Indiana University

Advanced Research & Technology Institute

James P Reilly

Noah P Christian

Steven M Colby

Timothy B King

Kirk S Boraas

David E Clemmer

Milos V Novotny

Yehia S Mechref

Liangyi Zhang

Tony J Tegeler

Matthew S Thompson

Methods of identifying polypeptides have been developed using a de novo sequencing technique. Methods use photodissociation and low-energy fragmentation and the spectra of peptide ions obtained therefrom, such as obtained by post-source decay (PSD), have been developed. The methods include photodissociation and the spectra therefrom obtainable from treating ions with predetermined wavelengths of radiation in the vacuum ultraviolet range of the electromagnetic spectrum. The confidence of amino acid assignments based on x-type ions is evaluated by observing complementary y-, v- and w-type ions that provide additional constraints to sequence identification.

Method of identifying peptides

Apparatus, device, and methods for fragmenting high molecular weight molecular ions, such as peptides or proteins, by treating the ions with predetermined wavelengths of light are described. Vacuum ultraviolet radiation as a source of predetermined wavelengths of laser light is described in one embodiment. A device () is described having a sample, such as a peptide, protein, protein digest, and the like enters through inlet () and is irradiated with a first source of light (), which illustratively may be a laser light. The first source of laser light is illustratively at a wavelength and energy sufficient to convert molecules in the sample into molecular or precursor ions.

Methods and apparatus for mass spectral analysis of peptides and proteins

A control system () for a power supply (), such as a high voltage power supply, includes a control circuit () and a feedback circuit (). The feedback circuit () is configured to produce a feedback signal indicative of the voltage of the power supply output. The control circuit () is configured to control the power supply () based on the feedback signal and a predetermined voltage value to maintain the output of the power supply () at about the predetermined voltage value. A portion of the feedback circuit () may be included in an isolation shield () to improve the accuracy of the feedback signal.

Control system for a power supply

A circuit and method for generating a delayed event following a trigger pulse occurring at a random time between clock pulses is disclosed. The circuit includes a clock circuit, a voltage converter, an analog-to-digital converter circuit, a memory storage circuit, and a summing circuit. The method includes representing the time between the triggering pulse and a subsequent clock pulse as a voltage, converting the voltage to a stored digital value, and defining a desired delay time by adding a first time determined by counting a predetermined number of clock cycles to a second time determined by converting the stored digital value first to an analog value and then to a time value.

Generation and measurement of timing delays by digital phase error compensation

A MALDI mass spectrometer directs a laser shot onto a MALDI sample to generate a sample spectrum which is analyzed to determine if the sample spectrum meets a predetermined criteria. If so, subsequent laser shots are directed to predetermined locations on the MALDI sample. In essence, if the analysis of a previous laser shot indicates that a 'sweet spot' of the MALDI sample has be located, subsequent laser shots may be directed to areas proximate to the previous shot thereby allowing the sweet spot to be thoroughly sampled. A method of operating a MALDI mass spectrometer is also disclosed.

Method and apparatus for controlling position of a laser of a MALDI mass spectrometer

A device for placement of effluent comprises a substrate positioner, a deposition conduit, and a conduit positioner. The substrate positioner supports and positions a substrate on which effluent exiting from the deposition conduit is to be deposited. The conduit positioner moves an exit end of the deposition conduit relative to the substrate.

Device for placement of effluent

An MALDI mass spectrometer for the composition analysis of large batch sizes of samples includes a mass spectrometer having an ionization chamber and a sample chamber coupled to the ionization chamber. A transport cart is positioned in the sample chamber with a sample cassette removably coupled thereto. A method of operating a MALDI mass spectrometer is also disclosed.

Method and apparatus for mass spectrometric analysis of samples

One illustrative embodiment of a voltage pulser circuit comprises a voltage source producing a first voltage, and a thyratron tube having an anode coupled to the output of the voltage source, a cathode connected to a reference potential and a grid responsive to a grid control voltage to electrically connect the anode to the cathode to thereby cause the first thyratron tube to switch the anode between the first voltage and the reference potential. A pulse-shaping circuit may be connected to the anode of the tube to effectuate desired rise and fall times of the voltage pulses produced by the voltage pulser circuit. Such a voltage pulser circuit is particularly suited for use in connection with the operation of pulsed spectrometer instruments, such as time-of-flight mass spectrometers and the like.

Voltage pulser circuit

A time-of-flight mass spectra calibration technique uses time-of-flight mass spectrometer instrument operational parameters and known mass and measured time-of-flight data pairs to optimize values of chosen ones of the instrument operational parameters. Electrostatic time-of-flight calculations are conducted in conjunction with an iterative procedure, preferably a simplex optimization procedure, to thereby minimize a residual error between the electrostatic time-of-flight calculations and the measured time-of-flight data values for each of the known mass values. While conventional curve fitting mass calibration techniques are devoid of information that describe ion behavior, the mass calibration technique of the present invention, by contrast, takes into account all of the instrument operational parameters in arriving at a final calibration. Because the electrostatic TOF calculation is a description of ion behavior in an actual TOF mass spectrometer instrument rather than a polynomial representation of a curve, it is well behaved and does not contain any instabilities where unpredictable calibration errors might occur. Moreover, unlike conventional curve fitting mass calibration techniques, the mass calibration technique of the present invention maintains mass accuracy in extrapolated mass ranges.

System and method for calibrating time-of-flight mass spectra

An ion mobility and mass spectrometer instrument includes an ion source region coupled to an ion mobility spectrometer having an ion outlet coupled to a quadrupole mass filter. An output of the filter is coupled to a collision cell which has an ion outlet coupled to an ion acceleration region of a mass spectrometer such as a time of flight mass spectrometer. The instrument is particularly well suited for sequencing analysis wherein a sample is ionized and a resulting three-dimensional ion spectrum (ion intensity vs. ion mobility and ion mass) is observed. If the spectrum reveals that no ions overlap in mobility values, the collision cell is filled with a suitable buffer gas and the instrument is reactivated whereby a complete three-dimensional spectrum of parent and daughter ions results. If, however, the original spectrum reveals that two or more ions overlap in ion mobility values, the collision cell is filled with a buffer gas and the quadrupole mass filter is controlled to selectively filter out all but one of the ions having overlapping mobility values. The instrument is reactivated, and the quadrupole mass filter is selectively controlled, as many times as mobility overlap occurs to thereby provide complete three-dimensional spectra of parent and daughter ions resulting from fragmentation. Various configurations of mass filter, ion trap and collision cell positioning, relative to the ion mobility and mass spectrometer instruments, are contemplated.

Ion mobility and mass spectrometer

A hybrid ion mobility and time-of-flight mass spectrometer includes an ion source region coupled to an ion mobility spectrometer (IMS) which feeds directly into an ion accelerating region of a time-of-flight mass spectrometer (TOFMS). In one embodiment, the TOFMS is positioned relative to the IMS so that the flight tube axis of the TOFMS is perpendicular to the drift tube axis of the IMS. In an alternate embodiment, the TOFMS is positioned relative to the IMS so that the flight tube axis of the TOFMS is non-perpendicular to the drift tube axis of the IMS. In the alternate embodiment, a known quadrupole ion trap is positioned between the IMS and the TOFMS to provide the capability of controlling the injection of ion packets into the TOFMS. The ion source may be a MALDI source, an electrospray ionization source, or an ion trap positioned between the IMS and any known ion source. In each case, the IMS, TOFMS and ion sources are preferably controlled by a computer.

Hybrid ion mobility and mass spectrometer

An apparatus and method for minimizing ion peak width measurements in a time-of-flight mass spectrometer to thereby minimize the effects of initial ion position distributions and initial ion velocity distributions on the mass resolution of the spectrometer are provided. Where the ion source and ion generation geometries indicate a functional relationship between the initial ion position and initial ion velocity, this relationship is substituted into the time-of-flight equation and the instrument parameters are thereafter optimized to achieve minimization of ion peak width broadening. Experimental results using MALDI indicate reductions in ion peak widths of up to 96% over those observed with traditional MALDI techniques.

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Bloomington, IN, United States of America

James P Reilly