Time-of-Flights and Traps: From the Histone Code to Mars

Abstract

Two very different analytical instruments are featured in this perspective paper on mass spectrometer design and development. The first instrument, based upon the curved-field reflectron developed in the Johns Hopkins Middle Atlantic Mass Spectrometry Laboratory, is a tandem time-of-flight mass spectrometer whose performance and practicality are illustrated by applications to a series of research projects addressing the acetylation, deacetylation and ADP-ribosylation of histone proteins. The chemical derivatization of lysine-rich, hyperacetylated histones as their deuteroacetylated analogs enables one to obtain an accurate quantitative assessment of the extent of acetylation at each site. Chemical acetylation of histone mixtures is also used to determine the lysine targets of sirtuins, an important class of histone deacetylases (HDACs), by replacing the deacetylated residues with biotin. Histone deacetylation by sirtuins requires the co-factor NAD+, as does the attachment of ADP-ribose. The second instrument, a low voltage and low power ion trap mass spectrometer known as the Mars Organic Mass Analyzer (MOMA), is a prototype for an instrument expected to be launched in 2018. Like the tandem mass spectrometer, it is also expected to have applicability to environmental and biological analyses and, ultimately, to clinical care.

Unveiling the Intricacies of the Curved-Field Ion Mirror

“…The 'curved field' as it appears in the literature is an ambiguous, vaguely defined term. 4,[19][20][21][22][23][24][25][26][27][28] An exact definition [equation (8)] is proposed here for the term 'curved field'. This definition, which is dimensionally sound, provides a basis upon which to investigate mathematically the characteristics of curved fields in terms of the dependence of ToF on significant parameters.…”

“…The term 'curved field' ion mirror introduced by Cotter 19 has a strong footprint in the literature [20][21][22][23][24][25][26][27][28][29] and is presumed to carry meaning beyond the self-evident. There are a number of questions, including whether the curved-field mirror refers to a definite potential distribution within an ion mirror and the extent to which the term has meaning beyond simply an ion mirror not falling into one of the three basic categories of one-stage, two-stage and ideal.…”

Enhancement of the design of a pulsed UV laser system for a laser-desorption mass spectrometer on Mars

“…The Mars Organic Molecule Analyzer (MOMA) is one of the major instruments on the rover's payload Pasteur. It consists of a gas chromatograph for the analysis of volatile constituents and a laser-desorption mass spectrometer (LDMS) for the analysis of non-evaporable components [1][2][3]. For the ionization of large organic molecules in samples of soil from Mars' surface or sub-surface, a pulsed ultraviolet laser is needed.…”