Ultrafast reversible photo-cross-linking reaction: toward in situ DNA manipulation

We describe a novel ultrafast reversible DNA interstrand photo-cross-linking reaction via 3-cyanovinylcarbazole nucleoside ( (CNV)K). Oligodeoxynucleotide (ODN) containing (CNV)K can be photo-cross-linked by irradiation at 366 nm for 1 s, and the photo-cross-linked ODN can be split by irradiation at 312 nm for 60 s.     

A comparison of EDI with solvent-free MALDI and LDI for the analysis of organic pigments

To evaluate the applicability of EDI to material analysis as a new ionization method, a comparison of EDI with solvent-free matrix-assisted laser desorption ionization (MALDI) and laser desorption ionization (LDI) was made for the analysis of organic pigments, e.g. Pigment Yellow 93, Pigment Yellow 180, and Pigment Green 36, as test samples, which are poorly soluble in standard solvents. In EDI, the samples were prepared in two ways: deposition of suspended samples in appropriate solvents and dried on the substrate, and the direct deposition of the powder samples on the substrate. No matrices were used. Both sample preparation methods gave similar mass spectra. Equally strong signals of [M + H](+) and [M - H](-) ions were observed with some fragment ions for azo pigments in the respective positive or negative mode of operation. For the powder sample of the phthalocyanine pigment PG36, M(+*) and [M + H](+) in the positive mode and M(-*) in the negative mode of operation were observed as major ions. Positive-mode, solvent-free MALDI gave M(+), [M + H](+) and [M + Na](+) and negative mode gave [M - H](-) depending on the sample preparation. As solvent-free MALDI, EDI was also found to be an easy-to-operate, versatile method for the samples as received.     

Highly selective and sensitive template-directed photoligation of DNA via 5-carbamoylvinyl-2'-deoxycytidine

We describe a highly efficient template-directed photoligation of oligodeoxynucleotides (ODNs) through 5-carbamoylvinyl-2'-deoxycytidine ((CV)C). When an ODN containing (CV)C at the 5' end was photoirradiated with an ODN containing a pyrimidine base at the 3' end in the presence of template DNA, efficient photoligation was observed without any byproduct formation. Single nucleotide differences can be successfully distinguished by using photoligation-based DNA chip assay. [structure: see text]     

Atmospheric-pressure Penning ionization of aliphatic hydrocarbons

A study has been made of the atmospheric-pressure Penning ionization (APPeI) of aliphatic hydrocarbons (pentane, hexane, heptane, and octane) with long-lived rare gas atoms (Rg*). The metastable rare gas atoms (He*, Ne*, Ar* and Kr*) were generated by the negative-mode corona discharge of atmospheric-pressure rare gases. In the Rg*APPeI mass spectra for aliphatic hyrocarbons, the relative abundances of fragment ions were found to increase in the order of He* --> Ne* --> Ar* --> Kr*. The order is in the opposite direction to the internal energies of the Rg*. The less fragmentation observed for He* may be because the nascent molecular ions [M(+.)]* formed by Penning ionization have lifetimes long enough for them to be collisionally deactivated in the atmospheric-pressure ion source. It was found that the relative abundances of fragment ions in Ar*APPeI increased when the sample pressure in the ion source was reduced. This is attributed to the collision of Ar* with molecular ions followed by fragmentation.     

Au-assisted visible laser MALDI

The excitation of UV-absorbing MALDI matrixes with visible laser (532 nm wavelength) and the desorption/ionization of biomolecules were performed by coating the analytes doped matrix with Au thin film (5–10 nm) using ion sputtering deposition. The Au film was first ablated with the laser of higher fluence, resulting in a crater/hole about the size of the laser beam spot on the target. After a few initial laser shots, analytes and matrix related ions were observed from the crater even at lower laser fluence. Electron microscopy inspection on the laser ablated region revealed the formation of nanoparticles with sizes ranging from <10 to 50 nm. Compared with the infra-red laser (1064 nm) excitation, the visible laser produced much higher abundance of matrix radical ions, and less heating effect as measured by the thermometer molecules. The results suggest the photo-excitation and photo-ionization of matrix molecules by the visible laser, possibly assisted by the gold nanoparticles and nanostructures left on the ablated crater.     

Observation of dimethylaminoethyl methacrylate-myoglobin binding reaction using laser spray mass spectrometry

Covalent bonds are often created by a reaction between chemicals and protein before causing various adverse effects in a cell. Dimethylaminoethyl methacrylate (DMAEMA), which has moderate toxicity, causes skin inflammation and throat irritation. For this study, we investigated a reaction mechanism between myoglobin and (DMAEMA) using a new analytical tool developed at our laboratory: laser spray mass spectrometry technique. It was found that initially DMAEMA was added to the amino group of protein by the Michael addition mechanism; the added DMAEMA was hydrolyzed to methacrylic acid using an autocatalytic system. The results of this study indicate the feasibility of the laser spray technique in analyses of reaction dynamics.