Wavelength markers

Additionally, in Laue geometry only cell ratios can be determined from the angular coordinates of spots. The absolute cell parameters therefore have to be provided from a monochromatic study. However, if the intensities of spots are also considered, then there appears to be scope to solve the problem by using knowledge of Amin (section 7.2.3) and the bromine K edge in the photographic film as wavelength markers. 

With a prism and a telescope that he manufactured by himself, he discovered numerous black lines in the spectrum of sunlight thrown by a prism. He made use of these lines as wavelength markers when he was developing his new lenses. Subsequently they would be recognized as optical fingerprints for identifying individual elements whose atoms absorbed only certain wavelengths from the sun. Soon after, he became one of the world s premier scientific instrument makers. ... 

If a small fraction of the laser output is sent through a long Fabry-Perot interferometer with a separation d of the mirrors (Fig. 1.1b), the photodetector PD3 receives intensity peaks each time the laser frequency is tuned to a transmission maximum at v = mcjd (Vol. 1, Sects. 4.2-4.4). These peaks serve as accurate wavelength markers, which allow one to calibrate the separation of adjacent absorption lines. With a = 1 m the frequency separation Avp between successive transmission peaks is Avp = cjld = 150 MHz, corresponding to a wavelength separation of 10 nm at A. = 550 nm. With a semiconfocal FPI the free spectral range is cfM, which gives Av = 75 MHz for d = 0.5 m. 

The identification and quantification of potentially cytotoxic carbonyl compounds (e.g. aldehydes such as pentanal, hexanal, traw-2-octenal and 4-hydroxy-/mAW-2-nonenal, and ketones such as propan- and hexan-2-ones) also serves as a useful marker of the oxidative deterioration of PUFAs in isolated biological samples and chemical model systems. One method developed utilizes HPLC coupled with spectrophotometric detection and involves precolumn derivatization of peroxidized PUFA-derived aldehydes and alternative carbonyl compounds with 2,4-DNPH followed by separation of the resulting chromophoric 2,4-dinitrophenylhydrazones on a reversed-phase column and spectrophotometric detection at a wavelength of378 nm. This method has a relatively high level of sensitivity, and has been successfully applied to the analysis of such products in rat hepatocytes and rat liver microsomal suspensions stimulated with carbon tetrachloride or ADP-iron complexes (Poli etui., 1985). 

Augustijns P, Mols R (2004) E1PLC with programmed wavelength fluorescence detection for the simultaneous determination of marker compounds of integrity and P-gp functionality in the Caco-2 intestinal absorption model. J Pharm Biomed Anal 34 971-978. 

The detection of M. aeruginosa toxins is readily achieved by HPLC and ultraviolet absorbance. Provisionally, components with identical retention times are considered identical. Confirmation is made by preparative isolation, amino acid analysis, and toxicity testing. The frequent, but not invariable, presence of toxin-LR as a principal toxin provides a useful HPLC marker. The wavelength used for detection of the toxins, 238 nm, is the principal absorbance maximum of toxin-LR. The 238 nm absorbance is probably... 

Similar in principle to this is the use of two different X-ray wavelengths on the same crystal, one near to and the other far from the absorption edge of a marker atom, to give different diffracting powers this is the "ideal isomorphism method advocated by Lipson and Cochran (195 ) and Pepinsky (1956). A comparison of the vector maps for the two wavelengths, or a vector map based on the differences of structure amplitudes for corresponding reflections for the two wavelengths, indicates which peaks are due to the marker atoms. 

The Lb transition for phenylalanine resembles that for benzene (Strickland, 1974), but the CD signal is of relatively low intensity, so that it is seen only as shoulders or minor peaks to the low-wavelength side of tyrosine and tryptophan bands (Fig. B3.5.10). As a result of the high degree of symmetry in the side chain, the presence of these peaks is an indication of a highly specific and well-packed environment and can act as a marker for native folding. 

Direct labeling of a biomolecule involves the introduction of a covalently linked fluorophore in the nucleic acid sequence or in the amino acid sequence of a protein or antibody. Fluorescein, rhodamine derivatives, the Alexa, and BODIPY dyes (Molecular Probes [92]) as well as the cyanine dyes (Amersham Biosciences [134]) are widely used labels. These probe families show different absorption and emission wavelengths and span the whole visible spectrum (e.g., Alexa Fluor dyes show UV excitation at 350 nm to far red excitation at 633 nm). Furthermore, for differential expression analysis, probe families with similar chemical structures but different spectroscopic properties are desirable, for example the cyanine dyes Cy3 and Cy5 (excitation at 548 and 646 nm, respectively). The design of fluorescent labels is still an active area of research, and various new dyes have been reported that differ in terms of decay times, wavelength, conjugatibility, and quantum yields before and after conjugation [135]. New ruthenium markers have been reported as well [136]. 

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