Decays of Proteins

Tlible 17.3. intensity Decays of Multi-tryptophan Proteii  

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HzS 0-40 pptv Biological decay of protein in anaerobic water Oxidation to SO2... 

J. R. Lakowicz, G. Laszko, I. Gryczynski, and H. Cherek, Measurement of subnanosecond anisotropy decays of protein fluorescence using frequency-domain fluorometry, J. Biol. Chem. 261, 2240-2245 (1986). 

The decay of proteins and amino acids in phytoplankton cultures, under oxic and anoxic conditions, indicated very little selectivity (Nguyen and Harvey, 1997). However, 15 to 95% of the total particulate amino acid pool consisted of polypeptides/proteins in anoxic treatments versus 8 to 65% in oxic conditions. The similarity of particulate amino acid composition during phytoplankton decay agrees with other work in the Delaware Bay estuary (USA), which showed similar composition in the dissolved combined amino acid (DCAA) pool (Keil and Kirchman, 1993). 

At present, there is widespread interest in directly measuring the time-dependent processes. This is because considerably more information is av lilable from the time-dependent data. For example, the time-dependent decays of protein fluorescence can occasionally be used to recover the emission spectra of individual tryptophan residues in a protein. The time-resolved anisotropies can reveal the shape of the protein and/or the extent of residue mobility within the protein. The time-resolved energy transfer can reveal not only the distance between the donor and acceptor, but also the distribution of these distances. The acquisition of such detailed information requires high resolution instrumentation and careful data acquisition and analysis. 

In addition to being affected by shape, anisotropy decays are affected by the segmental flexibility of the macromole-cule. For instance, tryj ophan anisotropy decays of proteins frequently display correlation times that are too short to be due to rotational diffusion of the whole macromole-cule. These short-coirelation-time components are often due to independent motions of the tryptophan residue within the protein. Measurements of these components... 

Die picosecond con onent in the anisotropy decays of proteins does appear to display some characteristic features. The fraction of the total anisotrqiy due to this component is typically larger for small unstructured peptides than for tryptophan residues buried in a protein matrix. Unfolding of a protein usually increases the an li-tilde of the fast motions. 

H2S (urban) 20-200 ppt V (remote) 0-40 pptv Oxidation of S gases Biological decay of protein in Earth surface, oxidation to sulphate Oxidation to SO2... 

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