Biomedical subjects

J Albert Schultz

Publications and source records attributed to J Albert Schultz.

10 recordsLinked to original sources

PubMed2006

IR-MALDI-LDI combined with ion mobility orthogonal time-of-flight mass spectrometry.

Most MALDI instrumentation uses UV lasers. We have designed a MALDI-IM-oTOF-MS which employs both a Nd:YAG laser pumped optical parametric oscillator (OPOTEK, lambda = 2.8-3.2 microm at 20 Hz) to perform IR-LDI or IR-MALDI and a Nd:YLF laser (Crystalaser, lambda = 249 nm at 200 Hz) for the UV. Ion mobility (IM) gives a fast separation and analysis of biomolecules from complex mixtures in which ions of similar chemical type fall along well-defined "trend lines". Our data shows that ion mobility allows multiply charged monomers and multimers to be resolved; thus, yielding pure spectra of the singly charged protein ion which are virtually devoid of chemical noise. In addition, we have demonstrated that IR-LDI produced similar results as IR-MALDI for the direct tissue analysis of phospholipids from rat brain.

Animals↗

PubMed2005

The Au(n) cluster probe in secondary ion mass spectrometry: influence of the projectile size and energy on the desorption/ionization rate from biomolecular solids.

A Au-Si liquid metal ion source which produces Au(n) clusters over a large range of sizes was used to study the dependence of both the molecular ion desorption yield and the damage cross-section on the size (n = 1 to 400) and on the kinetic energy (E = 10 to 500 keV) of the clusters used to bombard bioorganic surfaces. Three pure peptides with molecular masses between 750 and 1200 Da were used without matrix. [M+H](+) and [M+cation](+) ion emission yields were enhanced by as much as three orders of magnitude when bombarding with Au(400) (4+) instead of monatomic Au(+), yet very little damage was induced in the samples. A 100-fold increase in the molecular ion yield was observed when the incident energy of Au(9) (+) was varied from 10 to 180 keV. Values of emission yields and damage cross-sections are presented as a function of cluster size and energy. The possibility to adjust both cluster size and energy, depending on the application, makes the analysis of biomolecules by secondary ion mass spectrometry an extremely powerful and flexible technique, particularly when combined with orthogonal time-of-flight mass spectrometry that then allows fast measurements using small primary ion beam currents.

Bradykinin↗

PubMed2005

Direct tissue analysis of phospholipids in rat brain using MALDI-TOFMS and MALDI-ion mobility-TOFMS.

After water, lipids are the most common biomolecules found in the brain (12%). A brief perusal of the physiology, anatomy, and pathophysiology of the brain illustrates the importance of lipids. Recent advances in mass spectrometry have allowed the direct probing of tissues. However, most studies have focused on proteins. In the present work, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) and MALDI-ion mobility (IM)-TOFMS were employed for direct analysis of phospholipids in rat brain tissue. Molecular ions (MH+) corresponding to phosphatidylcholines, phosphatidylethanolamines, and sphingomyelin, were recorded. When studying pharmacology, we learn that many therapeutic compounds are stored in the body's adipose tissue. MALDI-TOFMS and MALDI- IM-TOFMS were thus used to analyze rat brain tissue with chlorisondamine added directly onto the tissue slice. With both techniques, noncovalent complexes between the tissue phospholipids and chlorisondamine were detected. In addition, MALDI-IM-TOFMS of noncovalent complexes between phospholipids and chlorisondamine displayed a mobility between that of an isobaric lipid and peptide.

Animals↗

PubMed2004

Matrix-implanted laser desorption/ionization mass spectrometry.

The implantation of low-velocity massive gold clusters is shown to be a method of choice for homogeneous incorporation of a metallic matrix into the near-surface region of a solid biopolymer for subsequent laser desorption/ionization (LDI) MS analysis. Matrix implanted (MI)LDI spectra from cluster-implanted pure test peptide or tissue exhibit molecular ion peaks similar to those observed by matrix-assisted LDI. Moreover, the ion emission is very reproducible from any spot on the surface of these test samples. MILDI promises to be a powerful technique for mass spectrometric analysis of native biological samples as demonstrated by the first results on rat brain tissues.

Animals↗

PubMed2004

MALDI matrices for biomolecular analysis based on functionalized carbon nanomaterials.

When used in small molar ratios of matrix to analyte, derivatized fullerenes and single wall nanotubes are shown to be efficient matrices for matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. The mixing of an acidic functionalized fullerene with a solution of bioanalyte, depositing a dried droplet, and irradiating with a pulsed nitrogen laser yields protonated or cationized molecular ions. Derivatized fullerenes could offer several advantages over conventional MALDI matrices: a high analyte ionization efficiency, a small molar ratios (less than 1) of matrix/analyte, and a broader optical absorption spectrum, which should obviate specific wavelength lasers for MALDI acquisitions. The major disadvantage to the use of fullerenes is the isobaric interference between matrix and analyte ions; however, it is overcome by using MALDI-ion mobility time-of-flight (IM-oTOF) mass spectrometry to preseparate carbon cluster ions from bioanalyte ions prior to TOF mass analysis. However, an alternative to the dried droplet preparation of fullerene MALDI samples is the aerosolization of matrix-analyte solutions (or slurries) followed by impacting the aerosol onto a stainless surface. We also demonstrate that the fullerene matrices can be used to acquire spectra from rat brain tissue.

Amino Acid Sequence↗

PubMed2004

Analysis of phosphorylated peptides by ion mobility-mass spectrometry.

An ion mobility-mass spectrometry technique for rapid screening of phosphopeptides in protein digests is described. A data set of 43 sequences (ranging in mass from 400 to 3000 m/z) of model and tryptic peptides, including serine, threonine, and tyrosine phosphorylation, was investigated, and the data support our previously reported observation (Ruotolo, B. T.; Verbeck, G. F., IV; Thomson, L. M.; Woods, A. S.; Gillig, K. J.; Russell, D. H. J. Proteome Res. 2002, 1, 303.) that the drift time-m/z relationship for singly charged phosphorylated peptide ions is different from that for nonphosphorylated peptides. The data further illustrate that a combined data-dependent IM-MS/MS approach for phosphopeptide screening would have enhanced throughput over conventional MS/MS-based methodologies.

Amino Acid Sequence↗

PubMed2004

Lipid/peptide/nucleotide separation with MALDI-ion mobility-TOF MS.

Matrix-assisted laser desorption/ionization when combined with ion mobility-orthogonal time-of-flight mass spectrometry is a viable technique for fast separation and analysis of biomolecules in complex mixtures. Isobaric lipid, peptide, and oligonucleotide ions are preseparated before mass analysis by differences of up to 30% in mobility drift time. Ions of similar chemical type fall along well-defined "trend lines" (with deviations of approximately 3%) when plotted in two-dimensional representations of ion mobility as a function of m/z. Discussion of fundamental and technical limitations of the technique point to its potential for being most useful when applied to systems such as bodily fluids and intact tissue, where an alternative chemical or chromatographic preseparation step prior to mass analysis is either impractical or undesirable.

Analgesics, Opioid↗

PubMed2003

Angiotensin II-acetylcholine noncovalent complexes analyzed with MALDI-ion mobility-TOF MS.

Matrix-assisted laser desorption ionization-ion mobility-orthogonal time-of-flight mass spectrometry (MALDI-IM oTOF MS) is a new technique that allows laser desorbed ion to be preseparated on the basis of their shape prior to mas analysis. Using this instrument, we tested the postulate that addition of a quaternary ammonium compound such as acetylcholine to the model phosphorylated peptide angio tensin II would enhance its detection by MALDI in two ways. First of all, the acetylcholine-peptide complex could ionize more efficiently than the bare phosphopeptide. Furthermore the ion mobility could separate the complex ion on the basis of its charge/volume from isobaric interferences, which would otherwise limit detection sensitivity.

Acetylcholine↗

PubMed2002

Oligonucleotide analysis with MALDI-ion-mobility-TOFMS.

Matrix-assisted laser-desorption ionization followed by ion-mobility separation and time-of-flight mass analysis (MALDI-IM-TOFMS) has been used to characterize native and chemically modified DNA oligonucleotides up to eight bases in length. Mobility resolution between 20 and 30 can be used to separate oligonucleotides of different length, but not to differentiate between isomers or even different compositions of the same length. MALDI-IM-TOFMS does, however, have additional utility in the analysis of mixtures of DNA oligonucleotides and peptides, because these classes of molecules can be distinguished on the basis of differences in their mobility. Oligonucleotide sequencing is also possible by MALDI-IM-TOFMS. Ion signals corresponding to nucleobase losses, w-type, and y-type fragments were identified by use of differences in ion mobility. MALDI-IM-TOFMS was also used to resolve DNA-platinum adducts from the corresponding unmodified oligonucleotides.

Ions↗

PubMed2002

A study of peptide-peptide interactions using MALDI ion mobility o-TOF and ESI mass spectrometry.

Matrix-assisted laser desorption ionization ion mobility coupled to orthogonal time-of-flight mass spectrometry (MALDI-IM-oTOF MS) is evaluated as a tool for studying non-covalent complex (NCX) formation between peptides. The NCX formed between dynorphin 1-7 and Mini Gastrin I is used as a model system for comparison to previous MALDI experiments (Woods, A. S.; Huestis, M. A. J. Am. Soc. Mass Spectrom. 2001, 12, 88-96). The dynorphin 1-7/Mini Gastrin I complex is stable after more than a ms drift time through the He filled mobility cell. Furthermore, the effects of solution pH on NCX ion signal intensity is measured both by MALDI-IM-MS analysis and by nanoelectrospray mass spectrometry. When compared to the previous MALDI study this work shows that all three techniques give similar results. In addition, fragmentation can be observed from of the non-covalent complex parent ion that occurs prior to TOF mass analysis but after mobility separation, thus providing NCX composition information.

Cyclic GMP-Dependent Protein Kinases↗