Banded biological associations with

Fig. 6. Proposed push-pull model for nematode sperm locomotion. Assembly and bundling of MSP filaments into fiber complexes (dark band spanning the lamellipo-dium) pushes the membrane at the leading edge forward. At the same time a second force, associated with disassembly of the fiber complexes at the base of the lamellipo-dium, pulls the cell body forward. In this model, attachments where the cytoskeleton is linked to the membrane and the membrane anchored to the substratum establish traction and separate mechanically the forces produced at opposite ends of the fiber complexes. Thus, rather than canceling each other, these forces can be exerted independently against the substratum. Reproduced from The Journal of Cell Biology, 2000, vol. 149, pp. 7-12 by copyright permission of the Rockefeller University Press.

Although the focus of this section has primarily been on iron and copper complexes, probably the most important transition metals biologically studied by the MCD technique, variable temperature and field dependence studies have also been carried out for complexes of other transition metals such as cobalt and manganese and the techniques described for iron and copper can easily be applied to other metals based on the nature of the ground state. MCD spectroscopy has the key advantage, over other techniques used to study bulk magnetic properties of an entire sample, that spectral bands associated with specific mefal cenfers can be sfudied in isolation. 

Nucleic acid also was found in association with the tuberculin protein. Spiegel-Adolf and Seibert investigated the problem spectrographically, and found that the tuberculin protein ( P.P.D. ) precipitated by trichloroacetic acid exhibited an absorption band at 2650-2670 A. This band was identical with that displayed by deoxyribonucleic acid. Precipitation of the tuberculin protein by ammonium sulfate afforded a product which did not display an absorption band in the ultraviolet region of the spectrum. The substance had a lower phosphorus content than that of products obtained by trichloroacetic acid precipitation. The biological activity was not impaired in any way. 

We have seen that, in the infrared region of the spectrum, there are spectral bands associated with both vibrational and rotational transitions. Pure rotational transitions are found in the microwave region of the spectrum, which is beyond the infrared, but studies of these are not of great value in the investigation of large molecules. Studies of the vibrational-rotational spectra in the infrared have, however, made very important contributions to biological research. 

Recently considerable interest has been centered on the near-infrared absorption spectra of biological pigments such as cytochrome c and cytochrome oxidase. Ferricytochrome c has an absorption band at 695 nm which is strongly dependent on the protein structure (Schejter and George, 1964), while oxidized cytochrome oxidase has an 830 nm band which is associated with the copper moiety of the enzyme (Griffiths and Wharton, 1961). 

Table 8.2 (Alpert et al., 1970) gives a summary of the important group frequencies of amines. These have also been discussed in Rao (1963) and Bellamy (1958). Table 8.3 (Alpert et al, 1970) presents vibrations associated with the CN structure for the series methyl, dimethyl, and trimethyl amines. The bands for the corresponding hydrochlorides are also given. The infrared spectra of water solutions of the hydrochlorides of several biologically important amines have been recorded in the range 1550-909 cm (Kirschenbaum and Parker, 1961). Bentley et al. (1968) have discussed alkyl and aromatic amine spectra recorded in the range 700 300cm V...

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