Dichroic fluorescence

In summary, LC-PTs and LC-PTVs were macroscopically aligned under a magnetic fleld. All polymers showed dichroic fluorescence and anisotropic electrical conductivity, suggesting that both LC-PTs and LC-PTVS might be advanced materials with linearly polarized fluorescence. 

I. Osaka, H. Goto, K. Itoh, K. Akagi, Dichroic fluorescence of liquid crystalline polythiophene and poly-thienylenevinylene derivatives, Synth. Met., 119, 541-542 (2001). 

Liquid crystal polymers are also used in electrooptic displays. Side-chain polymers are quite suitable for this purpose, but usually involve much larger elastic and viscous constants, which slow the response of the device (33). The chiral smectic C phase is perhaps best suited for a polymer field effect device. The abiHty to attach dichroic or fluorescent dyes as a proportion of the side groups opens the door to appHcations not easily achieved with low molecular weight Hquid crystals. Polymers with smectic phases have also been used to create laser writable devices (30). The laser can address areas a few micrometers wide, changing a clear state to a strong scattering state or vice versa. Future uses of Hquid crystal polymers may include data storage devices. Polymers with nonlinear optical properties may also become important for device appHcations. 

Measuring Protein Sta.bihty, Protein stabihty is usually measured quantitatively as the difference in free energy between the folded and unfolded states of the protein. These states are most commonly measured using spectroscopic techniques, such as circular dichroic spectroscopy, fluorescence (generally tryptophan fluorescence) spectroscopy, nmr spectroscopy, and absorbance spectroscopy (10). For most monomeric proteins, the two-state model of protein folding can be invoked. This model states that under equihbrium conditions, the vast majority of the protein molecules in a solution exist in either the folded (native) or unfolded (denatured) state. Any kinetic intermediates that might exist on the pathway between folded and unfolded states do not accumulate to any significant extent under equihbrium conditions (39). In other words, under any set of solution conditions, at equihbrium the entire population of protein molecules can be accounted for by the mole fraction of denatured protein, and the mole fraction of native protein,, ie. 

Intermediate methods include the earliest procedure based on Stein s equation [33] and one based on Samuels equation [34]. Among the direct methods is an IR spectroscopic method based on the measurement of the dichroic ratio (R), of amorphous absorption bands. In the investigations [35], the amorphous bands 898 cm" and 1368 cm", for which the angles of transition moment are a898 = 39 and aneg = 80 , respectively, were used. Other methods are spectroscopy of polarized fluorescent radiation [35,36], measurement of color di-... 

Figure 4.6 Block diagram of the apparatus for the fluorescence depolarization measurement. The dashed and solid arrows indicate the light paths ofthe excitation pulse and the fluorescence from the sample. OBJ microscope objective, M mirror, L lens, DM dichroic mirror, LP long-pass filter, PH pin-hole, PBS polarizing beam splitter, P polarizer, PMT photomultiplier.

In order to develop compounds that can selectively target duplex RNA, Sinha et al. [ 194] studied the interaction of berberine with two different conformations of poly(rC) poly(rG) structures. Poly(rC) poly(rG) has been shown [15,215] to exist in two conformations depending on the pH of the solution, the A-form at physiological pH and the protonated form at pH 4.3. These two conformations have been characterized to have clearly defined but distinctly different circular dichroic and absorption spectral characteristics. Both the A-form and the protonated form of the RNA induced moderate hypochromic change and bathochromic shifts in the absorption maxima peaks at 344 nm and 420 nm of the alkaloid with three isosbestic points centered around 357,382 and 448 nm. Binding of berberine to both forms enhanced the fluorescence intensity, which was higher with the protonated form than with the A-from, suggesting clear differences in the nature of orientation... 

Fang JM, Selvi S, Liao JH et al (2004) Fluorescent and circular dichroic detection of monosaccharides by molecular sensors bis[(pyrrolyl)ethynyl]naphthyridine and bis [(indoili)ethynyl]naphthyridine. J Am Chem Soc 126 3559-3566... 

Fig. 10.2. FSPIM analysis of the interaction between maize transcriptional coactivators—GCN5 and ADA2—fused to CFP and YFP. GCN5 is a histone acetyltransferase that, in conjunction with adaptor protein ADA2, modulates transcription in diverse eukaryotes by affecting the acetylation status of the core histones in nucleosomes [63]. CFP- and YFP-tagged proteins, expressed in protoplasts, were excited by the 458 nm and the 514 nm laser lines sequentially. CFP fluorescence was selectively detected by an FIFT 458 dichroic mirror and BP 470-500 band pass emission filter while YFP fluorescence was selectively detected by using an HFT 514 dichroic mirror and...

Procedure From bioassays, control and treated seedlings (seed and roots at 48 and 72 h of treatment) are stained for 10-15 min with 25 pM DCFDA in distilled water. Then fluorescence intensity of the dye is observed using the confocal microscope BIORAD 1024 (488nm dichroic and 510-560 nm emission). DCFDA fluorescence increases as the dye is oxidized by ROS to dichlorofluorescein (DCF). 

Fluorophores can be visualized in fluorescence microscopy using special filter blocks that are composed of the excitation filter, dichroic mirror and emission filter. The excitation filter must select wavelengths of light from a light source that fall in the maximum absorption region of the fluorophore. The emission filter must pass the fluorescent wavelengths but not the excitation wavelengths. The dichroic mirror... 

Fig. n.1. Principles of fluorescence up-conversion. NLC nonlinear crystal DM dichroic mirror HW half-wave plate PM photomultiplier. 

Fig. 11.2. Fluorescence up-conversion instrument. DM dichroic mirror HW halfwave plate GG420 Schott filter CCD video camera for the visual superposition of the...

In a confocal microscope, invented in the mid-1950s, a focused spot of light scans the specimen. The fluorescence emitted by the specimen is separated from the incident beam by a dichroic mirror and is focused by the objective lens through a pinhole aperture to a photomultiplier. Fluorescence from out-of-focus planes above and below the specimen strikes the wall of the aperture and cannot pass through the pinhole (Figure 11.3). 

Fluorescence microscope equipped with appropriate excitation filter, dichroic mirror, and barrier filter. For this example, an Olympus BHT compound microscope equipped with a BP490 excitation filter, BH-2DM500 dichroic mirror, and a LP515 barrier filter is used. 

FIGURE 2.1 A diagram of a multi-photon microscope. For AF, SFIG and exogenous probe fluorescence only one laser is used. The fluorescence or SHG signal passes through a dichroic mirror to the detector(s). One or two detectors and the appropriate filters can be used to collect multiple emission signals simultaneously. A spectrometer can be placed in the detector path to collect spectra, or a polarizer can be used to collect polarization data. 

The laser light travels through the epifluorescence or side port of the microscope. A dichroic mirror reflects the laser light and passes the green fluorescence to either of the detectors. Detectors are positioned on the bottom port of the inverted microscope or the top port of the upright microscope. The choice of detector is discussed in more detail below. Broadband and band-pass filters placed in the detection path prevent residual IR from reaching either of the detectors. 

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