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For deep imaging depth and least invasiveness, people commonly use 1100-1300 nm femtosecond laser sources to perform label-free in vivo microscopy. The modalities include reflectance confocal, two & three photon fluorescence, and second & third harmonic generation microscopy. However, most of the laser sources are typically based on bulky oscillators, which are sensitive to environment conditions and less stable for routine clinical use. In contrast, fiber-based lasers have simpler cavity design and potentially compact size for movable use. In this presentation, we demonstrate a fiber-based 1150 nm femtosecond laser source, with 6.5 nJ pulse energy, 86 fs pulse-width, and 11.25 MHz pulse repetition rate. It was achieved by a Bismuth Borate (BIBO) or Magnesium-doped periodically poled Lithium Niobate (MgO:PPLN) mediated frequency doubling of the 2300 nm solitons, generated from an excitation of 1550 nm Er:fiber femtosecond laser pulses on a large mode area photonic crystal fiber. Combined with a laser scanned microscope and a home-build data acquisition card, we achieve a pulse-per-pixel harmonic generation microscopy in vivo at a 30 Hz frame rate. In the future, this solution is potential to be used for label-free clinical virtual optical biopsy.

Amino acid phosphoramidates of adenosine were synthesized and determined by positive and negative ion electrospray ionization mass spectrometry (ESI-MS) in conjunction with tandem mass spectrometry (MS/MS). The fragmentation pathways were investigated. In the positive ion mass spectra abundant characteristic fragment ions appeared, and many complementary ions were found. In the negative ion mass spectra only a few fragment ions were observed, and most of them contained phosphoryl groups. The results show that ESI-MS is a useful tool for structural determination of amino acid phosphoramidates of nucleosides.

Reactions of fresh pentacoordinate phosphoric-amino acid mixed anhydrides with amine and alcohol yielded peptide analogs, N-phosphoamino acid esters, phosphodiesters and some products of ester exchange, which might provid some evidence that the formation of pentacoordinate intermediates was crucial to some bioorganic reactions of N-Phosphoamino acids.

Dimyristoylphosphatidylglycerol (DMPG), dimyristoylphosphatidylcholine (DMPC) and dimyristoylphosphatidylethanolamine (DMPE) were characterized by electron impact (EIMS), field desorption (FDMS) and liquid secondary ion (LSIMS) mass spectrometry. The results showed that the fragmentation processes of the three phospholipids are very similar. In the EI mass spectra, no molecule-ion peaks were found, the peaks of the fatty acid chains being dominant. The results of FDMS and LSIMS showed that both techniques worked particularly well with all three kinds of phospholipids. The FD mass spectra of all three phospholipid gave strong MH+ peaks, and no fragmental peaks were found except that of DMPC. With LSIMS, the fragmentations of all the phospholipids were extensive and clear, and gave dominant peaks of MH+. The cleavages around phosphate groups were the most abundant. An interesting phenomenon was found in the LSIMS measurements that all three kinds of phospholipids formed intense peaks of molecule-ion clusters, [2M+H]+, [3M+H]+ and [4M+H]+, etc. It was found that the formation of the molecule-ion clusters was related to several factors: concentration, ionic strength, pH, etc., among which concentration is the most important. The degree of cluster formation increased with increase in concentration of phospholipid. The results also showed that the nature of the matrix is critical to a successful LSIMS analysis of phospholipids, and (S)-glycerol was confirmed as a very satisfactory matrix for these phospholipids. © 1997 John Wiley & Sons, Ltd.

Harmonic generation microscopy (HGM) has become one unique tool of optical virtual biopsy for the diagnosis of cancer and the in vivo cytometry of leukocytes. Without labeling, HGM can reveal the submicron features of tissues and cells in vivo. For deep imaging depth and minimal invasiveness, people commonly adopt 1100- to 1300-nm femtosecond laser sources. However, those lasers are typically based on bulky oscillators whose performances are sensitive to environmental conditions. We demonstrate a fiber-based 1150-nm femtosecond laser source, with 6.5-nJ pulse energy, 86-fs pulse width, and 11.25-MHz pulse repetition rate. It was obtained by a bismuth borate or magnesium-doped periodically poled lithium niobate (MgO:PPLN) mediated frequency doubling of the 2300-nm solitons, generated from an excitation of 1550-nm femtosecond pulses on a large mode area photonic crystal fiber. Combined with a home-built laser scanned microscope and a tailor-made frame grabber, we achieve a pulse-per-pixel HGM imaging in vivo at a 30-Hz frame rate. This integrated solution has the potential to be developed as a stable HGM system for routine clinical use.

The fullerenes C 60 and C 70 were prepared in gram quantities by the Kraetschmer-Huffman method and purified by Al 2 O 3 column chromatography. The characterization of mass spectra of C 60 and C 70 were studied by EIMS, DEIMS, FDMS, and metastable ion MS techniques.

The self-assembly products of N-(O,O'-diisopropyl)-L-alpha-amino acids in aqueous media, N-(O,O'-diisopropyl)phosphoryl dipeptides and tripeptides, were identified by electrospray ionization mass spectrometry. A stepwise fragmentation of the [M + H](+) ions from the C-terminus of N-phosphopeptides was observed. Copyright 2000 John Wiley & Sons, Ltd.

Aminoacyl adenylate pentacoordinated phosphorus compounds were analyzed by field desorption (FD) and fast atom bombardment (FAB) mass spectrometries, together with the B/E linked scan technique, and their mass spectral fragmentation pathways were investigated. For the five bonds (one P-N bond, three P-O bonds and one mixed anhydride bond P-O-CO), the cleavage usually occurred more on the P-N bond, the mixed anhydride bond and the O-C bond adjacent to the P-O bond, and less on the P-O bond. Ion YH(+), corresponding to water loss from protonated 2',3'-O-isopropylidene-adenosine, was the base peak. The results reflect the structural characteristics of aminoacyl adenylate pentacoordinated phosphorus compounds. Copyright 1999 John Wiley & Sons, Ltd.

Amino acid-nucleotide conjugates have important biological functions and therapeutic applications. For example, aminoacyl adenylates are key intermediates in aminoacyl tRNA synthetase reactions. They may also be involved in the prebiotic synthesis of polypeptides. Finally, various amino acid carbomethoxy aryl phosphoramidates of nucleotide prodrugs may be activated through a mechanism involving a pentacoordinated phosphorane intermediates. In order to understand better the chemistry of these compounds, a phenylalanyl adenylate pentacoodinated phosphorane has been synthesized in 72% yield and its decomposition in aqueous solution studied. Hydrolysis gave 2′,3′-O-isopropylidene adenosine 5′-monophosphate, 2′,3′-O-isopropylidene adenosine, and phenylalanine. The results provide model chemistry for the enzymatic degradation mechanism of antiviral aryl amino acid phosphodiester amidates in cells, which leads to their activation.

In order to gain an insight into the mechanism of membrane insertion of the pore-forming protein colicin E(1) and the structure of its membrane-bound form, circular dichroism, fluorescence spectroscopy experiments were carried out. The results revealed the law of conformational changes by lipid membrane induction of the colicin E(1) molecule, and suggest that the lipid membranes with negative charges have a strong inducing action on colicin E(1) molecules. With the induction of membrane, the colicin E(1) molecules in different conformational states can all be recovered to the conformation of membrane insertion in native state. The induction intensity of different kinds of lipids on colicin E(1) was in the following order: DMPGDMPEDMPC. The binding of colicin E(1) with lipid vesicles was tight and the membrane-bound proteins were resistant to denaturation.