Fast Molecular Compression by a Hyperthermal Collision Gives Bond-Selective Mechanochemistry.

Using electrospray ion beam deposition, we collide the complex molecule Reichardt's dye (C_{41}H_{30}NO^{+}) at low, hyperthermal translational energy (2-50 eV) with a Cu(100) surface and image the outcome at single-molecule level by scanning tunneling microscopy. We observe bond-selective reaction induced by the translational kinetic energy. The collision impulse compresses the molecule and bends specific bonds, prompting them to react selectively.

Analysis of Complex Molecules and Their Reactions on Surfaces by Means of Cluster-Induced Desorption/Ionization Mass Spectrometry.

Desorption/Ionization Induced by Neutral SO2 Clusters (DINeC) is employed as a very soft and efficient desorption/ionization technique for mass spectrometry (MS) of complex molecules and their reactions on surfaces. DINeC is based on a beam of SO2 clusters impacting on the sample surface at low cluster energy. During cluster-surface impact, some of the surface molecules are desorbed and ionized via dissolvation in the impacting cluster; as a result of this dissolvation-mediated desorption mechanism, low cluster energy is sufficient and the desorption process is extremely soft.

Soft cluster-induced desorption/ionization mass spectrometry: How soft is soft?

Desorption/ionization induced by neutral clusters (DINeC) is used as an ultrasoft desorption/ionization method for the analysis of fragile biomolecules by means of mass spectrometry (MS). As a test molecule, the glycopeptide vancomycin was measured with DINeC-MS, and resulting mass spectra were compared to the results obtained with electrospray ionization (ESI), matrix assisted laser desorption ionization, and time-of-flight secondary ion MS. Of the desorption-based techniques, DINeC spectra show the lowest abundance of fragments comparable to ESI spectra.

Soft depth-profiling of mixed peptide/lipid samples by means of cluster induced desorption/ionization mass spectrometry-High depth resolution and low matrix effect.

Mixed peptide/lipid samples were analyzed with respect to their chemical composition by means of desorption/ionization induced by neutral SO clusters (DINeC) in combination with mass spectrometry (MS). Depth profiles of the mixed films indicated a segregation layer of lipid on top of all samples. The thickness of this layer as obtained by DINeC-MS was in the order of one nanometer what can be seen as an upper limit for the depth resolution of DINeC-MS.

Chemical Analysis of Complex Surface-Adsorbed Molecules and Their Reactions by Means of Cluster-Induced Desorption/Ionization Mass Spectrometry.

Desorption/ionization induced by neutral SO clusters (DINeC) is used for mass spectrometry (MS) of surface-adsorbed molecules. The method is shown to be a surface-sensitive analysis tool capable of detecting molecular adsorbates in a wide range of molecular weights as well as their reactions on surfaces, which are otherwise difficult to access. Two different surface/adsorbate systems prepared by means of electrospray ion beam deposition (ES-IBD) were investigated: For the peptide angiotensin II on gold, intact molecules were desorbed from the surface when deposited by soft landing ES-IBD.

Evaluation of matrix effects on TOF-SIMS data of leu-enkephalin and 1,2-dioleoyl-sn-glycero-3-phosphocholine mixed samples.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is one of the most powerful methods to analyze biomolecules in biological tissues and cells because it provides detailed chemical structure information and chemical images with a high spatial resolution. However, in terms of quantitative analysis, there are issues such as matrix effects that often cause secondary ion intensity changes regardless of the actual concentration in a sample. For instance, the intensity of secondary ions related to peptides is generally suppressed when lipids coexist.

Real-Time Investigation of the H/D Exchange Kinetics of Porphyrins and Oligopeptides by Means of Neutral Cluster-Induced Desorption/Ionization Mass Spectrometry.

The kinetics of the H/D exchange reaction in angiotensin II, hexaglycine (Gly), Co(II)tetra(3-carboxyphenyl)porphyrin, and tetra(4-carboxyphenyl)porphyrin were followed in real time by mass spectrometry employing desorption/ionization induced by neutral SO clusters. The change of the isotope patterns with increasing degree of deuteration was recorded as a function of DO exposure and the underlying H/D exchange kinetics, i.e.

Mass spectrometry of oligopeptides in the presence of large amounts of alkali halides using desorption/ionization induced by neutral cluster impact.

Oligopeptides in the presence of large amounts of salt were desorbed and ionized using desorption/ionization induced by neutral clusters (DINeC) for further analysis by means of mass spectrometry (MS). Using oligopeptides in alkali halide solutions as a model system, DINeC was shown to yield clear and fragmentation free mass spectra of the biomolecules even from environments with a large excess of salt. The results were traced back to a phase separation between salt and biomolecules during sample preparation.