Circular dichroism properties

Similarly, the analog 54 also forms a self-assembled dimer [54]2 in non-polar solvents. In the presence of pyridine, the dimer dissociates into the monomeric species 54 Py [53,54], Further addition of AgPF6 leads to the formation of a novel Ag-linked phthalocyanine dimer [54]2Ag PF6 (Scheme 5) [55]. On the basis of its electronic absorption and magnetic circular dichroism properties, it has been suggested that this dimer adopts a planar and nms-con formation. Addition of NH4C1, which can remove the silver ions as AgCl, regenerates the monomeric 54 Py. 

In a study47 of the ORD and circular dichroism properties of (— )-(8.R,9.fl)-(rcms-octahydrobenzo[c]thiophene and A-nor-2-thia-cholestane it was shown that the sulfur chromophore is useful for making stereochemical correlations. The two compounds show optically active transitions at 244 and 205 nm the signs of these transitions reflect the chirality of the neighboring centers. 

The absorption data and yields for the six complexes are reported in Table I. The specific and molar rotations at 546 nm and 365 nm are given in Table n. The optical rotatory dispersion and circular dichroism properties determined in aqueous solutions are given in Tables III and IV. The racemic complexes were calculated as monohydrate compounds, since the elemental analyses for the optically active complexes correspond to monohydrate compounds, and both the optically active and racemic complexes give similar absorption data. The ORD and CD spectra were obtained on modified computerized Perkin Elmer Model 241 and Cary Model 61 Spectropolarimeters, respectively.1314... 

Bernardi G. and TimashefFS.N. (1970). Optical rotatory dispersion and circular dichroism properties of yeast mitochondrial DNA s. J. Mol. Biol. 48 43-52. 

Circular dichroism properties (electronic circular dichroism, vibrational circular dichro-ism, and Raman optical activity). 

Optical properties of cyanines can be usefiil for both chiral substituents/environments and also third-order nonlinear optical properties in polymer films. Methine-chain substituted die arbo cyanines have been prepared from a chiral dialdehyde (S)-(+)-2-j -butylmalonaldehyde [127473-57-8] (79), where the chiral properties are introduced via the chiral j -butyl group on the central methine carbon of the pentamethine (die arbo cyanine) chromophore. For a nonchiral oxadicarbocyanine, the dimeric aggregate form of the dye shows circular dichroism when trapped in y-cyclodextrin (80). Attempts to prepare polymers with carbocyanine repeat units (linked by flexible chains) gave oligomers with only two or three repeat units (81). However, these materials... 

The UV spectrum of a complex conjugated molecule is usually observed to consist of a few broad band systems, often with fine structure, which may be sharpened up in non-polar solvents. Such a spectrum can often be shown to be more complex than it superficially appears, by investigation of the magnetic circular dichroism (MCD) spectrum, or by introduction of dissymmetry and running the optical rotatory dispersion (ORD) or circular dichroism (CD) spectrum. These techniques will frequently separate and distinguish overlapping bands of different symmetry properties <71PMH(3)397). 

Chirooptical properties give more subtle information on the conformational behavior of biopolymers and peptides in solution. In early experiments, optical rotation and optical rotatory dispersion (ORD) have been recognized as valuable techniques, followed more recently by significant progress and refinements in the equipment which have resulted in the routine measurements of applied circular dichroism (CD). 

Optically active molecules show circular dichroism. Their extinction coefficients f l and are different and change as a function of wavelength. Using a suitable spectroelectrochemical cell, Af = fl -which is usually small compared to conventional extinction coefficients, can be measured. Combined with the special properties of a thin layer cell kinetic data can be extracted from CD-data [01 Liu]. (Data obtained with this method are labelled CD.)... 

The magnetic and electronic properties of the D. gigas Fdll [3Fe-4S] center were revealed by different and complementary spectroscopic techniques EPR 89), Mossbauer 90, 91), resonance Raman (RR) 92), magnetic circular dichroism MCD) 93), EXAFS 94), saturation magnetization (95), electrochemistry 96), and NMR (97, 98). The [4Fe-4S] center is also well characterized and surprising information has been obtained in relation to cluster interconversions and noncysteinyl coordination, as illustrated for D. gigas Fdl and D. africanus Fdlll, as well as the possibility of generating unusual reduced states. 

Other spectroscopic properties such as nuclear magnetic resonance (NMR), mass spectrometry (MS), infra-red (IR), and circular dichroism (CD) spectra of chlorophyll compounds and derivatives have been valuable tools for structural elucidation. - ... 

Circular dichroism (CD) is another interesting example of an optical property of the small Au SR clusters. Since the first observation of Schaaff et al. [23,24], several reports have appeared regarding the CD activities of gold clusters protected by chiral thiols such as penicillamine [25] and A-isobutyryl-cysteine [26]. Figure 11 shows the CD spectra of 1-9, which is a good reproduction of the original report by Whetten s group [23,24]. 

The effect of formalin-treatment on the structural properties of RNase A was examined using circular dichroism (CD) spectropolarimetry. A brief introduction to CD spectropolarimetry is provided in Section 15.15.2 for those readers unfamiliar with this biophysical method. The secondary structure of RNase A consists of one long four-stranded anti-parallel p-sheet and three short a-helixes,44 which places RNase A in the a + p structural class of proteins. The effect of a 9-day incubation of RNase A (6.5mg/mL) in 10% formalin on the protein secondary structure was examined with CD spectropolarimetry in the far-UV region (170-240nm) as shown in Figure 15.6a. The resulting... 

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