§ PERSEPTIVE VOYAGER
§ APPLIED BIOSYSTEMS 4700 PROTEOMICS ANALYZER

» PERSEPTIVE VOYAGER

GENERAL INFORMATION
The Perseptive Voyager-DE RP Biospectrometry instrument is a MALDI-TOF (matrix-assisted laser desorption ionization-time of flight) mass spectrometer. The instrument is capable of measuring mass over the range of 1 to approximately 400,000 Da, with an optimal working range of 400 to 100,000 Da.

DESCRIPTION
The Perseptive Voyager is equipped with delayed extraction (DE) for improved mass accuracy and a reflector (RP) for fragmentation analysis. Samples are mixed into a saturated matrix solution and 1 ul of this mixture is loaded on a metal target and allowed to dry. The matrix is a low molecular weight UV absorbing substance such as sinapinic acid. The choice of matrix depends on the properties of the molecules in the individual sample (ie protein, peptide, DNA, etc.). The target plate is inserted in the mass spec and brought to high voltage (20,000V), then the individual sample spots are pulsed with ultraviolet laser. Matrix is required in order to facilitate the desorption of the sample from the surface of the target. As a result of the above, the sample and matrix molecules become ionized and are repelled by the high voltage from the target plate into the linear flight tube. The time needed for these ionized molecules to reach the detector at the end of the flight tube is a function of mass. This "travel time" forms the basis of mass measurement.

MASS RANGE
The instrument is capable of measuring mass over the range of 1 to approximately 400,000 Da. However below 300 Daltons, the matrix ions will obscure the sample, and above 100,000 Da, ionization is difficult. This means the instrument has an optimal working range of 400 to 100,000 Da.

SENSITIVITY
High quality spectra can be obtained from 1 uL of sample containing 100 fmol-10 pmol loaded onto the target plate. Too much material can broaden spectral peaks and in extreme cases may suppress ionization. The presence of salts or other small molecules at concentrations greater than 50 millimolar can cause significant ion suppression i.e. signal depletion.

ACCURACY
Mass accuracies depend on calibration of the instrument against a standard, and also upon the condition of the sample. Too much starting material, high salt content, or the presence of glycerol, detergents and urea can broaden spectral peaks, and compromise mass accuracy. Typical values when calibrating against an external mass standard for accuracy are 1% (10 Da per 1000). Including an internal mass standard with the sample can increase accuracy more than ten fold (1 Da per 2000).

CAPACITY AND THROUGHPUT
It takes 15 minutes to analyze and print out data per sample for a prespotted plate. Spotting of the plate should take approximately 1 minute per sample. Due to heavy use of the instrument during the day, prespotted plates will normally be run overnight.

We expect to return spectra to the investigator with 72 hours of receiving the samples.

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» APPLIED BIOSYSTEMS 4700 PROTEOMICS ANALYZER

GENERAL INFORMATION
The 4700 is a MALDI mass spectrometer that provides tandem (MS/MS) time-of-flight (TOF) optics to provide peptide structural information, in addition to high accuracy MS data. The 4700 is principally used for mass mapping identification of unknown protein samples.

DESCRIPTION
The 4700 combines delayed extraction and reflector optics for high resolution, high mass accuracy analysis. Peptide samples present in complex mixtures can be individually fragmented in a collision cell which provides amino acid composition and sequence information. The instrument’s high laser repetition rate of 200 Hz, and fully automated data analysis capability provide very high throughput rates for high confidence identification of unknown proteins by mass mapping analysis.

SENSITIVITY
The 4700 can detect 5 fmol Neurotensin (m/z 1672) at a 50:1 signal:noise ratio. For identification of unknown proteins in one- or two-dimensional gels, we recommend a minimum of 100 fmol of protein (low ng range).

ACCURACY
Typically, we achieve 25 ppm accuracy in mass mapping experiments without the need for introduction of an internal calibrant. With internal calibration, accuracy is +/- 5 ppm.

THROUGHPUT
The 4700 is capable of unattended analysis at a high laser repetition rate. Because of these design features, thousands of proteins can, in theory, be analyzed per day. At present, sample handling limitations prevent our attaining this ideal, but we process dozens of samples per order with a turnaround time of approximately one week, and we offer significant price reductions for large orders (see rates page).

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