Laser Spray Research Articles

Toward Nanopore Electrospray Mass Spectrometry: Nanopore Effects in the Analysis of Bacteria.

The shape and structure analyses capability of nanopore is powerful and complementary to mass spectrometry analysis. It is extremely attractive but challenging to integrate these two techniques. The feasibility of combining nanopore electrospray with mass spectrometry was explored in this study. A nanopore effect was observed during the nano-electrospray of single bacterium, through which the shape and dimension of a single bacterium could be obtained. Molecular information on these bacteria was then acquired by analyzing these bacteria deposited on the counter electrode through laser spray ionization mass spectrometry experiments. Proof-of-concept experiments were carried out for four types of bacteria. Results show that the combination of nanopore results with mass spectrum data could effectively improve the identification accuracy of these bacteria from 72.5% to 100%. Although initial experiments were demonstrated in this work, results showed that it is feasible and promising to integrate nanopore technology with mass spectrometry for large biomolecule studies in the near future.

Facile Synthesis of Uniform Metal Carbide Nanoparticles from Metal-Organic Frameworks by Laser Metallurgy.

We report the fast and efficient conversion of metal-organic frameworks (MOFs) to phase pure transition-metal carbide (TMC) nanoparticles with uniform size using laser as the energy source, consuming only 6 W power. Nanoparticles of HfC, ZrC, TiC, V8C7, α-MoC, Cr3C2, and FeCx with homogeneous sizes (varied between 6 and 20 nm) were successfully produced, among which HfC and ZrC nanoparticles were obtained, for the first time, with sizes less than 10 nm and in the pure phase. This method was operated directly in air, in stark contrast to traditional furnace heating and laser spray methods, where a protective atmosphere is required. The use of MOFs allowed us to precisely tune the composition of TMC nanoparticles by dialing in the right type and desirable amounts of organic linkers. FeCx nanoparticles doped with various percentages of nitrogen atoms were synthesized for the Fischer-Tropsch reaction without any pretreatment or activation. Extremely high iron time of yield (FTY) values were observed, 415 and 550 μmol gFe-1 s-1 (with addition of K), in a 40 h test without any decay in performance. A high olefin to paraffin ratio was achieved for C2 to C11 products, where the ratio for C3 was higher than 10.

Turbulences of the supersonic gas flow during cold spraying and their negative effects: A DNS CFD analysis coupled with experimental observation and laser impulse high-speed shadowgraphs of the particles in-flight flow

This paper investigates the phenomenological flow during cold spraying through DNS CFD analysis and experimental observations. The transient DNS computation shows that the gas flow begins to be instable inside the nozzle and generates self-sustained intermittent swirls across the nozzle exit due the shearing behavior of the flow. There is alternate swirling within the separated sheared layers on top and then on bottom of the jet, at sporadic time intervals. The swirls are not strictly periodic in nature, but they recur with an irregular frequency. The temperature field exhibits analogous variation and the thermal turbulence produces a heating confinement within the end zone of the nozzle, at the upper wall mostly. This phenomenon matches with the experimental erosion at the same zone due to a thermomechanical softening of the nozzle. The supersonic jet is self-oscillated along the flow direction and becomes more and more turbulent with a development of vorticity shedding at a certain distance from the nozzle exit. There is a transition from a rather stable jet towards a wake pattern that characterizes the vorticity regime. The thermal turbulence shows a development of turbulent plume which provides a clearer visualization of the straight jet and the abrupt transition into wakes. Experimental observations of particles motion ahead the nozzle exit confirm this turbulent behavior of the gas flow. High-speed shadowgraphy using nanoseconds pulsed laser spray illumination shows two regimes of particles kinematics, that is, a nearly straight jet prior to a progressive stream deviation, and then a full dispersion of the particles. Such dispersion makes possible an oblique collision of the particles on the substrate whose negative effects highlighted in the literature are high porosity within the deposit, difficulty of coating formation, and substantial decrease in deposition efficiency. These findings provide further clarifications about how both gas flow and particles flow behave during cold spraying, and how deviation effects due to turbulences of the supersonic expansion may further alter the deposition capability of LPCS that already suffers from a low DE less than 40%.

High-Throughput and Direct Sample Screening Using a Laser Spray Ionization Miniature Mass Spectrometer

Over the past two decades, great efforts have been made toward mass spectrometer instrument miniaturization. With increasing analytical performances, miniature mass spectrometers are on the edge of being applied to more application scenarios. Besides sensitivity, mass resolution, and instrument portability, high-throughput and little or no sample preparation are also critical features in practical applications. In this study, we report the development of a miniature mass spectrometry (MS) system equipped with a 2D moving platform and a laser spray ionization (LSI) source. The method to make a patterned sample holder was also introduced and optimized for automatic high-throughput sample analyses. With the LSI source, analytes in complex matrix could be directly mass analyzed; in addition to the 2D moving platform, different samples could be analyzed in a high-throughput fashion. Results show that good linearity of quantitation could be achieved for multiple samples. Tens of nanograms of drugs, peptides, and vitamin B could be identified in diluted whole blood samples, and it takes 10 s on average to scan one sample.

Structures and Properties of Laser-Assisted Cold-Sprayed Aluminum Coatings

In the cold spray process, solid particles impact on a surface with high kinetic energy, deform plastically and form a coating. This enables the formation of pure and dense coating structures. Even more, coating performance and deposition efficiency can be improved by assisting the process with a laser. Laser-assisted cold spraying (LACS) has shown its potential to improve coating properties compared with traditional cold spraying. In this study, coating quality improvement was obtained by using a co-axial laser spray (COLA) process which offers a new, cost-effective laser-assisted cold spray technique, for high-quality deposition and repair. In the COLA process, the sprayed surface is laser heated while particles hit the surface. This assists the better bonding between particles and substrate and leads to the formation of tight coating structures. This study focuses on the evaluation of the microstructural characteristics and mechanical properties (e.g., hardness and bond strength) of LACS metallic coatings.

Crystallization of zirconia based thin films.

The crystallization kinetics of amorphous 3 and 8 mol% yttria stabilized zirconia (3YSZ and 8YSZ) thin films grown by pulsed laser deposition (PLD), spray pyrolysis and dc-magnetron sputtering are explored. The deposited films were heat treated up to 1000 °C ex situ and in situ in an X-ray diffractometer. A minimum temperature of 275 °C was determined at which as-deposited amorphous PLD grown 3YSZ films fully crystallize within five hours. Above 325 °C these films transform nearly instantaneously with a high degree of micro-strain when crystallized below 500 °C. In these films the t'' phase crystallizes which transforms at T > 600 °C to the t' phase upon relaxation of the micro-strain. Furthermore, the crystallization of 8YSZ thin films grown by PLD, spray pyrolysis and dc-sputtering are characterized by in situ XRD measurements. At a constant heating rate of 2.4 K min(-1) crystallization is accomplished after reaching 800 °C, while PLD grown thin films were completely crystallized already at ca. 300 °C.

Laserspray and Matrix-Assisted Ionization Inlet Coupled to High-Field FT-ICR Mass Spectrometry for Peptide and Protein Analysis

We present the first coupling of laser spray ionization inlet (LSII) and matrix assisted ionization inlet (MAII) to high-field Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for generation of electrospray-like ions to take advantage of increased sensitivity, mass range, and mass resolving power afforded by multiple charging. We apply the technique to top-down protein analysis and characterization of metalloproteins. We also present a novel method for generation of multiply-charged copper-peptide complexes with varying degrees of copper adduction by LSII. We show an application of the generated copper-peptide complexes for protein charge state and molecular weight determination, particularly useful for an instrument such as a linear ion trap mass analyzer.

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.

Comparison of microstructure and electronic properties of TiO2 thin films grown by different techniques

Thin films of TiO2 were grown on alumina and silicon substrates through various deposition routes, namely, radio frequency sputtering, pulsed laser deposition and spray pyrolysis. The films were characterised using X-ray diffraction, Raman spectroscopy, scanning electron microscopy and ultraviolet-visible spectroscopy. The band gaps of the thin films were compared with respect to their morphology, phase structure and composition. The particle sizes obtained were in the range of 10–30 nm, and spherical or bead-like morphology was obtained depending on the processing route used. The band gaps showed an increase from 3·28 to 3·50 eV upon decrease in particle size, which correlated well with the theoretical studies. Nanoindentation studies performed on the films grown on Si showed higher hardness and modulus for radio frequency sputtering films compared to other techniques. The microstructurally tunable electronic properties can be exploited to derive specificity and sensitivity towards gas sensing.

Effectiveness of the erbium:YAG laser and new design radial and stripped tips in removing the smear layer after root canal instrumentation

The aim of this study was to analyze in vitro the debriding ability of an Er:YAG laser system (2,940 nm) equipped with a newly designed radial and stripped tip of 400 µm diameter by scanning electron microscopy (SEM). A total of 80 single-rooted extracted human teeth were endodontically prepared with rotary instrumentation and standardized chemical irrigation using 5.25% sodium hypochlorite. At the end of mechanical instrumentation, four different final protocols were used. Group 1 was irrigated for 2 min with saline water as a control group. Groups 2, 3 and 4 were irradiated with an Er:YAG laser at 25 mJ and 15 Hz with a pulse duration of 50 μs and laser spray off using the tip in the coronal opening of the wet root canal. Different solutions and irradiation times were used: group 2 20 s, laser irradiation in sterile distilled water, wet canal; group 3 20 s, laser irradiation in 17% EDTA, wet canal; and group 4 40 s, laser irradiation in 17% EDTA, wet canal. Debridement of and smear layer removal from the apical third of root canals were evaluated by SEM. The study showed that standardized instrumentation, followed by a final Er:YAG laser irradiation in wet canals with EDTA irrigation resulted in more cleaning of the root canal walls and a higher quantity of open tubules in comparison with the traditional irrigation method.

Measurement of sugars using the laser spray technique with a gold capillary

A gold (Au) capillary has higher thermal conductivity than a stainless steel capillary and can withstand capillary over-heating induced by high CO(2) laser irradiation (over 2.5 W) better than a stainless steel capillary. For this study, a laser spray using an Au capillary was applied for the detection of sugars. The signal of cationized compounds [M+Na](+) can be detected with higher sensitivity than with conventional laser sprays using high laser power (over 2.7 W). Using 3.5 W of laser power, the signal intensity is 15 times higher than the maximum value with stainless steel (2.3 W) in a 10(-5) M maltose aqueous solution. It is considered that almost all the water molecules evaporate by laser irradiation, which is impossible to achieve using a stainless steel capillary.

Thermal unfolding of proteins probed by laser spray mass spectrometry

The stability and conformational changes of cytochrome c (cyt c) at different temperatures and pH have been well examined so far by using various analytical methods. We have found that laser spray mass spectrometry enables much faster and more convenient monitoring of those changes of cyt c compared with other methods. The results correlated well with circular dichroism (CD) experiments under relatively acidic conditions, which destabilize the protein. Laser spray mass spectra of cyt c at various pH were obtained at different levels of laser power. Bimodal charge-state distributions of the protein were observed in laser spray mass spectra, indicating the two-state model of structural change; the lower charges correspond to the folded state, the higher charges to the unfolded state. Based on this result, the presumed denaturation curve of the protein was plotted as a function of laser power, and laser power by which 50% of the protein was assumed to be denatured, E50%, as obtained at each pH. We also examined the melting temperatures, Tm, of cyt c at various values of pH by using CD spectroscopy. The correlation coefficient between E50% and Tm for cyt c was 0.999, demonstrating an excellent correlation. Furthermore, laser spray analysis of ubiquitin, which is found to be more thermally stable than cyt c, gave a higher E50% than cyt c. These results indicate that laser spray mass spectrometry can be an extremely convenient method for probing thermal stabilities and dynamic conformational changes of proteins with subtle structural differences caused by slight changes in pH.

レーザースプレー質量分析が可能にした生体高分子複合体の結合親和性の定量的な解析

This commentary describes the advantages of laser spray, which was developed by Hiraoka et al., in the analysis of binding affinities of biomolecular complexes, such as DNA-protein and DNA-drug complexes. Since laser spray enables dissociation of the complexes without fragmentation of labile compounds such as DNA, a good correlation was found between the binding affinities and applied laser power for dissociation. We found that laser spray is promising for rapid characterization of binding affinities of complexes with small differences in structure.

新しい質量分析技術の法医学領域への応用

In the fields of legal medicine and forensic toxicology, numerous drugs and poisons obtained from diverse biological specimens such as whole blood, urine, and hair need to be identified and quantified. Therefore, it is necessary to develop new methods for analysis of drugs, especially mass spectrometric methods. In this paper, we introduce three methods—surface ionization organic mass spectrometry, a combination of mass spectrometry and cryogenic oven trapping (COT), and laser spray ionization (LSI)—and their application to legal medicine. Gas chromatography/surface ionization organic mass spectrometry is very sensitive in detecting drugs containing tertiary amine residues; for Phencyclidine (PCP), its sensitivity is 20 to 1,000 times higher than that of the conventional electron ionization method. Surface ionization organic mass spectrometry is suitable for compounds containing cyclic tertiary amino side chains. COT in combination with gas chromatography has enabled detection of many volatile organic compounds (VOCs) with high sensitivity. We have succeeded in quantifying several VOCs, such as chloroform, cyanide, thinner components, ethanol, and general anesthetics in whole blood by COT; COT affords a sensitivity that is 10 to 50 times higher than that of the conventional headspace gas chromatography method. Recently, we succeeded in identifying and quantifying 15 VOCs in human whole blood with the combination of COT and mass spectrometry. LSI is a new ionization method for liquid chromatography/mass spectrometry. We have succeeded in detecting aconitine alkaloids and psychopharmaceuticals using LSI. In the infusion mode, aconitine and haloperidol were ionized with higher efficiency compared to that in the conventional electrospray mode. However, since the signals in the LSI mode are not stable, it is necessary to improve the stability of signals in the LSI mode for applying LSI to forensic toxicology.

Supersonic laser spray of aluminium alloy on a ceramic substrate

Applying a ceramic coating onto a metallic substrate to improve its wear resistance or corrosion resistance has attracted the interest of many researchers during decades. However, only few works explore the possibility to apply a metallic layer onto a ceramic material. This work presents a novel technique to coat ceramic materials with metals: the supersonic laser spraying. In this technique a laser beam is focused on the surface of the precursor metal in such a way that the metal is transformed to the liquid state in the beam–metal interaction zone. A supersonic jet expels the molten material and propels it to the surface of the ceramic substrate. In this study, we present the preliminary results obtained using the supersonic laser spray to coat a commercial cordierite ceramic plate with an Al–Cu alloy using a 3.5 kW CO 2 laser and a supersonic jet of Argon. Coatings were characterized by scanning electron microscopy (SEM) and interferometric profilometry.

Denaturation of α‐lactalbumin and ubiquitin studied by electrospray and laser spray

Electrospray and laser spray mass spectra of human alpha-lactalbumin and bovine ubiquitin were studied, with an emphasis on the denaturation induced by laser spray. There were no remarkable differences in the electrospray and laser spray mass spectra for acidic and basic aqueous solutions of alpha-lactalbumin in positive and negative modes of operations. This originates from the fact that this protein is tightly folded with four disulfide bonds. For ubiquitin, however, denaturation was induced by laser spray for the positive mode of operation and the [M+nH](n+) with a maximum of n = 13 was observed, i.e., all the acidic amino acid residues are fully neutralized (protonated). In contrast, the laser-induced denaturation was not observed for the negative mode of operation, i.e., denaturation of ubiquitin is largely suppressed in the negatively charged liquid droplets. The marked difference observed in the positive and negative modes of operations for ubiquitin is ascribed to the difference in the susceptibility of side-chain/main-chain interactions in the positive-ion excess and in the negative-ion excess liquid droplets. That is, the interactions between the basic residues and main-chain amide carbonyl groups (-NH(3) (+)***O=C< or -NH(2)***O=C<) which play an important role in stabilizing the protein structures are not so affected in the negative mode of operation but are weakened in the positive mode of operation.

Effect of Two Polysaccharide Adjuvants on Glyphosate Spray Droplet Size and Efficacy

Laboratory and field studies were conducted to determine the effect of the drift control adjuvants HM 2005B and HM 9752 on the droplet spectra and efficacy of spray mixtures of a potassium salt formulation of glyphosate. Droplet spectra were examined using a laser spray droplet analyzer. The addition of each adjuvant decreased the percentage of the spray volume in small diam spray droplets (&lt;141μm) and either had no effect or increased glyphosate efficacy. These adjuvants could prove useful for providing management in potential drift situations.

Laser spray cladding of porous NiTi coatings on NiTi substrates

Laser spray cladding in N 2-rich atmosphere is a competitive technique for manufacture of porous NiTi shape memory alloy (SMA) and TiN surface film. In order to gain expected porous coating and porosity size, TiH 2 powder was considered to be used as porosity initiating agent, and nitrogen was used for shielding and active nitriding gas. A 2 kW continuous wave Nd:YAG laser equipped with a 3-way coaxial nozzle was used for laser spraying. NiTi alloy powder and TiH 2 powder were used as additive materials. The mixed powder of NiTi and TiH 2 was conveyed by a powder feeder, congregated at the laser interacting zone and sprayed onto the substrate with molten droplets. In order to improve the corrosion resistance of the surface of coating layer, a gas nitriding process is facilitated simultaneously during the laser spraying and cladding process in nitrogen-rich atmosphere. A gradient porous coating of NiTi alloy had been manufactured by laser spraying. The investigation shows that there are pores with size of 100–200 μm near the surface. XRD analysis shows that the coating consists of intermetallic compounds NiTi, NiTi 2 and nitrides TiN, Ti 2N. Corrosion test was carried out in Hank's balanced salt solution (H9269) by potentiostat/galvanostat model 273A. The polarization curves of the test result demonstrates the porous coating with TiN presents better corrosion resistance than NiTi substrate.

Stability analysis for double‐stranded DNA oligomers and their noncovalent complexes with drugs by laser spray

Laser spray, which is a newly developed ionization technique, can characterize the stability of noncovalent complexes in the solution phase. By using this advantage, laser spray has been applied to probe the intrinsic stability of double-stranded DNA (dsDNA) sequences and their binding affinities with various drugs in the solution phase. Systematic experiments were carried out using six 16-mer and three 22-mer dsDNA oligomers, together with the complexes of the 16-mer dsDNA with minor groove binders: berenil, Hoechst 33342, DAPI, and netropsin. Dissociation curves for each dsDNA or each complex were plotted as a function of laser power. The laser power (E50%), where 50% of each dsDNA or each complex was dissociated, was compared with its melting temperature (Tm) determined by UV spectroscopy. Linear correlations between E50% and Tm were obtained not only for the dsDNA oligomers (correlation factor r = 0.9835) but also for the 16-mer dsDNA complexes with minor groove binders (r = 0.9966). In addition, laser spray has successfully clarified the binding affinities of a 16-mer dsDNA with two intercalators: daunomycin and nogalamycin. In the case of the dsDNA-daunomycin complex, by changing the molar ratio of dsDNA : drug from 1 : 1 to 1 : 5, the concentration-dependent stability of the complex was confirmed by laser spray. The present results demonstrate that laser spray mass spectrometry can be a powerful and convenient method to investigate the relative binding affinities of dsDNA-ligand complexes in the solution phase, which could be applied to the early stage of high-throughput screening of drugs targeting for dsDNA.

Evaluation of Binding Affinity of Protein–Mutant DNA Complexes in Solution by Laser Spray Mass Spectrometry

We have applied laser spray mass spectrometry developed by Hiraoka et al. to investigate the binding affinity of protein-mutant DNA complexes. The results were compared with our previous data of collision-induced dissociation (CID) experiments using electrospray ionization mass spectrometry (ESI-MS). Systematic experiments were carried out on the complexes of the c-Myb DNA binding domain (c-Myb DBD) bound to eight kinds of 16- or 22-mer point mutant double-stranded DNA (dsDNA), whose solution K(d) values are different in the range from 10(-9) M to 10(-7) M. The dissociation curve as a function of laser power was plotted for each complex, and the laser power where 50% of complex was dissociated (E(50%)) in population was obtained. The correlation coefficient between E(50%) and the relative binding free-energy change (DeltaDeltaG) of each complex formation in solutions was 0.9808, which is much better than the coefficient obtained by the previous ESI-CID experiments that was 0.859. In addition, complexes of the c-Myb DBD with five other mutant dsDNA were also examined to confirm that laser spray can be used to estimate the K(d) values of a DNA-protein complex in solutions if an appropriate calibration curve is available. In the process of laser spray, dissociations of these noncovalent complexes occur in solutions, but not in the gas phase. This differs greatly from ESI-CID. Laser spray mass spectrometry has been found to be better than ESI-CID in evaluating binding affinity of a protein to various mutant DNA.