Desorption Of Peptides Research Articles

Liquid mixtures for matrix-assisted laser desorption

Binary matrix solutions are described which can be used for matrix-assisted laser desorption of peptides and proteins at 532 or 337 nm. The matrix solutions are composed of a strongly absorbing organic compound, such as rhodamine 6G or 1,4-diphenyl-1,3-butadiene, dissolved into a polar liquid, such as 3-nitrobenzyl alcohol or glycerol. Variations in absorber concentration are shown to affect the mass resolution, with higher resolution mass spectra being obtained at lower absorber concentrations. At the lowest absorber concentrations, mass resolution approaches that obtained with this instrument using the standard solid matrix, sinapinic acid

Matrix-assisted laser desorption ionization mass spectrometry with 2-(4-hydroxyphenylazo)benzoic acid matrix

A novel matrix substance, 2-(4-hydroxyphenylazo)benzoic acid, or HABA, has been found to be very advantageous for matrix-assisted ultraviolet laser desorption ionization mass spectrometry. This compound has been successfully used for the desorption of peptides, proteins, and glycoproteins up to approximately 250 kDa. For these materials, the most abundant analyte-related peaks correspond to [M + H] + ions and multiply protonated molecules. Comparisons with sinapic acid, 2,5-dihydroxybenzoic acid, and α-cyano-4-hydroxycinnamic acid indicate that the new matrix provides comparable sensitivity for peptides and smaller proteins but results in better sensitivity for larger proteins and glycoproteins in protein mixtures. Other matrices discriminate against the higher mass components in these cases. Somewhat reduced mass resolution has been found for smaller proteins, but for larger proteins and glycoproteins the best mass resolution can often be obtained with the new matrix. For other classes of compounds that form ions predominantly via cation attachment, at least as good sensitivity and even better resolution have been obtained. Derivatized glycolipids and synthetic polymers have been studied in detail. For the analysis of many synthetic polymers, the best performance in terms of sensitivity and mass resolution has been observed with HABA matrix. Mass resolution was higher for cation adducts than for the protonated peptide molecules in the same mass range. The new matrix exhibits grealty extended (in time) analyte ion production and reproducibility. Owing to the uniform sample surface with this matrix, barely any spatial variation of the ion signal could be observed. In addition, many hundreds of single-shot mass spectra could be accumulated from the same spot, even for larger proteins.

Experimental determination of thermal and nonthermal mechanisms for laser desorption from thin metal films

The mechanism of laser desorption of peptides as negative ions from Au thin films with 193, 248 and 351 nm laser radiation has been studied. Variation of the threshold laser power density with metal film thickness is used to distinguish between thermal and nonthermal mechanisms. The influence of laser wavelength on the desorption of peptides with different optical absorption spectra has been studied. Thermal desorption is observed when 351 nm laser radiation is utilized. However, both 248 and 193 nm radiation result in nonthermal desorption processes. At 248 nm, the threshold power density is observed to be independent of the optical absorption of the peptide adsorbate, supporting suggestions that a mechanism involving excitation of hot electrons in the metal is important.

Matrix‐assisted laser desorption of peptides in transmission geometry

AbstractThe possibility of performing matrix‐assisted laser desorption experiments in transmission geometry is demonstrated for two neuropeptides (substance P and bombesin), for six analogs of the melanocyte‐stimulating hormone (MSH) core and for coliagenase enzyme substrates. Positive‐ and negative‐ion spectra of several peptides are produced without the presence of a metallic substrate. Cationized quasi‐molecular ions are abundant in the positive spectra. Peak broadening in the high‐mass range can be the consequence of overlapping molecular and adduct ions. The presence of synthesis by‐products can be identified readily from the spectra. Ultimately, picogram detection limits are possible for important bioactive peptides and other large molecules. Because of the clearly demonstrated matrix‐assisted laser ionization in a homogeneous environment, metal substrate participation in the volatilization mechanism seems less likely.