Laser-induced Mass Spectrometry Research Articles

Towards multiproxy, ultra-high resolution molecular stratigraphy: Enabling laser-induced mass spectrometry imaging of diverse molecular biomarkers in sediments

Mass spectrometry imaging (MSI) collects mass spectra of organic compounds from individual micrometer-sized spots and yields high-resolution images of the spatial distribution of target analytes on sample surfaces. MSI can potentially open a new avenue to ultra-high resolution molecular stratigraphy by resolving the fine-scale distribution of molecular biomarkers in geological records. However, ionization of organic molecules within their sediment matrix remains a critical challenge. Building on the recent introduction of MSI of archaeal tetraether lipids, we have extended the analytical spectrum to additional biomarkers and provide guidelines for the generation of multiproxy, ultra-high resolution paleoenvironmental records. We evaluated the addition of artificial matrices to promote ionization, defined the most suitable MS settings, and increased analytical complexity from pure compounds to their investigation in sediment. Most compounds relevant to molecular stratigraphy are not properly ionized in the presence of conventional matrices, but require atypical ones, such as those based on carbon or silver. Sediments serve as a natural matrix, directly allowing detection of many of these compounds. However, the sediment matrix also inhibits some reactions that otherwise promote detection, such as derivatization of alkenones or silver-mediated ionization of n-alkanes. The robustness of MSI-based molecular stratigraphy is enhanced by analysis of target compounds in narrow m/z ranges, and by summation of mass spectra from several coeval measurement spots. We present an initial inventory of compounds readily detected in the sediment tested, including long chain alkenones and diols, sterols, and pigments, and provide an outlook into the use of MSI in multiproxy studies.

Application of laser microdissection ICP–MS for high resolution elemental mapping in mouse brain tissue: A comparative study with laser ablation ICP–MS

Mapping of elements in biological tissue by laser induced mass spectrometry is a fast growing analytical methodology in life sciences. This method provides a multitude of useful information of metal, nonmetal, metalloid and isotopic distribution at major, minor and trace concentration ranges, usually with a lateral resolution of 12–160µm. Selected applications in medical research require an improved lateral resolution of laser induced mass spectrometric technique at the low micrometre scale and below. The present work demonstrates the applicability of a recently developed analytical methodology – laser microdissection associated to inductively coupled plasma mass spectrometry (LMD ICP–MS) – to obtain elemental images of different solid biological samples at high lateral resolution. LMD ICP–MS images of mouse brain tissue samples stained with uranium and native are shown, and a direct comparison of LMD and laser ablation (LA) ICP–MS imaging methodologies, in terms of elemental quantification, is performed.

Mass spectrometry imaging (MSI) of metals by laser ablation ICP-MS and metallomics of biomedical samples

Trace metals are essential in life science and play a major role in biological processes. Knowledge of spatial distri- bution of metals and metal-containing proteins is fundamental for understanding the pathophysiology of metalloproteins, the impact of metal metabolism and metal-containing deposits in healthy brains and brains of patients suffering from neurological diseases. In recent years, there has been a growing interest in studying metal imaging in biological and especially in clinical tis- sues. In most neurodegenerative diseases, abnormal metal deposition has been observed within the brain (e.g., in Alzheimer's, Parkinson's or Wilson diseases). Laser-induced mass spectrometry is a novel emerging analytical tool to generate two- and three-dimensional maps of the distribution of elements, isotopes and molecules in different systems. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) is one of the most important inorganic mass spectrometric technique for solid materials and has been successfully applied to produce quantitative images of detailed regionally specific element distributions in thin soft tissue sections of biological and clinical samples. The spatial resolved BrainMet techniques (BrainMet - Bioimaging of Metals in Brain and Metallomics) developed at Research Centre Juelich have been created and established for metal distribution studies in thin biomedical cryosection and it can be employed for fundamental biomedical investigation of biochemical pathways up to single cell level and in future for disease diagnostics and neuroprotective therapies of neurological disorders.

The effect of nanosized titania-silica film composition on the photostability of adsorbed methylene blue dye

The effect of nanosized porous films (average density 10 g/m2) of TiO2. TiO2/SiO2, and SiO2 on the photostability of adsorbed methylene blue (MB) dye during UV irradiation in air was investigated by optical spectroscopy and laser-induced mass spectrometry. The effectiveness of the photodecomposition of MB decreases in the order TiO2 > TiO2/SiO2 > SiO2 with rate constants 1E-2, 0.6E-2, and 0.3E-2 min−1 respectively. A mechanism including the participation of both excited states of the dye molecules and photoexcited titanium dioxide is proposed for the photodecolorization of MB adsorbed on the surface of the investigated films.

Purification and characterization of d(+)-carnitine dehydrogenase from Agrobacterium sp. — a new enzyme of carnitine metabolism

d(+)-Carnitine dehydrogenase from Agrobacterium sp. catalyzes the oxidation of d(+)-carnitine to 3-dehydrocarnitine as initial step of d(+)-carnitine degradation. The NAD +-specific, cytosolic enzyme was purified 126-fold to apparent electrophoretic homogeneity by 4 chromatographic steps. The molecular mass of the native enzyme was estimated to be 88 kDa by size-exclusion chromatography. It seems to be composed of 3 identical subunits with a relative molecular mass of 28 kDa as found by sodium dodecyl sulfate polyacrylamide gel electrophoresis and laser-induced mass spectrometry. The isoelectric point was found to be 4.7–5.0. The optimum temperature is 37°C and the optimum pH for the oxidation and the reduction reaction are 9.0–9.5 and 5.5–6.5, respectively. The purified enzyme was further characterized with respect to substrate specificity, kinetic parameters and amino terminal sequence. Analogues of d(+)-carnitine ( l(−)-carnitine, crotonobetaine, γ-butyrobetaine, carnitine amide, glycine betaine, choline) are competitive inhibitors of d(+)-carnitine oxidation. The equilibrium constant of the reaction of d(+)-carnitine dehydrogenase was determined to be 2.2 × 10 −12. The purified d(+)-carnitine dehydrogenase has similar kinetic properties to the l(−)-carnitine dehydrogenase from the same microorganism as well as to l(−)-carnitine dehydrogenases of other bacteria.

Detection of xenophobic response in the periostracum of the bivalve,Corbicula fluminea, through laser-induced mass spectrometry

Aqueous-phased xenobiotic contaminant exposure can biochemically modify newly generated periostracum of the Asian freshwater bivalve,Corbicula fluminea. Laser-induced desorption of partially polymerized periostracum produces spectra distinguishable from mass spectral images generated from uncontaminated periostracum. Organic xenobiotic contamination putatively impedes full polymerization of the periostracin protein. The detection of the effects of pollution on periostracum by the laser microprobe mass analyzer constitutes a novel bioprobe for the definitive but qualified detection of xenobiotic contamination.

The chemistry of 3-mtro-1,2,4-triazol-5-one (NTO): thermal decomposition

This paper presents the results from a study of the thermal decomposition and thermal stability of NTO (3-nitro-1,2,4-triazol-5-one). Mass spectra of NTO are presented (electron impact 20 and 70 eV and chemical ionisation spectra). The large abundance of the molecular ion in these spectra shows that NTO is a more stable molecule than TNT or RDX. The data acquired for NTO is summarised as a proposed mass spectral fragmentation path. A number of laser ignition measurements were conducted. These measurements showed a strong pressure dependence, which clearly indicates a multiple phase (condensed and gas phase) ignition. The laser ignition measurements also showed that the sensitivity to ignition is slightly higher than that for TNT. The results of the LI-MS (laser induced mass spectrometry) method applied to NTO imply that the probable decomposition path is an elimination of NO 2 followed by a breaking of the azole ring. The chemiluminescence (CL) method was used for determination of the activation energy and the frequency factor ( E a= 140 kJ and K 0= 5 × 10 6s −1 in the temperature interval 100–140° C). Chemiluminescence data for RDX and TNT was acquired for comparison. The DSC spectrum of NTO showed only one peak, a very strong exothermic peak at 253°C. This study is complemented with some quantum mechanical calculations which were conducted in an attempt to verify the initial steps in the decomposition path and to explain the high stability of NTO. The results were computed with the mopac 6.0 code using the semi-empirical modified neglect of diatomic overlap (MNDO) method with the parametric method 3 (PM3) parameter set at the unrestricted Hartree-Fock level.

Some remarks about laser-induced mass spectrometry of bacteria.

In order to investigate the availability of laser-induced mass spectrometry for the determination of bacteria, ten strains of the genera Escherichia and Streptococcus were chosen. Gram-negative as well as Gram-positive lysogenic and non-lysogenic, pathogenic and non-pathogenic strains were examined. Giant pulses of a Nd: YAG laser (frequency quadrupled, wave-length 265 nm) were used to vaporize and partly ionize the bacterial material. The time-of-flight mass spectra obtained could be discriminated by using the stepwise discriminant analysis provided by BMDP software package. Two different methods relating centrifugation and washing procedures were used. With the first method a correct classification between 50.0 and 90.9 per cent (S. sanguis) by means of mass spectra of positive ions and a correct classification between 27.1 and 80.4 per cent (S. lactis-25) by means of mass spectra of negative ions was observed. Using the second method a correct classification between 40.7 and 93.3 per cent (S. lactis-25) by means of mass spectra of positive ions and a correct classification between 56.7 and 95.0 per cent by means of mass spectra of negative ions was obtained. Here S. sanguis with 93.3 and S. lactis-25 with 81.7 per cent were significantly differentiated. In this context it must be emphasized that a correct classification of 27 per cent must be considered statistically significant, if 10 different strains are used.

Laser induced mass spectrometry: Ion formation processes and recent developments

A summary of the ion formation processes in laser mass spectrometry is presented. Particular emphasis is placed on the process of solid state chemical ionization. Recent results on the direct analysis of materials using LMS are also presented.

Laser-induced mass spectrometry for the determination of the physiological state of single cells

The laser-induced mass spectrometry was utilized for the determination of the physiological state of single bacterial cells by measuring the intracellular concentrations of certain cations. Special emphasis was put on the examination of the influence of various drugs on the Na/K-ratio of single cells and on its distribution within a population as derived from the analysis of 400 individual cells.

Mass Spectrometric Analysis of Drug-induced Changes in Na+ and K+ Contents of Single Bacterial Cells

Time-dependent changes in the intracellular Na+/K+ ratio of Escherichia coli, induced by the nitrofuran derivative HN32 [2,4-diamino-6-(5-nitrofuryl-2)-5-ethylpyrimidine], were measured by laser-induced mass spectrometry of single bacterial cells. The results show good agreement with data on viable cell and total cell counts, release of ATP and 14CO2 production demonstrating that the single cell analysis of intracellular sodium and potassium concentrations may supply reliable information on cell viability and, furthermore, offer additional information not available from established gross methods.

Desorption and fragmentation studies of organic molecules by laser-induced mass spectrometry

Desorption, fragmentation, and cationization of a variety of organic molecules using a laser mass spectrometer are described. At low laser power densities, desorption of organic molecules takes place. With progressively higher laser power densities, fragmentation characteristic of molecular structure occurs and at very high laser power densities, indiscriminate fragmentation occurs. It is also possible to observe parent peaks from mixtures of organic molecules without any fragmentation.

Investigation of the biologically relevant amino acids and some small peptides by laser induced mass spectrometry

Investigation of the biologically relevant amino acids and some small peptides by laser induced mass spectrometry