Circular 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). 

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-... 

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 =... 

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).

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... 

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.

Fig. 4a-d. Absorption and circular dichroic spectra of nucleic acids in reverse micelles. Absorption (a) and ellipticity (b) properties (1 cm light path) of RNA (mol. weight 20,000-30,000 Dalton) in water and in hydrocarbon micellar solutions. (—) RNA in aqueous solution borate... 

Analogous shifts in protein spectra have been observed as a result of conformational changes associated with denaturation. Initial reports on this phenomenon (see Ref 24) attributed the spectral difference to the transfer of the aromatie amino acids from the hydrophobic interior of the protein to the more aqueous surface environment as a result of the conformational change. Spectral changes for several proteins correlated well with independent measurements of denaturation such as intrinsic viscosity, circular dichroic spectra, and heat capacity measurements. For example, Edelhoch [26] compared the ribonuclease UV spectrum in buffer with that obtained in 6M guanidine hydrochloride (GuHCI). 

The circular dichroic spectra vary with the Dnp derivatives tested (37,38). Spectra of e-Dnp-lysine and e-Dnp-aminocaproate, interacting with anti-Dnp antibody, are quite similar, reflecting the similarity in structure of the haptens, but they differ meirkedly from the spectra of Dnp-glycine or e-Tnp-lysine. 

The possibility of a conformational change is suggested by the work of Holowka et al. (50), who found significant changes in the circular dichroic spectra of three homogeneous preparations of rabbit anti-type... 

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