Optical rotatory dispersion types

A number of methods have been used for determining Kg values cation selective electrodes, pH-metric methods, conductimetry, calorimetry, temperature-jump relaxation measurements, membrane conductance measurements, nuclear magnetic resonance, optical rotatory dispersion. The results listed in Tables 7—10 have been obtained by various methods and at different ionic strengths so they may not always be strictly comparable. However, the corrections are probably small and the experimental accuracy is generally the same or very similar within a certain ligand type. 

Raney nickel) of the potassium salt of D-xy/o-5-hexulosonic acid oxime produces a mixture of 5-amino-5-deoxy-L-idonic and -D-glu-conic acid in the ratio of 2 1, which is converted into the methyl ester hydrochloride. Upon treatment with alkali, spontaneous cyclization to the pair of 1,5-lactams occurs. 5-Amino-5-deoxy-L-idono-l,5-lactam and 5-amino-5-deoxy-D-glucono-l,5-lactam were separated by recrystallization. The optical rotatory dispersion curves of both compounds were discussed. A new type of lactam, namely, 2-enamino-N,N -bis[(p-methoxycarbonyl)phenyl]-4-(D-gaiacfo-penta-acetoxypentyl)-4-butanelactam was prepared by tbe reaction of 5,6,7,8,9-penta-0-acetyl-3,4-dideoxy-D-ga/ocfo-nonulos- rcns-3-en-l-onic acid with methyl p-aminobenzoate. 

There are many other types of data which can be collected and reported in appropriate circumstances, uv, ord (optical rotatory dispersion), cd (circular dichroism) etc. 

One of the protein fractions obtained from wool by partial hydrolysis was nonhelical in aqueous solution at pH 3, 9, or 10.5 judging from optical rotatory dispersion measurements, but in 2-chloroethanol the helix content rose to about 30 % (Leach, unpublished observations, 1963). Also, proteins extracted from wool by aqueous urea containing reducing agents may be precipitated and drawn into fibers which show an a-type X-ray pattern (Mercer, 1949). Thus, the diffraction pattern and optical rotatory dispersion data show that intact disulfide bonds are not essential to the reformation of the a-structure. 

Reaction Mechanisms. Bailar (2 3) studied the formation of [Co (en) 2003]" from optically active m-[Co(en)2Cl2] and found that products of opposite configurations were obtained under different conditions. He proposed a Walden type inversion for the substitution process. The configurations of the original complex and the products were related using optical rotatory dispersion curves. Dwyer (19) studied these reactions in detail and concluded that the inversion occurs through a trans displacement process involving both Ag+ and OH ... 

The equilibrium and rate constants for NADH binding to the three isozymes EE, ES, and SS of the horse enzyme have been determined 305). Differences in binding to the two types of chains were found both for the binding strength and the pH dependence. Changes in the absorption spectrum 306,307), the fluorescence polarization spectrum (305), the optical rotatory dispersion spectrum 309), and the effect of DzO on the fluorescence spectrum 310) have been studied for the binary enzyme coenzyme complexes compared to the free molecules. 

Aside from purely spectroscopic techniques, other optical methods have been employed to study substances of interest to biologists. Examples are the study of optical rotation and of optical rotatory dispersion. These latter types of investigation will be considered in the next chapter with special application to biological problems. 

Studies concerning the interaction of DNA with metal ions - which has as an outcome the formation of DNA-M""" type adducts - were performed using various physico-chemical methods, including nuclear magnetic resonance (NMR), optical rotatory dispersion (ORD), and spectroscopy (CD, UV, IR and Raman) (Zimmer 1971, Yang and Samejima 1971, Balasubramanian and Kumar 1976, Marzilli 1977, Arnott 1978, Jack 1979, Theophanides 1976,... 

The two types of optical rotatory dispersion negative values. 

Optical rotatory Dispersion Rotation of the plane polarized light by asymmetric molecules in solution without and with variation in wavelength P, G Determination of relative and absolute configurations of asymmetric centers. Location of functional groups in certain types of compounds. Information about conformation. 

The method and accuracy of proving the presence of a chiral stmcture in a polymer vary depending on the types of study and the stmcture of the polymer. Stmctural questions can be addressed by (1) various methods based on computer calculations or observations of molecular models, (2) achiral spectroscopic evidence (nuclear magnetic resonance (NMR) spectra, absorption spectra, fluorescence spectra, Raman spectra, X-ray diffraction (XRD), and so on), (3) viscosity or light scattering data giving information on the shape and size of an entire molecule, (4) chiroptical properties (optical activity, optical rotatory dispersion, electronic circular dichroism... 

Type IV procollagen, optical rotatory dispersion, at neutral pH Heating rate 0.17°C min ... 

The study of the stereochemical course of organic reactions often leads to detailed insight into reaction mechanisms. Instrumental techniques including IR and NMR spectroscopy, optical rotatory dispersion, and circular dichroism make it possible to determine the stereochemical course of many reactions. Mechanistic postulates frequently make distinctive predictions about the stereochemical outcome of the reaction. Throughout the chapters dealing with specific types of reactions, consideration will be given to the stereochemistry of the reaction and its relationship to the reaction mechanism. As an example, the bromination of alkenes can be cited. A very simple mechanism for bromination is given below ... 

The Moffitt parameter b was evaluated from optical rotatory dispersion (ORD) da a measured by a Yanagimoto OR-100 Type spectropolarimeter using a tungsten lamp as the light source in a temperature range of 10 to 40 C. The reduced mean residue rotation, [m ], at a wave length X is obtained from the observed rotation a by... 

The 7-substitued polymer is crystalline with a melting point of 62 °C whereas the corresponding racemic material cannot be crystallized (/ )-(+)-ethyl-6-acetylthio-3-methylthiohexanoate and (/ )-(-)-ethyl-6-acetylthio-4-methylthiohexanoate were prepared as model compounds (Scheme LVI). A comparison of their optical rotatory dispersion spectra with those of the polymers indicates that the conformations around the asymmetric centers are the same in both types of compound. The macromolecules are too flexible to assume conformational order in dilute solution. 

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