorescence markers. Also, these results may provide insight into molecular design of peptide-based nanomaterials.     

Intramolecular carbozincation of unactivated alkenes occurs through a zinc radical transfer mechanism

The cyclizations of a number of terminally unsaturated alkenyl zinc iodides to cyclopentylmethylzinc iodides, formerly believed to be nonradical in nature, have been revealed as radical chain cyclizations initiated by adventitious oxygen. Five cases are presented in which the published carbozincation cis/trans selectivities are essentially the same as those found for the cyclizations of the unsaturated alkyl iodide precursors of the alkylzinc iodides by the iodine atom transfer method at approximately the same temperatures. In addition, it has been found that one of the organozinc cyclizations does not occur in a system in which oxygen has been rigorously excluded. The combined findings strongly suggest that these organozinc cyclizations occur by a zinc radical transfer mechanism rather than by a conventional carbometallation that is thought to occur with the analogous organolithium and organomagnesium cyclizations.     

Studies in the Total Synthesis of Himastatin: A Revision of the Stereochemical Assignment

A stereoisomer of the natural product and not himastatin, an unusual dimeric depsipeptide with promising antibiotic and antitumor properties, was obtained from pyrroloindoline anti-cis- 1 . This result led to a revision of the proposed stereostructure. The new stereostructure was confirmed by the total synthesis, which involves stereoselective access to the pyrroloindoline syn-cis- 1 and the 5-hydroxypiperazic acid subunit and features a Stille coupling for the formation of the central carbon–carbon bond.     

A nonlinear multi-classification knowledge-based kernel machine

This paper presents a knowledge-based nonlinear kernel classification model for multi-category discrimination of sets or objects with prior knowledge. A kernel function is employed to find a nonlinear classifier capable of discriminating future points into an appropriate class. The prior knowledge is in the form of multiple polyhedral sets belonging to one or more categories or classes, and it is introduced as additional constraints into the formulation of the regularized nonlinear kernel least squares multi-class support vector machine model. The resulting formulation leads to a linear system of equations that can be solved using matrix methods or iterative methods. This work extends previous work (Oladunni et al. in ICCS 2006, Lecture notes in Computer Science, Part I, LNCS, vol 3991. Springer, Berlin, pp 188–195, 2006) that incorporated similar prior knowledge into a regularized linear least squares multi-class model. To evaluate the model, data and prior knowledge from the two-phase flow regimes in pipes were used to train and test the proposed formulation.     

Dialogue on mathematics education: two points of view on the state of the art

On many fronts, the field of mathematics education does not speak with a single voice. There appears to be no firm consensus regarding the scientific character of mathematics education, the research methodologies it deems legitimate, the kinds of questions it addresses, the appropriate preparation for its practitioners, and its relationship with other disciplines, including, ironically, mathematics itself. Our field seems to be going through a new phase of self-definition, a crisis from which we shall have to decide who we are and what direction we are going. The authors of the present paper themselves tend towards different positions on these questions. The paper, then, takes the form of a letter in which one of us raises issues about the current state of mathematics education and the other responds. We see this as an attempt to initiate a dialogue on our field, which we consider urgently needed.