Carbon nanotubes as adsorbent of solid-phase extraction and matrix for laser desorption/ionization mass spectrometry

A method with carbon nanotubes functioning both as the adsorbent of solid-phase extraction (SPE) and the matrix for matrix assisted laser desorption/ ionization mass spectrometry (MALDI-MS) to analyze small molecules in solution has been developed. In this method, 10 muL suspensions of carbon nanotubes in 50% (vol/vol) methanol were added to the sample solution to extract analytes onto surface of carbon nanotubes because of their dramatic hydrophobicity. Carbon nanotubes in solution are deposited onto the bottom of tube with centrifugation. After removing the supernatant fluid, carbon nanotubes are suspended again with dispersant and pipetted directly onto the sample target of the MALDI-MS to perform a mass spectrometric analysis. It was demonstrated by analysis of a variety of small molecules that the resolution of peaks and the efficiency of desorption/ ionization on the carbon nanotubes are better than those on the activated carbon. It is found that with the addition of glycerol and sucrose to the dispersant, the intensity, the ratio of signal to noise (S/N), and the resolution of peaks for analytes by mass spectrometry increased greatly. Compared with the previously reported method by depositing sample solution onto thin layer of carbon nanotubes, it is observed that the detection limit for analytes can be enhanced about 10 to 100 times due to solid-phase extraction of analytes in solution by carbon nanotubes. An acceptable result of simultaneously quantitative analysis of three analytes in solution has been achieved. The application in determining drugs spiked into urine has also been realized. (C) 2004 American Society for Mass Spectrometry.

Kinetic energies of C-n(+) (n <= 58) fragment ions produced by nanosecond laser impact on C-60

Laser-induced fragmentation of C-60 has been studied using a time-of-flight mass spectrometric technique. The average kinetic energies of fragment ions C-n(+) (n <= 58) have been extracted from the measured full width at half maximum (FWHM) of ion beam profiles. The primary formation mechanism of small fragment ion C-n(+) (n < 30) is assumed to be a two-step fragmentation process: C60 sequential decay to unstable C-30(+) ion and the binary fission of C-30(+). Considering a second photo absorption process in the later part of laser pulse duration, good agreement is achieved between experiment and theoretical description of photoion formation. (C) 2009 Elsevier B. V. All rights reserved.

纳秒激光诱导C60分子碎裂中轻碎片离子C+n(n＜30)的产生机理研究

The time of flight mass spectrometric technique was used to determine the initial mean kinetic energy of small fragment ions C-n(+) (n <= 11) produced from C-60 excited by 532 nm nanosecond laser pulses. The measured kinetic energy shows little variation with the fragment mass and the laser fluence in a broad range. Based on the assumption that C-30(+) is produced predominantly by a single electron emission followed by successive C-2 evaporation from hot C-60 in the nanosecond laser field, the formation of small fragments is interpreted as the complete breakup of the unstable C-30(+) cage structure. The interpretation is consistent with the previously observed results.

Dynamics of excited m-dichlorobenzene

Dynamics of excited m-dichlorobenzene is investigated in real time by femtosecond pump-probe method, combined with time-of-flight mass spectrometric detection in a supersonic molecular beam. The yields of the parent ion and daughter ion C6H4CI+ are examined as a function of the delay between the 270 and 810 nm femtosecond laser pulses, respectively. The lifetime of the first singlet excited state S-1 of m-dichlorobenzene is measured. The origin of this daughter ion C6H4CI+ is discussed. The ladder mechanism is proposed to form the fragment ion. In addition, our experimental results exhibit a rapid damped sinusoidal oscillation over intermediate time delays, which is due to quantum beat effects.

利用电喷雾质谱技术研究复方中药的配伍原则

Traditional Chinese Medicine (TCM) based on natural products is one important part of the Chinese civilization.Owing to the complexity of the composition,the study on medical effective components and curative effects are very difficult;Fuzi (Radix Aconiti Lateralis Praeparata) has been widely used for cardiotonic and analgesics in China,however,the component-aconitine in which is very toxic and may cause some side-effect.This paper reported the application of electrospray iohization mass spectrometric(ESIMS) technique on study of the compound prescriptions containing fuzi,Renshensini concoction and Baweidihuang concoction,to explore the mechanism of synergy between fuzi and other herbs.From chemical point of view,the detoxification mechanism can be attributed to the hydrolysis of the solubility of toxic diester-alkaloids from concoctions of fuzi.Radix Glycyrrhizae Praeparata,Rhizoma Zingiberis,Radix Ginsengp promote the hydrolysis to produce the less toxic monoester-alkaloids and Fructus Corni reduce the solubility of hypaconitine from fuzi.

Direct patterning of negative nanostructures on self-assembled monolayers of 16-mercaptohexadecanoic acid on Au(111) substrate via dip-pen nanolithography

Both bare and self-assembled monolayer (SAM) protected gold substrate could be etched by allyl bromide according to atomic force microscopy (AFM), x-ray photoelectron spectroscopy (XPS) and inductively coupled plasma mass spectrometric (ICPMS) analysis results. With this allyl bromide ink material, negative nanopatterns could be fabricated directly by dip-pen nanolithography (DPN) on SAMs of 16-mercaptohexadecanoic acid (MHA) on Au(111) substrate. A tip-promoted etching mechanism was proposed where the gold-reactive ink could penetrate the MHA resist film through tip-induced defects resulting in local corrosive removal of the gold substrate. The fabrication mechanism was also confirmed by electrochemical characterization, energy dispersive spectroscopy (EDS) analysis and fabrication of positive nanopatterns via a used DPN tip.

Synthesis and spectroscopic studies of endohedral metallofullerenes Tb@C-2n

Endohedral metallofullerenes Tb@C-2n were synthesized and extracted with high-yield by K-H carbon-are evaporation and an effective pyridine extraction technique at high-temperature high-pressure. Laser-desorption-ionization time-of-flight (LD-TOF) mass spectrometry, X-ray photoelectron spectroscopy (XPS), solid-state fluorescent emission spectroscopy and gas phase derivation reaction with the self-chemical ionization mass spectrometric ion system of vinyl acetate were employed for studying the electronic structures, fluorescent properties and gas phase reactivities of metallofullerenes Tb@C-2n. The experimental results suggest that endohedral metallofullerenes Tb@C-2n would have the approximate structures of Tb3+@C-2n(3-) similar to other metallofullerenes, good fluorescent emission properties and active reactivities in gas phase ion-molecular reactions.

Theoretical study on the unimolecular fragmentation of ionized tetrahydroimidazole-substituted methylene beta-diketones

Semiempirical molecular orbital calculations on the unimolecular mass spectrometric fragmentation of tetrahydroimidazole-substituted methylene beta-diketones are carried out by Austin Model 1 method, and the calculated results give a strong support to our experimental results reported previously. The optimum of the investigated molecular configuration indicates that the two hydrogen atoms attached to nitrogen atom have different activities due to their chemical environment; the relative energies of the ions in fragmentation pathway of ionized tetrahydroimidazole-substituted methylene beta-diketones provide indirectly an evidence for both the existence of ion/neutral complex and the stabilities of these ions.

High-yield extraction of endohedral rare-earth fullerenes

The technique of high-temperature high-pressure extraction with pyridine has been successfully utilized to extract a wide variety of endohedral rare-earth fullerenes of the type Ln@C-2n (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb). Ln@C-80, Ln@C-82, and Ln(2)@C-80 for most of the rare-earth metals can be produced with high-yield and selectively extracted from the carbon-are evaporation soot. Metallofullerenes containing Sm, Eu, and Yb (which could have +2 oxidation states) are especially difficult to extract. Some possible reasons for the high-yield extraction are discussed. The laser desorption mass spectrometric characterization results indicate a relationship between the extraction yields of metallofullerenes and the oxidation states and ionic radii of the rare-earths.

Formation and special solubility of endohedral thulium metallofullerenes

Endohedral metallofullerenes Tm@C-2n were synthesized with the carbon-arc discharge method of activating the Tm2O3-containing graphite anode in situ and back-burning technique, Toluene soxhlet extraction, toluene and pyridine high-temperature and high-pressure extraction technique were employed for the effective extraction of Tm@C-2n. The formation of Tm@C-2n was confirmed by LD-TOF and DEIMS characterization. The mass spectrometric results indicate that Tm@C-2n have a better solubility in toluene and worse solubility in pyridine than other metallofullerenes.

Highly brominated mono- and bis-phenols from the marine red alga Symphyocladia latiuscula with radical-scavenging activity

Four new highly brominated and fully substituted mono- and bis-phenols, 1-(2,3,6-tribromo-4,5-dihydroxybenzyl)pyrrolidin-2-one (1), 1,2-bis(2,3,6-tribromo-4,5-dihydroxyphenyl)ethane (2), 6-(2,3,6-tribromo-4,5-dihydroxybenzyl)-2,5-dibromo-3,4-dihydroxybenzyl methyl ether (3), and 2,3,6-tribromo-4,5-dihydroxybenzyl methyl sulfone (4), were characterized from the marine red alga Symphyocladia latiuscula. In addition, five known bromophenols, bis(2,3,6-tribromo-4,5-dihydroxyphenyl)methane (5), bis(2,3,6-tribromo-4,5-dihydroxybenzyl) ether (6), 2,3,6-tribromo-4,5-dihydroxybenzyl methyl ether (7), 2,3,6-tribromo-4,5-dihydroxymethylbenzene (8), and 2,3,6-tribromo-4,5-dihydroxybenzaldehyde (9), were also isolated and identified. The structures of these compounds were elucidated by spectroscopic methods including 1D and 2D NMR as well as by low- and high-resolution mass spectrometric analysis. Structurally, all of these compounds are highly brominated and fully substituted, and contain one or two 2,3,6-tribromo-4,5-dihydroxyphenyl unit(s) in each of the molecules. In addition, compound 4 possesses a unique sulfone structural feature. Each of the isolated compounds was evaluated for alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH) radical-scavenging activity and all were found to be potent, with IC50 values ranging from 8.1 to 24.7 mu M, compared to the known positive control butylated hydroxytoluene (BHT), with an IC50 of 81.8 mu M.

Four viral proteins of white spot syndrome virus (WSSV) that attach to shrimp cell membranes

White spot syndrome virus (WSSV) is a major shrimp pathogen that has a widespread negative affect on shrimp production in Asia and the Americas. It is known that WSSV infects shrimp cells through viral attachment proteins (VAP) that bind with shrimp cell receptors. However, the identity of both WSSV VAP and shrimp cell receptors remains unclear. We used digoxigenin (DIG)labeled shrimp hemocyte and gill cell membranes to bind to WSSV proteins immobilized on nitrocellulose membranes, and 4 putative WSSV VAP (37 kDa, 39 kDa and 2 above 97 kDa) were identified. Mass spectrometric analysis identified the 37 kDa putative VAP as the product of WSSV gene VP281.

Characterization of proteolytic bacteria from the Aleutian deep-sea and their proteases

Six deep-sea proteolytic bacteria taken from Aleutian margin sediments were screened; one of them produced a cold-adapted neutral halophilic protease. These bacteria belong to Pseudoalteromonas spp., which were identified by the 16S rDNA sequence. Of the six proteases produced, two were neutral cold-adapted proteases that showed their optimal activity at pH 7-8 and at temperature close to 35 degrees C, and the other four were alkaline proteases that showed their optimal activity at pH 9 and at temperature of 40-45 degrees C. The neutral cold-adapted protease E1 showed its optimal activity at a sodium chloride concentration of 2 M, whereas the activity of the other five proteases decreased at elevated sodium chloride concentrations. Protease E1 was purified to electrophoretic homogeneity and its molecular mass was 34 kDa, as estimated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The molecular weight of protease E1 was determined to be 32,411 Da by mass spectrometric analysis. Phenylmethyl sulfonylfluoride (PMSF) did not inhibit the activity of this protease, whereas it was partially inhibited by ethylenediaminetetra-acetic acid sodium salt (EDTA-Na). De novo amino acid sequencing proved protease E1 to be a novel protein.