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1.
Anal Chem ; 73(24): 6000-7, 2001 Dec 15.
Article in English | MEDLINE | ID: mdl-11791572

ABSTRACT

A new technique for studying the time dependence of conformational changes of gas-phase protein ions is described. In this approach, a short pulse of electrosprayed protein ions is introduced into an ion trap and stored. After a defined time period, the distribution of ions is ejected from the trap into an ion mobility/time-of-flight mass spectrometer. Combined measurements of mobilities and flight times in the mass spectrometer provide information about the abundances of different conformer types and charge-state distributions. By varying the storage time in the trap, it is possible to monitor changes in ion conformation that occur over extended time periods (approximately 10-200 ms). The method is demonstrated by examining changes in cytochrome c ion conformations for the +7 to +10 charge states.


Subject(s)
Cytochrome c Group/chemistry , Animals , Horses , Myocardium/chemistry , Protein Conformation , Protein Folding , Spectrometry, Mass, Electrospray Ionization , Temperature
2.
Anal Chem ; 70(23): 4896-901, 1998 Dec 01.
Article in English | MEDLINE | ID: mdl-21644672

ABSTRACT

A cylindrical quadrupole ion trap (r(0) = 2.5 mm, z(0) = 2.88 mm, ∼(1)/(64) of the volume of commercial hyperbolic ion traps) has been constructed, its geometry optimized, and its performance examined in the mass-selective instability scan mode. Spectra of ionized perfluorotributylamine and o-dichlorobenzene show a resolution (m/Δm, 50% valley definition) of ∼100. The instrument has been coupled to a membrane introduction system to test its applicability for on-line reaction monitoring and to determine detection limits. Simulations using the ion trap simulation program are used to explore the effects of geometry on performance and to validate the experimental results.

3.
Anal Chem ; 70(17): 3545-7, 1998 Sep 01.
Article in English | MEDLINE | ID: mdl-21644702

ABSTRACT

Broad-band nondestructive ion detection based on induced image current measurement is performed in a quadrupole ion trap having cylindrical geometry. Spectra of krypton and acetophenone are shown to demonstrate the first use of nondestructive detection with a cylindrical ion trap.

4.
Anal Chem ; 70(3): 438-44, 1998 Feb 01.
Article in English | MEDLINE | ID: mdl-21644742

ABSTRACT

A cylindrical geometry ion trap is used to record mass spectra in the mass-selective instability mode. The geometry of the cylindrical ion trap has been optimized to maximize the quadrupole field component relative to the higher-order field content through field calculations using the Poisson/Superfish code and through experimental variation of the electrode structure. The results correspond well with predictions of the calculations. The trap has been used to record mass spectra with better than unit mass resolution, high sensitivity, and a mass/charge range of ∼600 Th. Multistage (MS(3)) experiments have been performed, and the Mathieu stability region has been experimentally mapped. The performance of this device compares satisfactorily with that of the hyperbolic ion trap.

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