Protein studies

The cross-correlation effects between the DD and CSA interactions also influence the transverse relaxation and lead to the phenomenon known as differential line broadening in a doublet [40], cf Figure Bl.13.8. There is a recent experiment, designed for protein studies, that I wish to mention at tire end of this section. It has been proposed by Pervushin etal [4T], is called TROSY (transverse relaxation optimized spectroscopy) and... 

Selenocysteine was identified in 1976 (57) in a protein produced by Clostridium stricklandii, and it is thought to be the form in which selenium is incorporated, stoichiometricaHy, into proteins. Studies with rats show that over 80% of the dietary selenium given them is incorporated into proteins, thus selenocysteine takes on metaboHc importance. Selenoproteins having known enzymatic activities contain selenocysteine at the active sites. Two other forms of metabohc selenium are recognized methylated selenium compounds are synthesized for excretion, and selenium is incorporated into some transfer ribonucleic acids (tRNAs) in cultured cells (58). Some of the more important seleno-compounds are Hsted in Table 4. Examples of simple ring compounds are shown in Eigure 4. 

M. Smith (University of British Columbia) fundamental contributions to the establishment of oligonucleotide-based, site-directed mutagenesis and its development for protein studies. 

Iron electronic configurations in proteins studies by Mossbauer spectroscopy. A. J. Bearden and W. R. Dunham, Struct. Bonding (Berlin), 1970, 8, 2-52 (196). 

Bearden, A. J., Dunham, W. R. Iron Electronic Configuration in Proteins Studies by Mossbauer Spectroscopy. Vol. 8, pp. 1-52. 

Bolton, J. L. Turnipseed, S. B. Thompson, J. A. Influence of quinone methide reactivity on the alkylation of thiol and amino groups in proteins studies utilizing amino acid and peptide models. Chem.-Biol. Interact. 1997, 107, 185-200. 

Tokarski, C., C. Cren-Olive, C. Rolando, and E. Martin (2003), Protein studies in cultural heritage, in Saiz-Jimenez, C. (ed.), Molecular Biology and Cultural Heritage, Proc. Int. Congress on Molecular Biology and Cultural Heritage in Sevilla, Spain, March 4—7, Balkema, Rotterdam, pp. 119-130. 

The direct whole-cell method of Holland et al. was extremely rapid, even in comparison to Lubman s MALDI analysis of fractions collected after bacterial sonnication. With the whole-cell approach bacteria were simply sampled from colonies on an agar plate, mixed with the matrix, air-dried, and introduced in batches into the mass spectrometer for analysis. In all of the spectra obtained in these and later experiments, each bacterial strain showed a few characteristic high-mass ions that were attributed to bacterial proteins. Studies demonstrating the whole cell methodology for strain-level differentiation were reported independently by Claydon et al. at almost the same time.18 Shortly thereafter a third study on whole-cell MALDI included bacteria from pathogenic and nonpathogenic strains appeared.19... 

UNFOLDED PROTEINS STUDIED BY RAMAN OPTICAL ACTIVITY... 

UNFOLDED PEPTIDES AND PROTEINS STUDIED WITH INFRARED ABSORPTION AND VIBRATIONAL CIRCULAR DICHROISM SPECTRA... 

The CD spectra of nine proteins in 6 M Gdm-HCl were studied by Cortijo etal. (1973). Those proteins with disulfide bridges were reduced and carboxymethylated. The spectra of individual proteins were not reported, but the range of values at wavelengths from 240 to 210 nm was given. The [0]222 values ranged from —800 to —2400 deg cm2/dmol. From this substantial variation, Cortijo etal. (1973) concluded that the proteins studied are not true random coils in 6 M Gdm-HCl, because random coils should have CD spectra essentially independent of amino acid composition and sequence. The observed variation was attributed to differences in the conformational distribution between allowed regions of the Ramachandran map or to residual interactions between different parts of the chain that are resistant to Gdm-HCl denaturation. 

Privalov et al. (1989) also reported the temperature dependence of the ellipticity at 222 nm for the proteins studied at various pH values (Fig. 28). At the highest temperature studied (80°C), the 222 nm ellipticity value for the thermally unfolded, acid-unfolded, and Gdm-HCl-unfolded proteins appear to be converging, but show a range of 2000 deg cm2/dmol out of a total of 5000 deg cm2/dmol. (ApoMb is an exception in that, as noted before, the thermally denatured protein is apparently an associated /1-sheet. However, the acid- and Gdm HC1-unfolded forms of apoMb have similar [0] 222 values at 80°C.)... 

Due to the fact that biarsenical-TC complex is stable under the denaturing conditions typically used for gel electrophoresis of proteins and has a molecular weight of less than 2 KDa, when bonded to the biarsenical dye [157], Kottegoda and collaborators [161] studied the biarsenical dyes, as fluorescent probes for in vitro, cellular peptide, and proteins studies using capillary electrophoresis. 

Lill MA, Helms V (2002) Proton shuttle in green fluorescent protein studied by dynamic simulations. Proc Natl Acad Sci USA 99 2778-2781... 

Bakhshi, A. K., P. Otto, and J. Ladik. 1988. On the Electronic Structure and Conduction Properties of Aperiodic Proteins Study of Six-Component Polypeptide Chains. J. Mol. Struct. (Theochem) 180, 113-123. 

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