A fully compensated versatile spectrofluorimeter

Inactivation of sarcoplasmic reticulum (Ca2+ + Mg2+)-ATPase by N-cyclohexyl-N'-(4-dimethylamino-alpha-naphthyl)carbodiimide

The synthesis and characterisation of N-cyclohexyl-N'-(4-dimethylamino-alpha-naphthyl)carbodiimide (NCD-4) is described. Only the N-acetylurea and urea corresponding to NCD-4 are appreciably fluorescent: the O-phenylisourea and S-ethylisothiourea derivatives have negligible fluorescence. NCD-4 inhibits the (Ca2+ + Mg2+)-ATPase of sarcoplasmic reticulum irreversibly: Ca2+ protects against inhibition. Covalent incorporation of NCD-4 occurs into the Ca2+-protected sites, with a stoichiometry of approximately 1 mole/mole of ATPase. The modified enzyme has fluorescence emission properties similar to those of NCD-4 N-acetylurea in a relatively hydrophobic environment: it is concluded that NCD-4 has modified a carboxylate group (s) located in or near the Ca2+-binding sites of the ATPase.

Mononuclear cell-membrane "fluidity": a study in some haematological malignancies

The polarization of fluorescence from diphenyl hexatriene embedded in the membranes of intact peripheral-blood mononuclear cells has been measured and used to assess the "microviscosity" or fluidity of the membrane. Cell preparations were examined from patients with various types of leukaemia and related conditions in which circulating primitive cells may occur. Significantly lower fluorescence polarization values were obtained in all samples from patients with chronic lymphocytic leukaemia, but normal results were obtained in cases of chronic granulocytic leukaemia, myelosclerosis, solid lymphomas and in acute leukaemias in remission. In relapsed acute leukaemia, fluorescence polarization indicated reduced "microviscosity" of the cell membrane when large numbers (greater than 10(9)/1) of primitive cells were present; normal "microviscosity" was indicated when less than 10(9)/1 primitive cells were present. However, exceptions occurred in both cases, and the technique failed to give warning of imminent relapse in one case. Our findings suggest that a reduction in "microviscosity" as indicated by this technique is not a general property of the blood leucocytes in all types of leukaemia, and that the technique cannot, at present, be regarded as an alternative method for detecting circulating primitive cells.

A Study of the Polarization of Fluorescence of Ordered Systems With Application to Ordered Liquid Crystals

The fluorescence polarization of uniaxial molecules dissolved in an ordered medium is studied. A theoretical model is developed which relates the polarization of the fluorescence emission to molecular structure, orientation of absorption and emission dipole oscillators and the degree of ordering. This theory was tested experimentally using all trans 1,6-diphenyl-1,3,5-hexatriene dissolved in an ordered liquid crystal.

High resolution luminescence spectrometer. 1: simultaneous recording of total luminescence and phosphorescence

A luminescence spectrometer is described that has the particular advantage of allowing the simultaneous recording of total luminescence and phosphorescence spectra. The basic design is straightforward and uses commercially available components. The measuring and recording system is completely digital. The technique of single-photon counting is employed, and the data are recorded digitally in the form of listings and punched paper tapes. This output is suitable for further data analysis on a computer. An additional analog recording system allows an instant examination of the quality of the incoming data.

Absolute Spectrofluorometry

The last 10 years has seen the increasing publication of the emission spectra of organic, inorganic and metal-chelate compounds, but there is no agreed method of presentation of such spectra. In the few cases where corrected emission spectra have been published, there is often no mention of the units used for the intensity coordinate or the method used for correcting spectra. A method of reporting absolute fluorescence spectra originally put forward in 1962 will be reexamined and improved. The two best known methods for calibrating spectrometers for absolute spectrofluorometry: (a) standard tungsten lamp, (b) quantum counter method, will be critically examined, and the limitations and possible improvements in accuracy will be proposed. The criteria for an emission standard will be examined and the use of emission standards for calibrating spectrorluorometers discussed. It is suggested that the distribution of emission standards to laboratories measuring corrected fluorescence spectra and the analysis and publication of the results should be done in the near future.

Apparatus for measurement of luminescence spectra with a digital recording system

An apparatus is designed for use in obtaining fluorescence spectra, excitation spectra, and delayed fluorescence spectra, usually at low temperatures. A photometrically regulated 6500-W xenon lamp is used as excitation source, a double monochromator or varioilluminator as excitation monochromator; a variable temperature liquid helium cryostat as specimen holder; a double grating monochromator or varioilluminator as detection monochromator; and a photomultiplier as detector. A quartz-iodine lamp calibrated against a standard tungsten-quartz lamp is used for intensity calibrations. Fluorescence spectra are recorded by a digital system with a shaft position encoder for digitizing wavelength and an analog-to-digital converter for intensity. Data are recorded on magnetic tape which can be processed directly by an IBM system 360 computer. The selection of components of adequate resolution, speed, and capacity is discussed, and the computer programs are described. Installation of the recording system 1ms facilitated greater wavelength accuracy and long calculations on the experimental data. Examples are given.

Absolute Luminescence Spectra via Digital-Technique and Time-Resolved Spectroscopy

Most instruments intended for luminescence spectroscopy fall in the category of uncorrected spectrofluorimeters. In many routine analyses, uncorrected spectra are useful, especially if they do not have to be compared with others from different laboratories. However, for theoretical work, results must be on an absolute basis. This paper describes a method and the related equipment that have been developed and used to obtain, on an absolute basis, many of the parameters that are important in photochemical research. The system can provide absolute emission spectra, absolute excitation spectra, and quantum efficiencies for luminescence, fluorescence, delayed fluorescence, and phosphorescence. Also, it can measure the half-life of phosphorescence and of delayed fluorescence. Provision is made for the independent and continuous control of the time between excitation and detection pulses, thus allowing the measurement of the half-life at any wavelength of emission. With these provisions it is possible to resolve overlapping fluorescence, delayed fluorescence, and phosphorescence spectra.