Detection and visualization

A variation on this method, called fluorescent in situ hybridization (FISH), uses fluorescent-labeled DNA and RNA probes for detection and visualization of single cells by microscopy or flow cytometry.7 80 The FISH technique is popular because of its sensitivity and speed of visualization fluorescent dyes can be used to produce probes with different colors for simultaneous detection of several organisms.76,81,82... 

While heme is not fluorescent, PpIX exhibits a fluorescence emission spectrum typical for porphyrins of this structural class (Fig. 9). Accordingly, PpIX fluorescence has been utilized to detect and visualize tumours and other tissue abnormalities in a large variety of clinical applications (see Chapter 4). 

FRET occurs when the electronic excitation energy of a donor chromophore is transferred to an acceptor molecule nearby via a through-space dipole-dipole interaction between the donor-acceptor pair.80 The strong dependence of the FRET efficiency on donor-acceptor distance has been widely exploited in studying the structure and dynamics of proteins and nucleic acids, in the detection and visualization of inter-molecular association, and in the development of intermolecular binding assays.81,82... 

Nichkova, M., Dosev, D., Perron, R., Gee, S.J., Hammock, B.D., and Kennedy, I.M. 2006. Eu3+-doped Gd203 nanoparticles as reporters for optical detection and visualization of antibodies patterned by microcontact printing. Anal Bioanal Chem 384(3) 631—637. 

L. S. Serafim, O. C. Lemos, C. Levantesi, V. Tandoi, H. Santos and M. A. Reis (2002). Methods for detection and visualization of intracellular polymers stored by polyphosphate-accumulating microorganisms. J. Microbiol. Methods, 51, 1-18. 

Once mounted in the diffractometer, the crystal is irradiated with X ravs, usuallv so-called CuKa raoiation with a wavelength of 0.154 nm. When the X rays strike the cnzvme crvstal, thev interact with electrons in the molecule and are scattered into a diffraction jxittern, which, when detected and visualized, appears as a series of intense spots against a null background. 

The retinal pool of 11 -cis-retinal is clearly critical for photon detection and visual signal transduction. There are two key aspects regarding this that are important to consider the precursor(s) from which 11 -cis-retinal derived, and, bioconversion of isomerized trans-retinal back to 11-cis-retinal that can recombine with opsin to re-form rhodopsin. The latter aspect is obligatory for restoration of the dark state, regenerating a photosensitive receptor capable of undergoing another cycle of photon detection and signal transduction. Considered together, these events represent the retinoid cycle in the visual process (22). The entire process of re-isomerization and formation of a new rhodopsin molecule occurs in two different retinal tissues and involves several enzymatic steps that are described below (see Fig. 7.14). 

Some of these, like ANS and ethidium bromide, will bind non-covalently to particular regions of proteins and nucleic acids, with large changes in their fluorescent properties. ANS lends to bind to hydrophobic patches on proteins and partially unfolded polypeptides, with a blue shift and increase in fluorescence intensity. Ethidium bromide molecules intercalate between the base pairs of double-stranded DNA, resulting in a large increase in fluorescence that is used routinely for detecting and visualizing bands of nucleic acids in gel electrophoresis, for example. 

Kamruzzaman, M. et al (2013) Fast detection and visualization of minced lamb meat adulteration using NIR hyperspectral imaging and multivariate image analysis. Talanta, 103, 130-136. 

Cortese-Krott, M. M. Rodriguez-Mateos, A. Kuhnle, G. G. C. Brown, G. Feelisch, M. Kelm, M. A multilevel analytical approach for detection and visualization of intracellular NO production and nitrosation events using diaminofluoresceins. Free Radical Biol. Med. 2012,53, 2146-2158. 

Q. Lin (2001) Enhancement, Detection, and Visualization of 3D Volume Data. PhD thesis, Linkoping University, Department of Electrical Engineering, Computer Vision Laboratory, Linkoping, Sweden, October 2001. 

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