Firma:              Perkin Elmer

Modell:                         LS 50 B

Kommentar:     Dokumente engl.

VERSATILITY WITH PERFORMANCE

Luminescence spectroscopy includes the measurement of fluorescence, phosphorescence and bio- and chemiluminescence. The technique is used in a wide variety of applications where high sensitivity and selectivity are important, particularly in biochemical and environmental analysis and pharmaceutical and industrial research.

Perkin-Elmer's Model LS-50B offers outstanding sensitivity and selectivity for all these analyses. The dual scanning monochromators are con­trolled by sophisticated PC software and a pulsed xenon lamp is used as an excitation source. A cut-off filter is automatically inserted in the excitation beam for eliminating stray radiation when exciting at long wavelengths and the emission monochromator has a filter wheel with five cut-off filters. The Instrument is fitted as standard with a sample photomultiplier covering the wavelength range 250-650 nm.

A comprehensive range of computer controlled accessories is avaliable for the Model LS-50B, permitting the measurement of widely differing samples including Iiquids, solids such as powders and films and suspensions of Iiving cells. The instrument has as standard a single position, water thermostattable cuvette holder.

VIEWING DATA

The experimental data are plotted on the screen in real time and are stored in a desti­nation file for recall. A VIEW menu provides the facility for rescaling, split screens, multi­ple overlays and a cursor for determining ordinate and abscissa values.

The stored data can be exported to other PC based software such an Enzfitter*. LabCalc or Lotus 1-2-3 etc.

DATA MANIPULATION

Several mathematical operations are available from the data menu, including; area calculations, arithmetic functions such as add, subtract, multiply, divide, derivatives, logs, antilogs and data normalization, automatic peak determination and variable point Savitzky Golay smoothing.

An exclusive macrolanguage OBEY routine allows you to create methods specific to your analysis which can be stored on disk for future use.

CORRECTED SPECTRA

The Model LS-50B produces excitation spectra which are automatically corrected for the wavelength artefacts of the excitation system. Emission spectra are corrected post run with an OBEY program which uses a correction factor curve generated relative to the NIST standard quinine sulphate spectrum or an NIST calibrated tungsten lamp. The spectra shown are the uncorrected and corrected emission spectra of protoporphyrin IX.

DEDICATED APPLICATIONS

Dedicated application routines are included for a variety of analyses. For example, measurement of intracellular ions with specific fluorescent probes can be made using the intracellular biochemistry, ICBC, software program. The method page of this program enables you to set up either an exci­tation or an emission measurement. Similarly, polarization spectra and phosphorescence lifetimes can be obtained through the application routines.

POLARIZATION

Fluorescence polarization is widely used in biological research to provide a valuable in sight into protein interactions and membrane mobility. Steady-state measurements and polarization scans are obtained with the standard polarization accessory. Rapid measurements every 40 msec can be obtained using the Fast Filter accessory. In both cases the Software automatically calcu­lates the polarization and anisotropy values. This example shows the effect of cholesterol on the phase transition of dimiristoyl phos­phatidyl lecithin (DML) deterimined by automatically measuring the fluorescence polarization of diphenylhexa-triene (DPH) - labelled DML vesicles incubated with increasing concentrations of added cholesterol.

FRONT SURFACE DETECTION

Solid samples such as thin films and powders or highly scattering samples are more con­veniently analyzed by measuring the emis­sion from the sample surface. This can easily be made using the optional Front Surface accessory. The example shows the phos­phorescence emission spectrum and the decay curve from a sorting code phosphor imprinted on a postage stamp.

MEASURING MODES

The Model LS-50B uses a pulsed xenon lamp as an excitation source providing high sen­sitivity while minimizing photobleaching. Fluorescence is measured by synchronizing the data collection to the pulse. Phosphores­cence is measured by selecting a user specified delay and sampling time together with a variable pulse rate. Bio- and chemiluminescence are measured by turning off the source and using extended integration times.

INSTRUMENT CONTROL

The menu driven software offers completely automated control of instrument function, applications and data management. Setting the pointer to INSTRUMENT reviews the menu for the various analytical modes and the computer controlled accessories. For example, TLC plates or gels can be scanned automatically by using the TLC PLATE com­mand or 96-well microplates measured using the WELL PLATE command.

SCANNING SPECTRA

Selecting the SCAN dialog displays all of the analytical parameters associated with scanning the excitation and emission mono­chromators independently or synchron­ously. Selecting PRESCAN enables the auto­matic determination of the peak excitation and emission wavelength maxima between user defined limits. This dialog shows the parameters used to automatically collect constant energy synchronous spectra (CESM) to obtain a 3 Dimensional CESM matrix.

ENZYME KINETICS

Reaction rates can be monitored in four cuvettes in real time using the automated cell changer accessory. OBEY programs can customize data treatment, e.g. KINETICS.OY, calculates 1st order reaction parameters from time drive data. This program uses the algorithm F(t) = In (l(max) - l(t)) and calculates the reaction rate constant by linear regression.

STOPPED FLOW ANALYSIS

Very rapid changes in fluorescence data can be monitored using the fast data collection mode of the Model LS-50B. In this mode data are collected and displayed for every pulse. The effect of adding nicotine and histamine to FURA-loaded bovine adrenal chromaffin cells using a HI-TECH stopped flow apparatus illustrates this fast data collection mode and remote start capability.

96-WELL PLATE READER

The computer controlled plate reader is used either for Scanning TLC plates and gels or for measuring samples in 96-Well Microplates. Sensitivity, accuracy and non destructiveness are of paramount importance when quantitating small amounts of DNA amplified using the Cetus GeneAmp Polymerase Chain Reaction PCR process. The Hoechst dye 33258 is specific for DNA in the presence of protein and enables excellent detection limits to be achieved in 250 µL samples.