Cholesterol Ions Research Articles

Lipid mapping in human dystrophic muscle by cluster-time-of-flight secondary ion mass spectrometry imaging

Human striated muscle samples, from male control and Duchenne muscular dystrophy-affected children, were subjected to cluster-time-of-flight secondary ion mass spectrometry (cluster-ToF-SIMS) imaging using a 25 keV Bi(3)(+) liquid metal ion gun under static SIMS conditions. Spectra and ion density maps, or secondary ion images, were acquired in both positive and negative ion mode over several areas of 500 x 500 microm(2) (image resolution, 256 x 256 pixels). Characteristic distributions of various lipids were observed. Vitamin E and phosphatidylinositols were found to concentrate within the cells, whereas intact phosphocholines accumulated over the most damaged areas of the dystrophic muscles, together with cholesterol and sphingomyelin species. Fatty acyl chain composition varied depending on the region, allowing estimation of the local damage extent.

On molecular ion formation by hydride abstraction in plasma desorption mass spectrometry

Positive molecular ion formation in plasma desorption (PD) by hydride abstraction leading to [M − H] + molecular ions is not a frequently observed phenomenon. An example of a compound that exhibits an [M − H] + molecular ion in its PD spectrum is the neutral lipid cholesterol. Data on the initial radial velocity distribution of the [M − H] + ion of cholesterol are presented and compared to data on the radial velocity distribution of the M + molecular ion of a structurally similar compound (ergosterol). The distribution for [M − H] + cholesterol ions is broader and its centroid is closer to zero radial velocity than the corresponding distribution for ergosterol M + ions. These data support a model suggesting formation of [M − H] + by a “self” chemical ionization type reaction.