V. V. Golovlev

Laser-induced acoustic desorption

Abstract The basic principles and experimental results of laser-induced acoustic desorption (LIAD) are reported in this work. LIAD was successfully used to desorb biomolecules in a mass spectrometer. LIAD holds some promise to eliminate many key factors which contribute to poor mass resolution in MALDI. Thus, it has potential for improvement in resolution of biomolecular mass analysis.

Reverse saturable absorption of C 60 in liquids irradiated by picosecond and nanosecond laser pulses

Reverse saturable absorption of C60 dissolved in different solvents has been investigated under irradiation with 7-ns or 25-ps laser pulses at 532 nm. The results show that the solutions act as efficient power-limiting media under laser fluence of as high as 3 J/cm2 for both picosecond and nanosecond laser pulses. The reversely saturated (clamped) level depends on the type of solvent used. It was found that the saturated level is the lowest with carbon disulfide in comparison with several other solvents. A phenomenological model is used to describe optical limiting phenomena, including the darkening effect of C60 and the possible contribution of the solvent at high laser intensity.

Laser-induced acoustic desorption of electrons and ions

Laser irradiation of absorbing materials can be used to generate acoustic pulses with extremely high amplitude and short pulse duration. Such acoustic pulses can transfer energy and momentum to atomic particles on solid surfaces to cause desorption of the particles. We report experimental observations of the effect of laser-induced acoustic desorption (LIAD) of electrons from metal film surfaces and hydrogen ions from the surface of palladium saturated with hydrogen. We believe LIAD can be used as a gentle technique to transfer analyte molecules and ions into gas phase for mass analysis and for other applications.

Matrix‐assisted laser desorption/ionization for short tandem repeat loci

Matrix-assisted laser desorption/ionization was used for the detection of four base short tandem repeats (STR) for clinical samples using a time-of-flight mass spectrometer. Since STR plays an important role in genetic disease and human identification, this work indicates that laser desorption mass spectrometry has the potential to achieve rapid DNA typing for both forensic applications and genetic disease diagnosis.

Detection of trinucleotide expansion in neurodegenerative disease by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Genotyping of the dentatorubral-pallidoluysian atrophy (DRPLA) locus in six patient samples, representing four normal individuals and two DRPLA patients, was successfully obtained using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). DRPLA is a dominantly inherited neurodegenerative disorder associated with the expansion of an unstable trinucleotide (CAG) repeat. The accurate determination of repeat length utilizing MALDI supports the use of this methodology for the analysis of genes containing unstable CAG trinucleotide repeats.

Matrix-assisted Laser Desorption/Ionization for Sequencing Single-stranded and Double-stranded DNA

The DNA sequence of a single-stranded and double-stranded template was determined. The templates were sequenced using the chain termination method and cycle sequencing method and detected by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The sequencing products were analyzed successfully without the laborious and expensive methods for removal of the template. Direct sequencing of the double-stranded template was achieved with minimal post-reaction purifications, which could be extremely important for mutation analysis and clinical diagnosis. A systematic study of the mechanisms and kinetics of sequencing reactions was also performed. The details of this analysis and directions for future improvements of the quality of sequencing are presented.

DIRECT MONITORING OF LASER ABSORPTION OF MALDI MATRICES BY FAST PIEZOELECTRIC TRANSDUCER

Abstract The absorption of laser energy by recently found matrices used in matrix assisted laser desorption ionization (MALDI) detection of large DNA segments: 3-hydroxypicolinic acid (3-HPA), picolinic acid (PA), composite matrix (PA + 3-HPA) and 3-aminopicolinic acid (3-APA), was studied by using a fast piezoelectric transducer for solid matrices and for their aqueous solutions. A nonlinear dependence of acoustical signal on laser fluence was found for PA, PA + 3-HPA and 3-APA matrices at 266 nm. Near linear dependence was found for 3-HPA at 266 nm. There was no strong deviation from linear power dependence for any of these matrices at 355 nm. Possible mechanisms to account for the observed nonlinearity are discussed.