Microscale Maldi Imaging of Outer-Layer Lipids in Intact Egg Chambers from Drosophila Melanogaster
Resource
ANALYTICAL CHEMISTRY v.83 n.10 pp.3918-3925
Journal
ANALYTICAL CHEMISTRY
Journal Volume
v.83
Journal Issue
n.10
Pages
3918-3925
Date Issued
2011
Date
2011
Author(s)
Pawel L. Urban
Chia-Hsien Chang
June-Tai Wu
Yu-Chie Chen
Abstract
Fruit fly (Drosophila melanogaster) is a standard model organism used in genetics and molecular biology. Phospholipids are building blocks of cellular membranes, and components of a complex signaling network. Here, we present a facile method, based on matrix-assisted laser desorption/ ionization (MALDI) mass spectrometry (MS), for molecular imaging of phospholipid distributions in submillimeter-sized components of the fruit fly reproductive system. Individual egg chambers were deposited on a specially prepared MALDI target comprising an aluminum slide with a rough surface created by ablation with a microsecond-laser: this helped to immobilize biological specimens, remove excess of saline solution by adhesive forces, carry out microscopic observations, and facilitated distribution of the MALDI matrix. A continuous-flow ultrasound-assisted spray was used for the deposition of MALDI matrix (9-aminoacridine) onto the sample. The upper surface of the specimen was then scanned with a 355- nm solid-state laser with a preset beam focus of 10 m to obtain negative -ion mode MALDI-MS images. Overall, this provided sufficient spatial resolution to reveal micrometer-scale gradient-like patterns of phospholipids along the anterior/posterior axis of egg chambers. Several phosphatidylinositols are seen to be segregated according to the number of unsaturated bonds, with an elevated abundance of polyunsaturated phosphatidylinositols within the oocyte compartment.