The Effect of Magnesium Ions on Chromosome Structure as Observed by Helium Ion Microscopy. (14th November 2013)

• Record Type: Journal Article
• Authors: Dwiranti, Astari; Hamano, Tohru; Takata, Hideaki; Nagano, Shoko; Guo, Hongxuan; Onishi, Keiko; Wako, Toshiyuki; Uchiyama, Susumu; Fukui, Kiichi
• Is Part Of: Microscopy and microanalysis. Volume 20:Number 1(2014:Feb.)
• Page Start: 184
• Page End: 188
• Publication Date: 2013-11-14
• Subjects: human chromosome, -- chromosome structure, -- helium ion microscopy (HIM), -- magnesium ion (Mg2+), -- osmium coating; Microscopy -- Periodicals; Microchemistry -- Periodicals; 502.82
• DOI: 10.1017/S1431927613013792
• Languages: English
• ISSNs: 1431-9276

Abstract

Abstract: One of the few conclusions known about chromosome structure is that Mg 2+ is required for the organization of chromosomes. Scanning electron microscopy is a powerful tool for studying chromosome morphology, but being nonconductive, chromosomes require metal/carbon coating that may conceal information about the detailed surface structure of the sample. Helium ion microscopy (HIM), which has recently been developed, does not require sample coating due to its charge compensation system. Here we investigated the structure of isolated human chromosomes under different Mg 2+ concentrations by HIM. High-contrast and resolution images from uncoated samples obtained by HIM enabled investigation on the effects of Mg 2+ on chromosome structure. Chromatin fiber information was obtained more clearly with uncoated than coated chromosomes. Our results suggest that both overall features and detailed structure of chromatin are significantly affected by different Mg 2+ concentrations. Chromosomes were more condensed and a globular structure of chromatin with 30 nm diameter was visualized with 5 mM Mg 2+ treatment, while 0 mM Mg 2+ resulted in a less compact and more fibrous structure 11 nm in diameter. We conclude that HIM is a powerful tool for investigating chromosomes and other biological samples without requiring metal/carbon coating.