Sulfation of Polysaccharides using Monomethyl Sulfate

ABSTRACT

The polysaccharides, curdlan, starch and dextran were sulfated when heated in DMSO with sodium methyl sulfate and a catalytic amount of H₂SO₄ or with pyridinium methyl sulfate. Use of diminished pressure and anhydrous CaSO₄ as a desiccant improved the degree of sulfation and recovery. Under conditions using sodium methyl sulfate, H₂SO₄ and CaSO₄ in vacuo, sulfation at O-6 was predominant in the cases of curdlan and starch, while sulfation at O-2 and O-3 was preferential in the case of dextran.     

Enhancing the lateral-flow immunoassay for detection of proteins using an aqueous two-phase micellar system

The lateral-flow (immuno)assay (LFA) has been widely investigated for the detection of molecular, macromolecular, and particle targets at the point-of-need due to its ease of use, rapid processing, and minimal power and laboratory equipment requirements. However, for some analytes, such as certain proteins, the detection limit of LFA is inferior to lab-based assays, such as the enzyme-linked immunosorbent assay, and needs to be improved. One solution for improving the detection limit of LFA is to concentrate the target protein in a solution prior to the detection step. In this study, a novel approach was used in the context of an aqueous two-phase micellar system comprised of the nonionic surfactant Triton X-114 to concentrate a model protein, namely transferrin, prior to LFA. Proteins have been shown to partition, or distribute, fairly evenly between the two phases of an aqueous two-phase system, which in turn results in their limited concentration in one of the two phases. Therefore, larger colloidal gold particles decorated with antibodies for transferrin were used in the concentration step to bind to transferrin and aid its partitioning into the top, micelle-poor phase. By manipulating the volume ratio of the two coexisting micellar phases and combining the concentration step with LFA, the transferrin detection limit of LFA was improved by tenfold from 0.5 to 0.05?μg/mL in a predictive manner. In addition to enhancing the sensitivity of LFA, this universal concentration method could also be used to improve other detection assays.     

Enhancing the lateral-flow immunoassay for viral detection using an aqueous two-phase micellar system

Availability of a rapid, accurate, and reliable point-of-care (POC) device for detection of infectious agents and pandemic pathogens, such as swine-origin influenza A (H1N1) virus, is crucial for effective patient management and outbreak prevention. Due to its ease of use, rapid processing, and minimal power and laboratory equipment requirements, the lateral-flow (immuno)assay (LFA) has gained much attention in recent years as a possible solution. However, since the sensitivity of LFA has been shown to be inferior to that of the gold standards of pathogen detection, namely cell culture and real-time PCR, LFA remains an ineffective POC assay for preventing pandemic outbreaks. A practical solution for increasing the sensitivity of LFA is to concentrate the target agent in a solution prior to the detection step. In this study, an aqueous two-phase micellar system comprised of the nonionic surfactant Triton X-114 was investigated for concentrating a model virus, namely bacteriophage M13 (M13), prior to LFA. The volume ratio of the two coexisting micellar phases was manipulated to concentrate M13 in the top, micelle-poor phase. The concentration step effectively improved the M13 detection limit of the assay by tenfold from 5?×?10⁸ plaque forming units (pfu)/mL to 5?×?10⁷ pfu/mL. In the future, the volume ratio can be further manipulated to yield a greater concentration of a target virus and further decrease the detection limits of the LFA.

Palladium-catalyzed cross-coupling reactions of (2-pyridyl)allyldimethylsilanes with aryl iodides

[reaction: see text] (2-Pyridyl)allyldimethylsilanes were found to be novel pyridyl transfer reagents in palladium-catalyzed cross-coupling reactions of various aryl iodides in the presence of silver(I) oxide as an activator.     

Analysis of vertical coupling between a 2D photonic crystal cavity and a hydrogenated-amorphous-silicon-wire waveguide

We present an efficient means of light extraction from two-dimensional photonic crystal (2D PC) cavities with SiO₂ cladding. We propose a vertically coupled system consisting of a 2D PC cavity and a hydrogenated-amorphous-silicon (a-Si:H)-wire waveguide, which we theoretically investigate using the 3D finite-difference time-domain method. Light can be extracted with an efficiency of greater than 95% to both output ports of the a-Si:H-wire waveguide or extracted with an efficiency of greater than 90% to a single output port of the a-Si:H-wire waveguide with a reflector.     

Crazing in polyethylene

The tensile stress—strain curves of various types of polyethylene were compared from 77 to 298 K in nitrogen, isopentane, and the inert environment of helium at various strain rates. It was found that in general polyethylene crazes in a gas such as nitrogen at a temperature below 1.6 times its boiling point and in isopentane. Although the behavior of polyethylenes is similar to that of other polymers with regard to crazing in gases at low temperatures, they are in general less sensitive to the gas. The decrease in tensile strength of polyethylene in an environmental gas increases with crystallinity. The differences in the intrinsic low-temperature brittle fracture stress are attributed to differences in the density of tie molecules. The intrinsic yield point at room temperature showed the usual increase with increasing crystallinity, but all the polyethylenes have the same yield point below the γ transition temperature.     

13C NMR Spectroscopy on the Complexation of α-Cyclodextrin with 1-Alkanols and 1-Alkanoate Ions

Binding constants for -cyclodextrin ( -CD) complexes with 1- alkanols and 1- alkanoate ions were determined by analyzing changes ( ) in chemical shifts of guest ¹³C NMR signals with -CD concentration. The guests gave well-separated ¹³C NMR signals. The curve-fitting analyses of for individual carbons upon assumption of a simple 1:1 complexation gave virtually the same binding constants (K₁) in the cases of guests with relatively short alkyl chains, such as 1-propanol, 1-butanol, 1- pentanol , 1- butanoate , 1- pentanoate , and 1-hexanoate. However, thus obtained individual K₁ values were significantly different from one another, when the guests had relatively long alkyl chains such as 1- hexanol , 1- heptanol , and 1-octanoate. In these guests, satisfactorily consistent K₁ values were obtained by the curve-fitting analyses of for individual carbons upon an assumption that not only 1:1 but also 2:1 (host:guest) complexation occurs.     

Unusually accelerated silylmethyl transfer from tin in stille coupling: implication of coordination-driven transmetalation

The palladium-catalyzed cross-coupling reaction of 2-PyMe2SiCH2SnBu3 with aryl iodide (Ar-I) exclusively produced the 2-PyMe2SiCH2 transferred product 2-PyMe2SiCH2Ar. The relative transfer ability of organic group from tin was found to be 2-PyMe2SiCH2 > Ph > Me > Bu > PhMe2SiCH2, which implies the beneficial pyridyl-to-palladium coordination effect. Thus, the transfer of the silylmethyl group from tin to palladium was remarkably accelerated by simply appending the 2-pyridyl group on silicon. The pyridyl-to-palladium coordination was validated in the palladium(II) complex 2-PyMe2SiCH2PdClPPh3 by 1H NMR and X-ray crystal structure analysis. The cross-coupling product was used for further transformations. The C-Si oxidation of the cross-coupling product 2-PyMe2SiCH2Ar afforded ArCH2OH in high yield. The fluoride ion-catalyzed 1,2-addition of 2-PyMe2SiCH2Ar to carbonyl compound (RR'C=O) gave ArCH2C(OH)RR' in high yield.