Electrospray mass spectrometry of pentacosasaccharides of blood group I-activity and related compounds

The structural characterization of large synthetic oligosaccharides and related glycoconjugates performed by the use of electrospray ionization mass spectrometry (ESIMS) is described. The largest molecules described here are unprotected and protected pentaantennary pentacosasaccharides 2 and 5 with average molecular masses of 4441 and 9416, respectively. The straight-chain neutral ceramide decasaccharide (d18:1/c24:0) 6 and the disialoganglioside GD2 (d18:1/c24:0) 7 were also successfully analyzed by ESIMS. In addition to exact mass determination, collision-induced dissociation (CID) spectrometry of these compounds provided saccharide chain sequence information.     

Phosphate ion-sensitive coated-wire/field-effect transistor electrode based on cobalt phthalocyanine with poly(vinyl chloride) as the membrane matrix

An ion-selective coated-wire/field-effect transistor electrode responding to dihydrogenphosphate is described. The device consists of a coated-platinum wire electrode connected to the gate of a conventional field-effect transistor. Cobalt phthalocyanine is used as ion-exchange electroactive substance and poly(vinyl chloride) as the membrane matrix. The characteristics of the device are investigated and its response is studied by two methods, the linear dependence of the square root of the drain current in the saturated region on the logarithm of ion activity for sodium dihydrogenphosphate, and the dependence of the gate-source potential on the logarithm of ion activity of the same ion. A linear response is obtained in the range of ion activity 10^?5-10^?1 mol dm^?3 and the response slope is 45 mV per decade change of H₂PO₄^? ion activity; the selectivity coefficients are discussed.     

Synthesis and reactivity of triethylborane adduct of N-heterocyclic carbene: versatile synthons for synthesis of N-heterocyclic carbene complexes

The reaction of an imidazolium salt with LiBEt(3)H afforded triethylborane adduct of imidazol-2-ylidene, which can act as a carbene precursor for the synthesis of a transition metal complex as well as a main group element complex.     

Polymerization of methyl methacrylate under ultrasonic irradiation. Part V. Effect of ultrasonic irradiation on stereoregularity of the polymers and oligomers produced by grignard catalyst in toluene–dioxane mixed solvent

Polymerization of methyl methacrylate with Grignard reagent in toluene–dioxane mixed solvent was carried out under ultrasonic irradiation. The effects of ultrasonic irradiation and the order of catalyst addition on Grignard reagent and the microstructure in the reacting sites were examined on the basis of the stereoregularity of polymers and oligomers produced. The formation of oligomers was also discussed on the basis of the consumption of initiator. The stereoregularity of the polymers in series A (no ripening of catalyst with solvent) is higher than that in series B (ripening of catalyst with solvent). The effect of ultrasonic irradiation on the stereoregularity was completely reversed in series A and B; it increased in the former and decreased in the latter with ultrasonic irradiation. Similar results were obtained for the stereoregularity of the oligomers, but the stereoregularity of the oligomers was lower than that of polymers.     

A synthesis of 2-aminonorbornene-2-carboxylic acid derivatives by diels-alder reaction using α,β-dehydroalaninates as a dienophile

The Diels-Alder reaction of N-acyl-α,β-dehydroalanine esters with cyclopentadiene afforded a mixture of the stereoisomers of acylaminonorbornene-2-carboxylic acid esters in good yields.     

Asymmetric porous emulsion film

The formation mechanism of an “asymmetric” porous structure for the film cast from ethyl acrylate-methyl methacrylate copolymer emulsion prepared by emulsifire-free emulsion polymerization was investigated. The formation of this structure was affected by the emulsion stability which was varied by the postaddition of sodium sulfate or sodium dodecyl benzene sulfonate. It is concluded that it is derived from the production of porous skin film at the emulsion-air interface and the precipitation of flocculated particles at the bottom of emulsion during drying process.     

Clustering structure of aqueous solution of kinetic inhibitor of gas hydrates

Poly-[N-vinylcaprolactam] (PVCAP) and its related compounds are specific polymeric compounds for inhibiting hydrate formation. To clarify the inhibition mechanism of these compounds on hydrate nucleation at the molecular level, we measured the mass spectra of clusters generated from the fragmentation of liquid droplets including N-methylcaprolactam (NMCAP; functional group of PVCAP). By comparing the mass spectra of clusters of the solutions--pure D2O, tetrahydrofuran (THF)-D2O, NMCAP-D2O, and THF-NMCAP-D2O--it was found that the interaction of NMCAP with D2O was much stronger than that of THF with D2O. The relative intensity ratio of D+(NMCAP)m(D2O)n clusters to all the clusters observed for the NMCAP-D2O (1:250) mixed solution was 0.45. On the other hand, the relative intensity ratio of D+(THF)1(D2O)n clusters to all the clusters observed for the THF-D2O (1:17) mixed solution was 0.15. In the case of the THF-NMCAP-D2O three-component mixed solution, the NMCAP-D2O interaction was more predominant than the THF-D2O interaction, even at a lower NMCAP concentration. NMCAP reduces free mobile water molecules around NMCAP, but THF does not. This correlates with the facts that THF forms its hydrate below the freezing point and that PVCAP works as an inhibitor of gas hydrates.     

Facile synthesis of 6a-carbaprostaglandin i2

The optically active 6a-carbaprostaglandin I₂ (2), a stable mimic of natural prostacylin (1), was synthesized from the lactone 4 or the hydroxy acid 5, which were general synthetic intermediates for natural prostaglandins.     

THEORETICAL STUDY OF COLOR CONTROL MECHANISM IN RETINAL PROTEINS.: I. ROLE OF THE TRYPTOPHAN RESIDUE, TYROSINE RESIDUE AND WATER MOLECULE

Abstract: We calculated the opsin shift due to the electrostatic interaction between tryptophan or tyrosine residues and the chromophore by the perturbation method for various mutual configurations. The obtained opsin shift maps for these configurations demonstrated that when the above residues reside around the ionone ring side, the positive opsin shift (bathochromic shift) is obtained, and when they reside around the Schiff-base side, the negative opsin shift (hypsochromic shift) is obtained. These properties hold true, irrespective of the orientation of those residues, indicating that higher order multipoles of the group play a central role. The maximum value of the opsin shift by these groups amounts to several hundred wavenumbers. These results indicate that the location of some of those amino acid residues at proper positions around the chromophore can cause a considerable opsin shift. We also calculated opsin shift maps for the various mutual configurations between a water molecule and the chromophore for comparison.