Direct coating of quantum dots with silica shell

This paper describes a method for direct coating of fluorescent semiconductor nanoparticles with silica shell. The fluorescent semiconductor nanoparticles used were CdSe _x Te_1–x nanoparticles coated with ZnS and succeedingly surface-modified with carboxyl groups, or quantum dots (Q-dots). The Q-dots were silica-coated by performing sol–gel reaction of tetraethyl orthosilicate (TEOS) using NaOH as a catalyst in the presence of the Q-dots. Quasi-perfect Q-dots/silica core-shell particles were formed at 5.0 M H₂O and 4.0 × 10⁻⁴ M NaOH. Under these concentrations of H₂O and NaOH, the particle size of Q-dots/silica particles could be varied from 20.1 to 38.1 nm as the TEOS concentration increased from 2.5 × 10⁻⁴ to 50 × 10⁻⁴ M. The Q-dots/silica particles showed fluorescence as well as the uncoated Q-dots.     

Synthesis of procyanidins by stepwise- and self-condensation using 3,4-cis-4-acetoxy-3-O-acetyl-4-dehydro-5,7,3′,4′-tetra-O-benzyl-(+)-catechin and (−)-epicatechin as a key building monomer

3,4-cis-4-Acetoxy-3-O-acetyl-4-dehydro-5,7,3′,4′-tetra-O-benzyl-(+)-catechin (1a) or (−)-epicatechin (1b) reacted high regio- and stereo-selectively with 1.5 equiv of the 5,7,3′,4′-tetra-O-benzyloxyflavan-3-ol (4a or 4b) in the presence of 1 equiv of TMSOTf to give the corresponding procyanidins. On the other hand, the self-condensation of 1a in the presence of a catalytic amount of B(C₆F₅)₃ afforded wide-range procyanidins from dimer to 15-mer like a biomass.     

Magnetite 3D colloidal crystals formed in the early solar system 4.6 billion years ago

Three-dimensional colloidal crystals made of ferromagnetic particles, such as magnetite (Fe(3)O(4)), cannot be synthesized in principle because of the strong attractive magnetic interaction. However, we discovered colloidal crystals composed of polyhedral magnetite nanocrystallites of uniform size in the range of a few hundred nanometers in the Tagish Lake meteorite. Those colloidal crystals were formed 4.6 billion years ago and thus are much older than natural colloidal crystals on earth, such as opals, which formed about 100 million years ago. We found that the size of each individual magnetite particle determines its morphology, which in turn plays an important role in deciding the packing structure of the colloidal crystals. We also hypothesize that each particle has a flux-closed magnetic domain structure, which reduces the interparticle magnetic force significantly.     

Synthesis of poly(dipeptide)s on the surface of functional micelle and reversed micelle

Amphiphilic active 4-dodecanoyl-2-nitrophenyl esters of dipeptide containing β-alanine ( 1 – 5 ) were prepared and their polycondensation was studied in detail. The critical micelle concentrations of the active esters 1 – 5 were determined in water by the dye method and the apparent mean aggregation number of reversed micelles formed by model compound 6 was determined by the osmotic method. The results of polycondensation can be explained by assuming that aggregations such as micelle and reversed micelle play an important role in polycondensation. The obtained new poly(dipeptide)s were examined by IR, ¹H NMR, x-ray diffraction, and circular dichroism spectra.     

The circular bacteriocins gassericin A and circularin A

Gassericin A, a bacteriocin produced by Lactobacillus gasseri LA39, shows antibacterial activity against a number of Gram-positive food-borne pathogenic bacteria. Circularin A produced by Clostridium beijerinckii ATCC25752 is active against C. tyrobutyricum, a known cheese-spoilage bacterium. Both bacteriocins were purified to homogeneity from culture supernatants by reverse-phase chromatography and the subsequently determined amino acid sequences were used to clone the bacteriocin structural genes. Mature gassericin A and circularin A are class V circular bacteriocins comprised of 58 and 69 amino acid residues, respectively. Both bacteriocins are resistant to several peptidases and proteases, as are other cyclic bacteriocins. Heterologous expression of gassericin A in Escherichia coli was used to produce a non-cyclic mature peptide, which was shown to have a specific activity 173-fold lower than the circular molecule. The minimal region for production and secretion of active circularin A is comprised of five genes, as was deduced by heterologous gene expression in Enterococcus faecalis. Gassericin A and circularin A have limited mutual similarity in their primary sequences. Unlike most bacteriocins, including gassericin A, circularin A has a three-amino-acid-leader sequence.     

MALDI-Q-TOF mass spectrometric determination of gold and platinum in tissues using their diethyldithiocarbamate chelate complexes

A rapid determination method is presented for gold (Au³⁺) and platinum (Pt⁴⁺) in tissues using matrix-assisted laser desorption ionization quadrupole time-of-flight mass spectrometry (MALDI-Q-TOF-MS). Au and Pt ions in wet-ashed tissue solution were reacted with diethyldithiocarbamate (DDC), and the resulting chelate complex ions Au(DDC)₂ ⁺ and Pt(DDC)₃ ⁺ were detected by MALDI-Q-TOF-MS using α-cyano-4-hydroxycinnamic acid as a matrix. The limit of detection (LOD) was 0.8 ng/g tissue and the quantification range was 2–400 ng/g for Au, and the LOD was 6 ng/g tissue and the quantification range was 20–4,000 ng/g for Pt. The Pt levels detected by MALDI-Q-TOF-MS in several tissues of a patient overdosed with cisplatin were nearly the same as those detected by flow-injection electrospray ionization mass spectrometry. The LODs of Au and Pt were 0.04 pg per well (sample spot) and 0.3 pg per well, respectively. To our knowledge, this is the first attempt to quantify Au³⁺ and Pt⁴⁺ ions in tissues by MALDI-Q-TOF-MS.

Synthesis of 6‐Aminoindolo[2,1‐a]isoquinoline‐5‐carbonitriles by the Cu‐Catalyzed Reaction of 2‐(2‐Bromophenyl)‐1H‐indoles with CH2(CN)2

A series of 6‐aminoindolo[2,1‐a]isoquinoline‐5‐carbonitriles 4 have been prepared by treatment of 2‐(2‐bromophenyl)‐1H‐indoles 1 , available from 1‐(2‐bromophenyl)ethanones or 1‐(2‐bromophenyl)propan‐1‐ones by using Fischer indole synthesis, with propanedinitrile in the presence of a catalytic amount of CuBr and an excess of K₂CO₃ in DMSO at 100°.     

Design and feasibility assessment of topically applied drug formulations for electroporation

Few studies have been reported on the design of topical formulations consisting of electrodes and active drugs for electroporation as a means to increase skin permeability of the drugs, although many studies were reported for the effect of this physical means using aqueous drug solutions. We, therefore, designed a prototypic reservoir and matrix topical formulations that are suitable for electroporation in the present study. Plate-plate Ag electrodes and sodium diclofenac were used as model electrodes and the drug, respectively. The in vitro skin permeations of the drug obtained from the reservoir and matrix formulations were slightly higher than that from an aqueous suspension. This may be due to slightly higher electric field in the skin barrier for the presently designed formulations than that for the aqueous suspension. The present feasibility test suggests that these reservoirs and matrix formulations are useful prototypic topical formulations for electroporation application to improve the drug permeability through skin.     

Stereochemistry of iejimalide B

The absolute configurations at five chiral centers, except for C-32(S) reported previously, in iejimalide B (1), a potent cytotoxic 24-membered macrolide isolated from a tunicate Eudistoma cf. rigida, were assigned as 4R, 9S, 17S, 22S, and 23S on the basis of detailed analysis of NMR data and chemical means. Furthermore, the structure of iejimalide B was revised from 2 (original: 13E) to its 13Z-isomer (1).