Molecular chlorine was photolyzed using circularly polarized radiation at 310 and 330 nm, and ori... more Molecular chlorine was photolyzed using circularly polarized radiation at 310 and 330 nm, and orientation moments of the chlorine-atom photofragment distributions were measured by resonance enhanced multiphoton ionization using circularly polarized light with Doppler resolution. ...
Molecular chlorine, methane and helium are co-expanded into the extraction region of a Wiley–McLa... more Molecular chlorine, methane and helium are co-expanded into the extraction region of a Wiley–McLaren time-of-flight spectrometer. After preparing the first overtone of the antisymmetric stretch ( 3 1⁄4 2) with direct IR excitation, the reaction is initiated by photolysing Cl2 with 355 nm light to produce mono-energetic Cl atoms with a translational energy of 0.18 eV. The CD3 and DCl products are state-selectively detected via resonance enhanced multiphoton ionization (REMPI) and analysed with the core-extraction technique. Unusual structure in the 3pz CD3 REMPI spectrum suggests the presence of a previously unobserved transition, which we assign to the stretch–bend combination (112 1 1) band. The product correlated energy disposal and the scattering distributions are compared with the same quantities for the ClþCH4( 3 1⁄4 2) reaction and found to be similar, although subtle differences are observed. The results for the ClþCD4( 3 1⁄4 2) reaction support a localized chemistry model in...
We describe procedures for the measurement of the differential-cross-section moments of the veloc... more We describe procedures for the measurement of the differential-cross-section moments of the velocity distribution of the state-selected products of photoinitiated bimolecular reactions using resonance-enhanced multiphoton ionization (REMPI) detection and some form of ...
Enzymatic digestion for protein sequencing usually requires much time, and does not always result... more Enzymatic digestion for protein sequencing usually requires much time, and does not always result in high sequence coverage. Here we report the use of aqueous microdroplets to accelerate enzymatic reactions and, in particular, to improve protein sequencing. When a room temperature aqueous solution containing 10 µM myoglobin and 5 µg mL−1 trypsin is electrosonically sprayed (−3 kV) from a homemade setup to produce tiny (∼9 µm) microdroplets, we obtain 100% sequence coverage in less than 1 ms of digestion time, in sharp contrast to 60% coverage achieved by incubating the same solution at 37 °C for 14 h followed by analysis with a commercial electrospray ionization source that produces larger (∼60 µm) droplets. We also confirm the sequence of the therapeutic antibody trastuzumab (∼148 kDa), with a sequence coverage of 100% for light chains and 85% for heavy chains, demonstrating the practical utility of microdroplets in drug development.
Isobaric ions having the same mass-to-charge ratio cannot be separately identified by mass spectr... more Isobaric ions having the same mass-to-charge ratio cannot be separately identified by mass spectrometry (MS) alone, but this limitation can be overcome using hydrogen-deuterium exchange (HDX) in microdroplets. Because isobaric ions may contain a varied number of exchangeable sites and different types of functional groups, each one produces a unique MS spectral pattern after droplet spray HDX without the need for MS/MS experiments or introduction of ion mobility measurements. As an example of the power of this approach, isobaric ions in urinary metabolic profiles are identified and used to distinguish between healthy individuals and those having bladder cancer.
Disinfectants are important for arresting the spread of pathogens in the environment. Frequently ... more Disinfectants are important for arresting the spread of pathogens in the environment. Frequently used disinfectants are often incompatible with certain surfaces, expensive and can produce hazardous by-products. We report that micron-sized water droplets can act as an effective disinfectant, which were formed by spraying pure bulk water with coaxial nebulizing airflow. Spraying for 20 min onto Escherichia coli and Salmonella typhimurium on stainless-steel discs caused inactivation of over 98% of the bacteria. Control experiments resulted in less than 10% inactivation (water stream only and gas only) and 55% inactivation with 3% hydrogen peroxide. Experiments have shown that cell death results from cell wall destruction. We suggest that the combined action of reactive oxygen species present in water droplets (but not in bulk water) along with the droplet surface charge is responsible for the observed bactericidal activity.
We report the use of an online electrochemistry/mass spectrometry platform to develop a redox neu... more We report the use of an online electrochemistry/mass spectrometry platform to develop a redox neutral electrosynthesis of 5-membered rings via [3 + 2] annulation of N-cyclopropylanilines and alkenes, without additional oxidant, reductant or catalyst.
Molecular chlorine was photolyzed using circularly polarized radiation at 310 and 330 nm, and ori... more Molecular chlorine was photolyzed using circularly polarized radiation at 310 and 330 nm, and orientation moments of the chlorine-atom photofragment distributions were measured by resonance enhanced multiphoton ionization using circularly polarized light with Doppler resolution. ...
Molecular chlorine, methane and helium are co-expanded into the extraction region of a Wiley–McLa... more Molecular chlorine, methane and helium are co-expanded into the extraction region of a Wiley–McLaren time-of-flight spectrometer. After preparing the first overtone of the antisymmetric stretch ( 3 1⁄4 2) with direct IR excitation, the reaction is initiated by photolysing Cl2 with 355 nm light to produce mono-energetic Cl atoms with a translational energy of 0.18 eV. The CD3 and DCl products are state-selectively detected via resonance enhanced multiphoton ionization (REMPI) and analysed with the core-extraction technique. Unusual structure in the 3pz CD3 REMPI spectrum suggests the presence of a previously unobserved transition, which we assign to the stretch–bend combination (112 1 1) band. The product correlated energy disposal and the scattering distributions are compared with the same quantities for the ClþCH4( 3 1⁄4 2) reaction and found to be similar, although subtle differences are observed. The results for the ClþCD4( 3 1⁄4 2) reaction support a localized chemistry model in...
We describe procedures for the measurement of the differential-cross-section moments of the veloc... more We describe procedures for the measurement of the differential-cross-section moments of the velocity distribution of the state-selected products of photoinitiated bimolecular reactions using resonance-enhanced multiphoton ionization (REMPI) detection and some form of ...
Enzymatic digestion for protein sequencing usually requires much time, and does not always result... more Enzymatic digestion for protein sequencing usually requires much time, and does not always result in high sequence coverage. Here we report the use of aqueous microdroplets to accelerate enzymatic reactions and, in particular, to improve protein sequencing. When a room temperature aqueous solution containing 10 µM myoglobin and 5 µg mL−1 trypsin is electrosonically sprayed (−3 kV) from a homemade setup to produce tiny (∼9 µm) microdroplets, we obtain 100% sequence coverage in less than 1 ms of digestion time, in sharp contrast to 60% coverage achieved by incubating the same solution at 37 °C for 14 h followed by analysis with a commercial electrospray ionization source that produces larger (∼60 µm) droplets. We also confirm the sequence of the therapeutic antibody trastuzumab (∼148 kDa), with a sequence coverage of 100% for light chains and 85% for heavy chains, demonstrating the practical utility of microdroplets in drug development.
Isobaric ions having the same mass-to-charge ratio cannot be separately identified by mass spectr... more Isobaric ions having the same mass-to-charge ratio cannot be separately identified by mass spectrometry (MS) alone, but this limitation can be overcome using hydrogen-deuterium exchange (HDX) in microdroplets. Because isobaric ions may contain a varied number of exchangeable sites and different types of functional groups, each one produces a unique MS spectral pattern after droplet spray HDX without the need for MS/MS experiments or introduction of ion mobility measurements. As an example of the power of this approach, isobaric ions in urinary metabolic profiles are identified and used to distinguish between healthy individuals and those having bladder cancer.
Disinfectants are important for arresting the spread of pathogens in the environment. Frequently ... more Disinfectants are important for arresting the spread of pathogens in the environment. Frequently used disinfectants are often incompatible with certain surfaces, expensive and can produce hazardous by-products. We report that micron-sized water droplets can act as an effective disinfectant, which were formed by spraying pure bulk water with coaxial nebulizing airflow. Spraying for 20 min onto Escherichia coli and Salmonella typhimurium on stainless-steel discs caused inactivation of over 98% of the bacteria. Control experiments resulted in less than 10% inactivation (water stream only and gas only) and 55% inactivation with 3% hydrogen peroxide. Experiments have shown that cell death results from cell wall destruction. We suggest that the combined action of reactive oxygen species present in water droplets (but not in bulk water) along with the droplet surface charge is responsible for the observed bactericidal activity.
We report the use of an online electrochemistry/mass spectrometry platform to develop a redox neu... more We report the use of an online electrochemistry/mass spectrometry platform to develop a redox neutral electrosynthesis of 5-membered rings via [3 + 2] annulation of N-cyclopropylanilines and alkenes, without additional oxidant, reductant or catalyst.
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