Controlled vesicle self-assembly in microfluidic channels with hydrodynamic focusing

Traditional liposome preparation methods are based on mixing of bulk phases, leading to inhomogeneous chemical and/or mechanical conditions during formation; hence liposomes are often polydisperse in size and lamellarity. Here we show the formation of liposomes that encapsulate reagents in a continuous two-phase flow microfluidic network with precision control of size from 100 to 300 nm by manipulation of liquid flow rates. We demonstrate that by creating a solvent-aqueous interfacial region in a microfluidic format that is homogeneous and controllable on the length scale of a liposome, we can facilitate the fine control of liposome size and polydispersity.     

Mittlere ringe-XIII Die intramolekulare acylierung der ω-(1-naphthyl)-fettsäuren

The intramolecular Friedel-Crafts cyclisation of ω-arylalkanoic acids, which is in the benzene series a valuable synthetic route to bicyclic ketones with medium-sized and large rings, has been investigated with ω-(1-naphthyl)alkanoyl chlorides. The lower members, including naphthyl-caproic acid, close the ring at position 2 to form IV. The higher homologous acids show a preference for annellation at 7, making available a new type of heteronuclear naphthalene cyclic ketones (VII). During cyclisation of ω-(1-naphthyl) decanoic acid, the 1,4 ring closure competes with the 1,7 type.

Steric hindrance of resonance as a consequence of “medium ring torsion” was studied in different classes of naphthocyclenones.     

The stereochemistry of quaternary N-methyl sparteinium cations, their derivatives, stereoisomers and analogues : Part II. Molecular and crystal structure, and IR spectra of methiodide and methperchlorate of 2-oxosparteine

The crystal and molecular structures of two quarternary salts of 2-oxosparteine (II), the methiodide (IICH⁺₃ • I⁻) and the methperchlorate (IICH⁺₃ • ClO⁻₄) have been determined on the basis of X-ray and IR data. The studies were performed by analogy to previously investigated quaternary salts of sparteine (I), the methiodide (ICH⁺₃ • I⁻) and the methperchlorate (ICH⁺₃ • ClO⁻₄). As expected, the configurations and conformations of cationic parts within the two pairs of quaternary salts are identical, except for the structure of their A/B fragments, which in ICH⁺₃ cations have the character of tertiary amines, but in IICH⁺₃ that of lactams.

On the basis of accumulated X-ray and IR data the similarities and differences in the modes of interaction of perchlorate and iodide anions with quaternary cations, and especially with their N⁺---CH₃ groups are discussed. In this discussion are also included the methiodide and methperchlorate of -isosparteine: IIICH⁺₃ • X⁻ (X⁻ = I⁻ or ClO⁻₄) where N⁺---CH₃ groups are cisoidally oriented to the basic nitrogen atoms. The most interesting observations are as follows: (i) When N⁺---CH₃ groups are easily accessible for direct quasi hydrogen bonding interactions with counter anions and when other positive charged groups, for instance lactam groups, are absent in quaternary cations, perchlorate anions interact more strongly than the iodide anions and in consequence introduce conformational changes into the ring with N⁺---CH₃ group as well as into further rings. (ii) Perchlorate and iodide anions interact with N⁺---CH₃ groups similarly and very weakly if at all, when the N⁺---CH₃ groups are for steric reasons inaccessible to counter anions or when in quaternary cations there are additional groups which attract the counter anions electrostatically. The last mechanism operates in both quaternary salts of 2-oxosparteine and this is the reason why their monocrystals are isosteric and IR spectra almost identical. (iii) The sterically hindered N⁺---CD₃ groups in both IIICD⁺₃ • X⁻ salts give rise in their IR spectra to two doubles of sharp, well resolved bands which indicate the presence of two different rotamers stabilized by two modes of weak intramolecular hydrogen bonds with basic N atoms. (iv) In IIICH⁺₃ • X⁻ and IIICD⁺₃ • X⁻ salts the perchlorate and iodide anions do not interact at all with the rotating and vibrating N⁺---CH₃ (N⁺---CD₃) group but the structures of these salts are not isosteric since the perchlorate anions interact more strongly than iodide anions with the A/B fragment of the IIICH⁺₃ cations. This is visible from the shapes and intensities of the so-called “trans” band in the IR spectra of both salts.     

Microchemical techniques as applied to radiochemistry

Microchimica Acta - The techniques for investigating the chemistry of radioactive elements usingμg quantities of material are described. These include methods of transfer and carrying out...     

A novel sensitized chemiluminescence: Infrared emissions from thiazine dyes sensitized by singlet oxygen

An unusual infrared chemiluminescence emission (8130Å) of methylene blue, and other thiazine dyes, sensitized by singlet molecular oxygen is reported. This chemiluminescence does not correspond to the ordinary fluorescence of the dye and cannot be explained by previously proposed mechanisms for singlet oxygen sensitized emissions of dyes. From energetic considerations singlet molecular oxygen in its ¹Σ_g⁺ state is postulated as the sensitizing agent for the thiazine dye chemiluminescences. Schemes in which ¹Σ_g⁺ oxygen transfers electronic excitation energy (a) to the lowest triplet state of the dye, (b) to a combined multiplicity state of the lowest triplet state of the dye, and triplet molecular oxygen, or (c) to a charge-transfer state between the dye and oxygen, are compared. The chemiluminescence of methylene blue in aqueous solution may be used as a luminescent probe for ¹Σ_g⁺ oxygen.     

High-tech breakthrough DNA scanner for reading sequence and detecting gene mutation

The 17″×14″ X-ray film, gels, and blots are widely used in DNA research. However, DNA laser scanners are costly and unaffordable for the majority of surveyed biotech scientists who need it. The high-tech breakthrough analytical personal scanner (PS) presented in this report is an inexpensive 1 lb hand-held scanner priced at 2–4% of the bulky and costly 30–95 lb conventional laser scanners. This PS scanner is affordable from an operation budget and biotechnologists, who originate most science breakthroughs, can acquire it to enhance their speed, accuracy, and productivity. Compared to conventional laser scanners that are currently available only through hard-to-get capital-equipment budgets, the new PS scanner offers improved spatial resolution of 20 μm, higher speed (scan up to 17″×14″ molecular X-ray film in 48 s), 1–32,768 gray levels (16-bits), student routines, versatility, and, most important affordability. Its programs image the film, read DNA sequences automatically, and detect gene mutation. In parallel to the wide laboratory use of PC computers instead of mainframes, this PS scanner might become an integral part of a PC-PS powerful and cost-effective system where the PS performs the digital imaging and the PC acts on the data.     

Sharpness of the phase transition in percolation models

The equality of two critical points — the percolation thresholdp _H and the pointp _T where the cluster size distribution ceases to decay exponentially — is proven for all translation invariant independent percolation models on homogeneousd-dimensional lattices (d1). The analysis is based on a pair of new nonlinear partial differential inequalities for an order parameterM(,h), which forh=0 reduces to the percolation densityP — at the bond densityp=1–e ^– in the single parameter case. These are: (1)MhM/h+M ²+MM/, and (2) M/|J|MM/h. Inequality (1) is intriguing in that its derivation provides yet another hint of a ³ structure in percolation models. Moreover, through the elimination of one of its derivatives, (1) yields a pair of ordinary differential inequalities which provide information on the critical exponents and . One of these resembles an Ising model inequality of Fröhlich and Sokal and yields the mean field bound 2, and the other implies the result of Chayes and Chayes that . An inequality identical to (2) is known for Ising models, where it provides the basis for Newman's universal relation and for certain extrapolation principles, which are now made applicable also to independent percolation. These results apply to both finite and long range models, with or without orientation, and extend to periodic and weakly inhomogeneous systems.Research supported in part by the NSF Grant PHY-8605164Also in the Physics Department