title: Phosphorus imaging of the 7-S ribonucleoprotein particle.
abstract: In this study an unprecedented demonstration of the detection sensitivity of electron spectroscopic imaging (ESI) is reported. This microanalytical technique is capable of forming elemental maps of a specimen with high sensitivity and resolution by forming images with electrons that have lost particular amounts of energy due to interactions with the atoms of the specimen. The 7-S ribonucleoprotein particle, composed of one molecule of 5-S RNA and one molecule of the 40K MW protein, TFIIIa, was used for this demonstration. As few as 120 phosphorus atoms of the 5-S RNA have been detected and their localization in the particle determined. The shape of the 7-S particle is ellipsoidal with a long axis of 15.0 nm and a shorter axis between 8 and 9 nm. Similarly, the 5-S RNA is also an elongated structure located asymmetrically on one side of the particle. The average signal-to-noise ratio over the particle in the net phosphorus images is 14 whereas the ratio measured for the nucleosome containing 2.4-fold more phosphorus is 30.
authors.affiliation: Department of Medical Biochemistry, University of Calgary, Alberta, Canada.
authors.forename: D P
authors.initials: DP
authors.lastname: Bazett-Jones
mesh_terms: D000818:Animals; D004577:Electron Probe Microanalysis; D008854:Microscopy, Electron; D010758:Phosphorus / Q000032:analysis*; D012335:RNA, Ribosomal / Q000032:analysis*; D012341:RNA, Ribosomal, 5S / Q000032:analysis*; D012261:Ribonucleoproteins / Q000032:analysis*; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors / Q000032:analysis*; D014981:Xenopus
chemical_list: D012335:RNA, Ribosomal; D012341:RNA, Ribosomal, 5S; D012261:Ribonucleoproteins; D035582:Transcription Factor TFIIIA; D014157:Transcription Factors; D010758:Phosphorus