Structural study on gold nanoparticle functionalized with DNA and its non-cross-linking aggregation

Hybridization of DNA tethered on colloidal nanoparticles with fully matched complementary one induces the aggregation of the particles in a non-cross-linking configuration. Here, we performed a structural study on DNA-functionalized gold nanoparticle and its non-cross-linking aggregation mainly using synchrotron radiation small-angle X-ray scattering. To understand the non-cross-linking aggregation, the nanoparticles with various DNA lengths and core sizes were used. In the aggregation, the surface distance between the gold nanoparticles increased with the length of DNA duplex, although the increment of the distance per base pair was not constant and showed the tendency to become small with increasing DNA length, meaning the interdigitation of DNA layers. The aggregation was also found to occur between the identical cores, without being affected by tethered DNA. Furthermore, it was proved that the relative increase in DNA length to core size leads to the increase in colloidal stability. Even the nanoparticles with full-matched DNA duplex were dispersed stably. These facts suggested that van der Waals interaction between core particles rather than end-to-end stacking between DNA duplexes is a dominant attractive interaction. The steric repulsion force arising from entropic loss of thermal fluctuation of DNA molecules might be a key factor to characterize the non-cross-linking aggregation.     

Fluid mixing using AC electrothermal flow on meandering electrodes in a microchannel

The mixing of fluids using AC electrothermal flow (AC-ETF) is presented. A pair of coplanar electrodes with a sinusoidal interelectrode gap was used to enhance the mixing in a microchannel. To demonstrate the performance of the mixer, conventional dilution experiments were conducted using Texas Red-labeled dextran. The dependence of mixing on the salt concentration (10(-3) ～ 10(-1) mol dm(-3) ) of the solutions and frequency (100 kHz ～ 5 MHz) of the applied voltage were investigated. AC-ETF was responsible for the mixing at salt concentrations >10(-2) mol dm(-3) , whereas the effect of AC-EOF was suggested to play a role at concentrations <10(-2) mol dm(-3) in the low-frequency region. The fluorogenic reaction of human serum albumin (HSA) with SYPRO Red in the mixer was also examined, and results showed that enrichment of fluorescence intensity and an almost uniform distribution of stained HSA were achieved. The present mixer can be employed as a powerful tool to facilitate efficient chemical and biomedical analysis on microfluidic devices.     

Chemistry of renieramycins. Part 13: Isolation and structure of stabilized renieramycin type derivatives,renieramycins W–Y,from Philippine blue sponge Xestospongia sp., pretreated with potassium cyanide

Three new bistetrahydroisoquinoline marine natural products, renieramycins W (1w), X (1x), and Y (1y), along with two known renieramycins M (1m) and T (1t), were isolated from the pretreated Philippine blue sponge Xestospongia sp. with KCN and their structures were elucidated by comparing their spectral data with those of 1m, 1t, and N-acetylsafracin B (11). Renieramycins W (1w) and X (1x) are the first examples of tiglic acid ester derivatives at the C-1 side chain. Renieramycin Y (1y) possesses a characteristic substitution pattern in A-ring and isolation of it from marine organism strongly evidences to link the possible precursor 3-hydroxy-5-methyl-O-methyltyrosine with both renieramycin and ecteinascidin marine natural products.     

Quantitative SNP genotyping by affinity capillary electrophoresis using PEG-oligodeoxyribonucleotide block copolymers with electroosmotic flow

Quantitative SNP detection was demonstrated with an ACE using a PEG-oligodeoxyribonucleotide block copolymer (PEG-b-ODN) as a probe in the presence of an EOF. The probe's PEG segment with large molecular weight and small polydispersity yielded a high resolution in the separation of a chemically synthesized 60-base ssDNA (WT) and its single-base-substituted mutant (MT). A mixture of WT and MT was clearly separated within 10 min by simultaneously using two types of PEG-b-ODN probes whose ODN segments were complementary to WT and MT and whose PEG segments were of different lengths. The peak area ratio between WT and MT was in good agreement with the feed ratio. The averaged difference between the feed and observed ratio of MT was determined to be 0.23%, which is lower than that of any other methods. The ACE using the PEG-b-ODN probes in the presence of EOF could be utilized as a facile method for estimating SNP allele frequency in various research fields.     

Structural analysis of three novel trisaccharides isolated from the fermented beverage of plant extracts

Background  

A fermented beverage of plant extracts was prepared from about fifty kinds of vegetables and fruits. Natural fermentation was carried out mainly by lactic acid bacteria (Leuconostoc spp.) and yeast (Zygosaccharomyces spp. and Pichia spp.). We have previously examined the preparation of novel four trisaccharides from the beverage: O-β-D-fructopyranosyl-(2->6)-O-β-D-glucopyranosyl-(1->3)-D-glucopyranose, O-β-D-fructopyranosyl-(2->6)-O-[β-D-glucopyranosyl-(1->3)]-D-glucopyranose, O-β-D-glucopyranosyl-(1->1)-O-β-D-fructofuranosyl-(2<->1)-α-D-glucopyranoside and O-β-D-galactopyranosyl-(1->1)-O-β-D-fructofuranosyl-(2<->1)- α-D-glucopyranoside.     

Post‐Modification of meso–meso‐Linked Porphyrin Arrays by Iridium and Rhodium Catalyses for Tuning of Energy Gap

Skillfully attached! meso–meso‐Linked diporphyrins can be efficiently and selectively functionalized with multiple unsaturated carboxylic acid groups through iridium and rhodium catalyses. This post‐modification strategy allows fine‐tuning of energy levels of each porphyrin unit.

     

Ab initio and DFT calculations of three-body interactions in chiral mixtures

In order to elucidate the enthalpic stabilization of a 2-methyl-1,4-butanediol system (2M14BD) and a 3-chloro-1,2-propanediol (3C12PDO) system by mixing of each (R)- and (S)-enantiomers, three-body interaction energies are obtained by PW91/6-311G** and MP2/6-311G** level calculations. The differences between homochiral interactions and heterochiral interactions in a 3C12PDO system are found. On the other hand, in 2M14BD systems, very slight differences can be observed between the three-body interaction energies of the three ternary systems. Further, the relationship between excess enthalpies and chiral interactions is discussed.     

Excess enthalpies of binary mixtures of <Emphasis Type="Italic">ortho</Emphasis>-, <Emphasis Type="Italic">meta</Emphasis>-, <Emphasis Type="Italic">para</Emphasis>-structural isomers containing aliphatic group

To obtain further systematic information for the isomer systems, the excess molar enthalpies for binary (o + m), (o + p), (m + p)-isomers of methoxymethylbenzene, ethylmethylbenzene, diethylbenzene, chloromethylbenzene, tolunitrile and fluorobenzonitrile, tolylacetonitrile were measured at 298.15 K. In this article, the results are discussed and compared with those of previous works. The excess enthalpies of binary systems in different solid and liquid states were measured when the pure component of o-/m-tolunitrile, fluorobenzonitrile was titrated into the prior (o + p) or (m + p) mixtures. A series calculation for the interaction energies (IE) between the isomers was carried out for the pair molecules by ab initio MO of Gaussian 09. Correlations between the excess enthalpies at a molar fraction of x = 0.5 and the intermolecular energy are discussed.     

Synthesis of (±)-chamobtusin A by a presumed biomimetic aza-cyclization

A total synthesis of (±)-chamobtusin A has been accomplished on the basis of our presumed biosynthetic pathway: the imine formation of keto aldehyde followed by intramolecular aza-Michael addition.