Full text loading...
(Color online) (a) Sketch of neutral cluster-induced desorption and ionization of biomolecules. Upon cluster-surface impact, a biomolecule is desorbed and ionized. Shattering of the cluster and subsequent evaporation of SO2 molecules lead to a bare or almost bare biomolecular ion in the gas phase.14 (b) Photograph of a Si substrate with three thick biofilms (n = 2.5 × 10−8 mol) which can be identified by eye and two sample spots with 10−10 mol angiotensin (in dashed circles) which cannot be observed visually. (c) SEM image taken at a cracked area of a thick angiotensin film. (d) SEM image taken on a sample covered with 10−11 mol angiotensin per 0.2 cm2. (e) AFM image of a sample covered with 10−12 mol angiotensin per 0.2 cm2.
(Color online) Top: positive ion mass spectrum as obtained after cluster-surface collision on a sample prepared with 50 × 10−10 mol angiotensin II (pH = 7) on SiO2. One single predominant peak at the position of the mass of the bare biomolecule is observed. Inset: blow-up of the main panel data; a weak signal of the doubly charged biomolecule is observed. Bottom: negative ion mass spectrum from the same sample as used for the data in the top panel.
(Color online) Positive ion mass spectra as obtained after cluster-surface collision on samples prepared with (a) 2.5 × 10−8 mol, (b) 5 × 10−9 mol, (c) 1 × 10−10 mol, and (d) 1 × 10−11 mol angiotensin II applied on SiO2 (pH = 2).
(Color online) (a) Positive ion signal intensity of the single charged angiotensin-II-peak as a function of the amount of substance on the surface as obtained from several different data sets. The data sets including n ≥ 10−10 mol were measured with a reduced detection efficiency and are scaled accordingly. Squares represent a data set which was measured with a mixture of angiotensin and bradykinin on the surface, dots indicate the data from Fig. 3. The dashed line represents an n 2/3-dependence. (b), (c) Sketch of multilayered adsorbate aggregates on the surface and the transition to a closed film in sideview (b) and topview (c).
Article metrics loading...