Dichroic spectra

The conformations of L-adenylyl-(3 5 )-L-adenosine (28) and L-adenylyl-(2 -> 5 )-L-adenosine (29), as deduced from circular dichroic spectra, are different from the corresponding DD-dinucleotides. < The n.m.r. and u.v. absorption spectra of (28) and (29) are the same as the DD-dimers and their chromatographic and electrophoretic properties appear identical. While (28) and (29) are resistant to enzymic hydrolysis they form complexes with polyU. 

Fig. 10 Extrinsic circular dichroic spectra of berberine-B-DNA (a) and berberine-H -DNA (b) complexes. Reprinted in part from [186] with permission from Elsevier...

The inclusion modes of flurbiprofen with beta cyclodextrin and with heptakis(2,3,6-tri-0-methyl)-beta cyclodextrin have been studied by Imai and coworkers. They showed that, although the Cotton effects in the circular dichroic spectra induced by beta cyclodextrin in / (-) and 5(+) flurbiprofen are identical, those induced by heptakis(2,3,6-tri-0-methyl)-beta cyclodextrin differ from each other and from those induced by beta cyclodextrin. C.p.-m.a.s. C-n.m.r. experiments showed that the cyclodextrin ring is probably more distorted in the flurbiprofen inclusion complex with methylated beta cyclodextrin than in that with beta cyclodextrin. 

Scanu, A. M., The effect of reduction and carboxymethylation on the circular dichroic spectra of pure polypeptide classes of serum high density lipoproteins. BwMm. Biophys. Acta 200, 570-572 (1970). 

Linear-dichroic spectra of SA monolayers prepared from mixtures of OTS and a cyanine-dye surfactant established the absence of dimerization and the orientation of the chromophore parallel to the substrate [183]. In contrast, the same cyanine dye underwent sandwich-type dimer formation in LB films and had its chromophore oriented perpendicular to the water surface [192]. These results highlight an important difference between LB and SA monolayers. Parameters which determine monolayer formation on an aqueous subphase are also responsible for the orientation and organization of the surfactants therein. Furthermore, the configuration of the surfactants is retained regardless of the structure of the substrate to which the floating monolayer was subsequently transferred to by the LB technique. Conversely, in SA monolayers, surfactant organization is primarily dependent upon the nature of the substrate [183]. 

Fig. 11. (a) Far ultraviolet rotatory dispersion of ribonuclease. Corrected mean residue specific rotation vs. wavelength [to R = [aLAf/100 [3/(n2 + 2)l where a — specific rotation, M mean residue weight, and n = solvent refractive index. Bars give maximal deviation at peaks. Reproduced from Jirgensons (311). (b) Near ultraviolet rotatory dispersion of 0.48% pancreatic ribonuclease in a 1-mm cell, in (a) 0.15 M phosphate buffer at pH 62 (b) 0.15 M glycine-NaOH buffer at pH 11.5 (c) 0.1 N HC1 (d) 15% sodium dodecyl sulfate. Reproduced from Glazer and Simmons (313). (c) Far ultraviolet circular dichroic spectra of RNase-A, RNase-S, and S-protein at 25° and 3°. Reproduced from Pflumm and Beychok (313). (d) Near ultraviolet circular dichroic spectra of RNase-A as a function of pH. Reproduced from Pflumm and Beychok (313). 

Fig. 11. Circular dichroic spectra of Co (II) carbonic aahydrase and complexes with...

CLM method can also be combined with various kinds of spectroscopic methods. Fluorescence lifetime of an interfacially adsorbed zinc-tetra-phenylporphyrin complex was observed by a nanosecond time-resolved laser induced fluorescence method [25]. Microscopic resonance Raman spectrometry was also combined with the CLM. This combination was highly advantageous to measure the concentration profile at the interface and a bulk phase [14]. Furthermore, circular dichroic spectra of the liquid-liquid interface in the CLM could be measured [19]. 

Methods. Measurements of absorption spectra and spectrophoto-metric titrations were carried out on a Cary 15 spectrophotometer equipped with a thermostated cell compartment. Circular dichroic spectra were recorded on a Cary 60 spectropolarimeter equipped with a 6001 CD attachment. Fluorescence spectra were measured on a Hitachi-... 

Another interesting method of investigating oriented films involves using polarized infrared radiation. Two different FTIR spectra are obtained of such samples if the electric field of the incident IR beam is polarized parallelly or perpendicularly to the primary axis of orientation of the sample. Such dichroic spectra may provide information concerning the orientation of subgroups in a biopolymen for example of the phosphate groups of nucleic acids, with respect to the helical axis (Sec. 4.7.1.3.4). 

Figure 3.14 shows the dichroic spectra observed in films of DE/PMMA and SP/PMMA. The insets in Figure 3.15A are expanded views of both the UV and the visible absorptions of the DE chromophore. These spectra were obtained 30 s after polarized UV irradiation (irradiation dose 78 mj/cm ). It is clear that Abs// and Abs are different in other words, the irradiated samples show anisotropic absorbance upon polarized UV irradiation. Identical spectra were recorded for Abs// and Absj before UV irradiation, demonstrating that the samples were in-plane isotropic at that time. 

The random coil and helical conformations of polypeptides and glycopolypeptides were characterized via circular dichroic spectra recorded on a JASCO 810 spectrophotometer (Jasco, Inc., Easton, MD) using a 1-mm path length quartz cuvette in the single-cell mount setup. Background scans of buffer (10 mM phosphate, 150mM NaCl (PBS) pH 7.3) were recorded and automatically subtracted from the sample scans. Samples were made with the... 

No particular ground-state interaction was detected in the absorption spectra of the two polypeptides. Circular dichroic spectra of the polypeptides are y y similar to each other and showed an exciton splittings at the La and the Bb absorption bands [61353 =... 

In the upper part of Figure 5.15 a superposition of the theoretical magnetic dichro-ism spectra A/xl2 and A/zl3 according to Equation (5.42) is given (here the very small contribution (d/dE)(TZ) has been neglected). This is compared with the spin polarization (d/d )(band-structure calculations. In the lower part of Figure 5.15 the superposition according to Equation (5.43) of the dichroic spectra is compared with the directly calculated orbital polarization (d/d )(/z)d of the d states. 

These analytical considerations support the analysis and interpretation of corresponding experimental and theoretical dichroic spectra in an appreciable way. As an example of such a combined investigation, valence-band photoemission spectra for a... 

Figure 6. Circular dichroic spectra of azophenol and azonaphthol Co(III)-EDDA complexes under various conditions...

Fig. 5.8 Circular dichroic spectra of 0.05 mM insulin and monoacyl derivatives (a) and insulin and diacyl derivatives (b).

Linear Dichroism. A linear dichroism study of the orientation of j8-carotene molecules in lamellar liquid-crystalline lipid systems has been reported/ Linear dichroic spectra of the cross-conjugated carotenals renierapurpurin-20-al (169), 20-(2,3,4-trimethylbenzal)renierapurpurin (170), and 8, 8 -diapocarotene-8,20,8 -trial (171) have been recorded/ The results support the assignment of the 13 -cis configuration to (169) and (170). 

For EGFP and GFP-S65T detailed pH titrations ranging from pH 5 to 8 indicated 10-fold reversible changes in absorbance and fluorescence with pKa values of 6.0 (EGFP), 5.9 (GFP-S65T) and apparent Hill coefficients of 1 [70], Under these conditions the fluorescence spectral shape, lifetime, and circular dichroic spectra were found to be pH independent, whereas at pH values below 5, the fluorescence response was slowed and not completely reversible. Due to this it was concluded that GFP pH sensitivity involves simple protonation events at a pH of 5 and above, but both protonation and conformational changes at lower pH values. 

ORD measurements are commonly extended into the far-ultraviolet region where the Cotton effects characteristic of the a-helix (a trough at 233 m/z and a maximum near 200 m/z) (8, 56) are found. By analyzing the circular dichroic spectra of a-helical polypeptides, Holzwarth and Doty (24) have shown that three rotatoiy bands (the n1 — w transition at 222 m/z, the parallel-polarized w° — 7r exciton transition at 206 m/z, and the perpendicularly polarized t° — w exciton transition at 190 m/z) can account for these Cotton effects. When the polypeptide chain becomes disordered, only a single Cotton effect with a trough at 204 m/z is seen (8). 

Figure 1. Circular dichroic spectra and absorption spectra of dimer ApA...

A glance at the circular dichroic spectra shown in Figures 1, 2, and 3 demonstrates a fundamental point starting from the dimer, all of these substances in neutral solution at low temperature exhibit the same kind of dichroic spectrum. While there are small differences in the positions and... 

Figure 2. Circular dichroic spectra of adenylate oligonucleotides at pH 7.4 at various...

The validity of a model, such as that suggested above, can be tested by such data as circular dichroic spectra only if an adequate theory of optical activity is available. While several such theories have been developed, those based upon the exciton theory seem particularly appropriate to the investigation of polymeric structures 1,19, 23). As in a molecular crystal, such theories depict the interaction of the identical residues in an... 

The predicted features of the dichroic spectra are in good agreement with observations for the adenylate oligomers in neutral solution. Taking the simplest case, the dimer, we see that there should be two bands of opposite sign, spaced above and below the position of the monomer band their rotational strength should be given by... 

Circular Dichroism and Magnetic Circular Dichroic Spectra.—There have been two papers concerned with the theory of c.d. one concerned with vibronic coupling,187 the other with radiationless decay.188 Circular dichroism detected 78 80 81 84 88... 

Figure 2. Circular dichroic spectra for the X-D and X-O peptides, (a) CD scans reported at 5 °C in water, (b) Thermal unfolding scans of peptides in water.

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