Quantum dots-based reverse phase protein microarray

CdSe nanocrystals, also called quantum dots (Qdots) are a novel class of fluorophores, which have a diameter of a few nanometers and possess high quantum yield, tunable emission wavelength and photostability. They are an attractive alternative to conventional fluorescent dyes. Quantum dots can be silanized to be soluble in aqueous solution under biological conditions, and thus be used in bio-detection. In this study, we established a novel Qdot-based technology platform that can perform accurate and reproducible quantification of protein concentration in a crude cell lysate background. Protein lysates have been spiked with a target protein, and a dilution series of the cell lysate with a dynamic range of three orders of magnitude has been used for this proof-of-concept study. The dilution series has been spotted in microarray format, and protein detection has been achieved with a sensitivity that is at least comparable to standard commercial assays, which are based on horseradish peroxidase (HRP)-catalyzed diaminobenzidine (DAB) chromogenesis. The data obtained through the Qdot method has shown a close linear correlation between relative fluorescence unit and relative protein concentration. The Qdot results are in almost complete agreement with data we obtained with the well-established HRP-DAB colorimetric array (R² = 0.986). This suggests that Qdots can be used for protein quantification in microarray format, using the platform presented here.     

Novel electrophoresis mechanism based on synchronous alternating drag perturbation

We present a novel means of transporting molecules in solution by applying a zero-time-average alternating motive force to the molecules, and perturbing the molecular drag coefficient synchronously with the applied force, thus causing a net drift in a direction determined by the phase of the alternating drag perturbation relative to the alternating force. We apply an electrophoretic form of the method to transport and concentrate DNA in a gel, such that all molecules migrate on average away from the nearest electrode and toward a central region. Since an electrode does not occupy this central region, this method presents the possibility of transporting and focusing DNA and other charged molecules in regions free from electrodes and the associated electrochemistry.     

A cyclic hexapeptide comprising alternating alpha-aminoxy and alpha-amino acids is a selective chloride ion receptor

In nonpolar solvents, the cyclic hexapeptide 2, which comprises alternating D-alpha-amino and D-alpha-aminoxy acids, adopts a C3-symmetric conformation with alternating eight (N--O turns)- and seven (gamma turns)-membered-ring hydrogen bonds. A series of anion-binding studies has suggested that 2 can function as an effective anion receptor that not only displays a high selectivity for chloride ions, but also the capability to extract chloride ions from aqueous solutions into organic phases.     

Mass spectrometric studies of the formation and reactivity of trans-[PtCl2(Am)(piperidinopiperidine)] x HCl complexes with ubiquitin

trans-[PtCl2(Am)(pip-pip)] x HCl complexes, where Am = ammine, methylamine and dimethylamine, react with ubiquitin to form 1:1 covalent adducts. The platinum complexes bind exclusively to Met1 of ubiquitin forming trans-[PtCl(S-Met1-Ub)(Am)(pip-pip)] adducts. These adducts are reactive towards nucleophiles and react with deoxyguanosine (dGMP) to form the ternary trans-[Pt(dGMP)(S-Met1-Ub) (Am)(pip-pip)] complex which is stable in water and even in the presence of excess glutathione (GSH). Reaction of trans-[PtCl(S-Met1-Ub)(Am)(pip-pip)] with GSH resulted in the rapid formation of the ternary complex trans-[Pt(GS)(S-Met1-Ub)(Am)(pip-pip)] which was not stable and slowly lost the platinum moiety; after 7 days the platinum moiety was completely removed and the native ubiquitin was regenerated.     

Liquid-core capsules via interfacial polymerization: a free-radical analogy of the nylon rope trick

Liquid-core capsules have wide-ranging applications in the high-efficiency encapsulation and controlled release of drugs, dyes, enzymes, and other substrates. Their great utility has driven the rapid development of various preparation techniques. However, there remains no convenient technique for the preparation of submicrometer liquid-core capsules with shell thicknesses less than 100 nm. Here, we demonstrate a new interfacial free-radical polymerization approach for the straightforward preparation of liquid-core polymer capsules. Conceptually, this interfacial free-radical polymerization is analogous to the classical "nylon rope trick" wherein hydrophobic and hydrophilic monomers alternately copolymerize to constrain the polymerization at interfaces, but its free-radical mechanism allows precise control of initiation, which makes it possible to finely disperse the immiscible phases prior to polymerization.     

Processable stabilizer-free polyaniline nanofiber aqueous colloids

Aqueous polyaniline colloids can be readily prepared by purifying polyaniline nanofibers and controlling the pH and self-stabilized via electrostatic repulsions without the need for any chemical modification or steric stabilizer, thus providing a simple and environmentally friendly way to process the conducting polymer in its conductive state both in bulk and at the nanometre level.     

A simple proof of a theorem by Uhlenbeck and Yau

A subbundle of a Hermitian holomorphic vector bundle (E, h) can be metrically and differentially defined by the orthogonal projection onto itself. A weakly holomorphic subbundle of (E, h) is, by definition, an orthogonal projection π lying in the Sobolev space L²₁ of L² sections of End E with L² first order derivatives in the sense of distributions, which satisfies furthermore (Id−π)∘D′′π=0. A weakly holomorphic subbundle of (E, h) is shown to define a coherent subsheaf of (E), and implicitly a holomorphic subbundle of E in the complement of an analytic subset of codimension ≥2. This result provided the key technical argument to the proof given by Uhlenbeck and Yau for the Kobayashi-Hitchin correspondence on compact Kähler manifolds. We give here a much simpler proof based on current theory. The idea is to construct local meromorphic sections of Im π which locally span the fibers. We first make this construction on one-dimensional submanifolds of X and subsequently extend it by means of a Hartogs-type theorem of Shiffman’s.     

Karl Fischer-Reagentien ohne Pyridin

Zusammenfassung Karl Fischer-Reagentien, die SO₂ und Amin im üblichen Molverhältnis 12 enthalten, können nur mit Pyridin hergestellt werden. Stark basische Amine bewirken eine rasche Zersetzung der Reagenslösung und einen instabilen Endpunkt. Erhöht man den SO₂-Anteil soweit, daß das Molverhältnis SO₂Amin mindestens 11 ist, geben auch stark basische Amine hervorragende KF-Reagentien. Sie zeichnen sich durch stabile Endpunkte und hohe Reaktionsgeschwindigkeit aus. Besonders vorteilhaft ist die Anwendung als Zweikomponentenreagens, da beide Komponenten absolut lagerstabil und titerkonstant sind.

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Karl Fischer Reagents without pyridine

Summary Karl Fischer-Reagents containing SO₂ and amine in the normally applied molar ratio of 12 can be prepared only by using pyridine. Strong basic amines lead to a rapid decomposition of the reagent solution and to an instable endpoint. By raising the SO₂-content to a molar ratio SO₂amine of 11, even strong basic amines can be applied yielding KF-reagents of superior quality. They are characterized by stable endpoints and a high speed of reaction. Application as a two-solution reagent gives an additional advantage, because the single components are absolutely stable for storage and the titre remains constant.